Eexperimental Study On Flow Evaporation Heat Transfer Characteristics Inside Horizontal Three-Dimensional Enhanced Tubes

Experimental investigation was performed to measure the vaporation heat transfer coefficients of R410A inside three hree-dimensional enhanced tubes (1EHT-1, lEHT-2 and 4LB). The inner and outer enhanced surface of the 4LB tube is composed by arrays of grooves and square pits, while lEHT-1 tube and 1EHT-2 tube consist of longitudinal ripples and dimples of different depths. All these tubes have an inner diameter of 8.32 nm and an outer diameter of 9.52 mm. Experiment operational conditions are conducted as follows: the saturation temperature s 279 K, the vapor quality ranges from 0.2 to 0.8, and the mass flux varies from 160 kg/(m(2). s) to 380 kg/(m(2)- s). With the mass flux increasing, the heat transfer coefficient increases accordingly. The heat transfer coefficient of lEHT-2 is the ighest of all three tubes, and that of 1EHT-1 is the lowest. The eat transfer coefficient of 4LB ranks between the lEHT-1 and lEHT-2 tube. The reason is that the heat transfer areas of the EHT-2 and 4LB tube are larger than that of lEHT-1 and interfacial turbulence is enhanced in lEHT-2.