论文部分内容阅读
搭建适用于多种结构微小通道的沸腾换热试验系统,研究了制冷剂R134a在当量直径分别为0.63mm和0.72mm的多孔扁管微小通道内的沸腾换热特性。试验参数包括制冷剂质量流率为82~621kg/(m~2·s),饱和压力为0.22~0.63MPa,干度为0~1;采用等热流密度方式加热,热流密度范围为9.7~64kW/m~2。结果表明:R134a在扁管内沸腾换热中,当干度在0~0.6区间时,微小通道的传热系数明显高于常规通道,换热类型主要为核态沸腾,传热系数随热流密度和饱和压力的增大而增大,与质量流率关系不大;当干度大于0.6之后,传热系数随着干度的增大急剧减小,且在此干度区间,传热系数受热流密度和饱和压力影响较小,而受质量流率的影响相对较大。利用该结论和公开文献中R134a沸腾换热试验数据对Gungor-Winterton公式进行改进,改进后的公式对所有试验点的平均相对误差为-1.17%,平均绝对误差为19.24%,预测精度有了明显提高。
The boiling heat transfer test system is designed for a variety of microstructures. The boiling heat transfer characteristics of refrigerant R134a in the porous microchannels with equivalent diameters of 0.63mm and 0.72mm are studied. The experimental parameters include the mass flow rate of refrigerant is 82 ~ 621kg / (m ~ 2 · s), the saturation pressure is 0.22 ~ 0.63MPa and the dryness is 0 ~ 1. The isothermal heat flux density is 9.7 ~ 64kW / m ~ 2. The results show that the heat transfer coefficient of R134a is significantly higher than that of conventional channels when the dryness is in the range of 0 ~ 0.6, and the type of heat transfer is mainly nucleate boiling. The heat transfer coefficient varies with the heat flux density and When the dryness is greater than 0.6, the heat transfer coefficient decreases sharply with the increase of the dryness, and in this dryness interval, the heat transfer coefficient is affected by the heat flow The effect of density and saturation pressure is small, but the influence of mass flow rate is relatively large. The Gungor-Winterton formula is improved by using the R134a boiling heat transfer test data in this conclusion and in the open literature. The improved formula has an average relative error of -1.17% and an average absolute error of 19.24% for all the test points, and the prediction accuracy is obvious improve.