分离型热管充液率运行边界探讨

Research on the Envelope of Initial Filling Ratio for Separate Heat Pipe

首先基于质量守恒原理推出充液率方程,综合考虑分离型热管的尺寸、工质蒸发温度及热输入量对充液率的影响,同时结合两相流换热流动特性,引入工质液膜速度沿膜厚度方向上的分布关系,建立一维、稳态数学模型,计算了分离型热管充液率的上、下边界,并分析了蒸发段长度、工质蒸发温度及热输入量对充液率运行边界的影响.结果表明蒸发段长度对充液率上边界值几乎无影响,但是对下边界的影响很大;工质蒸发温度升高,容易达到下边界值.对于不同的工质,热管可运行的充液率范围不同,本文列举了经常使用的水和甲醇,结果表明甲醇的充液率范围较大.通过实验对模型结果进行验证,表明模型与实验能够较好的吻合.

The filling ratio of the working fluid in the evaporator section was determined by the overall mass balance in the separate heat pipe. A one-dimensional steady-state model was developed to determine the upper and the lower running boundaries of the initial filling ratio of the working fluid, the functions of separate heat pipe dimension, type and vapor temperature of the working fluid and power throughput, combined with the two-phase heat exchange characteristics and the distribution of the liquid film velocity along with the liquid film thickness direction. Therefore, the upper and the lower boundaries of the separate heat pipe were obtained. A parametric analysis was performed to investigate the effects of the length of the evaporator,vapor temperature, and power throughput on the critical values of the upper and the lower boundaries. The results showed that the length of the evaporator had almost no influence on the upper boundary, but great effect on the lower boundary. The increase of vapor temperature led to the easier arrival of the lower boundary. Moreover, different operation envelopes of the separate heat pipe were connected with different working fluids. Water and methanol were used separately, and operation envelope with methanol was larger. An experiment was done to verify the simulated results. It was concluded from the test results that the experimental data agreed well with the predicted data. 