An experimental study on falling-film evaporation on horizontal rectangular tubes, the external geometry of extruded flat, microchannel tubes, was conducted. Previous falling-film evaporation studies have focused on horizontal and vertical round tubes, and the usage of microchannel tubes provides a promising new heat exchanger design option. The test sections used in this study have external dimensions of 203 × 1.42 × 27.4 mm (length × width × height) and were tested with water as the refrigerant. Heat transfer coefficients were measured for saturation temperatures from 10 to 30°C, test section spacings from 5 to 15 mm, heat fluxes from 10 to 20 kW m⁻², and film Reynolds numbers of 48 to 544. This paper, Part I, reports the experimental methodology and the results, while in the companion paper, Part II, models for predicting heat transfer are presented.

对水平矩形管上的降膜蒸发进行了实验研究，水平矩形管是挤压的扁平微通道管的外部几何形状。以前的降膜蒸发研究集中在水平和垂直圆形管上，而微通道管的使用提供了一种有希望的新的热交换器设计选择。本研究中使用的测试部分的外部尺寸为203×1.42×27.4 mm（长×宽×高），并以水作为制冷剂进行了测试。在10至30的饱和温度下测量了传热系数°C，测试段间距为5到15 mm，热通量为10到20 kW m ^-2，薄膜雷诺数为48到544。本文第一部分报告了实验方法和结果论文第二部分介绍了预测传热的模型。