R-1234ze(E)를 사용한 브레이징타입 판형열교환기에서의 증발 압력강하 및 열전달 특성 분석

This study is to analyze pressure drop and HTC(Heat Transfer Coefficient) in a BPHE(Brazing type Plate Heat Exchanger) using R-1234ze(E) which is known as a substitutional refrigerant of R-134a. The BPHE was installed as a evaporator in the test section and the temperature for evaporating conditions are set to 5, 10 and 15℃. Secondary fluid was used to supply heat to the evaporator and a cooling chiller was used to cool the refrigerant after it has absorbed heat from the test section. Quality of refrigerant entering into the test section was controled by regulating power supplied to the pre-heater that a electricity heater is inserted to copper pipe. The trend of the pressure drop and HTC with respect to average vapor quality has been analyzed to make reasonable explanation for the phenomena. The trend of the pressure drop was varied depending mainly on the mass flux G because dominance of either frictional or gravitational pressure drop was different for each G. The trend of the HTC also depends critically on the mass flux G showing different patterns for each G as the dependance of convective heat transfer and nucleate boiling heat transfer varies for each G.