화학공학소재연구정보센터
International Journal of Heat and Mass Transfer, Vol.38, No.8, 1347-1361, 1995
Nucleate Pool Boiling of R-114 and R-114-Oil Mixtures from Smooth and Enhanced Surfaces .1. Single Tubes
Measurements of pool-boiling heat-transfer coefficients in pure R-114 and R-114-oil mixtures are reported for a smooth tube and eight enhanced tubes (five finned and three re-entrant cavity). Tests were carried out at atmospheric pressure while decreasing the heat flux. For pure refrigerant, the finned tubes typically provide enhancements of between 3 and 4, whilst the re-entrant cavity tubes provide enhancements of more than 10 at low heat fluxes, decreasing to around 4 at high heat fluxes. With addition of oil, performance of the finned tubes at first increases (with 3% oil) before dropping off. For the reentrant cavity tubes, addition of oil causes a steady drop-off in performance; especially for the porous tube where heat transfer rates similar to that of the smooth tube were obtained.