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Computational Fluid Dynamics (CFD) investigations of air flow and temperature distribution in a small scale bread-baking oven

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Abstract

Experimental and computational fluid dynamics (CFD) analyses of the thermal air flow distribution in a 3-zone small scale forced convection bread-baking oven are undertaken. Following industrial bread-making practise, the oven is controlled at different (constant) temperatures within each zone and a CFD model is developed and validated against experimental data collected within the oven. The CFD results demonstrate that careful selection of the flow model, together with implementation of realistic boundary conditions, give accurate temperature predictions throughout the oven. The CFD model is used to predict the flow and thermal fields within the oven and to show how key features, such as regions of recirculating flow, depend on the speeds of the impinging jets.

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... The transient governing equations for the heat transfer inside the oven, air, and bread are discussed in this section. It should be mentioned that Reynolds Averaged Navier-Stokes (RANS) models have been effectively employed in prior studies to accurately forecast the air flows within baking ovens [5,23], wherein the continuity and momentum equations are formulated as follows: ∂ ∂t ...
... The third term on the right-hand side is the viscous stress tensor, where the µ is the dynamic viscosity and δ ij is the Kronecher delta function. The realizable k-ε model is used to consider the turbulent regime through the oven chamber recommended by some researchers [5,23]. This model consists of two further equations, including k (turbulent kinetic energy) and ε (turbulent dissipation rate), as follows: ...
... If the fit clearance is large, the overflow is serious and the flow rate is difficult to control. If the fit clearance is small, the deformations of the valve trims caused by high temperature and pressure fluid lead to the stuck phenomenon between the matching surface [5][6][7]. For the deformations of the valve trims, some scholars mostly use the finite element method to analyze the deformations due to the difficulty of internal measurement. ...
... where G is the mass flow rate of the fluid; C 0 is the flow coefficient of the single-hole; M is the molar mass of the fluid; Z is the compression coefficient of the fluid; T is the fluid temperature; k is Adiabatic index. The orifice configuration of the pressure reducing components can be designed by Eq (6). The flow characteristic of the valve refers to the ratio between the relative flow rate and the relative stroke in the valve. ...
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A multistage pressure reducing valve with specially designed pressure reducing components is presented in this paper. As the deformation of the valve trims under fluid-solid-heat coupling has an important influence on the operation reliability of the valve, a numerical simulation is carried out to analyse the flow field characteristic in the valve and radial deformation of the valve trims using the ANSYS software. And a deformation experiment is designed to validate the deformations of the valve trims at high temperature of 693.15 K. The results indicate that the simulation results agree well with the experimental data. Moreover, it is found that the temperature field has the most significant influence on the deformation of the valve trims, the radial deformations of the matching surface vary from 0.439 to 0.442 mm. And the radial deformations caused by other factors vary from 0.005 to 0.015 mm. In addition, as a novel indicator, the clearance after deformation of the matching surface is used to evaluate the operation reliability of the valve. By using the GAP function in ANSYS static module, the clearances of the matching surface are obtained at different openings under the condition of fluid-solid-heat coupling, further indicating that the initial clearance between the valve plug and inner sleeve should be greater than 0.014 mm to ensure the operation reliability of the valve.
... Electric ovens are among the least energy efficient appliances, with the efficiency of only 10-12%. Considering that an electric oven consumes about 100-300 kWh per year [11] and that the electric ovens in EU are more less 61% of 213.8 million households [12], an electric energy consumption of about 26 TWh per year can be assigned to domestic ovens. Therefore, the possibility to increase by 20% the product efficiency can achieve an annually energy saving about 5 TWh. ...
... Some CFD simulations also included radiation models such as surfaceto-surface (S2S) and discrete ordinate (DO) to reproduce the virtual performance of electric ovens [24]. Other research works describe the use of CFD tools to analyze the thermal transitory in industrial ovens [25] considering the effect of radiation on the walls, the temperature profiles in multisection cavity [26], and the temperature distribution due to convective phenomena [27]. For the gas oven, Özdemir [28] has developed models for simulation of turbulent combustion, demonstrating that the use of numerical simulations allows to improve both the performance of the burner and the uniformity of cooking inside the cavity of oven [29]. ...
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Nowadays, the increasing of global climate change and warming is leading governments, consumers, and firms towards a low-carbon economy. A lot of research shows that about 75% of the environmental impacts related to energy-related products is due to the use phase. Therefore, energy-related products, such as household appliances, are responsible for the consumption and depletion of natural resources. The eco-design of household appliances is a necessary approach to analyze and reduce the environmental impacts related to these products, considering materials, efficiency, and energy consumptions. In Europe, as well in China and America, the eco-design is becoming an Integrated Product Policy to support the Energy Labelling of several energy-related and consuming products. This paper deals with a design methodology to support the eco-design of cooking ovens by the simulation of the product performance. Two simulation cases have been analyzed: the energy consumption, which is provided by EU regulations No 66/2014 and No 65/2014 and the baking test. Even if regulations only provide the energy consumption test, the baking test is necessary to analyze the functional quality of the product. Therefore, two levels of simulations are necessary to complete the eco-design approach of cooking ovens. The results show that the proposed methodological approach can reduce the time-to-market and enhance the design optimization from the early design phases.
... This research provides valuable insights for designing and constructing such dryers in the food industry, focusing on technical specifications, energy balances, and heat transfer coefficients [29]. Khatir et al. [30] highlight using two-dimensional CFD modeling to assess temperature profiles and airflow patterns within bread-baking ovens. ...
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Recent developments in alternative drying techniques have significantly heightened interest in innovative technologies that improve the yield and quality of dried goods, enhance energy efficiency, and facilitate continuous monitoring of drying processes. Artificial intelligence (AI)-enabled optical sensing technologies have emerged as promising tools for smart and precise monitoring of food drying processes. Food industries can leverage AI-enabled optical sensing technologies to gain a comprehensive understanding of drying dynamics, optimize process parameters, identify potential issues, and ensure product consistency and quality. This review systematically discusses the application of selected optical sensing technologies, such as near-infrared (NIR) spectroscopy, hyperspectral imaging, and conventional imaging (i.e., computer vision) powered by AI. After covering the basics of optical sensing technologies for smart drying and an overview of different drying methods, it explores various optical sensing techniques for monitoring and quality control of drying processes. Additionally, the review addresses the limitations of these optical sensing technologies and their prospects in smart drying.
... Researchers in recent times have analyzed diverse types of baking ovens. For example, Ploteau [9] and Khatir [16], focused on bread baking whereas Mirade [8] anticipated the air temperature in an industrial biscuit baking oven. Some research studies on the design and fabrication of baking ovens obtained good results for transient reactions [3]. ...
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The supply and control of heat within an oven with minimal loss is an integral process in optimizing the bread-baking process. Research over the years reports on measures to control heat, however, there is limited data on optimizing burner designs for efficient heat supply. Challenged with enhancing the functionality of a bread baking oven made locally, three different burner concepts (i.e., U, H and Rectangular shaped) were designed, fabricated and evaluated in a locally manufactured bread baking oven. The study investigated the three burner configurations to enhance the locally manufactured ovens' environmental sustainability, cost-effectiveness, and efficiency. The study also assessed each burner design concept's performance in relation to heat distribution, fuel consumption, and emissions through thorough experimentation and analysis. Thermocouples were used to determine the temperature differences within the oven and outside the oven walls to verify heat losses. The results showed that the concept burner design can be used to bake bread with good quality parameters like colour, texture and taste within efficient baking time. Computational Fluid Dynamic (CFD) analysis performed on the proposed burner design concepts in relation to heat flow show that continuous flow of heat was assured during baking. Also, simulation performed on the baking trays show an acceptable stress and strain levels as well as favorable factor of safety, indicating that the designs proposed is suitable for the purpose. Data analysis performed on the heat generated within the oven chamber considering the lower and upper trays for all the burners evaluated can be ranked in terms of percentage as RB > HB > UB (41.39% > 30.72% > 27.89%). Based on the study conducted, the authors can suggest the best design concept for heat generation in locally manufactured ovens should be rectangular-shaped.
... This makes it possible to design optimal thermal conditions, minimize energy losses and maintain uniform quality of food products. CFD simulations allow for an accurate understanding of the temperature distribution inside food during thermal processes, which is crucial to avoid excessive overheating or underheating [44][45][46]. In the area of mechanical process simulation, CFD can be used to model the mixing, transport and grinding of raw materials and cleaning. ...
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Atlantic salmon is characterized by highly acceptable sensory qualities and a nutritional composition rich in fatty acids. However, food processing procedures, including improper heat treatment, can lead to unfavorable changes in quality and nutritional value. In this study, a computational fluid dynamics computer simulation was used to model the quality attributes of the roasted salmon product by controlling input parameters such as temperature, humidity, and air movement speed. Including the degree of denaturation of myosin, collagen, sarcoplasmic proteins, and actin, as well as docosahexaenoic acid decomposition and weight loss. Based on the conducted simulations, a prediction model was developed using the response surface methodology. According to the optimized model, salmon samples should undergo processing at a temperature of 151.38 ℃, with 20% humidity, and the fan speed set to 452.78 RPM. After the optimized heat treatment process, the degree of denaturation of salmon proteins was as follows: myosin denaturation at 95.12 ± 1.35%, collagen denaturation at 84.97 ± 1.72%, sarcoplasmic proteins denaturation at 37.71 ± 1.52%, and actin denaturation at 16.43 ± 0.71%. Furthermore, the weight loss was measured at 17.88 ± 0.55%, and docosahexaenoic acid decomposition at 0.56 ± 0.07%. This innovative hybrid method, using computational fluid dynamics and response surface methodology, for forecasting and optimization, can be applied to model thermal processes in the food industry.
