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The use of a variable refrigerant flow (VRF) is being specified as an alternative solution to centralize HVAC systems in domestic building. This manuscript presents a comprehensive description of the configuration for the indoor and outdoor units of a multi-split VRF system. A case study of a hotel in Amman, Jordan was implemented. The suitable ind...
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... load demand. Nowadays, VRF technology uses an inverter-driven scroll compressor to derive more indoor units from one outdoor unit. The inverter-driven scroll compressors has a capability of changing its speed to keep track of the variations in the total cooling/heating load by measuring the suction gas pressure mounted on the con- densing unit. Fig. 2 shows a schematic VRF ...
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ABSTRACT
The purpose of Heating, Ventilating and Air Conditioning (HVAC) system is to provide and maintain a desired indoor thermal comfort. Modelling process of HVAC systems leads to inherent nonlinearity of the large scale system including pure lag time, big thermal inertia, uncertain disturbance factors and constraints which lead to inability t...
The increased demand of energy in domestic applications necessitates the development of innovative engineering solutions in building heating, ventilating, and air conditioning (HVAC) systems. As the largest energy intensive sector is domestic buildings, more focus is currently directed to reduce air conditioning energy consumption. Double-pipe heat...
Citations
... With these various methods of heat transfer intensification and advanced heat exchanger circulation contours, including jet devices [69,70], increasing heat flux and reducing temperature differences in intake heat exchangers has been proposed in order to decrease the sizes of heat exchangers and corresponding power spent to cover their aerodynamical resistance [71,72] with lowering the leaving temperature of cooled air. They are used in stationary applications for combined cooling, heating, and the power supply of buildings and districts [73,74] as well as in ship [75] and railway applications [76]. Such combined in-cycle trigeneration technologies [77] provide maximum fossil fuel savings accompanied by minimal release of nitrogen oxides and sulfur oxides in exhaust gas. ...
Cogeneration or combined heat and power (CHP) has found wide application in various industries because it very effectively meets the growing demand for electricity, steam, hot water, and also has a number of operational, environmental, economic advantages over traditional electrical and thermal systems. Experimental and theoretical investigations of the afterburning of fuel oil in the combustion engine exhaust gas at the boiler inlet were carried out in order to enhance the efficiency of cogeneration power plants; this was achieved by increasing the boiler steam capacity, resulting in reduced production of waste heat and exhaust emissions. The afterburning of fuel oil in the exhaust gas of diesel engines is possible due to a high the excess air ratio (three to four). Based on the experimental data of the low-temperature corrosion of the gas boiler condensing heat exchange surfaces, the admissible values of corrosion rate and the lowest exhaust gas temperature which provide deep exhaust gas heat utilization and high efficiency of the exhaust gas boiler were obtained. The use of WFE and afterburning fuel oil provides an increase in efficiency and power of the CPPs based on diesel engines of up to 5% due to a decrease in the exhaust gas temperature at the outlet of the EGB from 150 °C to 90 °C and waste heat, accordingly. The application of efficient environmentally friendly exhaust gas boilers with low-temperature condensing surfaces can be considered a new and prosperous trend in diesel engine exhaust gas heat utilization through the afterburning of fuel oil and in CPPs as a whole.
... Untuk mempertahankan tingkat kenyamanan termal yang dapat diterima, respons sistem Yan dan Deng[19] untuk triple evaporator dengan suhu sasaran yang berubah dan reaksi kelembaban relatif yang lebih rendah dari variasi beban dibenarkan. Menanggapi saran Yan dan Deng[19] bahwa upaya yang harus dilakukan untuk mengurangi kelembaban relatif saat suhu naik di zona untuk mempertahankan dalam kisaran kenyamanan yang dapat diterima, Alahmer dan Alsaqoor[21] ...
Sistem VRV adalah sistem HVAC multi-split yang mempertahankan porsi berbeda dengan memvariasikan volume refrigeran. Sistem ini mengontrol volume zat pendingin/refrigeran untuk efisiensi dan keandalan. Kajian ini bertujuan untuk mengidentifikasi elemen sistem VRV yang mempengaruhi faktor operasional dan kinerja. Studi sebelumnya sangat penting untuk pengembangan VRV skala besar di masa depan.
