Effect of surface conditions on boiling heat transfer of refrigerants in shell-and-tube evaporators

Experimental results are presented for the boiling heat transfer performance of R 22 and R 717 on surfaces with porous metallized coatings. A calculational-theoretical model is given for predicting the heat transfer of refrigerants boiling on a bundle of finned tubes. The results of the experiments are given. On all of the specimens with coatings an increase in the coefficient of heat transfer α from 2 to 5 fold as compared with that for a smooth surface αsm was observed. For R 22 the effect of the heat flux density on the heat transfer for tubes with coatings turned out to be weaker than for a smooth surface.