18 May 2017

P.4.1.3 Pool boiling Heat Transfer Characteristics of Low GWP Refrigerants on Enhanced tube used in Flooded Evaporator for Turbo-Chiller


Recently, researches on the finding a next-generation refrigerant that does not destroy the ozone layer or affect on global warming are growing globally. In this study, pool boiling heat transfer characteristics of low GWP refrigerants on plain and enhanced tube were investigated experimentally. The measurement of heat transfer coefficients was carried out through the Wilson plot method. The method was validated and used to characterize the inside heat transfer coefficient of the cooling water. Tests were performed for three different refrigerants (R-134a, R-1234ze(E), R-1233zd(E)) at two different saturation temperatures 4.4 ? and 26.7 ?, heat flux was varied from 10 to 50 kW/m2. Results were shown that the pool boiling heat transfer coefficients of R-1234ze(E) was obtained 5.0% ~ 11.5% lower than the those of R-134a. Heat transfer coefficients of R-1233zd(E) were 64.6% ~ 71.7% lower than those of R-134a. Compared with the heat transfer performance of the plain tube, the heat transfer enhancement ratios of enhanced tube were obtained 2.3 for R-134a, 2.1 for R-1234ze(E) and 1.8 for R-1233zd(E) respectively.