Forced Convective Boiling Experiments f Binary Mixtures

抄録

Forced convective boiling heat transfer data are obtained for R 12-R 22 mixtures and R 114-R 22 mixtures flowing in a horizontal tube. The test section is a stainless steel tube 8 mm ID and 4 m long, which is uniformly heated by direct current. Assuming a thermodynamic equilibrium state, the vapor quality and the saturated temperature of the mixture are calculated from the pressure data, the heat flux and the mass velocity. The local heat transfer coefficient normalized by the single-phase heat transfer coefficient, assuming that the liquid phase is flowing alone, is correlated to the function of the Lockhart and Martinelli parameter and the boiling number. Since the R 12-R 22 mixture has a small temperature difference between saturated liquid and saturated vapor at constant pressure (less than 3 degrees), the boiling heat transfer coefficient of binary mixtures lied between those of its component. For R 114-R 22 mixtures a significant reduction in the boiling heat transfer coefficient due to mass transfer effects is observed. This behavior is examined by means of a bubble growth model in a superheated binary liquid mixture.