Experimental Research On Heat Transfer Characteristics Of Climbing Film Evaporation For Desalination Device

As growing of population in the world and development of industry and agriculture, fresh water demand is growing day by day. Solving the problem of fresh water depletion is becoming a crucial challenge. Desalination technique, as a most effective way to supply fresh water, is adopted by more and more countries. Vertical tube climbing film technique becomes an effective heat transfer way for the characteristics of high heat transfer rate, small temperature difference and good heat transfer performance, especially for utilization of low temperature exhaust heat.The mini-type vertical tube climbing-film evaporation desalination device mentioned in this paper can use directly the exhaust heat of diesel engine as the heat resource. The liquid film is formed by the traction force which is generated by upon-moving steam flow. The advantage makes the climbing-film evaporation desalination device can generate stable film, even in an awag condition, such as sea-going vessel.At first, the theoretical analysis on heat transfer mechanism of climbing film evaporation is carried out. Then, a minitype climbing film evaporation test rig is built for the measuring of heat transfer rate in order to get the data of various influencing factors on climbing film.HAL77-2A aluminum brass tubes (φ20×2, length of evaporation zone: 2000mm) are used as the heat transfer tube, and the experiment is carried out with the absolute pressure from 0.01MPa to0.02MPa, and the heat transfer temperature difference from 5℃to 15℃. The factors and tendency influencing climbing film evaporation are analyzed by recording and adjusting the parameters of hot water inlet temperature, evaporation tube inner temperature, evaporation zone liquid level, condensation zone liquid level and so on.The experiment results indicate that higher temperature difference can bring better heat transfer effect on the condition of same pressure and liquid level. On the same pressure and temperature difference condition, if without the drying out phenomena, the lower liquid level is good for climbing film evaporation. On the same temperature difference and liquid level condition, lower absolute pressure benefits heat transfer, but the vacuum degree is higher..