Two-phase frictional pressure gradient of R236ea, R134a and R410A inside multi-port mini-channels

In the present paper the pressure drop characteristics of a 1.4 mm hydraulic diameter multiport minichannel tube during adiabatic two-phase flow of HFC refrigerants are discussed. The tube consists of eleven parallel rectangular cross section channels. Although much experimental research has been devoted to investigate the pressure drop characteristics of R134a inside multiport minichannels in the last years, very little information is available on different refrigerants, such as R236ea (low pressure) and R410A (high pressure), whose behaviour is different from R134a. The experimental runs are carried out at mass velocities ranging from 200 to 1400 kg/(m2 s), depending on the refrigerant under test, at constant value of vapour quality. The frictional pressure gradient is obtained from the saturation temperature drop measurement. The results presented here cover a wide range of the reduced pressure, from 0.1 up to 0.5. The experimental frictional pressure drop data is compared against models available in the literature for prediction of frictional pressure gradient in channels. The comparison of calculated to experimental values shows that the R134a frictional pressure gradient in the multiport minichannel test tube can be fairly well predicted by available correlations, but not satisfactory agreement is found for R236ea data and even worse in the case of R410A data.