超温水体蒸发系数通用公式的研究与应用

Study and application of universal formula for evaporation coefficient of heated water bodies

在环境参数可控风洞中对影响蒸发的风速、水气温差、水温、相对湿度等物理量进行系统试验。试验结果表明蒸发系数取决于风速的强迫对流和水气温差的自由对流。分析试验数据得到了水面蒸发系数的建议公式和相应的水面散热系数公式以及附加蒸发系数公式。用参数变幅很大的天然水体和受纳废热水体的实测资料和研究成果检验了建议公式的通用性。建议公式已为DL/T5084—98《电力工程水文技术规程》及GB/T50102—2003《工业循环水冷却设计规范》推荐应用于计算水面蒸发、水面散热及附加蒸发。

Experiments were conducted in a specially designed wind tunnel with concerned environmental parameters precisely controllable. The emphasis was placed on some influencing factors on evaporation, including the wind velocity, the air-water temperature difference, the water temperature, and the relative humidity. The result shows that the evaporation coefficient mainly depends on the wind velocity-induced forced convection and air-water temperature difference-induced free convection. By analysis of experimental data recommended, formulas for the surface evaporation coefficient, the coefficient of heat dissipation from water surface, and the additional evaporation coefficient were derived. The universality of the formulas for evaporation coefficient was tested with the measttred data and research results about natural water body and heated waste-water with the values of relevant parameters varying in a large range. The formulas were accepted by Technical Code of Hydrology for Electrical Power Projects （DL/T 5084-98） and Code for Design of Cooling for Industrial Recirculating Water （GB/T50102-2003） for calculation of water surface evaporation, heat dissipation from water surface, and additional evaporation.