Heat transfer mechanisms for condensation and vaporization inside a microfin tube

Experimental tests using R22 were conducted to measure the condensation coefficient and the vaporization coefficient inside a given microfin tube (Wolverine DX-75). Data were also taken for nucleate pool boiling on a plain surface and on the microfin surface. A key objective of the present work is to define the contribution made by nucleate boiling to the microfin tube evaporation performance. An asymptotic model is used to combine the nucleate boiling and convective terms to account for both contributions. This was done using the experimental condensation and nucleate boiling curves. The convective contribution for vaporization is the same as for convective condensation below 70% and also below the dryout point. The tests show that nucleate boiling makes a significant contribution to vaporization for vaporization of R22 in a microfin tube.