STUDIES ON BOILING OF LIQUIDS

Abstract

The present investigation discusses the development of a model for the boiling of saturated liquids. Basically, analysis has been done for the determination of the validity of transient ,heat conduction model due to Mikic & Rohsenow [3l and latent heat transport model due to Rallies & Jawurek [4The analysis has yielded that neither of them can determine the total heat flux during boiling of liquids. Therefore, a model has been developed assuming transient heat-conduction during waiting period, 'latent heat transport during growth period and natural convection in the region unaffected by bubble activity. The calculated values of heat flux by this model have been found to compare well with the experimental values. Analysis has been extended for the development of a correlation to see the effect of various parameters like — heat flux and pressure on wall superheat. The validity of such correlation has been successfully examined by comparing the calculated values with experimentally' obtained values taking data of several investigators. This investigation also develops a method to evaluate the value of surface- liquid combination factor of the power law of nucleate pool boiling. The method has been used to calculate the surface-liquid combination factor for the boiling of distilled water from the known contact angle of the heating surface. The predicted values have been found to compare well with the experimental values. Boiling heat transfer from a porous layer sintered on a horizontal heater surface and heated from the base has been analyzed for laminar region. A dimensionless equation for the two- phase flow in a porous matrix has been derived and analyzed in laminar region. For very thick bed, expression for dimensionless heat flux has been developed which is dependent on Cv, A and Se. An equation for dryout heat flux has been derived in terms of particle diameter and liquid physical properties. When log gery is plotted against log d, by taking data from several investigators, gives slope equal to 2 which verifies the developed equation.