Development of New Critical Heat Flux Correlation for Microchannel Using Energy-Based Bubble Growth Model

Abstract

Critical heat flux (CHF) is a key design consideration for the systems involving heat dissipation through boiling application. It dictates the maximum limit of performance of heat transfer systems. Abrupt and substantial decrease in heat transfer coefficient is an indirect indication of occurrence of the CHF, which may cause complete burnout of heat transfer surface. Unlike conventional channels, CHF correlations for microchannels are limited and associated with significant variations. In the present paper, effort has been made to develop new CHF models applicable to a frequently occurring scenario of flow boiling in microchannels. The approach combines nondimensional analysis and an energy analysis based bubble growth model at an arbitrary nucleation site. Two separate CHF correlations for refrigerants and water have been developed following a semi-empirical approach. The proposed correlations show good agreement with available experimental data. The mean errors for the refrigerant and water cases are, respectively, found to be 21% and 27% for seven and six relevant datasets. Around 77% data of the refrigerant and 60% data of water are predicted within error band of ±30%. It is also found that influence of a certain energy ratio term (gravity to surface tension, denoted as πE4) is negligible for examined water CHF conditions.