水平管外R404A降膜蒸发传热的实验研究

搭建了降膜蒸发实验台,研究了水平单管外的降膜蒸发传热特性。测试管为外径19mm、有效实验长度为2500mm的光滑管和强化管。实验采用R404A作为管外降膜蒸发工质,与管内热水进行换热。布液采用喷嘴喷淋的方式,通过21个喷口当量直径为2mm的喷嘴完成。分别在变饱和温度(0、5、10、15℃)、变热流密度(从8到30kW/m2)和变喷淋量(从0.07到0.11kg/(m·s)时进行实验,研究了降膜蒸发换热性能相应的变化情况,得到R404A的管外降膜蒸发换热的一些规律,这对降膜蒸发器的设计及应用具有一定的参考作用。

Experimental Investigation on the Falling Film Evaporation of R404A Outside a Horizontal Tube

An experimental study was carried out in order to investigate the heat transfer performance of falling film outside a single horizontal tube with a new test facility. Two types of commercial evaporation tubes were tested: a plain tube and an enhanced tube, which have the same outer diameter of 19 mm and the same effective test length of 2500 mm. Refrigerant 404A was used as working fluid to transfer heat with heating water inside the tube. Spraying feeding method was adopted by using 21 spray nozzles with the equivalent diameter of 2 millimeters. Experiments were performed at saturation temperatures of 0, 5, 10 and 15 oC, heat fluxes from 8 to 30 kW/m2 and mass flow rate per unit length of tube from 0.07 to 0.11 kg/ms. The regularity of falling film heat transfer performance of R404A outside a horizontal tube was obtained which is meaningful for the design and application of falling film evaporator.