... Radiation is transmitted heat from the heating sources located inside the oven and from the hot metal surfaces. Convection occurs when air, coming into contact with the heating source and hot metal parts of the oven, transfers heat to the baking surface of the product, and from here a conduction transfer takes place inside the product [3,20,[22][23][24]. It should be noted that the process of thermal convection can be natural or forced. ...
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The baking process in tunnel ovens can be influenced by many parameters. Among these, the most important can be considered as: the baking time, the volume of dough pieces, the texture and humidity of the dough, the distribution of temperature inside the oven, as well as the flow of air currents applied in the baking chamber. In order to obtain a constant quality of bakery or pastry products, and for the efficient operation of the oven, it is necessary that the solution made by the designers be subjected to modelling, simulation and analysis processes, before their manufacture, and in this sense it can be applied to the Computational Fluid Dynamics (CFD) numerical simulation tool. In this study, we made an analysis of the air flow inside the baking chamber of an oven. The analyzed oven was used very frequently on the pastry lines. After performing the modelling and simulation, the temperature distribution inside the oven was obtained in the longitudinal and transverse planes. For the experimental validation of the temperatures obtained in the computer-assisted simulation, the temperatures inside the analyzed electric oven were measured. The measured temperatures validated the simulation results with a maximum error of 7.6%.
... Penelitian Analisis eksperimental pada Computational Fluid Dynamic (CFD) dari distribusi aliran udara termal dalam oven pemanggang roti skala kecil. menunjukkan bahwa dengan CFD dan pemilihan model aliran yang cermat, juga penerapan kondisi batasan yang realistis, dapat memberikan prediksi suhu yang akurat di seluruh bagian oven [2]. Adapun menggunakan CFD untuk alat penelitian eksperimental yaitu perubahan bentuk geometri pada alat pengering yang awalnya tidak terdistribusi panas dengan baik dengan melakukan perubahan geometri pada diffuser yang awalnya panjang kemudian dipendekkan. ...
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Selama proses pengeringan bekerja akan terjadi perpindahan panas dalam ruangan pengering. Perpindahan panas terjadi akibat aliran fluida di dalam pipa dari tungku pemanas dan blower kedalam ruangan pengering belum merata. Maka dari itu analisa perpindahan panas perlu dilakukan agar tidak terjadi distribusi panas menyebar hanya ke satu bagian rak atau sudut ruang pengering yang mengalami panas berlebih dan ada bagian rak atau sudut yang bertemperatur rendah (panas tidak merata). Tujuan penelitian ini untuk mengetahui pengaruh variasi posisi pipa dan diameter pipa penghantar panas terhadap distribusi panas menggunakan computational fluid dynamic (CFD), laju pengeringan rengginang dan efesiensi pengeringan rengginang. Penelitian ini menggunakan metode simulasi menggunakan laptop dan melakukan metode eksperimen untuk validasi data. Hasil penelitian menunjukkan posisi 3 (pipa dibelakang horizontal dan pipa berukuran 1 inch) mendistribusikan udara panas yang cukup merata keseluruh bagian rak mesin pengering rengginang otomatis, yang memiliki temperatur paling tinggi di sensor ke 3 dan paling rendah disensor ke 4. Posisi ini memiliki rata-rata temperatur 46,9℃ dan toleransi temperatur 2,1℃. Kemudian melakukan validasi eksperimen dengan hasil <5% dan didapatkan laju pengeringan rengginang sebesar 1,04 g/menit atau 0,0624 kg/jam serta efesiensi pengeringan rengginang sebesar 1,25%.
... Electric resistance heating has various advantages over systems based on fuel combustion, such as increased control accuracy and heating rate. Researchers have analyzed diverse types of ovens (Khatir et al., 2012;Mirade et al., 2004). ...
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An improved electric baking oven was designed and fabricated using locally available materials for baking cakes and biscuits. Provisions of necessary adjustments were employed for ensuring uniform distribution of heat in all trays of the baking chamber. Its baking characteristics in terms of baking time, specific volume, and product quality in terms of sensory attributes were evaluated. The oven was found to be quite satisfactory in functioning for baking cakes and biscuits. Total time was only 15–28 min for baking the cake samples in the oven. On the other hand, comparatively, a bit longer time 18–35 min required for baking the biscuit samples. Baking cost was lesser in baking small‐sized cakes and biscuits than those of large sized. The quality of baked products was better in terms of taste, color, flavor, texture, and appearance than ordinary market products. Loaf volume of each cake (with 4 × 5 × 8 cm³) was 100%, which gave specific volume of 652.8 cm³/kg. Similarly, the specific volume of biscuits was 810 cm³/kg. The electric baking oven is quite efficient in baking quality cakes and biscuits uniformly, which can be provided to rural small entrepreneurs for commercial manufacturing of biscuits and cakes.
... In addition to CFD, this calls for the experimental investigation of fluid flow and heat transfer in impingement systems. The thermal airflow distribution in an air impingement furnace for baking bread was recently examined by Khatir et al. (2012), utilizing CFD simulation to forecast the flow and thermal fields inside the oven. It was observed that careful flow model selection and the application of believable boundary conditions effectively anticipated the temperature and air velocity spread over the whole oven. ...
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Air impingement method has been widely used in a variety of industrial applications, such as textile and paper drying, turbine cooling, and glass quenching, because it is an efficient technology with high heat and mass transfer rates. This technology has received increasing interest in the field of food processing over the last two decades, such as drying, baking, blanching, freezing, and thawing. In a food processing equipment using air impingement, jets of high‐velocity air (with speeds of 10–50 m/s) are directed at a food product. The performance of the system is influenced by several critical elements, including jet velocity, nozzle array diameter and layout, jet distance, and boundary layer characteristics. The use of computational fluid dynamics, an emerging tool, has been shown to be valuable in the analysis of fluid flow and heat and mass transfer in jet impingement systems. The physical properties of impinging jets, such as turbulent mixing in the free jet zone, stagnation, boundary layer formation, recirculation, and their interactions with food products in terms of heat and mass transfer, have been discussed in this article. The benefits and disadvantages of air jet impingement technology in different food processing applications together with potential trends for improving impingement technology performance were identified and discussed. This review not only contributes to a better understanding of the research status of impingement technology on food processing but also triggers new research opportunities in this field in order to provide more healthy and nutritious food in a more sustainable way to the world's growing population.
... production or devices with continuous operation (tunnel ovens) [61][62][63][64][65]. Such solutions allow, among other things, to predict the degree of starch gelatinisation during baking [66]. ...
Article
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Computational fluid dynamics (CFD) is a tool for modelling and simulating processes in many industries. It is usually used as a choice to solve problem involving flow of fluids, heat transfer, mass transfer and chemical reaction. Moreover, it has also found application in the optimization of processes in branches of the food industry, including bread baking, cooling beef roast, or spray drying. CFD has enormous potential and many opportunities to improve the quality and safety of food products, as well as to reduce the costs of production and the use of machines and production equipment. In addition, empirical models only permit data to be extracted at a limited number of locations in the system (where sensors and gauges are placed). CFD allows the designer to examine any location in the region of interest, and interpret its performance through a set of thermal and flow parameters. Computer simulations are the future of every field of science, and the presented overview provides the latest information on experts and experiences related to CFD application in food production. Despite some disadvantages, such as the need to have a large reserve of computing power, the development of digital and IT technologies will make this problem insignificant in the nearest future. Then the CFD will become an indispensable element in the design of equipment and technological lines in the food industry.
... Studies are being conducted to examine the effects of the types of heat sources and the deformities and thermal properties of structures on the distillation efficiency. Many studies claimed that the computational fluid dynamics (CFD) method can be an effective tool (Khatir et al., 2012;Rousseau et al., 2006;Sharma et al., 2018;Xia & Sun, 2002). The CFD analysis is performed to convert Navier-Stokes equations, which are nonlinear partial differential equations describing fluid phenomena, to algebraic equations by discretization using the Finite Difference Method, Finite Element Method, Finite Volume Method, and so on, and then to solve and analyze fluid flow problems using the algorithm of numerical methods (Blocken et al., 2007;Griffiths & Boysan, 1996). ...
