Evaluating performance of different alternative refrigerants for automotive air conditioning systems

Governments and international organizations started to work and regulate for stop and reduce the effect of global warming due to the environmental impacts. One of the important regulation is limiting the usage of high global warming potential (GWP) refrigerants, which widely used in automotive air conditioning systems. European Parliament decided to restrict the use of high global warming refrigerants that have GWP more than 150 in this connection. R134a is extensively used refrigerant in automotive air conditioning systems currently. In spite of high performance in refrigeration systems, R134a has a high global warming potential refrigerant and it will banned by the European Parliament. The best lowGWP alternatives of R134a are R1234yf, R1234ze(E) and R152a. However, these refrigerants cannot fulfill the performance needs or cannot satisfy the flammability requirements of the industry despite meeting European Parliament regulations. There must be certain improvements in air conditioning system designs for using low-GWP refrigerants and obviate failure to fulfillment. A lot of methods for improving the coefficient of performance (COP) has been proposed. The most common method is integrating an internal heat exchanger to condenser exit that exchanges heat with compressor suction line. The performance of low-GWP refrigerants R152a, R1234yf and R1234ze(E) has compared within the scope of this thesis. An experimental heat pump (EHP) system was developed for comparing performance parameters. The EHP system gives opportunity of testing the performance of low-GWP refrigerants at heating and refrigeration modes. Effect of the brazed plate heat exchanger on low-GWP weak refrigerant's refrigeration performance was conducted meanwhile. Because COP of R152a is %11 more than R134a, it doesn't require performance improvements. After the activation of the internal heat exchanger, the COP of R1234yf and R1234ze(E) has increased %5-6 and %4-5, respectively. R152a has %2 more COP than R134a when the experimental heat pump system working at heating mode. The COP of R1234yf and R1234ze(E) has %11 and %4 lower than R134a, respectively. Keywords: Automotive heat pump, internal heat exchanger, GWP, R152a, R1234yf, R1234ze(E)