Stratification and heat transfer characteristics for R32-partially miscible oil mixture flow boiling inside a micro-fin tube

IF 3.5 2区 工程技术 Q1 ENGINEERING, MECHANICAL International Journal of Refrigeration-revue Internationale Du Froid Pub Date : 2024-08-06 DOI:10.1016/j.ijrefrig.2024.08.005
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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%.
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微型鳍管内沸腾的 R32 部分混油混合物流的分层和传热特性
室内空调中常用的 R32 具有易燃性,如何减少充注量(如减少制冷剂在润滑油中的溶解)对于降低燃烧风险非常重要。使用部分混溶油而非完全混溶油可以降低 R32 的溶解度,但可能会因形成纯油层而恶化传热效果,因此有必要了解 R32 部分混溶油混合物的分层和流动沸腾传热特性。本研究旨在通过实验研究 R32 和部分混溶 POE 油混合物的分层和流动沸腾传热特性,并提出一种新的传热相关性。实验条件为蒸发温度在 -5 °C - 15 °C 之间变化,总油浓度在 1 % - 5 % 之间变化,蒸汽质量在 0.1 - 0.9 之间变化,质量通量在 200 kg m-2 s-1 - 400 kg m-2 s-1 之间变化。由于贫油层的粘度较低,R32-部分混油混合物的流动沸腾传热系数高于 R32-完全混油混合物。新的流动沸腾传热系数反映了分层的影响,预测结果与 91% 的测试结果一致,相对偏差在 ±20% 之间。
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来源期刊
CiteScore
7.30
自引率
12.80%
发文量
363
审稿时长
3.7 months
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.
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