R32 および R410A 冷媒の水平内面溝付細管内の凝縮熱伝達および圧力損失

－第 1 報：単相乱流熱伝達および圧力損失の相関式－

抄録

An experimental study into pressure drop and heat transfer in single-phase turbulent flows was carried out using 10 types of internally helical-grooved and smooth small-diameter tubes with an outer diameter of 4.00 mm. The geometric groove parameters for the test heat-transfer tubes were: number of grooves (40 to 50); helix angle (0 to 25 deg. ); and fin height (0.10 to 0.20 mm). In the experiments, water was used as a test fluid; the inlet temperature was kept constant at 20°C; and the flow rate was varied from 0.001 to 0.047 kg/s. During the experiments, the electric heating capacity was adjusted within a range so that the difference between inlet and outlet temperatures in the experimental heat-transfer section did not exceed 6 K. The results showed: (1) The effect of the geometric groove parameters on pressure drop and heat transfer coefficient for 4 mm small-diameter tubes was clearly shown. (2) Correlations to predict the friction factor and heat-transfer coefficient were developed based on the experimental values, which can predict experimental values within ±15% and ±25%, respectively. (3) We evaluated the performance of the heat-transfer tube in single phase by using Colburn's analogy.