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The design of the Korean traditional distiller ‘sojutgori’ was extracted as a digital sketch, and the internal fluid flow in the distillation process was tracked through computer simulation. Based on this, a new design was derived to improve distillation efficiency and its changes were researched. The ethanol particles vaporized inside the distiller were stagnated or their discharge was accelerated according to the magnitude and frequency of vortex. If the center is narrow and the fluid rotates, the vortex decreases or changes to a regular form. To effectively control the vortex, six simple models and two materialized models were designed and the optimal design was derived. When compared with the traditional distiller, the outlet fluid speed of the final design increased by 78% and the residence time dispersion of ethanol particles decreased by 39%. Furthermore, to suppress the temperature spread of fermented wash, a streamlined blade structure that can promote convection current was added. This structure had the effect of reducing the temperature spread of fermented wash by 57%. In addition, a reflux ring structure that can control the recondensed fermented wash caused by heat loss at the inner wall of the distiller was designed and applied. The reflux ring structure minimized the temperature change of the fermented wash and decreased temperature change by 23% compared to the condition without the reflux ring structure. This study suggests a new design for tracking and modernizing the flow of fluid that changes inside according to the shape and material of "Sojutgori", a traditional Korean distiller.
... Purlis (2011) used the values of previously developed mathematical models to study the baking process' mass and heat transfer phenomena involving phase change in moving boundary. Computational fluid dynamics (CFD) is a modeling method such might be utilized to study the influence of product geometry and over configurations during heat and mass transfer (Khatir et al., 2012). It can visualize heat transfer and airflow within the baking chamber and the entire product. ...
Article
Conventional hot air baking is a widely used food processing technology, which involves simultaneous heat and mass transfer processes. Chances of acrylamide and hydroxymethylfurfural formation is high in baked products due to high-temperature treatment. Since acrylamide and hydroxymethylfurfural are harmful to human health, it becomes crucial to develop novel baking technologies to mitigate these harmful components without affecting the sensorial properties of the final baked product. The formation of hydroxymethylfurfural and acrylamide are closely related to baking temperature, baking time, and ingredients. Novel technologies and pretreatments are shown promising results to mitigate these harmful components in the end products. This review describes the suitable pretreatment methods, novel baking technologies, and effective post-baking techniques that help mitigate the development of harmful compounds without affecting the textural attributes of baked products. Novel baking technologies, such as vacuum baking, high voltage electrical discharge, supercritical carbon dioxide extrusion process, power ultrasound, infrared, microwave and halogen lamp baking; different pretreatment technologies – ozone treatment, plasma treatment, high-pressure processing, ohmic heating, ultraviolet irradiation and ligh emitting diode treatment are discussed together with a comprehensive insight to the understanding of mechanisms involved in the formation of harmful components during processing and post-baking.
... The proposed regime, as suggested, was able to maintain the uniformity of heat transfer and reduction of moisture accumulated inside the oven. As highlighted by Khatir et al. [18], the radiation was the predominant mode of heat transfer during lower velocities of airflow, and contrarily, at a higher velocity, the heat transfer was forced convection. ...
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This paper presents the study of infrared (IR) reflow oven characteristics for suitable operating conditions of the flexible printed circuit board (FPCB) in the reflow soldering process. A computer-based model that imitates a real-time oven was developed with practical boundary conditions. Since the radiation effect is dominant in the reflow process, a discrete ordinate (DO) model was selected to simulate the effect. The experimental work acts as a benchmark and the reflow profile was set to follow the standards of JSTD-020E. The simulation of the model has a great consensus between the experimental data. It was found that the temperature distribution was inhomogeneous along with the phases. The FPCB surface also has a higher surface temperature than oven air during the operating reflow profile. An in-depth study using the simulation approach reveals that the temperature distribution of the desktop reflow oven is dependent on several factors, namely fan speed, FPCB position, and FPCB thickness. The rotational fan generates an unsteady flow that induces inhomogeneous temperature at different positions in the reflow oven cavity. The results are useful for studying further improvements to achieve temperature uniformity within the oven chamber.
... Several experimental works have been carried out to investigate airflow uniformity inside the different drying chamber configurations (Khatir et al., 2012, Misha et al., 2013a, Ribeiro and Andrade, 2004, Santos-Sánchez et al., 2012Yongson et al., 2007). On the other hand, computational fluid dynamics (CFD) have been employed to simulate and optimize various drying chamber designs for uniform solar drying (Misha et al., 2013b, Misha et al., 2013cMisha et al., 2015). ...
Article
Solar drying is an important industrial technology with expanding segment in the industrial solar market. The main drawback in commercializing solar dryers is the non-appropriate design of the drying chamber to perform uniform drying and hence producing a nonhomogeneous product. Uniformity of airflow inside the drying chamber has a significant role in the drying process. The current article presents an experimental and computational analysis of a hybrid solar-thermal dryer with a multi-chamber drying cabinet. A prototype was designed and fabricated to including three separate chambers, and each has one angular-movable tray for experimental measurements. The computational model was developed in ANSYS Fluent software for CFD simulation and validated by comparing the experimental results. A statistical analysis of the simulation results has been performed. The focus was made on the effect of tray inclination angle, 0 • , 10 • , 20 • , 30 • and 35 • , air velocity and turbulence intensity distribution inside the drying cabinet at various operational conditions. Experimental and numerical analysis results indicate that the best uniformity is achieved in the tray with 30 • inclination. Statistical analysis results revealed that around 93% of velocity frequency is obtained at 0.7-0.8 m/s air velocity level for 30 • tray angle. The article can be downloaded by the link: https://authors.elsevier.com/a/1dJ04,tRdGz1f
... Technology designers look for simple and accurate prediction methods to simulate different processes in order to obtain appropriate material characteristics and operating conditions (Purlis, 2019). Indeed, the products qualities such as the temperature uniformity, heating efficiency, baking time, humidity and limited consumption of energy, highly depend on an efficient optimization of oven parameters (Chhanwal et al., 2019;Pask et al., 2014;Boulet et al., 2010;Khatir et al., 2012). ...
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In this work, we propose a mathematical model describing thermal behavior and heating process optimization of solid fuel bread ovens. Numerical simulation leads to temperature profiles of the oven. The design and implementation of an operating prototype permits us to obtain, with type K thermocouples, experimental temperature profiles in some points of the oven. There is a good agreement between the experimental results and those obtained from the numerical simulation of the proposed model. A permanent temperature value of 220 °C is reached in the baking chamber. It is obtained that the energy efficiency of the oven is 49%. Making use of the objective gain function, it is found that the optimal parameters of the oven are the following: 50 W as optimum operating value of the electric power of the blower, 3 m² as the optimum operating value of the total surface of the baking chamber; and 0.67 as the optimum operating value of the filling factor between the heating chamber and the baking chamber. The developed model serves to better understand the operation, the optimization and to rationally manage energy expenditure related to solid fuel bread ovens in developing countries.
... On the contrary, in the indirect-fired ovens, the heat energy is produced in a chamber separated by a steel wall from the tunnel where biscuits are placed (Williamson and Williamson, 2009). Usually, the baking chamber consists of around three to five different zones along the oven (Khatir et al., 2012), where extraction chimneys promote air movement and allow exhausted air to be removed (Yanniotis and Sundén, 2007). Fans of variable speed are also placed along the tunnel with the aim of moving air so as to improve the transport phenomena which normally occur in cooking processes. ...
... Investigation of Tank et al. [39] of the effect of the number of baking trays within the oven on the temperature profiles, showed an uneven temperature distribution with a temperature differences within the oven of up to 30°C. Khatir et al. [40,41,42], used numerical simulations for the optimization of the tunnel oven size and flow conditions. They also measured local convective heat transfer coefficient on the baked product and analyzed the effects on the required baking time. ...
Thesis
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Food industry is commonly among the top ten energy most intensive industrial branches. Its annual energy requirements record constant increase. Within the food industry, bakeries are one of the largest energy consumers, due to the energy requirements of the baking ovens, which account for more than a half of the total energy required in the whole production process. The baking oven, a key element of every bakery, directly influences the time and energy efficiency of the production process itself, but also the quality and the cost of the final product. Due to the strict food safety and quality regulations and requirements, improvement of the existing processes is usually related to the significant technical, ecological and economical challenges. In the frame of here presented work, an innovative baking oven concept is proposed and developed. The core of this novel baking oven is an employment of the specific properties of the volumetric ceramic burners (VCB) in order to improve overall baking process performances. The VCB principles of operation, its features and characteristics of NIR thermal emissions are discussed in order to provide the basic understanding of the proposed concept and properties of the developed baking oven prototype. With the help of the innovative Validated Virtual Engineering (VVE), a fully functional prototype of the novel baking oven in industrial scale size is designed. In this way, costly conventional trial-and-error procedures are avoided. The simulation tools enable virtual analysis of various constructional and operational modifications of the baking oven. Amongst others, the influence of the burners shape and their planar distribution, the influence of the quartz glass in front of the burners and the design of the exhaust gas guiding system and its recirculation, were investigated. The validation experiments proved i.a. the operating stability of the designed prototype in a wide power and air-fuel equivalence ratio range, the homogeneity of the thermal radiation and the uniform temperature distribution over the baking plates. This novel, VCB-based, gas-powered, deck oven combines the advantages of near-infrared (NIR) thermal radiation, mainly in the wavelength range of 1.3-1.7 μm, with the unique control dynamics, enabling fast power adjustment to the production process requirement. Furthermore, new findings were extracted out of the numerous experimental investigations, regarding the influence of the novel VCB-based baking oven concept on the product quality and improved energy efficiency, production ecology and economy of the baking process. Using 800 g wheat bread loaves, baking properties of the newly developed oven were compared with the baking properties of the conventional electric deck oven of the same size and geometry. The analysis showed that the VKB oven provides the baked goods of the comparable quality and similar sensory properties i.a. crust thickness, desired crust color, crumb porosity, taste, smell, elasticity, etc. In addition, the VCB-based baking oven reduces preheating and baking time of up to 20 %. The resulting reduced fuel input and the use of gas heating instead of electrical energy provide the significant saving of the primary energy and reduction of CO2 emis-sion. The presented results demonstrate the suitability of the innovative baking oven concept with regard to the product quality, process economy and ecology. At the same time, they confirm the high untapped potential of the application of the porous VCB technology in the food industry.