... According to statistical research, refrigeration and air conditioning accounted for 70% of this building's overall energy demand [10,11]. In residential cities, cooling and refrigeration operations often need between one-third and fifty percent of the annual total electricity consumption. ...
In this study, the performance of a Tri-Generation cooling system employing two adsorption chillers will be analysed experimentally and theoretically utilizing the TRNSYS software. The purpose of this study is to assess the performance of two adsorption chillers and to evaluate how operational and design factors affect the performance of the tri-generation cooling system.The system was developed and validated at the Mutah University in Jordan, it consists of 240 m2 parabolic trough solar matrix. The trough matrix heated thermal oil to 260 °C, producing 13.7 bar of 210 °C superheated steam. The power cycle is completed by evaporating brackish water with the engine's 120 °C steam. Distillation yields 150 L of distilled water each hour. The rejected heat from distillation is stored in a thermally isolated hydraulic storage tank and used to power a unique two-stage air cooled adsorption chiller with a cooling capacity of 10 kW each.As a result, adsorption chillers' COP and normalized capacity were calculated. Their optimum values were obtained at 94 °C hot water, 15 °C chilled water, and 35 °C condensation temperature. The lowest COP and normalized capacity values were recorded at 65 °C hot water, 7 °C chilled water, and 38 °C condensation temperature.
... Using optimization methods to reduce the requirement for extensive experimental testing is a useful approach [26]. Many researchers have developed and used a wide range of meta-heuristic algorithm optimization methodologies in design analysis, such as genetic algorithm optimization, particle swarm optimization (PSO), whale optimization algorithm (WOA), response surface methodology (RSM), artificial neural network (ANN), Taguchi optimization, grey wolf optimization (GWO), and intelligent grey wolf optimization (IGWO) [27][28][29][30][31]. According to Hoseini and Sobati [32], the optimal formulation for the W/D emulsion diesel fuel was 5% water and 2% surfactant after applying multi-objective optimization. ...
Water-in-diesel (W/D) emulsion fuel is a potentially viable diesel fuel that can simultaneously enhance engine performance and reduce exhaust emissions in a current diesel engine without requiring engine modifications or incurring additional costs. In a consistent manner, the current study examines the impact of adding water, in the range of 5-30% wt. (5% increment) and 2% sur-factant of polysorbate 20, on the performance in terms of brake torque (BT) and exhaust emissions of a four-cylinder four-stroke diesel engine. The relationship between independent factors, including water addition and engine speed, and dependent factors, including different exhaust released emissions and BT, was initially generated using machine learning support vector regression (SVR). Subsequently, a robust and modern optimization of the sea-horse optimizer (SHO) was run through the SVR model to find the optimal water addition and engine speed for improving the BT and lowering exhaust emissions. Furthermore, the SVR model was compared to the artificial neural network (ANN) model in terms of R-squared and mean square error (MSE). According to the experimental results, the BT was boosted by 3.34% compared to pure diesel at 5% water addition. The highest reduction in carbon monoxide (CO) and unburned hydrocarbon (UHC) was 9.57% and 15.63%, respectively , at 15% of water addition compared to diesel fuel. The nitrogen oxides (NOx) emissions from emulsified fuel were significantly lower than those from pure diesel, with a maximum decrease of 67.14% at 30% water addition. The suggested SVR-SHO model demonstrated superior prediction reliability, with a significant R-Squared of more than 0.98 and a low MSE of less than 0.003. The SHO revealed that adding 15% water to the W/D emulsion fuel at an engine speed of 1848 rpm yielded the optimum BT, CO, UHC, and NOx values of 49.5 N.m, 0.5%, 57 ppm, and 369 ppm, respectively. Finally, these outcomes have important implications for the potential of the SVR-SHO approach to minimize engine exhaust emissions while maximizing engine performance.
... Using optimization methods to reduce the requirement for extensive experimental testing is a useful approach [26]. Many researchers have developed and used a wide range of meta-heuristic algorithm optimization methodologies in design analysis, such as genetic algorithm optimization, particle swarm optimization (PSO), whale optimization algorithm (WOA), response surface methodology (RSM), artificial neural network (ANN), Taguchi optimization, grey wolf optimization (GWO), and intelligent grey wolf optimization (IGWO) [27][28][29][30][31]. According to Hoseini and Sobati [32], the optimal formulation for the W/D emulsion diesel fuel was 5% water and 2% surfactant after applying multi-objective optimization. ...
