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实验研究了R245fa在水平单管外的降膜蒸发换热特性。实验采用的蒸发管是直径为19mm的双侧强化管,有效长度为2,500mm。本文采用威尔逊法获得管内换热特性,采用热阻分离方法获得管外降膜蒸发换热系数数据;进行了变热流密度(15kW∕m~2~55kW∕m~2)、变蒸发温度(30℃~50℃)和变喷淋流量(0.08kg/(m·s)~0.16kg/(m·s))的实验,获得了管外降膜蒸发换热系数及其变化规律。研究结果表明:随着热流密度的增加,传热系数先增大后减小;随着蒸发温度的升高,传热系数逐渐增大;随着喷淋流量的增加,传热系数先增大后减小。
Experimental study of R245fa falling film evaporation heat transfer characteristics outside the horizontal single tube. The tube used in the experiment was a double-sided tempered tube 19 mm in diameter with an effective length of 2,500 mm. In this paper, the heat transfer characteristics of the tube were obtained by the Wilson method, and the data of the falling film evaporation heat transfer coefficient outside the tube was obtained by thermal resistance separation method. The heat transfer density (15kW / m ~ 2 ~ 55kW / m ~ 2) ℃ ~ 50 ℃) and variable shower flow rate (0.08kg / (m · s) ~ 0.16kg / (m · s)). The results show that the heat transfer coefficient first increases and then decreases with the increase of heat flux density. With the increase of evaporation temperature, the heat transfer coefficient increases gradually. As the spray flow rate increases, the heat transfer coefficient increases first After the decrease.