Performance Simulation of Single- and Double-Effect Absorption Refrigeration Systems Used for Solar Cooling Applications

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The British University in Dubai (BUiD)
Cooling is very essential for the various aspects of modern life. One of the important applications is the air conditioning field. With increasing oil prices, alternative ways are needed to ensure energy conservation. One of the promising ways is the solar energy use for cooling. The absorption refrigeration system (ARS), which uses thermal energy, is market available but researches on improving their performance are still needed. In this study, simulation of two design configurations of ARS is performed. These configurations are single- and double-effect ARS. In order to compare the performance predictions of these configurations, similar assumptions are used. Condenser and absorber temperatures are assumed 40 degree C. Evaporator temperature is varied as 4, 5, 6 and 7 degree C and the generator temperature is varied as 100, 110, 120, 130, 140, and 150 degree C. The results for the single-effect ARS show enhanced COP with generator temperature, at any evaporator temperature. The COP of single-effect ARS was highest of 0.693, at generator temperature of 120 degree C and evaporator temperature of 7 degree C. Moreover, the performance degraded with lower evaporator temperature. The simulation study for the double-effect ARS shows that the increase of generator-I temperature from 100 to 150 degree C decreases generator-I thermal energy by 7.52%. Moreover, the increase of generator-I temperature increases the COP, at any evaporator temperature to reach maximum of 1.164 at temperature of 130 degree C and evaporator temperature of 7 degree C. The comparison show that the double-effect ARS has higher COP compared with single-effect, at any evaporator temperature. The percentage increase of COP varies from 49.5% (at generator temperature of 100 degree C and evaporator temperature of 4 degree C) to 68.6% (at generator temperature of 150 degree C and evaporator temperature of 7 degree C). The energy storage tank response is studied based on night and daytime operation. For the night operation, electric heat is used whereas for the daytime operation, the heat is supplied to the tank through solar panels. Simulink models are used to investigate the open loop and closed loop responses of the tank. Moreover, appropriate controller is used. The simulation results showed improved performance with closed system but generally the response of the system is slow. Based on the outcomes of the study, it is recommended to consider other designs of absorption system for simulation. Also, simulation at other absorber and condenser temperatures can be performed.
cooling, performance simulation, refrigeration systems, air conditioning