INVESTIGATION OF HEAT TRANSFER CORRELATION IN POOL BOILING

Abstract

The heat transfer correlations proposed earlier by different investigators do not give satisfactory result when compared to experimental data. This is because these correlations are based on their own proposed mechanism and obtained with limited data in the range experimentally investigated. In this work, the experimental data of heat flux for various fluids under different conditions have been consolidated and compared with the corre].- ations proposed by various investigators in the entire regime of pool boiling. It was observed that the existing correlations fail to provide the accurate value of heat transfer coefficient in the entire regime. Besides this, a significant change in the slope of the boiling curve is observed at the heat flux approximately 0.57 qc. Therefore, the entire boiling regime is divided into two regions and separate correlations are proposed for these two as below 1. Low heat flux region (0.17 qc to 0.57 qc) and Nu = 9.39667 x 10-4(Pr)-0.211284 (p)0°713472 x (K)C.669816 2. Macrolayer region (0.57 qc to 1.0 qc) and N = 0.152527 (Pr)-0.150858 (Pe)0.39046 x(K )0.402676 p These equations correlate the available. experimental data with average deviation of +36 / and iv —30 / for 0.17 qc to 0.57 qc and + 27°o and --34/ for 0.57 qc to 1.0 qc. A method known as 'coefficient of correlation method', is used to compare the present correlations as well as the correlations proposed by Rohsenow, Kutateladze, Borishanskii, Nishikawa and Fujita with experimental values of heat transfer coefficient. It gives the value of coefficient of correlation as 91J and 92/ for present correlations, 89/ and 55/ for Kutateladze correlation. , 90°o and 41/ for Borishanskii correlation in low heat flux region and macrolayer region respectively whereas the correlations of Rohsenow and Nishikawa and Fujita give an imperfect relationship with the experimental value in both the. regions.