Abstract
Evaporative cooling equipment has advantages of energy and water conservation and compact structure, is widely used in various industrial sectors. To better characterize the heat transfer capacity of the evaporative cooling process, the falling-film evaporation heat transfer process outside horizontally closed arranged tubes (horizontal tubes plate) was analyzed. A theoretical model was established to divide the total heat transferred by the tube wall into two parts: the convective heat transfer of the air and that of the liquid film. The latter was divided into three parts: the heat transferred by the convective heat transfer between the liquid film and the air, the mass and latent heat transfer between the liquid film and the air, and the heat absorbed by the rise in temperature of the liquid film. Experiments were performed with both smooth and ribbed tubes. Correlations of the heat transfer coefficients between the tube wall surface and the air and between the tube wall surface and the liquid film and the coverage rate of the liquid film were obtained. The experimental results indicated that using ribbed tubes effectively enhanced the liquid film coverage on the tubes, resulting in a maximum reinforcement of 122.73% compared with that of smooth tubes. Moreover, the experimental results verified the correlation equations, with the deviation between the calculated and experimental results was within ±10%.
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