Flow Boiling Heat Transfer In Mini-/Micro-Channels

With the rapid development of the modern industry, the issue of improving the cooling efficiencyof high heat flux heat sink equipments has been of great significance. The urgent need to resolve thisproblem has also promoted the development of the flow boiling in mini-/micro-channels. Manydomestic and foreign scholars have been doing the research on this subject, and considerable amountof the achievements on this field have been applied to engineering practice. The fluid flow and heattransfer in mini-/micro-channels are different from that in conventional channels since thecomplicated flow characteristics and the unknown heat transfer mechanism of the fluid within thechannels. Under this circumstance, the research of the flow boiling in mini-/micro-channels remainsan issue.A number of correlations for flow boiling heat transfer in channels have been proposed. Most ofevaluations of the applicability of existing correlations to R134a used limited experimental dataand/or limited correlations. Therefore, the results were often not consistent, even controversial. Inorder to get a reliable evaluation,1916datas of R134a flow boiling heat transfer are collected from19papers, which are used as the database in this work.This paper collects19correlations of flow boiling heat transfer in mini-/micro-channels fromrelevant references, moreover, and the experimental data collected from the R134a are used to analyzethe above19correlations. The evaluation result reveals that Gungor-Winterton correlation performsbest, following by the Bertsch, Sun-Mishima, Tran, and Cooper correlations. Based on the evaluationresults, the Gungor-Winterton correlation is chosen as the baseline to develop the new correlation ofR134a flow boiling heat transfer, using the experimental data collected. The new correlation has anMARD of27.9%, much better than the35.1%the best existing correlation has.On the purpose of validating the new correlation, this paper conducts the experimental researchon the R134a flow boiling in tube. The experiment uses the copper tube with1.299mm and4.004mmID as the test sections, and the results showed that the prediction effect of the new correlation with1.299mm is better than other correlations; however, the prediction effect is after Sun-Mishimacorrelation. The limited experimental range is among the reasons. Through the observation of theexperimental data, the flow boiling heat transfer coefficient increases with the increasing vaporquality in most cases, and it probably decreases at a certain vapor quality.