Development of New Correlations for Critical Heat Flux Point Wall Temperature and Transition Boiling under Steady-State Saturated Pool Boiling of Cryogens

The present study addresses the limited availability of reliable data and predictive tools for transition boiling (TB) of cryogens and the lack of methods for predicting the wall temperature at the critical heat flux (CHF) point (TCHF) during saturated pool boiling from flat surfaces. A thorough literature review was conducted which identified six existing TB correlations but none for TCHF. To fill this gap, extensive steady-state cryogenic fluid data from global sources were compiled, focusing on saturated pool boiling under Earth gravity. Two databases were amassed: one for TCHF (200 datapoints for clean and 36 for treated surfaces) and another for TB (133 datapoints for clean surfaces). The existing TB correlations performed poorly against the consolidated database. Since TB is affected by both the CHF and minimum heat flux (MHF) points, accurate correlations for heat flux and temperature at both points are essential. The authors' recent work has already provided correlations for heat fluxes at the CHF and MHF points, and wall temperature at the MHF point. This study introduces a new predictive method for TCHF and utilizes it to predict the heat transfer coefficient (HTC) in the TB regime. The new correlations show very good predictive accuracy with mean absolute errors (MAEs) of 10.71 % and 14.84 % for TCHF and the TB HTC, respectively. Additionally, the present study emphasizes the need for further experiments to expand the cryogenic database, covering more cryogens and broader ranges of operating conditions.