DETERMINATION OF WALL HEAT FLUX BASED ON BUBBLE DEPARTURE AND LIFT-OFF DIAMETERS FOR VARYING PRESSURE AND FLOW VELOCITY CONDITIONS

Abstract

In this study, the bubble departure and lift-off (BDL) boiling model has been improved by implementing the subcooling suppression factor and flow-related parameters, with the aim of developing an accurate heat transfer model for various engineering applications. The BDL model has been exploited using a MATLAB program to determine the variation of wall heat flux that controls the boiling curve. Three different parameters, namely, bulk flow velocity, operating pressure, and bulk flow temperature have been considered in this study. Experimental conditions were simulated as per Chen's BDL model algorithm, and the resulting wall heat flux was compared with the measured values. Additionally, different boiling curves for bubble departure and lift diameters were generated and their effect on varying operating conditions was studied. The resultant boiling curves were compared with the experimental data by means of mean absolute error (MAE) and regression coefficient (<i>R</i><sup>2</sup>) values. In general, with a reasonable margin of error, i.e., MAE = 3.35%, and <i>R</i><sup>2</sup> = 0.99, the algorithm performed well in comparison with the experimental data. The bubble departure and lift diameters were also correlated with the experiment and the predictions were satisfactorily close.