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Thermodynamic Analysis of a Combined Ejector-assisted System for Electric Equipment Cooling and Air Conditioning in Electric Vehicles

Khaleghizadeh, Sara | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54467 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Morad, Mohammad Reza
  7. Abstract:
  8. Transportation is one of the essential parts of human life and at the same time one of the main sources of greenhouse gases emissions that are harmful to the environment. Therefore, the use of electric vehicles have become widespread in recent years due to limited capacity of natural resources and environmental issues. As a result, attention to climate control systems for electric vehicles and electric aircrafts is growing rapidly. According to multiple studies, the integrated air conditioning-heat pump system is a suitable option as the climate control system.In this research, an air conditioning-heat pump system has been proposed and studied, which works based on the vapor compression refrigeration cycle. The proposed system works in two modes of cooling and heating for the passenger cabin and thermal management for electrical equipment including batteries. In order to improve the performance of the system, the refrigerant pressure in the evaporator and the chiller is set to be different, and to complete the process, an ejector is used to mix the two refrigerant streams before entering the compressor. The performance of the proposed system has been studied under different operating conditions and for different refrigerants using engineer equation solver (EES) software. Since the vapor compression refrigeration cycle is also used in aircrafts, this system can also be used in aviation applications. According to previous studies on more electric and all-electric aircrafts, this proposed system can be used to control the temperature of the aircraft cabin and electronic equipment including batteries and engines.The simulation results in both cooling and heating modes show that the coefficient of performance (COP) of the proposed system in all conditions and for all refrigerants is higher than the coefficient of performance of the basic system (without ejector). At present, R134a refrigerant, which has a global warming potential of 1300, is still common in air conditioning systems, but due to environmental considerations and restrictive laws, other refrigerants with much less environmental impact are considered as alternatives in this study. 5 alternative refrigerants were studied, and results indicated that R1234ze (E) and R600a, have a better performance than other refrigerants and can be considered as a potential replacement for R134a.The results of exergy analysis of the proposed system show that the highest exergy destruction occurs in the compressor followed by expansion valves and the ejector respectively. Moreover, the highest exergy efficiencies are 63% for R600a and 64% for R1234ze(E)
  9. Keywords:
  10. Coefficient of Perfomance (COP) ; Exergy Analysis ; Ejector ; Heat Pumps ; Air Conditioning ; Climate Control System

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