... Researchers face problems in achieving sufficient uniformity in the treatment or process parameters even in laboratory-scale designs and the hindrance appears multifold when these equipments are scaled up for industrial usage. For example, in the process of bread baking nonuniform heating profiles inside the oven can lead to variation in color, moisture content, nonuniform starch gelatinization, and volume expansion (Khatir et al., 2012). Lack of proper validation of pilot-scale design is the key reason why most laboratory-scale designs are not acceptable for industrial usage. ...
... Later, through another study authors developed a CFD model to study the temperature and browning profile of bread (Chhanwal, Indrani, Raghavarao, & Anandharamakrishnan, 2011). Another research was carried out to study CFD and experimental analyses of the thermal air flow distribution in a three-zone small scale forced convection bread-baking oven (Khatir et al., 2012). ...
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Bakery products are appreciably consumed by the populace of all age groups globally, owing to their flavor and easily digestible nature. The availability of diversified products like bread, cookies, biscuits, muffins, cakes, tortillas, rolls, wafers, and pies has further facilitated their consumption. However, variation in processing parameters and raw material quality triggers many biochemical changes, complex reactions, and physical modifications which are intricate and least understood in the food industry till date. Many operational and product failures have been discovered owing to this poor assimilation of controls in the baking process. In this scenario, bakery manufacturers are increasingly considering the adoption of process analytical technology initiated by the United States Food and Drug Administration to facilitate the production of bakery products with increased safety, product quality, and process efficacy. Studies on the applications of process analytical technology for the bakery industry are outlined and reviewed through this article. Practical Applications Process analytical techniques are suitable in monitoring various unit operations within a bakery industry that requires process optimization and are sensitive to process extremities of time and temperature. Applications of process analytical technology (PAT) in the bakery unit varies from ingredient metering to optimizing mixing parameters, monitoring baking process and quality analysis of the final product. It possesses fast, reliable, real‐time, and nondestructive evaluation, which makes it a process of choice. Moreover, the need for the development of calibration models, sensors, and chemometrics restrict the adoption of PAT in the bakery industry. Therefore, future research aiding to the progress of PAT technique equipped with strong data tools that enhance understanding of critical points in the process and product line is warranted.
... Controlling the air distribution characteristics inside the drying chamber is based on drying chamber design which has a significant effect on the uniformity of drying. Hence, the experimental investigation of air flow uniformity inside the different designs of drying chamber is very expensive and time consuming [2,[4][5][6][7]. Therefore, computational fluid dynamics (CFD) simulation has been adopted to investigate different configurations and to optimize drying chamber design for uniform solar drying [8][9][10]. ...
Conference Paper
Multi tray solar dryer is commonly used for thin layers drying type due to its ease of manufacturing and economical aspects. However, the drawback of this dryer design is the non-uniformity in the required moisture content of end product. This work presents the development of multi chamber solar drying cabinet using numerical analysis. The main objective is to ensure uniform velocity distribution inside the multi chamber dryer. This aim has been achieved by series of modifications of design concepts based on the aerodynamic behavior of air flow. The results showed that four design phases to come out with optimum design configuration of the multi chamber drying cabinet. The velocity above the splitter has a significant difference of around 0.1 m/s at the end of splitters among the chambers. It is concluded from this result that the cross section flow area has an impact on the uniformity of velocity and a further modification is recommended.
... Ovens in general have been studied extensively in the literature. These research pertain mainly ovens for baking bread (Zinedine et al. 2012(Zinedine et al. , 2013 shortbread (Uroš et al. 2017), coke (Buczynski et al. 2016), whereas studies regarding automotive paint ovens are much rarer. In these studies, computational fluid dynamic (CFD) modeling and simulation have been applied to predict car body temperature in the oven or to analyze oven thermal performance. ...
Article
Full-text available
Car paint ovens consume a lot of energy within the automobile factory. For this reason, proper selection or design of this unit can yield substantial reduction in costs. In addition, car paint ovens that operate in existing factories quite often cannot assure adequate indoor air temperature and they need to be redesigned. In such an instance, simulating the oven operation is very important as it allows optimal selection of parameters that need to be changed in order that paint oven meets the requirements. In this paper, mathematical model for simulation of energy flows in car paint oven is presented. The model can be used to easily analyze which variables and to what extent affect the operating parameters (such as air temperature or car body temperature) of car paint oven, that could help designers to select optimal scenario for designing new or redesigning existing car paint ovens in order to achieve desired indoor air temperature.
... Throughout the literature there are several documented attempts to increase the efficiency of ovens using the three heat transfer mechanisms; conduction, convection, and radiation. These attempts include evaluations of the performance of domestic gas ovens [7,8] and the development of methodology for bread making ovens [9][10][11][12], while both convection and radiation have been specially considered for the domestic electric oven. ...
Article
Full-text available
In this study, the radiative properties of the surfaces of an electric oven were investigated. Using experimental data related to an oven-like enclosure, a novel combination of surface properties was developed. Three different surface emissivity combinations were analysed experimentally: low-emissivity, high emissivity (black-coated), and hybrid emissivity. The term “hybrid emissivity design” here corresponds to an enclosure with some high emissive and some low-emissive surfaces. The experiments were carried out according to the EN 50304 standard. When a brick (load) was placed in the enclosure, the view factors between its surfaces were calculated with the Monte Carlo method. These and the measured surface temperatures were then used to calculate the radiative heat fluxes on the surfaces of the load. The three different models were compared with respect to energy consumption and baking time. The hybrid model performed best, with the highest radiative heat transfer between the surfaces of the enclosure and the load and minimum heat loss from the cavity. Thus, it was the most efficient model with the lowest energy consumption and the shortest baking time. The recent European Union regulation regarding the energy labelling of domestic ovens was used.
... Other works describe the application of CFD in identifying: the transitory state of industrial ovens (Wong et al., 2007), the effect of radiation on the walls of batch ovens (Boulet et al., 2010), the temperature profiles in multi-section industrial ovens (Khatir et al., 2012) and validation of the calculation of temperature uniformity in convective ovens (Smolka et al., 2013). CFD has been linked to the optimization of the baking system as the essential calculation tool. ...
Article
Convective ovens require a pre-heating stage to achieve a homogenous temperature. Energy consumption is high during the pre-heating stage and proportional to pre-heating time. The pre-heating time depends on the set-point temperature. In this work a pilot scale convective oven was represented as a nominal scenario, and provided experimental data for temperature. The strategy consisted of 3-D computational fluid dynamic (CFD) simulations at different temperatures and geometrical variants of the internal baffle plate. The simulations were carried out using the ANSYS CFX package and were contrasted with experimental measurements. Results proved that the baffle plate geometry exerted an important hydrodynamic influence in the reduction of the pre-heating time.
... Baking ovens come in a variety of different configurations, from small domestic units to large tunnel ovens. Industrial ovens are typically gas powered and are usually classified as direct (forced convection), indirect, microwave, radiation, or infrared systems (Keskin et al., 2004; Mirade et al., 2004; Sakin et al., 2009; Khatir et al., 2012; Khater and Bahnasawy, 2014). Other energy sources include oil, electricity and woodchip burners. ...
Article
Full-text available
The main aim of the present work is to study and evaluate energy consumption in bread baking. This was achieved by determining the energy consumed in each stage of bread baking processing to assess the most consumable stage of bread baking process. Magr baladi, Mawi and French bread baking were evaluated processes. Thermal, electrical and human energy sources were determined. The results indicated that the total specific energy consumed were 3038.11, 2831.85 and 4823.53 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively. The specific electrical energy consumed were 42.21, 40.33 and 59.92 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively. The specific human energy consumed were 5.35, 5.42 and 10.72 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively. The specific thermal energy consumed were 2990.50, 2786.10 and 4752.89 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively, which represent 98.43, 98.38 and 98.54% of the total energy consumed. The Total costs of different types of bread baking were 2.32, 1.76 and 4.80 LE kg-1 for Magr baladi, Mawi baladi and French bread, respectively.
... Computational fluid dynamics (CFD) has been widely applied to provide the dynamic behavior such as concentration distributions [6], velocity profiles [7], velocity patterns [8] distributions [9] of several processes with great success. Furthermore, many researchers have reported the modeling and studied the fluid dynamic behavior in several types of ovens such as a convective drying oven [10], a heating oven with natural air circulation [11], a microwave oven [12], a bakery pilot oven [13], a small scale bread-baking oven [14], a paint curing oven [15] and an infrared oven [16]. ...
