Buoyancy influences on local heat transfer characteristic of supercritical LNG across the pseudo-phase transition in variable cross-section horizontal channels

Abstract

The regasification process within the printed circuit heat exchanger (PCHE) channel for supercritical liquefied natural gas (S-LNG) will produce a large temperature difference. This process is considered a pseudo-phase transition process, and the resulting density difference driving buoyancy has a crucial action in influencing the heat transfer and flow of S-LNG. Three horizontal variable cross-section channels are established to examine the buoyancy impact on the local heat transfer and flow of S-LNG within the pseudo-phase transition process in the PCHE channel. It comprehensively analyzes the buoyancy impact on local heat transfer and flow under different channel shapes and mass flow rates. The findings demonstrated that the eddy blockage caused by buoyancy mainly acts on the top of the channel and mainly occurs in the liquid-like and pseudo-critical regions, resulting in the deterioration of local heat transfer on the upper and lower walls of the channel. The hybrid channel achieves the intended design goal, and the diverging channel is almost unaffected by buoyancy. The overall performance evaluation criterion (PEC) is used to evaluate the thermal and hydraulic performance of each channel under different mass flow rates. The data show that the diverging channel has the best thermal and hydraulic performance, and its PEC can reach 1.28. The hybrid channel also achieves the expected effect, and its PEC can reach 1.09.