TWO-PHASE PRESSURE DROP OF R-410A, R-407C AND CO2 IN HORIZONTAL EVAPORATOR WITH MINICHANNELS
Two-phase pressure drop during evaporation process of R-410A, R-407C and CO2 were studied in horizontal minichannels of 1.5 and 3.0 mm inside diameters with heated length of 1.5, 2.0 and 3.0 m. Experiments were performed at mass flux ranges from 200 to 600 kg/m2s, heat flux from 5 to 20 kW/m2, and the inlet saturation temperature of 10oC. For these refrigerants, the intermittent, wavy, and annular flow appear on the Wang et al. flow pattern map, whereas the intermittent, stratified-wavy, and annular flow appear on the Kattan et al. flow pattern map. The higher mass flux and heat flux give a higher pressure drop. The experimental pressure drop of R-407C is higher than that of R-410A and CO2, successively, and the pressure drop in 1.5-mm tube is higher than that in 3.0 mm. The experimental results were then compared against six previous two-phase pressure drop prediction methods. By using 666 data points of R-410A, R-407C, and CO2, a new correlation of two-phase frictional pressure drop is developed on the basis of the Friedel correlation. The comparison of the two-phase frictional multiplier of the present study with the prediction of the new correlation shows 18.00% mean deviation and 0.03% average deviation.