Article
In the drying process of a can making industry, the drying efficiency of a thermal drying oven can be improved by adjusting the volumetric air flow rate of the blower. To maximize drying efficiency, an optimal flow rate is needed. Consequently, a three-dimensional computational fluid dynamics (CFD) is used to provide simulation according to the response of air velocity, air temperature and evaporated solvent concentration with respect to changes in volumetric air flow rate in the drying oven. An experimental study has been carried out to determine the evaporation rate of the solvent. To validate the models, the process data obtained from the CFD is compared with that obtained from actual data. In the accurate models, the simulation results demonstrate that the decrease in volumetric air flow rate provides no major discrepancy of the air velocity patterns in all dimensions and decreases the maximum temperature in the oven. Consequently, this decrease in volumetric air flow rate rapidly increases the evaporated solvent concentration in the beginning and then gradually decreases over the length of the oven. In addition, further reduction of the flow rate gives lower heat loss of the oven up to 83.67%.
... production cost). For this reason, while many researchers are focusing on the new technologies, some are more interested in optimising the food processing based on the consolidated technologies (Khatir et al., 2012). This could be made through the assessment of the energy demand of food together to that related to the process itself, belonging to a combination of energy sources. ...
Article
Full-text available
A recent guideline from the European Commission declared that several highly energy consuming domestic equipment should be better regulated or avoided at all in the near future. Together with this, several EU nations are abandoning the gas ovens in favour of the electric ones, also due to the home energy rating regulations, that make impossible to get the highest rating with gas ovens. Due to this fact, the study of the technologies related to the energy efficiency in cooking is increasingly developing. The combination of several energy sources (e.g. forced convection, irradiation, microwave, etc.), as well as optimisation of each of them, is an emerging target for oven manufacturers, in matter of oven design and better use of the oven capabilities. Within this context, an energy consumption analysis and optimisation is targeted in this work, by the application of a bread baking model, validated on experimental data. Each source of energy is given the due importance and the practically applicable process solutions are compared. A basic quality standard is guaranteed by taking into account some quality markers, which are relevant on the basis of a consumer point of view. This work is a part of a more comprehensive study on oven cooking and energy integration, and could lead to practical applications in the design of energy efficient cooking programs.
... On the other hand, some researches have analyzed diverse types of ovens by means of accurate although time consuming CFD of FEM models. See, e.g., the work in [5] for predicting the air temperature in an industrial biscuit baking oven or the intensive research in bread baking in [6] or in the works by Khatir et al. in [7] and later papers. Some works obtained valuable results for transient responses [8,9], but the high computational requirements of the CFD and FEM approaches make them unviable for processes involving a high number of simulations, e.g., sensitivity analyses of the model parameters or optimization of temperature controllers. ...
Article
Full-text available
In this paper, a new heat and mass transfer model for an electric oven and the load placed inside is presented. The developed model is based on a linear lumped parameter structure that differentiates the main components of the appliance and the load, therefore reproducing the thermal dynamics of several elements of the system including the heaters or the interior of the product. Besides, an expression to estimate the water evaporation rate of the thermal load has been developed and integrated in the model so that heat and mass transfer phenomena are made interdependent. Simulations and experiments have been carried out for different cooking methods, and the subsequent energy results, including energy and power time-dependent distributions, are presented. The very low computational needs of the model make it ideal for optimization processes involving a high number of simulations. This feature, together with the energy information also provided by the model, will permit the design of new ovens and control algorithms that may outperform the present ones in terms of energy efficiency.
... Dou [4] has simulated the gas flow of oven, and proposed an optimized design for the stability of the oven. Khatir et al. [5] has studied the air flow and temperature distribution of bread oven with experiments and numerical simulation. However, the relation between the uniformity of temperature and impeller's speed hasn't been given. ...
Article
Full-text available
Baking treatment is one of the most important processes of cigarette production, which can significantly enhance quality of tobacco. Theoretical and numerical investigation on temperature distribution in a cigarette oven during baking was carried out. The finite volume method was used to simulate the flow field. The relationship between the uniformity of temperature field and impeller’s speed was given finally, which is helpful to optimize cigarette oven with better quality and less energy consumption.
... De Bonis and Ruocco (2007) modelled the local heat and mass transfer in food slabs under air jet impingement drying conditions and predicted local moisture, temperature, and velocity distributions using CFD. Recently, Khatir et al. (2012) analyzed the thermal air flow distribution in an air impingement oven for bread baking using CFD simulation to predict the flow and thermal fields within the oven. It was found that careful selection of the flow model, together with implementation of realistic boundary conditions, accurately predicted the temperature and air velocity distribution throughout the oven. ...
Chapter
Drying is one of the most popular methods used for preserving products and extending their shelf lives by reducing moisture content to a low level to prevent microbial spoilage and moisture-mediated deteriorative reactions. As an efficient technology with high heat and mass transfer rates, impingement drying has been commonly used in various industrial drying such as tissue paper, textiles, photographic films, coated paper, nonwovens, carpets, lumber etc. In the past two decades, air impingement technology has got more and more attention in the field of food and agricultural products processing.This chapter reviews the applications of impingement drying in food and agricultural products drying, including vegetables and fruits (seedless grapes, Hami melon flakes, apricots, carrot cubes, line pepper etc), herbs (American ginseng slices, yam slices etc), foods (tortilla chips, potato chips, fish cake, fish particles, shrimp etc), seeds, soy residue etc. In addition, the future trends to enhance the performance of impingement drying are identified and discussed. We hope that this chapter not only contributes to a better understanding of the research status of impingement drying, but also triggers new research opportunities in this field in order to provide more healthy and nutritious food for the growing global people in a more sustainable way.
... Therefore, it is interesting to distinguish how these changes may influence oven temperature, baking process and finally product properties. Some previous studies have reported the effects of process condition in tunnel type oven (Baik et al., 2000a), pilot plant oven (Zareifard et al., 2009;Khatir et al., 2012), electric oven (Lostie et al., 2002) and infrared-microwave combination oven (Turabi et al., 2007), to name a few. However, the effects of the airflow to the oven temperature, process condition and product quality during cake baking have not been substantially reported. ...
Article
Full-text available
The objective of this study was to evaluate the effects of milling methods on tensile properties of polypropylene (PP) / oil palm mesocarp fibre (OPMF) biocomposites. Two types of mills were used; Wiley mill (WM) and disc mill (DM). Ground OPMF from each milling process was examined for its particle size distribution and aspect ratio by sieve and microscopic analyses, respectively. Results showed that DM-OPMF had smaller diameter fibre with uniform particle size compared to the WM-OPMF. Surface morphology study by SEM showed that DM-OPMF had rougher surface compared to WM-OPMF. Furthermore, it was found that PP/DM-OPMF biocomposite had higher tensile strength compared to PP/WM-OPMF, with almost two-fold. Thus, it is suggested that small diameter and uniform size fibre may improve stress transfer and surface contact between the fibre and polymer matrix and cause welldispersion of filler throughout the polymer resulted in better tensile strength of PP/DM-OPMF compared to PP/WM-OPMF biocomposite. Overall, it can be concluded that disc milling could serve as a simple and effective grinding method for improving the tensile properties of biocomposite.
... The optimization found 21.69% improvement on the ETC for the given range of design parameters. Khatir et al. [2] studied the temperature and browning profiles of bread inside the oven by using CFD model and validated the results with the experimental measurements of bread temperature. The results showed that the baking process completed within 25 min of processing time after the temperature of crumb becomes stable at 98 °C and CFD can precisely predict the browning index. ...
Article
One of the most critical steps in brick making is firing, performed to harden the bricks. In a typical non-industrial setting, many pieces of extruded clays are stacked into a box-shaped kiln with equally-spaced rectangular vertical holes and another set of equally-spaced horizontal holes at the bottom across two sides. Roman roof tiles are used to cover the vertical sides, while leaving the horizontal holes opened, to complete the kiln assembly. Rice husk is filled in the holes of the kiln and is used as the fuel for firing. However, approximately 10% of the bricks, stacked conventionally, are always not appropriately fired. Therefore, this research aimed at simplifying model and redesigning the clay brick kiln using three-dimensional computational fluid dynamics (CFD). The studied parameters for 23 factorial designs were as follows: kiln height (200 – 225 cm), horizontal holes width (7.5 – 15 cm) and height (45 – 60 cm). The total volume of brick stack, averaged steady-state temperature and time to reach a steady-state temperature were selected as the response parameters. The analysis of variance (ANOVA) of 23 factorial design showed that the width and height of holes affected the time to reach steady-state but the averaged steady-state temperature and the total volume of brick stack were dependent on all 3 parameters. Then, a kiln was constructed according to the model with the maximum number of bricks and only 4% of the bricks were not appropriately fired.
... As energy prices and globalisation continue to escalate, food manufacturers seek opportunities to reduce production costs without adversely affecting output, profitability and the quality of the final products. Improving energy efficiency can contribute to the reduction of energy resource depletion rates and mitigate emissions of greenhouse gases and other pollutants [6][7][8][9][10]. Frying is a common process in food manufacture. ...
