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Schematic of a direct absorption solar collector  

Schematic of a direct absorption solar collector  

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Solar thermal collectors are applicable in the water heating or space conditioning systems. Due to the low efficiency of the conventional collectors, some suggestions have been presented for improvement in the collector efficiency. Adding nanoparticles to the working fluid in direct absorption solar collector, which has been recently proposed, lead...

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Citations

... Solar thermal systems are widely utilized for capturing and converting solar energy to thermal energy. Conventional solar collectors have relatively high heat losses [2]. In the 1970s, volumetric solar collectors, also known as direct absorption solar collectors (DASC), were introduced in an effort to increase solar collector efficiency [3]. ...
... Various researches have been done on the subject of DASCs [2][3][4]. Gorji and Ranjbar [5] investigated a two-dimensional computational fluid dynamics simulation for different water-based nanofluids. They found that the thermal efficiencies are increased by 33-57% adding nanofluids. ...
... Both numerical and experimental investigations are carried out to help increase the efficiency of these collectors. Karami et al. (2014) did a numerical investigation on nanofluid-based solar collectors and developed a two-dimensional thermal transfer model for analysis. Their result revealed that the efficacy of a flat-plate solar collector could be enhanced by augmenting carbon nanohorn concentration to a certain limit, beyond which its effect becomes negligible. ...
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The daily increase in the demand for energy consumption is partly caused by the global population explosion and advancements in technology. Humanity relies on energy to fulfil its daily routines, such as electricity for lighting, heating, cooling, and running electronic devices. There are continuous attempts by researchers and industry experts to optimize and enhance the efficiency of various sustainable energy generation devices. Solar collectors play a critical role in the renewable energy sector, which is vital in helping the world achieve a clean, green, and sustainable environment. Over the last two decades, researchers have made significant efforts to explore various techniques for enhancing the effectiveness of solar thermal collectors. Their effort has been centered around improving the fluid thermal properties, which act as the heat transfer medium in solar collectors. The discovery of nanofluids will help resolve some of the challenges associated with conventional fluid used in solar collectors. Enhancement through nanofluids is influenced by several factors, which include nanoparticle types, nanoparticle concentration, base fluid, and the purpose of its application. This review provides a technical summary of the application of nanofluids in the two main types of collectors: non-concentrating and concentrated thermal collectors. Findings from this study showed that TiO 2 + Cu hybrid nanofluids with a mass fraction of 0.03 augment heat transfer coefficient by 21% in parabolic trough collectors. The merits of employing nanofluids as heat transfer fluids in solar collectors are examined, while also outlining the obstacles and areas where further research is needed.
... According to Ladjevardi et al. [7] by utilizing graphite nanofluids with a volume fraction of roughly 0.000025% more than half of the incident irradiation energy can be absorbed. The features of nanofluids include PVP-coated silver nanofluid, carbon nanotubes, carbon nanoballs, copper oxide, Nanodiamond, and hybrid Fe 3 O 4 /SiO 2 nanofluid were studied separately by Delfani and Karami et al. [2,[8][9][10][11]. According to their findings, the nanoparticles indicated may have a significant impact on a solar collector's energy and exergy efficiency by significantly improving its radiant and thermal properties. ...
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Direct Absorption Solar Collectors (DASCs) are a widely utilized technology in residential applications. However, having known the limitation in DASC size, the efficiency must be enhanced by applying effective modifications and optimizing design parameters. In this study, the performance of a wavy bottom-shaped collector filled with an aluminum porous medium was investigated and the most influential characteristic parameters are specified. Then a design for DASC using Polyvinylpyrrolidone-coated silver nanofluid is proposed and characteristic parameters are optimized based on the full factorial design of the experiment methodology. The model consists of four primary factors, including nanofluid volume concentration (C=0.025%,0.05%,0.1%), porosity (ε=0.8,0.88,0.95), bottom wave amplitude (A=2.5,5,7.5mm), and bottom wavenumber (λ=15,30,60m−1). The results indicated that lowering porosity and increasing nanofluid concentrations improves collector efficiency, whereas rising the wave amplitude and wavenumber causes a higher pressure drop. Additionally, by employing the full factorial design, the main and interaction effects of factors on the efficiency and pressure drop of DASC as the response variables are evaluated. Thus, an optimum value is observed for wave amplitude to reach maximum efficiency and minimize pressure drop. By integrating a porous medium and a wavy bottom with nanofluid, the efficiency of DASC is enhanced from 52 to 93.7%, paving the way for their use in residential applications.
... Thus there is a need of designing a collector which has optimum working fluid height. Fig. 5 shows a typical DASC [17]. ...
