升膜蒸发器管内传热性能的实验研究

Experimental study of heat transfer and flow visualization in climbing film evaporation pipe

为了探究热流密度、真空度和流量对升膜蒸发器传热性能的影响,建立了升膜蒸发系统传热实验平台,实验所用升膜管管长2 800 mm,升膜管采用TP2紫铜管,工作介质为纯水,升膜管采用电加热方式加热;研究了热流密度(4.20 k W/m^2≤q≤16.81 k W/m^2)、流量(40 L/h≤M≤200 L/h)和真空度(20 k Pa≤P≤40 k Pa)对升膜管传热特性的影响。结果表明,升膜管沿轴线方向内壁温度是先急速增大到最大值然后再逐渐减小。当热流密度为6.05 k W/m^2,流量为80 L/h时,相对应的管内换热系数最大。流量为40~80 L/h时,流量越大相对应的管内换热系数越大。真空度越大,升膜管的内壁温度越低。

In order to explore the effect of heat flux, vacuum degree and flow rate on the heat transfer of climbing film evaporator, the heat transfer experimental platform of climbing film evaporation system is established. The length of the climbing film pipe is 2800 mm. The climbing film pipe is TP2 copper tube. The working medium is water. Electric heating is employed in the climbing film evaporation pipe. The effect of heat flux （4. 20 kW/m2 ≤ q ≤ 16. 81 kW/m2 ）, flow rate（40 L/h≤M≤200 L/h） and vacuum degree（20 kPa≤P≤40 kPa） on fluid flow pattern and heat transfer of the climbing film pipe are studied. The results show that the inner wall temperature along axis direction of copper climbing film tube firstly increases rapidly to a maximum and then decreases gradually. When the heat flux density is 6. 05 kW/m2 and flow rate is 80 L/h, the corresponding tube heat transfer coefficient is the largest. When the flow rate is 40 L/h to 80 L/h, a greater flow rate leads to a larger tube heat transfer coefficient. But higher vacuum degree results in a lower inner surface temperature of copper climbing film tube.