Heat transfer and enhancement analyses of flow boiling for R417A and R22

The experimental study on heat transfer of R417A and R22 flow boiling inside a horizontal smooth and two internally grooved tubes with different geometrical parameters was conducted. Based on the experimental results, evaporation heat transfer characteristics of R417A and R22 flowing in different tubes, the influence of micro-fin geometrical parameters, vapor quality and mass flux of refrigerants on heat transfer enhancement factors, and the difference of enhancement factors between R417A and R22 were analyzed and discussed. The result indicates: whether for R22 or for R417A, the enhancement effect of Tube III having the narrower distance between micro-fins excels than Tube II. The influence of vapor qualities and mass fluxes on enhancement factors for R417A is different from R22. And the difference of enhancement factors between R417A and R22 appears different cases at different vapor quality regions.