Studies on Heat Transfer Coefficient of a Circular Tube With Twisted Tape Insert for High Heat Flux Cooling Applications

Abstract

Herein, the heat-transfer characteristics of the subcooled flow boiling of swirl tubes are evaluated experimentally under one-side high heat load conditions. As the twist ratio of the tape decreased and the flow rate increased, the forced convective heat transfer was enhanced; thus, the single-phase heat transfer was enhanced, and the onset of nucleate boiling (ONB) heat flux increased. As the degree of subcooling increased, the ONB heat flux increased because of the faster condensation rate. As the pressure increased, the ONB heat flux increased, and the critical heat flux increased, due to the suppression of boiling and the decrease in the bubble size. The authors analyzed the heat transfer characteristics of the one-side heated swirl tube in the single-phase regime, the partially developed nucleate boiling (PDB) regime, and the fully developed nucleate (FDB) boiling regime. And the prediction performance of the existing heat-transfer correlations developed for application to each regime was evaluated. The PDB correlations showed a mean absolute error rate (MAE) of approximately 30%. However, the existing FDB correlations a high error rate (MAE higher than 48%) at a high heat flux of several MW/M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> outside the developed experimental range. Therefore, we develop a new swirl tube FDB heat-transfer correlation that can also be used in the development of a swirl tube flow boiling map using the Python code grafted with the artificial intelligence (AI) regression method.