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

本研究旨在通过实验研究小直径平行通道的局部换热和压降特性，为开发超小型高性能冷凝器做出贡献。结果总结如下：(1)提出了Chischolm-Laird型相关。在此关联关系中，第二项系数由21变为4.81，用X_<11>代替以改变出口质量和质量速度为参数的总压降实验结果中的X。结果表明，利用相关性对大部分总压降数据的预测值误差在±30%以内。(2)在±30%的误差范围内，证实了本相关性预测值与沿流向压力分布数据吻合。(3)将压降数据与Mishima-Hibiki相关性进行比较，采用X_<11>时，数据与相关性在±30%以内一致。该数据还与Haraguchi等人的数据进行了比较。然而，数据并不支持这种相关性。在这项研究中,液压管的直径是0.7到0.9,三岛和科诺提出了相关数据的基础上1到4毫米直径的管,但是Haraguchi等人提出了基于相关性的管直径8.5毫米,因此,Mishima-Hibiki同意相关的数据,但数据不同意的相关性Haraguchi et al。(4)相比传热数据的相关性莫泽et al .,在质量速度大于300kg/m^2s的情况下，数据与误差在±30%以内的相关性一致，而在质量速度小于200kg/m^2s的情况下，数据与相关性不一致。这是因为Moser等人没有考虑自然对流凝结换热的影响，所以在低质量速度的情况下，当自然对流的影响不小时，很难用这种相关性来表示现象。(5)该数据也与Haraguchi等人基于直径为8.5mm管的数据得出的相关性不一致。然而，使用Mishima-Hibiki对压降乘数因子的相关性，而不是Haraguchi等人在传热相关性中对压降的相关性，大多数数据都在±50%的范围内同意这种修正的传热相关性。这是因为Haraguchi等人同时考虑了强迫对流和自然对流冷凝换热，因此在考虑管径影响的情况下，预测精度更高。(6)从(4)和(5)的结果可以看出，即使是小直径管，在质量速度较低的情况下，重力的影响也是存在的。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