Article
Continuous frying systems are very energy intensive. They also involve the interaction of many variables and complex heat and mass transfer processes. Better control of these processes can lead not only to improved product quality but also energy reduction. This paper presents a model that can simulate the dynamic behaviour of a continuous frying system in sufficient detail that enables the influence of controls on the important product attributes of moisture and oil content to be investigated. A conjugate 2-D transient model of the fryer was used to develop correlations for the oil and moisture content based on the important fryer control variables, namely supply oil temperature, potato mass throughput, fryer paddle velocity and crisp takeout velocity. The correlations were validated against data for an industrial continuous fryer system and used within the overall frying system model which was implemented in MATLAB. Proportional Integral (PI) controls implemented within the MATLAB/Simulink environment have shown that closer control of the important parameters can lead to 10% energy savings compared to the actual industrial frying system. The modelling approaches developed can also be used to investigate further improvements in the design and control of continuous frying systems.
... These airflow simulations were consistent with the heterogeneity of drying usually observed in practice. Khatir et al. [11] investigated the thermal airflow distribution in a 3-zone small scale forced convection bread-baking oven by experimental and CFD analyses. The CFD results demonstrated that careful selection of the flow model with implementation of realistic boundary conditions could give accurate temperature predictions throughout the oven. ...
Article
Full-text available
Micro-electrical-mechanical system (MEMS) has become important for many industries such as automotive, home appliance, portable electronics, especially with the emergence of Internet of Things. Volume testing with temperature compensation has been essential in order to provide MEMS based sensors with repeatability, consistency, reliability, and durability, but low cost. Particularly, in the temperature calibration test, temperature uniformity of thermal cycling based calibration chamber becomes more important for obtaining precision sensors, as each sensor is different before the calibration. When sensor samples are loaded into the chamber, we usually open the door of the chamber, then place fixtures into chamber and mount the samples on the fixtures. These operations may affect temperature uniformity in the chamber. In order to study the influencing factors of sample-loading on the temperature uniformity in the chamber during calibration testing, numerical simulation work was conducted first. Temperature field and flow field were simulated in empty chamber, chamber with open door, chamber with samples, and chamber with fixtures, respectively. By simulation, it was found that opening chamber door, sample size and number of fixture layers all have effects on flow field and temperature field. By experimental validation, it was found that the measured temperature value was consistent with the simulated temperature value.
Article
Full-text available
In this review, the application of computational fluid dynamics (CFD) simulations in analyzing thermal processes within food technology is explored. The focus is on understanding heat transfer, fluid flow, and temperature distribution during various food processing methods, such as baking, frying, pasteurization, and cooling. Detailed insights that are often challenging to obtain through experimental methods alone are provided by CFD simulations, allowing for the optimization of process parameters to enhance product quality and safety. It is demonstrated that CFD can effectively model complex thermal phenomena, providing valuable data on temperature gradients and flow patterns. These simulations assist in the designing of more efficient processing equipment, improving energy consumption, and ensuring uniform heat treatment, which is crucial for maintaining the nutritional and sensory attributes of food products. Furthermore, the integration of CFD in the food industry leads to significant advancements in product development, reducing the time and cost associated with experimental trials. Future research should focus on refining these models for greater accuracy and exploring their application in emerging food processing technologies.
Article
The application of computational fluid dynamics (CFD) for controlling quality boundaries in light of temperature and moisture profiling is detailed in this review. For the mapping of intricate stream design inside the baking oven and its product-based baking interaction, efficient utilization of CFD perspectives can be observed. The most crucial element in baking that affects product quality is temperature. Based on heat transfer, the CFD model proved effective in estimating the product's crumb and crust temperatures. In addition to time and temperature, the position of the dough inside the oven affects the quality of the finished product during baking. CFD demonstrating angles effectively predicts the temperature profiles inside the baked product and henceforth, assists with controlling the extreme quality of the product. Regardless, also demonstrating studies ought to be embraced including mass transport and volume extension during the baking process. A piece of the issues related to moisture and heating measures during exhibiting of bread, bun, and cookies baking process, have been included. This study exhibits CFD to be a significant tool for the simulation of the baking oven and relative expectation of temperature and moisture profiles which eventually impacts starch gelatinization and browning issue during the baking process. The mass transfer during baking and volume expansion of various bakery products can also be modelled using CFD.
Chapter
Baking and roasting both use hot air to alter the eating quality of foods. This chapter begins with a description of heat and mass transfer during baking followed by details of batch and continuous baking equipment. The final part describes the effects of baking on microorganisms and changes to the sensory characteristics and nutritional value of baked and roasted foods.
Article
The Idly is a crispy rice cake from India’s Subcontinent that is very popular in Sri Lanka and the southern states as a breakfast food. So many research was carried out on the baking of bread in oven. In this research a novel attempt has been made for the reduction of baking time of idly in a vessel. The temperature, pressure and velocity distributions, and mass fraction were investigated via a CFD method in an idly vessel which is readily available in market. The computational fluid dynamics in the food processing of idly makers and the steam flow inside the vessel have been applied in these studies. This study was extended to investigate the impacts of the spread of temperatures in and around foodstuffs and reduces the baking time of the idly. And also, in this research baking time were determined using both analytical and experimental approach with two design modification in idly trays. By analytical approach, baking time is about 10.8 min. With experimental setup, time required to bake the idly in vessel is 8.53 min. But after making holes in idly trays, time requires to bake idly is 6.3 min. Around 4.5 min of baking time were saved and it is clearly witnessed in this research. This technique is very efficient in reducing the baking time of any food products where oven or vessel were utilized to cook.
Article
Numerical study of heat transfer between circular jet arrays and the flat moving surface is carried out. Two jet patterns: inline and staggered, are chosen. Total nine circular jets are used in both jet patterns. The analysis is carried out for steady-state and transient conditions with the turbulent flow of jet fluid. In steady-state analysis, the influence of surface motion on the flow field and heat transfer by the array of jets is analyzed. The surface-to-jet velocity ratio (r) varies from 0 to 2. In transient analysis, the effect of jet pattern on the cooling of hot moving plate is analyzed. The two-equation shear stress transport (SST) k-? turbulence model is used for solving Reynolds averaged Navier-Stokes (RANS) equations of conservation of mass, momentum, and energy for incompressible turbulent flow. The steady-state analysis shows that surface motion has a significant effect on the flow field and heat transfer. The transient analysis results show that a staggered jet pattern cools the plate more uniformly than an inline jet pattern.
Article
The complex airflow in convection ovens directly influences the heat transferred to the product placed inside, thereby affecting product quality. Characterization of related airflow profiles can provide scientific understanding for improvement of oven designs as well as important parameters for simulation of involved thermal processes. In this study, the particle-imaging velocimetry (PIV) technique was applied to visualize airflow inside a household convection oven with samples placed at three different locations on a baking tray. The oven cavity was modified for optical access, and airflow was measured at room temperature. A 30 mW green laser was used for illuminating tracer particles in a laser sheet that were generated using incense sticks. The flow patterns were captured using a high-speed camera at 1000 fps. The vorticity and turbulent kinetic energy parameters derived from velocity fields reflected adequate mixing of air inside the cavity. The computed heat transfer coefficient distribution from the boundary layer flow fields to the sample surface ranged between 2.0 and 18.3 W m⁻² K⁻¹. The results showed separation of the laminar boundary layer from the object surface at angles of 85°–90°. The PIV-algorithms and boundary layer flow derived parameters developed in this study can be used for refined characterization of complex air or gas flows and related heat transfer characteristics in closed cavity convection ovens and the like arrangements.
Article
Baking temperature and time are among the conditions for producing good quality cakes. The aim of this study was to investigate the effects of baking temperature and time on the volume expansion, moisture content, and texture of moist cakes baked in either an air fryer or a convection oven. The cakes were baked under different conditions: (1) baking temperature of 150 °C, 160 °C, and 170 °C for both air fryer and convection oven and (2) baking time of 25, 30, 35 min for air fryer and 35, 40, 45 min for convection oven. Baking temperature and time were found to have a significant (p < 0.05) effect on the relative height, moisture content, firmness and color of the product but no significant effect on the springiness of the product. Based on the numerical optimization method, the optimum condition in an air fryer was 150 °C for 25 min. These optimized conditions resulted in higher relative height (37.19%), higher moisture content (28.80%), lower crumb firmness and chewiness (5.05 N and 1.42 N respectively) as well as higher overall acceptance score (5.70) as compared to optimum condition in convection oven (150 °C at 55 min). Moreover, baking in the presence of rapid air flow in an air fryer may be declared that it is possible to produce high-quality moist cake with minimum baking temperature and shorter baking time.
Article
Combined use of microwave and infrared technologies for reheating food may be considered an efficient technique in food industry and fast food chains, as the overall quality and identity standard are maintained. The aim of this study was to test a new methodology for reheating baked foods, using both radiations. Computer simulation and preliminary tests were carried out controlling radiations emissions. The tests were conducted with biphasic foods to show the effectiveness and action of technologies. Preliminary studies were carried out to verify the effect of radiations in each food phase, which provided the action times of 15 s of microwave and 30 s of infrared. It was possible to measure the internal and external temperature of the samples, as well as moisture migration from the center to the surface. The results showed that the process was effective to reheat samples, providing attractive samples to consumers, according to sensorial analysis.
