Experimental study on flow boiling of refrigerant R1233zd(E) in microchannels: Heat transfer

Abstract

The paper reports accurate experimental data for flow boiling heat transfer of a new environmentally friendly refrigerant R1233zd(E) in parallel horizontal microchannels. The aluminium test section consists of two blocks and has 10 parallel channels with 1.0 mm in width, 1.5 mm in height and 440 mm in length. Five small thermocouple holes with diameter 0.6 mm and depth 20 mm were drilled at 10 locations along the channel on the two aluminium blocks, respectively. The local heat flux and channel surface temperature along the channel were obtained by using the inverse heat conduction method based on the temperatures in the test blocks accurately measured by 100 thermocouples. The local saturation temperatures were obtained by assuming the linear distribution of pressure in the two-phase flow region along the channel. Experiments were conducted in a wide range of working conditions. The refrigerant mass flow rate varied from 100 kg/m2 s to 450 kg/m2 s. The heating water mass flow rate varied from 600 ml/min to 1200 ml/min. The saturation pressure of refrigerant R1233zd(E) varied from 200 kPa to 350 kPa. The refrigerant liquid was maintained subcooled with 4.0 K at the inlet before entering the microchannels. The heat balance between the refrigerant and heating water sides agree well within 7.3%. The inverse results show effects of gravity, saturation pressure and heat flux on flow boiling heat transfer in microchannels. The work is of important value for understanding the fundamentals of flow boiling heat transfer in microchannels and development of accurate prediction method.