中文摘要：

随着节能减排要求的不断提高,制冷系统用铜管的换热性能成为研究重点。为得到3种不同规格的内螺纹管管内冷凝的换热与流动阻力特性,以R134a为工质,研究质量流速和螺纹管几何参数等对冷凝换热的影响。实验结果表明制冷剂侧换热系数与压降均随着质量流速的变化而增加,其中小流速下的增幅明显小于大流速下的增幅。使用hr/Δp作为综合性能评价的指标,发现6.35 mm管径中hr/Δp先下降后上升的趋势较为明显,转折点质量流速约为600 kg·m-2·s-1,在质量流速大于此点后,换热系数的增幅超过了压力损失的增幅,表明较小管径铜管在较大质量流速区间内综合性能较强。

英文摘要：

With the continuous improvement of energy saving and emission reduction requirements, the heat transfer performance of copper pipes used in refrigeration systems becomes the research focus. To obtain the heat transfer and flow resistance characteristics of three types of internally threaded tubes, influence of mass velocity and geometrical parameters of the internally threaded tubes on condensation heat transfer was investigated by using R134a as the working substance. The experimental results show that both the heat transfer coefficient and pressure drop increase with the mass velocity, and the increase at low velocity is much less than that at high velocity. Using hr/△p as the index of comprehensive performance evaluation, it is found that the trend of hr/Ap decreases first and then increases in the 6.35 mm tube, and the turning mass velocity is about 600 kg · m-2 · s-1 When the mass velocity is greater than the point, the increase in the heat transfer coefficient exceeds that in pressure loss, it shows that the comprehensive performance of smaller diameter pipes in larger mass flow rate range is higher.