STUDY ON THE CONDENSATION HEAT TRANSFER AND FLOW MECHANISM OF ALTERNATIVE REFRIGERANTS IN MICRO CHANNELS

本文旨在通过实验研究小直径平行通道内的局部换热和压降特性，为开发小型高效冷凝器提供理论依据。结果总结如下。(1)提出了Chischolm-Laird型关联。在该关联式中，第二项系数由21变为4.81，并<11>以出口干度和质量流速为参数，用X_代替了总压降实验结果中的X。结果表明，利用该关联式，对绝大多数总压降数据的预测值误差在±30%以内。(2)计算结果表明，该关联式的预测值与沿着流动方向的压力分布数据在±30%的误差范围内吻合良好。(3)将压降数据与Mishima-Hibiki的关联式进行比较，用X_（？<11>）数据还与t ...更多信息 Haraguchi等人的相关性。然而，数据不同意相关性。在本研究中，管的水力直径为0.7至0.9，三岛和Hibiki基于直径为1至4 mm的管的数据提出了相关性，但Haraguchi等人基于直径为8.5mm的管的数据提出了相关性，因此，数据与Mishima-Hibiki的相关性一致，但数据与Haraguchi等人的相关性不一致。(4)将传热数据与Moser等人的关联式进行了比较，在质量流速大于300 kg/m^2s时，数据与关联式在±30%误差范围内一致，而在质量流速小于200 kg/m^2s时，数据与关联式不一致。这是因为Moser等人没有考虑自然对流凝结换热的影响，因此，在低质量流速的情况下，当自然对流的影响不小时，很难用这种关系式来表示这种现象。(5)这些数据也与Haraguchi等人的相关性不一致，其基于直径为8.5mm的管的数据。然而，使用Mishima-Hibiki的压降乘数因子的关联式代替Haraguchi等人的传热关联式中的压降的关联式，大多数数据在± 50%内与该修正的传热关联式一致。这是因为Haraguchi等人考虑了强制对流和自然对流冷凝传热，因此当考虑管径的影响时，预测精度变得更高。(6)根据结果（4）和（5），当质量速度低时，即使在小直径管的情况下，也存在重力的影响。少

In this study, it is aim to contribute to develop the very small and high performance condensers by clarifying the characteristics of local heat transfer and pressure drop in parallel channels with small diameter experimentally. The results are summarized as follows.(1) The Chischolm-Laird type correlation is proposed. In this correlation, the coefficient of second term changed from 21 to 4.81 and using X_<11> instead of X from the experimental results of total pressure drop with changing the outlet quality and mass velocity as a parameter. As a result, by using the correlation, predicted values are within ±30% error for most of all data of total pressure drop.(2) It is confirmed that the predicted values of the present correlation agree with the data of pressure distribution along the flow direction within ±30% error.(3) Compared the pressure drop data with the correlation of Mishima-Hibiki, the data agree with the correlation within ±30% by using X_<11>. The data also compared with t … More he correlation of Haraguchi et al. The data, however, don't agree with the correlation. In this study, hydraulic diameters of the tubes are 0.7 to 0.9, Mishima and Hibiki proposed the correlation based on the data of the tube with 1 to 4mm in diameter, but Haraguchi et al. proposed the correlation based on the tube with 8.5mm in diameter, therefore, the data agree with the correlation of Mishima-Hibiki, however, the data don't agree with the correlation of Haraguchi et al.(4) Compared the heat transfer data with the correlation of Moser et al., the data agree with the correlation within ±30% error in the case of the mass velocity above 300kg/m^2s, but disagree with the correlation in the case of the mass velocity below 200kg/m^2s. This reason is that Moser et al. didn't take account of the influence of the natural convective condensation heat transfer, and so, in the case of low mass velocity, when the influence of natural convection isn't small, it is hard to present the phenomena by using this correlation.(5) The data also disagree with the correlation of Haraguchi et al., which is based on the data of the tube of 8.5mm in diameter. However, using the correlation of Mishima-Hibiki for the pressure drop multiplier factor instead of the correlation of Haraguchi et al. for the pressure drop in their heat transfer correlation, most of all the data agree with this modified heat transfer correlation within ±50%. This reason is that Haraguchi et al. take account of both of the forced convective and natural convective condensation heat transfer, and so predicting accuracy becomes higher when the influence of tube diameter is took account of.(6) From the results (4) and (5), there is the influence of gravity even in the case of small diameter tubes when the mass velocity is low. Less