Boiling heat transfer, Pressure drop, Microfin tube, Small-diameter, R32
Currently, the development of high-performance and compact heat exchangers using small diameter tubes of hydraulic diameter less than 5 mm is required to improve the performance of heat exchanger and reduce the charge amount of refrigerant for air-conditioning systems. For microfin tubes, the tube diameter become smaller, however, the effects of surface tension and shear stress on boiling heat transfer and flow characteristics in small diameter tubes are different from those in conventional large diameter tubes. This study experimentally investigates the flow boiling heat transfer and pressure drop characteristics of low global warming potential refrigerant R32 in horizontal small-diameter microfin tube with 3.0 mm outer diameter and 2.6 mm mean diameter. The flow boiling heat transfer and pressure drop characteristics are measured in a range of mass velocities from 50 to 400 kg/(m2 s) and a range of heat fluxes from 5 to 20 kW/m2 at saturation temperature of 15Â°C. The flow boiling heat transfer characteristics were compared with those of the 4 mm microfin tube.