Comparison of the flow characteristics and performance of low-GWP refrigerants in expansion capillary used in air conditioning units

Refrigerants are one of the major contributors for earths Global Warming Potential which is resulting in extreme weather conditions. In the present study, Finite Volume-based VOF (volume of fluid) model is used to investigate the flow behavior of ecofriendly friendly refrigerants (R161, R1123 and R454b) flowing inside the capillary tube. To estimate mass transfer during flashing, Lee model is used. The present study considers different lengths and diameters of straight capillary tube to analyze their effects on flow characteristics of refrigerant such as pressure, temperature, volume fraction and velocity. It is understood that larger diameter expansion capillary results in high capillary exit pressures for the same operating conditions. It was found that the order of velocities are almost 1.2 times higher for R161 when compared to R1123. It is also calculated that mass flow rate of R454B is 25% less and 50% high when compared with refrigerant R1123 and R161.The numerical investigation also showed that under the same operating conditions, R161 has higher COP as compared to other refrigerants whereas in terms of refrigeration effect R454B is better than other refrigerants.