Evaluation of performance an air conditioning systems using t-junction flash gas refrigerant
The purpose of this study was to determine the performance of air-cooled chiller system using T-junction flash gas bypass refrigerant. The experiment was conducted by installing T-junction after expansion device to separate the phase of refrigerant liquid and gas which flows to the evaporator. The working fluid is used as a cooling medium is R-290. To get performance data, measurements performed at the time of steady state when the water chilling temperature T = 15 C up to T = 10 C and flow rates kept constant at 1 GPM (6.3 x 10-5 m3/s). Finally, the use of T-junction mode in AC system generates an increase in the refrigerating effect and coefficient of performance systems (CoP) by 6% and 17.8 %, respectively. Also, it can decrease the heat of compression by 8.5%. This has implications for the lighter compressor work and saving the power consumption of the AC system.
Flash gas bypass in mobile air conditioning system with R134a
Abstract This paper demonstrates that the performance of a mobile air conditioning system (with a microchannel evaporator modified to be single pass) operating normally with R134a in direct expansion mode can be significantly improved when switched to flash gas bypass (FGB) mode. When operated at the same compressor speed, the system in FGB mode produces about 13%–18% more cooling capacity at 4%–7% higher COP than DX mode. When the compressor speed was adjusted to maintain the same cooling capacity, the COP improved 37%–55%. Two main reasons are identified and discussed: 1) improved refrigerant distribution and 2) reduction of refrigerant pressure drop.
Thermodynamic performance of R502 alternative refrigerant mixtures for low temperature and transport applications
Abstract In this study, two pure hydrocarbon refrigerants, R1270 (propylene) and R290 (propane), and three binary mixtures composed of R1270, R290 and R152a were tested in a refrigerating bench tester with a scroll compressor in an attempt to substitute R502, which is used in most low temperature and transport refrigeration applications. The test bench provided 3–3.5 kW capacity, and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions, resulting in the average saturation temperatures of −28 and 45 °C in the evaporator and condenser, respectively. The test results showed that all refrigerants tested had 9.6–18.7% higher capacity and 17.1–27.3% higher COP than R502. The compressor discharge temperature of R1270 was similar to that of R502, while those of all the other refrigerants were 23.7–27.9 °C lower than that of R502. For all alternative refrigerants, the charge was reduced up to 60% as compared to R502. There, of course, was no problem with mineral oil, since the mixtures were mainly composed of hydrocarbons. Since some of them are mixtures, one can change their compositions a little to suit various needs in many applications without significant deterioration of the performance. Overall, these alternative refrigerants offer better system performance and reliability than R502 and can be used as long term substitutes for R502 due to their excellent environmental properties.