水平管束低压降膜蒸发换热特性研究

Research on Heat Transfer Characteristics of Falling Film Evaporation on Horizontal Tubes at Low Pressure

本文主要对水平管在较低压力的降膜蒸发进行研究,设计了滴淋降膜蒸发试验台,以去离子水为工质,在不同的喷淋流量、温度和压力下,对水平管束进行降膜蒸发传热实验。试验结果表明,在较低过冷度下,管外换热系数和总传热系数随着喷淋流量的增大变化不明显。当过冷度增加时,管外换热系数和总传热系数变小,但随着喷淋流量的增大而明显增大。换热系数随过冷度下降而增加,过冷度为零时,换热系数最大。此外,蒸发器水流量对换热几乎没有影响。

The experimental investigation for the heat transfer performance of the falling film evaporation on horizontal tubes at lower pressure was conducted. With deionized water for the working fluid, the experiments were done by using different spray flow rate, evaparating temperature and pressure. The test results show that the outer tube heat transfer eoefficient and the total heat transfer coefficient keeps almost constant while flow increases, but when the subcooling degree increases to a certain extent, the spray flow rate has obvious effect on the heat transfer of falling film evaporation. Flow rate of water in the tubes of evaporator almost has no effect on heat transfer.