Article
To address the global challenge of the climate change, more strict legislations worldwide on carbon emission reductions have put energy intensive industries under immense pressure to improve the energy efficiency. Due to the lack of technical support and financial incentives, a range of technical and economic barriers still exist for small-medium enterprises (SMEs). This paper first introduces a point energy technology, which is developed for SMEs to improve the insight of the energy usage in the manufacturing processes and installed in a local bakery. Statistical analysis of electricity consumption data over a seven-day period is conducted, including the identification of operational modes for individual processing units using an enhanced clustering method and the voltage unbalance conditions associated with these identified modes. Two technical strategies, namely electrical load allotment and voltage unbalance minimisation, are then proposed, which could attain more than 800 kwh energy saving during this period and the current unbalance could be reduced to less than 10%. In addition, the genetic algorithm is deployed to solve the job shop scheduling problem based upon the commercial electrical tariffs, and this reduces the electricity bill by £80 per day in the case study. Implementation of the recommendations based on the above analysis therefore may potentially yield significant financial and environmental benefits.
Article
This paper discusses the effect of the hole location in the fan case on the thermal performance of a gas oven range. A computational fluid dynamics (CFD) study was carried out in ANSYS FLUENT. A DO model was used to include the effect of thermal radiation in the oven cavity. A test geometry was developed by referencing a real product, including the oven cavity, external walls, fan cases, fans, and burners. The simulation was validated with experimental data and showed that the maximum difference in temperature is 2.5%, while the difference in average temperature is 0.44%. A total of 15 cases were examined using different hole locations in the fan case. The direction of the velocity vector at the holes was changed by the different hole locations, and the flow pattern and temperature distribution inside the oven cavity also changed dramatically as a result. The thermal performance was evaluated based on the average temperature and temperature uniformity inside the oven cavity.
Chapter
The present paper discusses an experimentally validated three-dimensional CFD analysis of the flow and thermal processes in a laboratory drying oven with a forced air circulation. The thermal field within an oven has significant impact on the quality of cooked food and reliable predictions are important for a robust design and performance evaluation of an oven. A numerical simulation was carried out to predict the three-dimensional isothermal airflow in an industrial electrical forced convection oven using a computational fluid dynamics code. The CFD model is based on the fundamental equations for the conservation of mass, momentum, and the k-ε turbulence model. The performance of the CFD model was assessed by means of point measurements of the velocity with a directionally hot-film velocity sensor. The simulated results were consistent with the actual velocity measurements from the industrial oven. The calculation error was on average 18.14% of the actual velocity, caused by the limitations in turbulence modeling and numerical grid density.
Article
Metal sheets have to be coated with food grade lacquer and dried at thermal drying oven for metal can making process. At the thermal drying oven, exhaust gas is delivered out by the blower to eliminate the solvent. This leads to the temperature decreasing at the drying zone of the thermal drying oven, especially to unloading. To handle this, an inverter has been implemented to provide saving of electricity bill. In this work, temperature distribution and flow pattern of gas mixture between air and solvent have been studied. A three-dimensional model of the transient heat transfer has been developed and validated against the real data. Comparison of the temperature distribution and flow pattern between the conventional system or full speed and the new system with the inverter by changing speed of outflow has been made. Simulation results show that the system with the inverter obtains low temperature of the exhaust gas released out to the incinerator leading to heat loss decreasing of 10.4%. It is applicable to energy saving for the thermal drying oven.
Article
An oven has been commonly employed to cure powder painted on metal parts for an air-conditioning production. There are many options to improve efficiency in fuel use for the paint curing oven; however some options need deep understanding to prove the possibility of thermal performance. In this work, computational fluid dynamic (CFD) modeling and simulation have been applied to study the temperature distribution and the flow pattern in the paint curing oven on a large scale. The CFD model has been validated against real data. The validated CFD model is used to investigate the temperature distribution and the flow pattern for two proposed options: eliminating stored heat and rearranging airflow. Results demonstrate that both cases provide temperature increase of 1.9 and 1.3. °C for air compared to the present paint curing oven. It can be concluded that the two proposed options are applicable for further implementation to the present paint curing oven.
Article
The presence of airflow during heating process is expected to increase heat uniformity in a closed heating chamber. Circulation of hot air increases the percentage of convective heat transfer. In this study, effects of airflow on oven temperature, cake temperature and several cake qualities were investigated. Experimental studies were conducted in convective oven using two different baking modes; with and without airflow. During baking, oven temperatures and internal cake temperature were measured, and images of cake expansion were captured. Results of the study showed that the presence of airflow could maintain the oven temperature within a small range of set point temperature. Temperature in the oven exhibited ±5.5°C fluctuation, approximately 3.5% overshoot that occurred continuously during baking with airflow. On the contrary, higher overshoot (ranging from 15 to 30%) was observed in oven temperature without airflow. Airflow also showed a significant effect (p<0.01) during the second stage of baking. The presence of airflow increased the heating rate and resulted in a faster volume expansion, which was 3.21mm/min, as compared to 2.88mm/min without the airflow. However, airflow dried off the cake surface, resulted in quicker browning, higher weight loss and lower moisture content of cakes.
Article
A model for the formation of a “crust” during bread baking is presented. The crust is the outermost part of the loaf where the final bread density is significantly higher than in the “crumb”, the interior of the loaf. The model is based on a collapse mechanism, whereby raised pressures due to thermal expansion and water evaporation squash bubbles in the bread as the dough sets and fractures; the latter process allows vapour within bubbles to escape.A preliminary analysis of some aspects of the model and an indication of the numerical solution are also presented. Fuller results and their implications for bread manufacture will be given in a second paper.
Article
A multiphase model for simultaneous heat and mass transfer in porous medium was developed to simulate the baking process of a bread product. The model was based on Fourier’s law for conductive heat transfer and Darcy’s and Fick’s laws for mass transfer of liquid (water) and gas (water vapour and CO2) phases. Explicit formulation was adopted for the evaporation rate allowing direct solution of the system of equations. The use of the non equilibrium approach, allowed the implementation of the model in commercial software. Numerical Finite Element Method (FEM) scheme was used to solve the equations. The model was compared with experimental results reported in literature. Results show a good agreement between experimental and numerical results. Sensitivity analysis of the effect of the evaporation rate constant and process operating conditions on the temperature and moisture content were conducted and showed that the baking process was affected mainly by the convective heat transfer and the product initial moisture characteristics.
Article
Heating heterogeneity is often observed in laboratory/kitchen ovens, medium size equipments such as rotary ovens, and industrial tunnel-type ovens. Losses of bakery products are mainly due to the effect of not a uniform heat flux delivered to the product. Discarding products of not desired shape and color, from non uniform heat fluxes, is a common practice in the bakery industry resulting in waste of energy and food ingredients. A static pilot plant oven was designed and constructed to simulate industrial continuous ovens. The oven is equipped with computerized on line control system to simulate baking parameters such as wall and air temperature, velocity and humidity of air inside the baking chamber corresponding to the real baking profile of a given commercial product. A mathematical method was developed to establish appropriate coefficients and correlations for oven performance providing a uniform baking zone. Heat fluxes in the baking zones of the oven both for top and bottom chambers at various positions were experimentally measured using a specially designed total heat flux meter, the h-monitor. Results showed an acceptable uniform heat flux of less than 5% variation within the baking zone except at the corners of the oven. Several baking trials of various industrial cake products confirmed that the desired heat flux uniformity was achieved.
Article
This paper discusses the validation of a Computational Fluid Dynamics (CFD) model to calculate the heat transfer in an industrial electrical forced-convection oven. The CFD model consists of the continuity, momentum and energy equation with the standard k–ε approach to model the flow turbulence. Density effects are accounted for through a weakly compressible formulation. Time-dependent boundary conditions and source terms are derived from a simplified lumped model, which results in a good qualitative agreement of the calculated oven temperatures and the measured temperature distribution. The average oven temperature difference between measurements and predictions is 4.6°C for a set point of 200°C. The heating uniformity of PVC bricks in different configurations was calculated with the CFD model, but the wall functions in the k–ε model limit the accuracy to a qualitative agreement. A correlation was established between the calculated flow field variables and measured surface heat transfer coefficients.
Article
In an industrial continuous bread-baking oven, dough/bread is travelling inside the oven chamber on its top and bottom tracks connected by a U-turn. The temperature profile of dough/bread during this whole travelling period, which depends on the distribution of temperature and air flow in the oven chamber, dominates the final product quality. In this study, a two-dimensional (2D) CFD model for the whole baking oven chamber has been developed to facilitate a better understanding of the baking process. The transient simulation of the continuous movement of dough/bread in the oven was achieved using the sliding mesh technique. The U-turn movement of bread was successfully simulated by dividing the solution domain into two parts, then flipping and aligning them along the travelling tracks. The 2D CFD modelling was proven to be a useful approach to study the unsteady heat transfer in the oven as well as the heating history and temperature distribution within dough/bread.
