水膜蒸发空冷器传热传质实验研究

发布时间：2018-04-14 04:28

本文选题：空冷器 + 传热　；参考：《华中科技大学》2015年硕士论文

【摘要】：水膜蒸发空冷器具有的高效传热、节能和节水特点使其应用日益广泛,但由于水风耦合作用的复杂性,其管外传热传质系数的确定一直以来都是设计计算的难点。本文在水膜蒸发空冷器小型实验台上,搭建了3管程的水膜蒸发空冷管束,配置了流量计、风速仪、干湿球温度计等传感器,并自主设计和配置了测量管外水膜温度的72个热电偶。在125个工况(5个热水流量×5个热水温度×5个迎面风速)下,测量了热水温度、管外空气温湿度和压力沿管程的分布,测量了管外水膜温度沿管程、管束宽度和管束高度的分布。根据测量数据,分析了不同工况对各管程空气状态的影响,对空气进出口比焓差、喷淋水平均温度和设备总压降的影响,以及对管内外平均传热系数的影响;描述了管外水膜温度场和传热传质系数场,探讨了工况参数对水膜温度场的影响,研究了从热水温度分布和水膜温度分布到热流密度,再到壁水传热系数的计算方法。实验及分析表明:水膜蒸发空冷器中,水膜温度沿流动方向呈锯齿状分布,且在上管程的波动幅度较大,在下管程波动趋于平缓;上管程的壁水传热系数和水风传质系数较大,下管程的水风传热系数较大;水膜蒸发空冷器的空气吸热量中蒸发潜热占85%左右,上管程和中管程主要为蒸发传热,下管程对流传热和蒸发传热大体相当;水膜温度峰值位置主要受迎面风速影响,风速越大,峰值越靠近管束顶部迎水面;热水温度对水膜温度的影响大于热水流量对水膜温度的影响;管外各处壁水传热系数hw(x,z)可由水膜温度场算得。
[Abstract]:Water film evaporative air cooler is widely used because of its high efficiency heat transfer, energy saving and water saving. However, due to the complexity of water-wind coupling, the determination of heat transfer coefficient of water film evaporator has always been a difficulty in design and calculation.In this paper, a water film evaporative air cooling tube bundle with 3 tubes is built on a small experimental bench of water film evaporator, with sensors such as Flowmeter, anemometer, dry-wet bulb thermometer and so on.72 thermocouples were designed and configured to measure the temperature of water film outside the tube.Under 125 working conditions (5 hot water flow rate 脳 5 hot water temperature 脳 5 direct wind speed), the distribution of hot water temperature, air temperature, humidity and pressure outside the tube was measured. The distribution of water film temperature along the tube side, the width of tube bundle and the height of tube bundle were measured.According to the measured data, the effects of different working conditions on the air state of each pipe, on the difference of specific enthalpy of air inlet and outlet, on the average temperature of spray level and on the total pressure drop of equipment, as well as on the average heat transfer coefficient inside and outside the pipe are analyzed.This paper describes the temperature field and heat and mass transfer coefficient field of water film outside the tube, discusses the influence of operating conditions on the temperature field of water film, and studies the calculation method of heat transfer coefficient from hot water temperature distribution and water film temperature distribution to heat flux, and then to wall water heat transfer coefficient.The experiment and analysis show that the water film temperature is sawtooth distribution along the flow direction in the water film evaporative air cooler, and the fluctuation amplitude in the upper tube is larger, and the fluctuation in the lower pipe tends to be gentle, and the wall water heat transfer coefficient and the water wind mass transfer coefficient of the upper tube side are larger.The heat transfer coefficient of the water wind in the lower tube side is larger, the latent heat of evaporation in the air of the water film evaporator is about 85%, the heat transfer between the upper and the middle pipe is mainly evaporative heat transfer, and the convection heat transfer and the evaporation heat transfer in the lower tube side are about the same.The peak position of water film temperature is mainly affected by the direct wind speed. The higher the wind speed is, the closer the peak value is to the water surface at the top of the tube bundle, the influence of hot water temperature on water film temperature is greater than the influence of hot water flow on water film temperature.The water heat transfer coefficient (HWX) can be calculated from the water film temperature field.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ021.3

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