Boiling heat transfer with binary mixtures: Part II — Flow boiling in plain tubes
Abstract
Flow boiling heat transfer with pure fluids comprises convective and nucleate boiling
components. In flow boiling of binary mixtures, in addition to the suppression effects
present in pool boiling, the presence of flow further modifies the nucleate boiling
characteristics. In the present work, the flow boiling correlation by Kandlikar (1990,
1991b) for pure fluids is used as the starting point, and the mixture effects derived
in Part I (Kandlikar, 1998) of this paper are incorporated. Three regions are defined
on the basis of a volatility parameter, Vt = (Cp/AhLG)(K/D]2)1/2\(yi — x,)dT/
dxt\. They are: region I—near azeotropic, region II—moderate diffusion-induced
suppression, and region III—severe diffusion-induced suppression. The resulting
correlation is able to correlate over 2500 data points within 8.3 to 13.3 percent mean
deviation for each data set. Furthermore, the a-x trend is represented well for R-
12/R-22, R-22/R-114, R-22/R-152a, R-500, and R-132a/R-123 systems. Electrically
heated stainless steel test sections as well as fluid-heated copper test sections are
both covered under this correlation.