... The experimental optimization of numerous processes, including CO2 adsorption, is restricted, time and effort consuming, and expensive. Although physical and mathematical modeling have made significant progress in simulating various processes, their accuracy is still constrained by the constants and parameters that are often presupposed [28,29]. Artificial intelligence has demonstrated high effectiveness in the accurate modeling and optimization of various processes, such as biodiesel production from palm kernel shell [30], electricity generation in fuel cells [31][32][33], microbial fuel cells [34][35][36], alternative fuels [37], heat transfer and waste heat recovery [38][39][40], biohydrogen production [41,42], etc. ...
This study aims to identify the optimal operating parameters for the carbon dioxide (CO2) capture process using a combination of artificial intelligence and metaheuristics techniques. The main objective of the study is to maximize CO2 capture capacity. The proposed method integrates fuzzy modeling with the RUNge Kutta optimizer (RUN) to analyze the impact of three operational factors: carbonation temperature, carbonation duration, and H2O-to-CO2 flow rate ratio. These factors are considered to maximize the CO2 capture. A fuzzy model was developed based on the measured data points to simulate the CO2 capture process in terms of the stated parameters. The model was then used to identify the optimal values of carbonation temperature, carbonation duration, and H2O-to-CO2 flow rate ratio using RUN. The results of the proposed method are then compared with an optimized performance using the response surface methodology (RSM) and measured data to demonstrate the superiority of the proposed strategy. The results of the study showed that the suggested technique increased the CO2 capture capacity from 6.39 to 6.99 by 10.08% and 9.39%, respectively, compared to the measured and RSM methods. This implies that the proposed method is an effective approach to maximize the CO2 capture capacity. The results of this study can be used to improve the performance of the CO2 capture process in various industrial applications.
... Table 1 shows the U values assumption. (1) where: Q -the rate of heat loss by conduction (W); U -overall heat transfer coefficient (W/ m 2 °C); A -area of the surface (m 2 ); Tin -the inside temperature (°C); Tout -the outside temperature (°C). ...
... Components of VRF systems(Alahmer and Alsaqoor, 2017) ...
Retrofitting heating, ventilation, and air conditioning (HVAC) systems in existing buildings and applying energy-efficient technologies can significantly reduce energy consumption and greenhouse gases emissions. In this work, two options of HVAC retrofitting were proposed and discussed for the existing heating system of school of engineering at the University of Jordan as a case study. The experimental tests showed that only one of the three diesel boilers work normally while the other two boilers are not efficient, with actual efficiency of 25%. The first retrofitting was to upgrade the existing heating system to a liquefied petroleum gas (LPG) boiler system with estimated annual saving of 29,757 Jordanian dinar (JOD), and a payback period of 3.9 years. The second option for retrofitting was a new HVAC system for the building including heating and air conditioning with a variable refrigerant flow (VRF) system and heat pump chiller. The estimated cost showed that the VRF system was the lowest one in running cost in winter. The diesel boilers had the highest greenhouse gas emissions with an average value of 377.3 tons of CO2 per year, while LPG boilers achieved the second highest emissions of around 279 tons of CO2 per year, whereas the heat pump chiller in winter produced 199 tons of CO2 and the VRF system emitted 180 tons in winter. The LCCA economic analysis was performed for the proposed systems, showing that the LPG boilers system was more feasible than the diesel boilers system, while the VRF system was more feasible than the heat pump chiller system.
... Such deep waste heat recovery techniques are quite appropriate for combined cooling (air conditioning as a widespread version [1,2]), trigeneration or integrated energy systems [3,4], as well as for transport applications [5,6]: railway [7,8] and marine [9,10]. They are promising to be implemented into other technologies to decrease harmful particles in exhaust gases from marine ICE to compensate for a reduction in efficiency of engines [11] when applying refrigeration and jet technologies [12]. ...
