순수 및 혼합냉매의 흐름 비등 열전달 특성

초록

Flow boiling heat transfer coefficients of R22, R134a, R407C, and R410A were measured experimentally for a horizontal plain and microfin tube in an apparatus composed of three major loops : a refrigerant loop, a water loop, and a water-glycol loop. Test section in a refrigerant loop was made of a copper tube of 8.8mm inner diameter and 1000mm length respectively. The refrigerant was heated by passing hot water through an annulus surrounding the test section. All tests were performed at a fixed refrigerant saturation temperature of 5℃ with mass fluxes of 100∼300kg/m2s. The results showed that at similar mass flux the flow boiling heat transfer coefficients(HTCs) of R134a were similar to those of R22 for both plain and microfin tube. HTCs of R407C were similar to those of R22 for a plain tube but were lower by 25∼48% for a microfin tube. HTCs of R410A were higher than those of R22 by 20∼63% for a plain tube and were similar to those of R22 for a microfin tube. In general, HTCs of a microfin tube were 1.8∼5.7 times higher than those of a plain tube.