The heat transfer characteristics of fin-and-tube heat exchangers with 5 mm diameter tubes under wet conditions were investigated by experiments on 11 louver fin-and-tube heat exchangers. The effects of fin pitch and inlet relative humidity on air-side performance were analyzed. The results indicated that the effect of inlet relative humidity on the heat transfer rate is small, and heat transfer rate decreases with the increase of fin pitch, which is more obvious than that of fin-and-tube heat exchanger with 7 mm or larger diameter tubes. The water bridge was observed at the bottom of fin in experiments;however, it did not occur on the fin with 7 mm or large diameter tubes. A correlation for j factor was developed to predict the heat transfer performance of fin-and-tube heat exchanger with 5 mm diameter tubes. The deviations of the proposed j correlation are within ±20%.% 在湿工况下，对11个采用百叶窗翅片的5 mm管换热器进行了实验研究，并分析了翅片间距、进口空气相对湿度等因素对空气侧换热性能的影响。研究结果表明：换热量随翅片间距的增加而减小，且比7 mm管或更大管径换热器更明显；换热量受进口空气相对湿度的影响小；在翅片底部出现水桥，而在7 mm管或者更大管径换热器中不曾出现。根据实验数据开发了预测5 mm翅片管换热器换热性能的j因子关联式，误差在±20%以内。
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