R12在水平管内流动沸腾换热实验研究

本文对R12在水平管内流动沸腾换热特性作了实验研究。实验结果表明,管内流动沸腾换热与单相对流换热一样,存在热进口效应,国外早期的实验数据由于未能考虑热进口效应而偏大。实验结果还表明,水平流动沸腾周向不均匀换热主要受流动结构影响;截面平均换热系数则与质量流速、热流密度、质量干度和蒸发压力密切相关。分析实验数据证实,流动沸腾换热是由气泡产生而引起的流动充分发展核态沸腾和双相对流蒸发两部分组成的。本文的实验数据与国外已有的换热关系式能较好吻合。

AN EXPERIMENTAL INVESTIGATION OF R12 FLOW BOILING HEAT TRANSFER IN A HORIZONTAL TUBE

The flow boiling heat transfer of refrigerant 12 in an electrically heated horizontal tube is investigated, The experimental results indicate that the heat entrance effect must be taken into account for flow bolling heat transfer in the tube. The early expertmental data which, neglected the entrance effect are larger than the real values. The investigations also illustrate the effect offlow patierns on non-uniform heat transfer around the perimeter of the tube. The perimeter averaged heat transfer coefficients depend on heat flux, mass flow rate, quality and saturated pressure. It is proved that heat transfer of flow boiling consists of the fully developed nucleate boiling heat transfer and the convcctive evaporation heat transfer. The experimental data are in good greement with some existing correlations in the foreign literature.