하이브리드 유하액막 증발기 성능에 관한 수치적 연구

Abstract

The purpose of this study was to develop steady-state model of hybrid falling film evaporator, and to analyze performance of the heat exchanger. R1233zd(E) which is one of the low GWP refrigerants was selected as a working fluid. The steady state model was developed, based on the heat transfer correlations from previous studies for falling film evaporation and pool boiling using R1233zd(E). Based on the analysis results according to the number of nodes, the number os axial nodes was selected as 24. Performance analysis was conducted with respect to evaporator pressure, axial direction liquid refrigerant supply ratio from tray, rows of pipe for pool boiling region, and maximum heat transfer coefficient of falling film region. For the same heat capacity of the evaporator, the length of the pipe should extend approximately 3.6 times, when evaporator operation pressure increases from 49.2 to 58.4 kPa. The length of the pipe can be reduced approximately 18% as the number of rows for pool boiling region increases from one to three. The axial direction liquid refrigerant supply ratio from the tray also affects the performance of the evaporator. Compared to the equal supply ratio case, the pipe length must increase approximately 9%, when the axial direction liquid refrigerant supply ratio is 9:1 for the same cooling capacity. As the maximum heat transfer coefficient at falling film region increases from 5000 to 11000 W/m2K,the length of the pipe can be reduced approximately 27%.