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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。
In this paper, the experimental study of R12 flow boiling heat transfer in a horizontal tube was carried out. The experimental results show that the boiling heat transfer inside the tube is the same as that of the single-phase convective heat transfer, which has the effect of hot inlet. The experimental data from abroad are too large due to the failure to consider the heat import effect. The experimental results also show that the uneven heat transfer in the horizontal flow boiling is mainly affected by the flow structure. The average heat transfer coefficient of the cross section is closely related to mass flow rate, heat flux, mass dryness and evaporation pressure. Analysis of experimental data confirmed that the flow boiling heat transfer is due to the bubble generated due to the full development of nuclear flow boiling and two-phase convective evaporation composed of two parts. The experimental data in this paper can be well consistent with the existing heat transfer relations abroad.