냉매 R-134a의 수평 응축관내 응축 전열 특성에 관한 연구

An experimental investigation to examine the chracteristics of condensing heat transfer of R-134a is reported. The apparatus was constructed to investigate flow patterns, pressure drop, and heat tranfer coefficients during condensation inside a horizontal tube with an inner diameter of 7.5 ㎜ and length of 1 518 ㎜. The working fluids R-134a and R-12 were used. The ranges of parameters, such as mass velocities were varied from 60 to 210 ㎏/(㎡ s), and qualities from 1 to 0.2. The flow pattern data showed that the flow patterns for R-134a are similar to that of R-12, and that the Baker map is inadequate for predicting the condensing flow pattern except for annular flow with high mass velocities(200~400 ㎏/(㎡ s)) and wavy flow for with low mass velocities(60~200 ㎏/(㎡ s)). In the same given experimental conditions, the pressure drops of R-134a were 15 ~ 20 % higher than that of R-12. The experimental data of heat transfer showed that the heat transfer coefficients for R-134a were 20 % higher than that of R-12. and that the Cavallini Zecchin equation using condensing two phase equilibrant Reynolds numbers is a very effective way of predicting the heat transfer of R-134a during condnsation inside horizontal tubes.