Experimental Study Of Heat Thansfer Performance Of Mechanical Draft Salt-water Cooling Tower

Wet-cooling tower is widely applied in many fields of national economic, such as electronic systems, petroleum, chemical and process plant cycles and so on. It uses a combination of convective heat and mass transfer to cool water. Since a portion of the water is evaporated and this process requires much energy, the water is cooled fast. However, in arid areas where insufficient or no cooling water is available, the dry-cooling system is the only effective method of heat rejection. As the performance of dry-cooling cooler is determined by the drybulb temperature of the air, some problems such as the limited effort and high coal consumption in summer, winter air-cooling units antifreeze, arise in actual operation. The purpose of this paper is to study a new water-conserving wet-cooling tower:salt-water cooling tower.This paper mainly makes an experimental study of the heat transfer performance of cooling tower which relies on a double-effect LiBr absorption refrigerator system. Therefore, we have to make the system completed on the basis of the precious work so that it can work in the vicinity of the design conditions. Based on the theory of heat and mass transfer, the paper analyzes thermodynamic calculation methods of cooling tower and the water-conserving principles of salt-water cooling tower. With the experimental fitting formulas from literatures, the paper compares three properties(vapor pressure, density and thermal capacity) of four salt solutions (CaCl2、 MgCl2、LiCl and LiBr). We conclude that among the four the LiCl solution is the best choice for its lowest vapor pressure and biggest thermal capacity.The heat-transfer test of cooling tower with fresh water is also carried out. The experimental conditions include changing the circulating water flow rate and the temperature of inlet water. The flow rate series are as follows:16m3/h.15.5m3//h、15m3/h、14.5m3/h、14m3/h、13.5m3/h、13m3/h and12m3/h. The temperature series are as follows:31.5℃、30.5℃、29.5℃. By measuring several physical quantities, we calculate some parameters (cooling water range, the efficiency of cooling tower, cooling number, total heat rejection and water evaporation rate) of cooling tower and search the variation with G/L. We then compare the heat transfer performance of the cooling tower with CaCl2solution and fresh water. It’s concluded that when the inlet-temperature are32℃and28℃, the total heat rejection with salt solution is6%-8.6%and2%-7.7%lower than that with fresh water. Finally, taking600MW unit for example, we make a simple estimate about the water-saving rate and economy of salt-water cooling tower. It seems that if the amount of evaporation decreases half, the water-saving rate of salt-water tower is59.4%which is lower than that of air-cooling system. But when take the coal consumption into account, the latter is in a dominant position.