The present study investigates low-grade heat utilization in ejector refrigeration systems under ... more The present study investigates low-grade heat utilization in ejector refrigeration systems under hot climatic conditions. A variable area ejector is used to maximize the harvested heat from the generator of the solar system at peak times. Exergy, economic, and exergoeconomic analyses are conducted to evaluate the performance of the system. A thermodynamic model of the system has been developed using Ebsilon Professional software. Available experimental and theoretical data validate the results. The effects of properties of the working fluids, ejector geometry, and operation conditions are also evaluated. It was found that the coefficient of performance of the system reached 0.45 at a generator pressure of 3 bars. Furthermore, it was noticed that the overall exergy efficiency could be increased for a fixed generator temperature while increasing the ejector area ratio. A value of 21% exergetic efficiency was calculated for the system. The exergoeconomic analysis of the system demonstr...
Waste heat from the gas cooler is a form of free energy, which can be utilized to drive an ejecto... more Waste heat from the gas cooler is a form of free energy, which can be utilized to drive an ejector cooling cycle. This paper presents a new CO2 ejector-cascade refrigeration cycle. The effects of important parameters on the thermodynamic performance of the new cycle are theoretically investigated based on energetic and exergetic analyses. Furthermore, the performance comparison of the proposed cycle and conventional cycle is carried out. The theoretical study shows that the new cycle exhibits a reasonable value of COP (coefficient of performance) and system second law efficiency. For the same cooling capacity, the improvements of the maximum COP and second law efficiency could reach 37% and 12%, respectively, over those of the conventional cascade cycle under the given operating conditions and at the optimum gas cooler pressure.
This paper proposes a new combined multi-cooling and power generation system (CMCP) driven by sol... more This paper proposes a new combined multi-cooling and power generation system (CMCP) driven by solar energy. Carbon dioxide is used as a refrigerant. A parabolic trough collector (PTC) is employed to collect solar radiation and convert it into thermal energy. The system includes a supercritical CO2 power system for power production and an ejector refrigeration system with two ejectors to provide cooling at two different evaporating temperatures. The CMCP system is simulated hourly with weather conditions for Tunisia. The PTC mathematical model is used to calculate the heat transfer fluid outlet temperature and the performance of the CMCP system on a specific day of the year. A 1D model of an ejector with a constant area is adopted to evaluate the ejector performance. The system’s performance is evaluated by an energetic and exergetic analysis. The importance of the system’s components is determined by an exergoeconomic analysis. The system is modeled using MATLAB software. A genetic ...
A novel integrated solar absorption refrigeration system with a thermoelectric generator and ther... more A novel integrated solar absorption refrigeration system with a thermoelectric generator and thermoelectric cooler is presented. The proposed system is of a 20-kW single-stage lithium bromide absorption cycle driven by solar evacuated tube collectors or by the heat rejected by the thermoelectric cooler module. The governing equations of the thermodynamic model are solved, and the results are validated. It was found that the coefficient of performance of the system approaches a constant value at a generator temperature of 100 °C. The best performance of the system was found in the case of placing the thermoelectric cooler between the generator and the condenser. The coefficient of performance and the overall thermal efficiency were found to be 1.12 and 73.4%, respectively. Furthermore, a 20% rise in the generator temperature would increase the power produced by thermoelectric generator modules by 60%. An increase of 20% in the thermoelectric generator modules would result in a reduction of 11.5% in its efficiency, while doubling the temperature difference would increase the generated power by a factor of three.
Evaporative cooling can be integrated into fresh-air-handling units, to reduce cooling demand. Th... more Evaporative cooling can be integrated into fresh-air-handling units, to reduce cooling demand. This study considers a hybrid fresh-air-handling unit which incorporates a vapor-compression cooling cycle and indirect evaporative cooling to condition an ambient primary airstream to a desired supply air state. The cooling effects of using various modes (vapor compression only; direct expansion with mist; direct expansion with water shower; and direct expansion with mist and water shower) are compared when the fresh-air-handling unit operates in harsh (hot and humid) climatic conditions experienced in Qatar. Experimental analysis is based on actual ambient conditions measured from August 2018 to July 2019. It is found that the best-performing wet mode of operation saves more than 60% of the energy required by a conventional direct expansion cooling system operating under the same ambient conditions. In hot, dry conditions, the coefficient of performance of the fresh-air-handling unit whe...
International Communications in Heat and Mass Transfer, 1993
This paper reports an analytical technique for the prediction of some of the transient thermal an... more This paper reports an analytical technique for the prediction of some of the transient thermal and hydrodynamic characteristics of a Trombe wall. The present analytical technique when compared with the numerical techniques based on the finite difference method, seems to predict ...
