EFFECT OF ASPECT RATIO ON EVAPORATION HEAT TRANSFER AND PRESSURE DROP OF R-410A IN FLATTENED MICROFIN TUBES

摘要

In this study, evaporation heat transfer coefficients and pressure drops of R-410A were obtained in flattened microfin tubes (AR = 2, 4) made from 7.0 mm O.D. round microfin tube. The test range covered mass flux from 200 to 400 kg/m(2)s. The heat flux and saturation temperature were fixed at 10 kW/m(2) and 15 degrees C. Both the evaporation heat transfer coefficient and the frictional pressure drop increased as quality or mass flux increased. They also increased as the tube aspect ratio increased. The heat transfer enhancement ratio ranged from 1.51 to 3.08, which increased as mass flux decreased. However, the pressure drop penalty factors were less than 1.0. Comparison with existing round microfin tube correlations was made.