The falling film flow has gained wide attention in recent years, due to its extraordinary performance in different heat exchangers in terms of high heat transfer coefficient and low energy consumption. In this paper, a series of experiments are conducted in a smooth tube and a finned tube respectively, in order to investigate the heat transfer characteristics of the cooling falling film flow outside vertical tubes in open rack vaporizer (ORV). Different control variables affecting the heat transfer characteristics are studied, including the mass flow rate and the temperature of water, the heat flux and the tube shape. The experimental data are compared with the predicted values from existing correlations, and all of them show large discrepancies. Therefore, a new correlation is proposed to accurately predict the heat transfer coefficient of the falling film flow based on the experimental data. The predicted values of the new correlation are within an error band of 10% of the experimental data. The study may provide reference for the research on the falling film flow and effective design and operation of ORV.

由于降膜流在高传热系数和低能耗方面在不同的换热器中具有非凡的性能，因此近年来受到了广泛的关注。在本文中，分别在光滑管和翅片管中进行了一系列实验，以研究开放式机架蒸发器（ORV）中垂直管外冷却降膜流的传热特性。研究了影响传热特性的不同控制变量，包括水的质量流量和温度，热通量和管形。将实验数据与现有相关性的预测值进行比较，所有这些都显示出较大的差异。因此，提出了一种新的相关性，可以根据实验数据准确地预测降膜流的传热系数。新相关性的预测值在实验数据的10％的误差范围内。该研究为ORV降膜流动研究和有效设计与运行提供参考。