本文实验研究了非共沸混合制冷剂R134a/R245fa（质量比为0.7/0.3）在长度为45 mm、65 mm的平行微通道内的流动沸腾特性。微通道由30个截面为0.5 mm×0.5 mm矩形微通道组成。得到了质量流速在542.22-995.56kg·m^-2·s^-1、热流密度在4.9-100.2 W·cm^-2时的流动沸腾传热系数,并对R134a/R245fa和R134a的换热系数进行对比,结果表明热流密度、质量流速、通道长度对换热系数均有影响。考虑R134a/R245fa相变时的附加传质阻力对换热的影响下,在纯工质关联式中引入混合物影响因子,得到了适用于本实验工况下R134a/R245fa的关联式。
In the present study, the flow boiling heat transfer characteristics of zeotropic mixtures R134 a/R245 fa which in the length of micro-channels on the test sections were 45 mm and 65 mm, were experimentally investigated. Both of the test sections included 30 parallel rectangular microchannels with the cross-section of 0.5 mmx0.5 mm. The flow boiling heat transfer coefficients of working fluids were obtained under the experimental conditions, heat flux and mass flux ranging from 4.9-100.2 W·cm^-2 and 542.22-995.56 kg·m^-2·s^-1, respectively. The flow boiling heat transfer coefficients of R134 a/R245 fa as well as its pure component R134 a was experimentally investigated. It was found that the heat transfer coefficient was a strong function of heat flux, mass velocity and channel length.Taking account of the influence of additional mass transfer resistance of R134 a/R245 fa, the new correlation was developed with the introduction of mixture factor Cmix.
Journal of Engineering Thermophysics
heat transfer coefficients
heat transfer characteristics