... A typical direct absorption collector[17]. ...
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... There are some numerical studies [39][40][41] that investigate the effect of collector geometrical parameters on its efficiency. In this study, the validity of the numerical results has been considered experimentally. ...
... More solar absorption is absorbed by the upper layers of the nanofluid with high concentration which cause the larger heat loss to the ambinet and no solar radiation is reached to the low layers. These experimental results are in agreement with the numeical results [39][40][41]. Fig. 6 reveals that the efficiency affected by the collector length slightly. Although there is a more surface for solar absorption by increasing the collector length, the more heat loss to the ambient is occurred as a results of larger surface area. ...
... Based on the results of Fig. 7, the higher efficiency enhancement of 0.5% is obtained by increasing the collector length from 300 mm to 900 mm at nanofluid concentration of 500 ppm and flow rate of 45 lit/ h. This result is also confirmed by the earlier studies [39][40][41]. Fig. 8 displays the variation of Nusselt number with nanofluid concentration for different collector depths. It is found that Nusselt number has grown considerably by collector depth, because Nusselt number is directly proportional to the convective heat transfer coefficient and channel depth. ...
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Recently, artificial neural network techniques have been widely used for the performance prediction of the renewable energy systems, in which solar collectors are one of the most used mechanical equipment. In this paper, the thermal performance of a nanofluid-based direct absorption solar collector is predicted using an artificial neural network based Multi-Layer Perceptron system. In the experimental part of study, nine collector prototypes with different geometries were tested at different conditions to investigate the effect of the collector depth and length on the collector thermal performance and also, to provide the required data for the network evaluation. The collector depth and length, the working fluid flowrate and concentration and the reduced temperature difference are selected as input parameters of the network to estimate the collector efficiency and Nusselt number. The proposed artificial neural network approach proved that the variation of the collector depth of 5–15 mm increases the collector efficiency about 9%, while the collector length has an insignificant effect on the collector efficiency. The Nusselt number of the collector increases considerably by the collector depth and nanofluid flowrate. The proposed network has the best performance for predicting the collector efficiency with nanofluid concentration of 1000 ppm as the input parameter by achieving the MAPE of 1.470%. In the case of predicting Nusselt number, the best performance with MAPE of 2.576% is obtained with collector length of 300 mm. Using the forward stepwise regression selection method, the best combination of input parameters for predicting the Nusselt number is obtained using all input parameters. The consistency of the experimental and predicted results confirms the great ability of artificial neural network to predicting the thermal performance of direct absorption solar collectors.
... As finite difference method (FDM) is easy to implement, many researchers with different type of geometry condition also applied this method to solve the radiative transport equation (RTE) and energy balance equation [45][46] [47][48] [49][50] [51]. Besides, a numerical code can be developed for structured spatial discretization for simple geometry such as flat receiver. ...
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Research on direct absorption solar collector (DASC) has been quite intensive in the past decade. Solar thermal collector plays a vital role to determine the performance of DASC by utilized the heat transfer fluid to harvest the energy while the use of nanofluid (nanoparticle dispersion in a base fluid) enhanced the thermal conductivity. A lot of researchers have studied the influence of several parameters such as collector geometry and nanoparticle materials on the solar thermal collector efficiency for the past decade. This paper presents a recent progress on numerical modelling of nanofluid direct absorption solar collector (NDASC) for different type of geometry including flat type, parabolic trough and cylindrical tube. In this review, a more comprehensive numerical methods and solar collector geometry on NDASC are summarized. Finally, some recommendations are presented for future research guidance.
... Another review paper on thermal performance enhancement of flat- plate and evacuated tube solar collectors by using nanofluids was written by Muhammad et al. (2016). Karami et al. (2014) used carbon nanohorn nanoparticles in a solar collector and observed that im- plementation of nanofluid can increase the collector performance about 17%. Delfani and Karami (2016) conducted experimental and numer- ical investigations on a residential type solar collector -as a low cost and useful energy system which is used in buildings -by using MWCNT- water nanofluid. ...
