الفهرس 
Chapter 1 : IntroductionOnly 14 pages are availabe for public view
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Abstract
Vapor compression refrigeration systems consume high-grade electrical energy and contribute to environmental impacts due to the used traditional constant speed compressor and harmful working fluids. Utilization of a capacity control technology can reduce energy consumption and improve life-time of the compressor. Variable speed compressor is considered as the most efficient system of capacity control methods. Hydrocarbons can also be considered as the most proper alternatives to the traditional refrigerants in terms of energy efficiency of the system and environmental impacts. A comparison between performance and daily energy consumption of a household refrigerator (382 liters) with constant and a variable speed compressors subject to the same operation conditions are carried out. In addition, the overall performance of the system was investigated and compared using HC-600a and HFC-134a refrigerants.
The experimental results showed that the optimum charges for HC-600a and HFC-134a were 55 g and 110 g, respectively. The pull-down time for HC-600a was found lower than that of HFC-134a system by 5.6%. The variable speed compressor system with HC-600a saves about 39% of energy consumption in comparison to constant speed compressor system associated with 9.6 % enhancement in COP. When the variable speed compressor working with HC-600a refrigerant was used, the energy saving was about 40.5% and the COP improved by 10.8% comparing to constant speed compressor system with HFC-134a.
In general, variable-speed capacity control method offers more energy savings with better performance compared to constant speed compressor. The overall system performance and the daily energy consumption have proved that HC-600a could be the best long-term alternative to phase out of HFC-134a.