One of the most effective methods towards improving the environmental safety of combustion engines is the application of specially prepared water-fuel emulsions (WFE). The application of WFE makes it possible to reduce primary sulfur fuel consumption and reveals the possibility of capturing the pollutants from exhaust gases by applying condensing low-temperature heating surfaces (LTHS). In order to realize such a double effect, it is necessary to investigate the pollution processes on condensing LTHS of exhaust gas boilers (EGB), especially the process of low-temperature condensing a sulfuric acid vapor from exhaust gases to investigate the influence of condensing LTHS on the intensity of pollutants captured from the exhaust gases. The aim of this research is to assess the influence of the intensity of pollutants captured from exhaust gases by condensing LTHS in dependence of water content in WFE combustion. Investigations were carried out at a special experimental setup. The processing of the results of the experimental studies was carried out using the computer universal statistical graphic system Statgraphics. Results have shown that in the presence of a condensing heating surface, the degree of capture (purification) of pollutants from the exhaust gas flow is up to 0.5–0.6.
... Since Daikin launched the first VRV air conditioner in 1982, ongoing development on air-cooled variable refrigerant volume/flow systems (VRV, also known as VRF), as shown in Fig.1 has been achieved due to its energy saving potential, design flexibility in a maximum connection of 64 indoor units to 1 outdoor unit, larger allowances for piping length and level difference [1,2]. The needed minimum amount of refrigerant flowing to the multiple evaporators (indoor units) is controlled usually by electronic expansion valve (EEV), which enables individual climate control of air conditioning zones equipped with different indoor units [3]. So far coefficient of performance (COP) could be 146.5% higher under heat recovery mode than under cooling-only mode [4]. ...
Variable refrigerant flow systems (VRF), in which refrigerant flows directly through long connecting pipes into different indoor units, are nowadays having more and more market share in central air-conditioning industry. A special flat structure of air-cooled VRF outdoor unit is expected in European market due to local architecture characteristics. Centrifugal fans with forward-curved blades are suitable under this situation. However, the layout concerning the fan position is of key importance for the heat exchange performance. Four layouts with different fan position arrangement in a VRF outdoor unit supposed to reach nominal cooling capacity of 22kW were initially designed and optimized by Ansys. Air volume rate and uniformity through the fin and tube heat exchanger (FTHE) were investigated with velocity contours. When FTHE was set perpendicularly forming a triangle compact space with neighboring cabinet shells, simulations showed a better layout in which the two fans were put side by side but with one near front and the other near rear shell in the bigger empty space. Further adjustment in position details was also carried out via more simulation on selected planes and finally, air volume measurement and nominal capacity measurement were made, matched with four ducted indoor air-conditioning units, showing good performance.
... There has been gradual development of HVAC systems from complete building to individual zones independent of other zones in the same building. Such systems (called as "multi-split air conditioning systems") focuses on zone specific comfort management, the overall comfort conditions increase significantly at the same time reducing the energy consumption from the zones in which heating is not required [110][111][112]. ...
... 18: ASHP-VRF system with multiple indoor units[110]. ...
Low cost smart sensors, intelligent controllers, and IoT systems constitute key components to develop smart buildings. These smart systems produce optimal control strategies by continuous analysis of building performance. Two major parameters are controlled in the building: occupants’ comfort and heating or cooling load consumption optimization. For such intelligent controllers applications, it is essential to have building model with high performance accuracy and computational efficiency. The existing building models range from complete analytical to fully data-driven and hybrid models. The analytical model is extremely complex to model and computationally inefficient, whereas the data-driven models require a large amount of data. However, in the case of data unavailability, application of datadriven models become impossible. This work presents, hybrid modeling for heat transfer dynamics of the building using lumped parameter thermal network modeling technique. An efficient building model is developed by having proper structural knowledge of low-order model and identifying its parameter values. Simplified low-order systems are developed using 2nd order thermal network models with optimal thermal resistors and capacitors value.In order to determine the low-order model parameter values, a specific approach is proposed using a stochastic particle swarm optimization. This method provides a significant approximation of the parameters when compared to the reference model whilst allowing low-order model to achieve 40% to 50% computational efficiency than the reference analytical model.Furthermore, extensive simulations are carried out to evaluate the proposed simplified model with a more advanced complex solar gains model and identified parameters value. The developed simplified model is afterward validated with measured data from a case study building where the achieved results clearly show a high degree of accuracy compared to the actual data. Finally, an MPC controller is applied for the same case study building for thermal comfort optimization. Simulation results demonstrate the significance of the MPC controller in handling the constraints, multi-objective control, and producing optimal control strategy. The energy optimization results of the MPC have shown 31% of energy consumption reduction compared to a conventional controller.
