Experimental performance evaluation of an R1234yf automobile air conditioning system employing an internal heat exchanger

Abstract

A bench-top automobile air conditioning (AAC) system using a thermostaticexpansion valve was developed. The system was equipped with a coaxial internalheat exchanger (HEX) and charged with R1234yf, a new refrigerant used as analternative to R134a. The system was tested at the compressor speeds rangingbetween 1000 rpm and 2600 rpm with increments of 400 rpm. For eachcompressor speed, the air temperatures at the evaporator and condenser inlets wereconcurrently changed between 30 °C and 40 °C with increments of 5 °C. Thesystem was operated for the cases of employing and not employing the HEX, andtotally 30 test runs were performed. Then, the first law of thermodynamics wasapplied to the system components to evaluate various steady state performanceparameters. The considered parameters were the refrigerant mass flow rate,evaporating temperature, cooling capacity, compressor power, coefficient ofperformance (COP), condenser heat dissipation rate and discharge temperature ofthe compressor. It was determined that the experimental system employing theHEX yielded on average 0.8 °C lower evaporating temperature, 2.2% highercooling capacity, 2.0% lower compressor power and 3.0% higher COP valuesrelative to the system not employing the HEX. These findings reveal that the useof HEX causes a better system performance in terms of the cooling capacity,compressor power and COP. Consequently, the performance of R1234yf AACsystems can be improved with the use of HEX, and thus, the AAC systems usingR1234yf can be more competitive with those using R134a