【作者】 许旺发；

【导师】 张旭；

【作者基本信息】 同济大学 ， 供热供燃气通风及空调工程， 2007， 博士

【摘要】 板式湿式空冷器结合了空冷、蒸发冷却与板式换热器的技术优点，在夏季气温较高时，启用喷淋装置湿工况运行，采用喷淋水蒸发冷却强化空冷器换热以达到降低工艺流体出口温度的目的。板式湿式空冷器是一种新型的冷却设备，具有广阔的市场应用前景。本文通过理论分析与实验研究，对湿式空冷器传热传质过程、空气湿球温度迁移特性、以及结构与运行优化等关键技术问题进行了深入探讨，为板式湿式空冷器的推广应用奠定一定的理论与实验基础。本文分别建立了壁面完全润湿传递模型与同时考虑空气中夹杂液滴且壁面不完全润湿条件下的板式湿式空冷器传递模型，数值计算得到传递模型应用刘易斯关系式对冷却效率的预测相对误差小于2％；提出了既适用于热流体为热水、也适用于热流体为空气的湿空气过程平均斜率的确定方法。分析结果表明壁面润湿率对冷却性能具有显著影响，而夹杂在空气中的液滴对传递过程的影响相对较小，工程计算可忽略夹杂液滴对传递模型的影响。引入湿球比热容和湿球换热系数，建立了板式湿式空冷器湿球温度迁移模型。分别得到了平行流型式微分方程组的解析解与交叉流型式的近似解析解，实验验证了该解析解具有较高的计算精度；探讨了空气干湿球温度与喷淋水温的迁移特性；分析得到基于湿球温度迁移模型的对数平均温差法在湿式空冷器的设计与校核计算中是适用的，给出了空气湿球换热系数与空冷时空气对流换热系数比值的理论与实验确定方法，比值系数理论值与实验值比较最大相对误差小于7％。提出了湿式空冷器干湿工况运行界限温度的确定方法，建立了板式湿式空冷器多目标结构优化模型，结合实验得到的干湿工况下板束内外侧阻力、传热传质关联式以及喷淋水膜对流换热关联式，该优化模型可用于干湿工况运行界限温度与结构参数的优化。更多还原

【Abstract】 The plate wet air cooler combines the technical advantages of plate heat exchangers with dry cooling and evaporative cooling. When hot climates in summer, water spraying runs and outlet temperature of hot fluids plays down because heat transfer is enhanced by evaporative cooling. The plate wet air coolers are new type of cooling equipments and have a great market foreground. By theoretical and experimental methods, some key problems were lucubrated, such as heat and mass transfer, transfer characteristic of the wet bulb temperature, optimization for the frame and running for the plate wet air cooler. The research results can be used to popularize the plate wet air cooler.Transfer models were developed with overall wetting condition and part overall wetting and some water droplets larding in air condition. The relative errors of efficiency prediction are small than 2 percent because Lewis factor is equal to 1.The method to determine the mean saturated line slope of moist air was presented, which can apply to hot water and air. The wall wetting rate has remarkable effect on cooling efficiency. But water droplets in air effects are small and can be ignored in engineering calculations.Introducing the wet bulb specific heat capacity and the wet bulb heat transfer coefficient, a new mathematical model for the plate wet air cooler was developed based on the wet bulb temperature transfer characteristic. Analytical solutions for the parallel-flow and approximate analytical solutions for the cross-flow were presented. The solutions were found to be good agrees with experimental results. The transfer characteristic of air dry/wet bulb temperature and spraying water temperature were discussed. The LMTD method based on this mathematical model is applicable to design and verify for the plate wet air cooler. The ratio of the wet bulb heat transfer coefficient to the heat transfer coefficient under air-cooled conditions was investigated theoretically and experimentally. The relative errors of the ratio between theoretical and experimental valves are small than 7 percent. The method to determine the limited temperature for dry/wet running conditions was presented. Multi-object frame optimization model were developed. Combined with the thermal and hydraulic correlations for dry/wet conditions of plate wet air cooler, the optimization model can be used to optimize the dry/wet limited temperature and frame parameters.更多还原