Article
The hydrodynamics of impinging flow are considered along with the variables and boundary conditions of heat and mass transfer, the local variation of the transfer coefficients for single nozzles and arrays of nozzles, integral mean transfer coefficients, and the influence of outlet flow conditions on transfer coefficients for arrays of nozzles. Attention is also given to turbulence promoters, wire-mesh grids on the surface of the material, impinging flow on concave surfaces, the angle of impact, optimal spatial arrangements of nozzles, and the design of high-performance arrays of nozzles.
Book
This book looks at the problems of energy engineering from a systems point of view. It encompasses the disciplines of electrical, mechanical, industrial, and process engineering as well as project/system management.
Article
A study was made of the energy used in production of standard, white, sliced bread in three UK bakeries. The production chain studied covered all stages from receipt of flour at the bakery to arrival of bread at the retail outlet: primary energy use from all sources averaged 6.99 MJ kg-1 bread. In the complete production system for standard bread, including wheat growing, flour milling, baking and retailing, primary energy consumption was 14.8 MJ kg-1 bread and the energy subsidy (primary energy input: food energy output) for the system was 1.49. Primary energy used in home baking was dependent on the degree of loading of the oven and varied from 4.24–16.05 MJ kg-1 bread baked in a gas oven and from 10.84–54.76 MJ kg-1 bread baked in an electric oven. In comparison with mashed potato, roast beef and reheated canned corn, standard bread showed the lowest energy subsidy by a factor of at least five. The energy subsidy for standard bread production was only one-seventh of the figure which applies to the food system as a whole. The findings suggest that bread is the most energy efficient staple food product of an industrialised food production system.
Article
The industrial baking of cereal products is commonly performed in tunnel ovens, which give operators high flexibility for adjusting baking conditions to optimum values. This paper discusses the application of a CFD approach to predict the air temperature and velocity profiles inside the baking chamber of an industrial indirect gas-fired tunnel oven used for biscuit baking. We used two three-dimensional CFD models (one not covering the conveying band of biscuits and the other including it) to describe the complex air circulation resulting from the mechanisms of air input and exit at the ends of the oven and of air extraction through the different extraction points located along the oven length. Comparison of numerical results with experimental measurements shows a fairly close agreement in the qualitative prediction and a few inaccuracies in the quantitative prediction of the air temperature profiles within the baking chamber. Furthermore, the comparison also reveals great differences in the air velocity profiles.
Article
In an industrial continuous bread baking oven, dough/bread is travelling inside the oven chamber and it is the oven temperature distribution in this whole travelling period that dominates the product quality variations. To establish a model covering the temperature distribution of the whole oven chamber, computational fluid dynamics (CFD) may be the most effective method. This paper presents the results of a CFD study on an industrial continuous bread baking oven. A two-axis CFD model was established to simulate the temperature profile and airflow pattern due to the convective and radiation heat transfer. With several oven operating parameters including heat supply and fan volume, the heat distribution trend in the oven was satisfactorily simulated. Based on the simulation results, positioning of the controller sensors was investigated through a sensitivity study. The simulation results can also be used to modify the oven configuration for better heat distribution.
Article
To simulate the dynamics of an industrial continuous baking process where dough was conveyed continuously into the oven chamber as a first-in-first-out system, a three-dimensional computational fluid dynamics (CFD) model with moving grids was developed. With a transient state assumption, the model could predict the dynamic responses during the continuous baking. By integrating it with the mathematical models developed earlier by the authors, variations in bread quality due to changes in the oven load were estimated. The results were consistent with the actual measurements from the industrial baking process. The model was further used to investigate the oven operating conditions which could produce the optimum baking condition. According to the simulation results, the heat supply could be reduced whereas the airflow volume should be increased. With this modification, the weight loss of bread could be reduced by 1.4% with an acceptable crust colour and a completed baking as indicated by its internal temperature.
Article
A bakery pilot oven is modeled using computational fluid dynamics software. This approach relies on integration of an instrument into modeled geometry. The instrument is a heat flux measuring device that can be used in the industrial baking process. All three heat transfer mechanisms are considered and coupled with turbulent flow. Turbulence is taken into account via the k–ε realizable model whereas the surface-to-surface model simulates the radiation. Additionally, buoyancy forces are introduced by means of a weakly compressible formulation. The model predictions show a good qualitative agreement with the experimental measurements. A quantitative agreement was obtained to some extent. Limitations came from the difficulty to measure the temperature of the radiant surfaces of the oven. Operating conditions used are typical of bakery products and, as expected, radiation was the dominant mode of heat transfer. The integration of the instrument was useful for assessing the model. Since it is designed for industrial use, it may be a valuable tool for future challenges in the field, such as simulation of an industrial scale oven.
Article
Bread is a basic dietary item dating back to the Neolithic era, which is prepared by baking that is carried out in oven. Control of the production and distribution of bread has been used as a means of exercising political influence over the populace for at least the last two millennia. Several experimental and mathematical models are developed for clear understanding of baking. This article presents a review of published literatures on experimental and mathematical studies on bread baking during the last two decades. Baking technology, evolution of baking ingredients, thermophysical properties of bread as functions of moisture content and baking time are reviewed. Experimental and simulative studies on profiling of temperature, moisture content, pore volume, expansion ratio during baking are also reviewed.
Article
This article discusses the application of computational fluid dynamics (CFD) to calculate the three-dimensional isothermal airflow in an industrial electrical forced-convection oven. The governing fluid flow equations were expanded with a fan model and a turbulence model. The standard and the renormalisation group (RNG) version of the k–ε turbulence model produced comparable results. The performance of the CFD model was assessed by means of point measurements of the velocity with a directionally calibrated hot-film velocity sensor. From the validation it was found that important aspects of the model are the fan head-capacity relationship, the fan swirl and the oven geometry. The calculation error was on an average 22% of the actual velocity, caused by the limitations in turbulence modelling and numerical grid density.
Article
Computational fluid dynamics (CFD) is a powerful numerical tool that is becoming widely used to simulate many processes in the food industry. Recent progression in computing efficacy coupled with reduced costs of CFD software packages has advanced CFD as a viable technique to provide effective and efficient design solutions. This paper discusses the fundamentals involved in developing a CFD solution. It also provides a state-of-the-art review on various CFD applications in the food industry such as ventilation, drying, sterilisation, refrigeration, cold display and storage, and mixing and elucidates the physical models most commonly used in these applications. The challenges faced by modellers using CFD in the food industry are also discussed.
Chapter
Engineers are presently turning to the power of computational fluid dynamics (CFD) to model industrial processes, accomplish comprehensive analyses, and design more efficient systems. The adoption of CFD over the recent years has been inevitable and progressive, as the high costs and time consumption associated with experimentation have often precluded the desire to produce efficient in-depth results. Moreover, associated assumptions, general- izations, and approximations have inhibited analytical models from developing comprehen- sive flow solutions. By coupling these limitations with the recent advances in the development of numerical solutions for the Navier-Stokes equations, and the enhancement of computing power and efficiency, it is easy to understand why the application of CFD has developed into a viable alternative in the food industry.
Article
This book covers the following topics: Fundamentals of energy engineering; Energy economic analysis; Energy auditing and accounting; Electrical system optimization; Waste heat recovery; Utility system optimization; Heating, ventilation, air conditioning, and building system optimization; HVAC equipment; Cogeneration: theory and practice; Control systems; Computer applications; Thermal storage; Passive solar energy systems; and Energy management.
Article
A range of new experimental techniques is developed to quantify drying-air induced disturbances on low viscosity single and multi-layer coating systems. Experiments on prototype slide-bead coating systems show that the surface disturbances take the form of a wavelike pattern and quantify precisely how its amplitude increases rapidly with wet thickness and decreases with viscosity. Heat transfer measurements show that the redistribution of water to form an additional lower viscosity carrier layer while increasing the solids concentration of the upper layer or layers enables the maximum drying rate, for which drying-air induced surface disturbances are acceptably small, to be increased with significant commercial benefits.
An overview of CFD applications in the food industry Computational fluid dynamics in food processing
  • Norton T Sun
Norton T, Sun D-W. An overview of CFD applications in the food industry. In: Sun Da-Wen, editor. Computational fluid dynamics in food processing. CRC Press; 2007. p. 1–41.
Applications of CFD in jet impingement oven Computational fluid dynamics in food processing
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Kocer D, Nitin N, Karwe M. Applications of CFD in jet impingement oven. In: Sun Da-Wen, editor. Computational fluid dynamics in food processing. CRC Press; 2007. p. 469–85.
CFD modeling of jet impingement during heating and cooling of foods Computational fluid dynamics in food processing
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Olsson EEM, Trägårdh C. CFD modeling of jet impingement during heating and cooling of foods. In: Sun Da-Wen, editor. Computational fluid dynamics in food processing. CRC Press; 2007. p. 487–503.
Normalised velocity magnitude at the centre line of the baking chamber (i.e. H/D = 10) at various nozzle jets velocity
  • Fig
Fig. 10. Normalised velocity magnitude at the centre line of the baking chamber (i.e. H/D = 10) at various nozzle jets velocity: (...)