{"title":"Stratification and heat transfer characteristics for R32-partially miscible oil mixture flow boiling inside a micro-fin tube","authors":"","doi":"10.1016/j.ijrefrig.2024.08.005","DOIUrl":null,"url":null,"abstract":"<div><div>R32 commonly applied in room air-conditioners has flammability, and the ways to decrease the charging amount, e.g. reducing the dissolution of refrigerant in the lubricating oil, are important to reduce combustion risk. The application of partially miscible oil rather than completely miscible oil can decrease R32 solubility but may deteriorate the heat transfer by the forming of pure oil layer, and thus the understanding of the stratification and flow boiling heat transfer characteristics of R32-partially miscible oil mixture is necessary. The purpose of this study is to experimentally investigate the stratification and flow boiling heat transfer characteristics of a mixture of R32 and partially miscible POE oil, and to propose a new heat transfer correlation. The experiments are carried out at evaporation temperature varying from -5 °C – 15 °C, total oil concentration varying from 1 % to 5 %, vapor quality varying from 0.1 – 0.9 and mass flux varying from 200 kg m<sup>-2</sup> s<sup>-1</sup> to 400 kg m<sup>-2</sup> s<sup>-1</sup>.The results indicate that the stratification of R32-partially miscible oil mixture occurs at the high liquid oil concentrations, and an oil-poor layer and an oil-rich layer are involved in the stratified annular layer. R32-partially miscible oil mixture has higher flow boiling heat transfer coefficients than R32-completely miscible oil mixture due to the low viscosity of the oil-poor layer. A new flow boiling heat transfer correlation reflecting the effect of stratification is developed, and the predicted results agree with 91 % of the test results as the relative deviation ranges in ±20%.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Refrigeration-revue Internationale Du Froid","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0140700724002792","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0
Abstract
R32 commonly applied in room air-conditioners has flammability, and the ways to decrease the charging amount, e.g. reducing the dissolution of refrigerant in the lubricating oil, are important to reduce combustion risk. The application of partially miscible oil rather than completely miscible oil can decrease R32 solubility but may deteriorate the heat transfer by the forming of pure oil layer, and thus the understanding of the stratification and flow boiling heat transfer characteristics of R32-partially miscible oil mixture is necessary. The purpose of this study is to experimentally investigate the stratification and flow boiling heat transfer characteristics of a mixture of R32 and partially miscible POE oil, and to propose a new heat transfer correlation. The experiments are carried out at evaporation temperature varying from -5 °C – 15 °C, total oil concentration varying from 1 % to 5 %, vapor quality varying from 0.1 – 0.9 and mass flux varying from 200 kg m-2 s-1 to 400 kg m-2 s-1.The results indicate that the stratification of R32-partially miscible oil mixture occurs at the high liquid oil concentrations, and an oil-poor layer and an oil-rich layer are involved in the stratified annular layer. R32-partially miscible oil mixture has higher flow boiling heat transfer coefficients than R32-completely miscible oil mixture due to the low viscosity of the oil-poor layer. A new flow boiling heat transfer correlation reflecting the effect of stratification is developed, and the predicted results agree with 91 % of the test results as the relative deviation ranges in ±20%.
期刊介绍:
The International Journal of Refrigeration is published for the International Institute of Refrigeration (IIR) by Elsevier. It is essential reading for all those wishing to keep abreast of research and industrial news in refrigeration, air conditioning and associated fields. This is particularly important in these times of rapid introduction of alternative refrigerants and the emergence of new technology. The journal has published special issues on alternative refrigerants and novel topics in the field of boiling, condensation, heat pumps, food refrigeration, carbon dioxide, ammonia, hydrocarbons, magnetic refrigeration at room temperature, sorptive cooling, phase change materials and slurries, ejector technology, compressors, and solar cooling.
As well as original research papers the International Journal of Refrigeration also includes review articles, papers presented at IIR conferences, short reports and letters describing preliminary results and experimental details, and letters to the Editor on recent areas of discussion and controversy. Other features include forthcoming events, conference reports and book reviews.
Papers are published in either English or French with the IIR news section in both languages.