The present study investigates low-grade heat utilization in ejector refrigeration systems under ... more The present study investigates low-grade heat utilization in ejector refrigeration systems under hot climatic conditions. A variable area ejector is used to maximize the harvested heat from the generator of the solar system at peak times. Exergy, economic, and exergoeconomic analyses are conducted to evaluate the performance of the system. A thermodynamic model of the system has been developed using Ebsilon Professional software. Available experimental and theoretical data validate the results. The effects of properties of the working fluids, ejector geometry, and operation conditions are also evaluated. It was found that the coefficient of performance of the system reached 0.45 at a generator pressure of 3 bars. Furthermore, it was noticed that the overall exergy efficiency could be increased for a fixed generator temperature while increasing the ejector area ratio. A value of 21% exergetic efficiency was calculated for the system. The exergoeconomic analysis of the system demonstr...
Waste heat from the gas cooler is a form of free energy, which can be utilized to drive an ejecto... more Waste heat from the gas cooler is a form of free energy, which can be utilized to drive an ejector cooling cycle. This paper presents a new CO2 ejector-cascade refrigeration cycle. The effects of important parameters on the thermodynamic performance of the new cycle are theoretically investigated based on energetic and exergetic analyses. Furthermore, the performance comparison of the proposed cycle and conventional cycle is carried out. The theoretical study shows that the new cycle exhibits a reasonable value of COP (coefficient of performance) and system second law efficiency. For the same cooling capacity, the improvements of the maximum COP and second law efficiency could reach 37% and 12%, respectively, over those of the conventional cascade cycle under the given operating conditions and at the optimum gas cooler pressure.
This paper proposes a new combined multi-cooling and power generation system (CMCP) driven by sol... more This paper proposes a new combined multi-cooling and power generation system (CMCP) driven by solar energy. Carbon dioxide is used as a refrigerant. A parabolic trough collector (PTC) is employed to collect solar radiation and convert it into thermal energy. The system includes a supercritical CO2 power system for power production and an ejector refrigeration system with two ejectors to provide cooling at two different evaporating temperatures. The CMCP system is simulated hourly with weather conditions for Tunisia. The PTC mathematical model is used to calculate the heat transfer fluid outlet temperature and the performance of the CMCP system on a specific day of the year. A 1D model of an ejector with a constant area is adopted to evaluate the ejector performance. The system’s performance is evaluated by an energetic and exergetic analysis. The importance of the system’s components is determined by an exergoeconomic analysis. The system is modeled using MATLAB software. A genetic ...
A novel integrated solar absorption refrigeration system with a thermoelectric generator and ther... more A novel integrated solar absorption refrigeration system with a thermoelectric generator and thermoelectric cooler is presented. The proposed system is of a 20-kW single-stage lithium bromide absorption cycle driven by solar evacuated tube collectors or by the heat rejected by the thermoelectric cooler module. The governing equations of the thermodynamic model are solved, and the results are validated. It was found that the coefficient of performance of the system approaches a constant value at a generator temperature of 100 °C. The best performance of the system was found in the case of placing the thermoelectric cooler between the generator and the condenser. The coefficient of performance and the overall thermal efficiency were found to be 1.12 and 73.4%, respectively. Furthermore, a 20% rise in the generator temperature would increase the power produced by thermoelectric generator modules by 60%. An increase of 20% in the thermoelectric generator modules would result in a reduction of 11.5% in its efficiency, while doubling the temperature difference would increase the generated power by a factor of three.
Evaporative cooling can be integrated into fresh-air-handling units, to reduce cooling demand. Th... more Evaporative cooling can be integrated into fresh-air-handling units, to reduce cooling demand. This study considers a hybrid fresh-air-handling unit which incorporates a vapor-compression cooling cycle and indirect evaporative cooling to condition an ambient primary airstream to a desired supply air state. The cooling effects of using various modes (vapor compression only; direct expansion with mist; direct expansion with water shower; and direct expansion with mist and water shower) are compared when the fresh-air-handling unit operates in harsh (hot and humid) climatic conditions experienced in Qatar. Experimental analysis is based on actual ambient conditions measured from August 2018 to July 2019. It is found that the best-performing wet mode of operation saves more than 60% of the energy required by a conventional direct expansion cooling system operating under the same ambient conditions. In hot, dry conditions, the coefficient of performance of the fresh-air-handling unit whe...
International Communications in Heat and Mass Transfer, 1993
This paper reports an analytical technique for the prediction of some of the transient thermal an... more This paper reports an analytical technique for the prediction of some of the transient thermal and hydrodynamic characteristics of a Trombe wall. The present analytical technique when compared with the numerical techniques based on the finite difference method, seems to predict ...
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Papers by Bourhan Tashtoush