Flow Boiling of R141b on Externally Sintered High-Flux Tubes
The sintered high-flux tube is an innovative heat transfer element that exhibits enhanced heat transfer capabilities.It is capable of inducing vigorous nuclear boiling even at low wall super-heat conditions,thereby facilitating the efficient heat transfer of the working medium.In order to investigate the impact of a sintered porous layer on the characteristics of flow boiling heat transfer,this study conducted experimental research on externally sintered high-flux tubes.The tubes had an outer diameter of 25 mm,a coating thickness of 0.3 mm,and porosities of 65％and 75％respec-tively.The experimental working medium used in this study was refrigerant R141b.The results indicate that,when subjected to identical wall superheat conditions,the high-flux tube exhibits a substantial increase in wall heat flux compared to the smooth tube.Furthermore,it is observed that the high-flux tube with greater porosity demonstrates an even higher wall heat flux.Increasing the porosity of the high-flux tube has been found to have a positive effect on the number of vaporized cores and the frequency of bubble detachment.However,it should be noted that when the heating wall temperature reaches a certain threshold,the bubbles are unable to escape from the porous layer and instead form a localized vapor film.This phenomenon ultimately leads to a decrease in the heat transfer coefficient of the high-flux tube.
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