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Optimization of oil production from petroleum reservoirs is an interesting and complex problem which can be done by optimal control of well parameters such as their flow rates and pressure. Different optimization techniques have been developed yet, and metaheuristic algorithms are commonly employed to enhance oil recovery projects. Among different metaheuristic techniques, the genetic algorithm (GA) and the particle swarm optimization (PSO) have received more attention in engineering problems. These methods require a population and many objective function calls to approach more the global optimal solution. However, for a water flooding project in a reservoir, each function call requires a long time reservoir simulation. Hence, it is necessary to reduce the number of required function evaluations to increase the rate of convergence of optimization techniques. In this study, performance of GA and PSO are compared with each other in an enhanced oil recovery (EOR) project, and Newton method is linked with PSO to improve its convergence speed. Furthermore, hybrid genetic algorithm-particle swarm optimization (GA-PSO) as the third optimization technique is introduced and all of these techniques are implemented to EOR in a water injection project with 13 decision variables. Results indicate that PSO with Newton method (NPSO) is remarkably faster than the standard PSO (SPSO). Also, the hybrid GA-PSO method is more capable of finding the optimal solution with respect to GA and PSO. In addition, GA-PSO, NPSO, and GA-NPSO methods are compared and, respectively, GA-NPSO and NPSO showed excellence over GA-PSO.
... Another review paper on thermal performance enhancement of flatplate and evacuated tube solar collectors by using nanofluids was written by Muhammad et al. (2016). Karami et al. (2014) used carbon nanohorn nanoparticles in a solar collector and observed that implementation of nanofluid can increase the collector performance about 17%. Delfani and Karami (2016) conducted experimental and numerical investigations on a residential type solar collectoras a low cost and useful energy system which is used in buildingsby using MWCNTwater nanofluid. ...
Article
In the current study, thermal efficiency of a direct absorption solar collector, using single-walled carbon nanohorn (SWCNH)-water nanofluid as the working fluid, is numerically investigated. An in-house, parallel, multi-relaxation time, lattice Boltzmann method (MRT-LBM) code is developed, and the effects of nanofluid concentration, presence of aluminum absorber sheet and its position on design parameters of the collector are discussed. Results are discussed for two cases: with and without the absorber plate, and the effects of nanoparticles concentration (φφ), nanofluid’s mass flow rate (View the MathML sourceṁ), collector height (H), absorber plat position (Y) and radiation heat flux (q″q″) on efficiency and maximum temperature of the collector are studied. The importance of these parameters have been proven and it was shown that, in some cases, optimal working conditions exist. It has been demonstrated that low concentrations of nanoparticles can improve the collector efficiency, while its larger amounts can lead to negative performance. The absorber plate highly improved the collector performance especially when the working fluid is the pure water. Simultaneous use of nanofluid with the absorber plate is not recommended except for low mass flow rates. Also, the bottom of the collector is the best position for the absorber plate in order to gain the maximum efficiency.
... As light passes through the channel the spectral intensity decreases via fluid attenuation. For fluids enclosed in deeper channels, the attenuation will be greater due to the larger [14] suggest a physical explanation for the levelling off phenomenon. They report that for a collector height of 5 mm, approximately 95% of incoming solar radiation is absorbed by a water-based nanofluid containing single wall carbon nanohorns. ...
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In this paper we present an approximate analytical solution to the steady state, two-dimensional model for the efficiency of an inclined nanofluid-based direct absorption solar collector. The model consists of a system of two differential equations; a radiative transport equation describing the propagation of solar radiation through the nanofluid and an energy equation. The heat source term is obtained via the radiative flux integral, which is highly non-linear with respect to wavelength due to the spectral-dependent fluid and nanoparticle indices of refraction and absorption. To make analytical progress we introduce an approximate power-law function for the radiative flux. Applying the method of separation of variables, the resulting solution is used to investigate the efficiency of the collector subject to variation in model parameters. In addition our approach allows for the inclusion of wavelength-dependent absorption and scattering due to both the base fluid and nanoparticles and also an approximation for reflectance and absorptance due to the collector and its associated surfaces.
... As light passes through the channel the spectral intensity decreases via fluid attenuation. For fluids enclosed in deeper channels, the attenuation will be greater due to the larger [14] suggest a physical explanation for the levelling off phenomenon. They report that for a collector height of 5 mm, approximately 95% of incoming solar radiation is absorbed by a water-based nanofluid containing single wall carbon nanohorns. ...
Article
Abstract In this paper we present an approximate analytical solution to the steady state, two-dimensional model for the efficiency of an inclined nanofluid-based direct absorption solar collector. The model consists of a system of two differential equations; a radiative transport equation describing the propagation of solar radiation through the nanofluid and an energy equation. The heat source term is obtained via the radiative flux integral, which is highly non-linear with respect to wavelength due to the spectral-dependent fluid and nanoparticle indices of refraction and absorption. To make analytical progress we introduce an approximate power-law function for the radiative flux. Applying the method of separation of variables, the resulting solution is used to investigate the efficiency of the collector subject to variation in model parameters. In addition our approach allows for the inclusion of wavelength-dependent absorption and scattering due to both the base fluid and nanoparticles and also an approximation for reflectance and absorptance due to the collector and its associated surfaces.