CHARACTERISTICS OF HEAT-TRANSFER COEFFICIENT DURING NUCLEATE POOL BOILING OF BINARY-MIXTURES - IMPROVEMENT OF CORRELATION AND ITS PHYSICAL MEANING

Experimental studies were conducted on heat transfer on a horizontal p latinum wire during nucleate pool boiling in nonazeotropic binary mixt ures of R12+R113, R134a+R113, R22+R113 and R22+R11, at pressures of 0. 25 to 0.7 MPa and at heat fluxes up to critical heat flux. The substan ces employed were chosen such that the components of a given mixture h ad a large difference in saturation temperatures. The boiling; feature s of the mixtures and the pure substances were observed by photography . The relationship between the boiling: features and the reduction in heat transfer coefficient in binary mixtures is discussed in order to propose a correlation useful for predicting the experimental data meas ured over a wide range of low and high heat fluxes. It is shown that t he correlation is applicable also to alcoholic mixtures. The physical role of k, which was introduced to evaluate the effect of heat flux on the reduction in heat transfer coefficient, is clarified based on the measured nucleate pool boiling heat transfer data and the visual obse rvations of the boiling features.