Performance Of Closed Heat Source Tower Under Spraying Conditions

Currently,with the adjustments of the national policy and energy structure,the application of renewable energy has developed strongly in the field of industrial and civil construction as an important way of saving energy and reducing consumption.Based on the analysis of the development trend of cold and heat source scheme and the energy structure adjustments,and the adaptation of the coil heat exchanger in low temperature,heat source tower heat pump technology arises at the historic moment.With the technologies of wide fins and small temperature difference and spraying frost prevention,the closed heat source tower greatly reduces the risk of frost.By inputting a small amount of high grade energy,the closed heat source tower absorbs sensible heat and latent heat from the environment in winter and releases heat as a traditional closed cooling tower in summer,greatly improves the efficiency of the equipment.The successful application in engineering practice of closed heat source tower well verifies the feasibility and the application prospect,but also it has exposed many problems,such as the concentration of spraying solution,which need to make in-depth research from the aspect of theory and technology.Firstly,the experiment platform of the closed and open heat source tower heat pump were set up,then the operation parameters of the open heat source tower and the closed heat source tower under spraying condition were measured under low temperature and high humidity conditions in winter.Based on the experimental data,the following three aspects were done mainly:(1)The heat absorption efficiency was defined to characterize the performance of the heat source tower,which reflected the proximity of heat transfer capacity of the actual operation condition to the ideal operation;(2)Under the same conditions,the performances of closed and open heat source tower were compared,and the optimization methods to improve the heat transfer performance of the closed heat source tower were recommended by the liquid gas ratio theory;(3)Heat and mass transfer numerical model of the closed heat source tower was built under the spraying condition,and the reliability of the model was verified by the experimental results;Then the differences of the performance were analyzed by comparing the lewis factor of real value to the lewis equation.The results showed that the heat absorption efficiency of the closed and open heat source tower is about 0.16～0.16,0.35～0.55 respectively;Under the same conditions,the temperature differences of heat transfer of open heat source tower is higher than closed heat source tower about 1.0～2.0℃;Based on the liquid gas ratio theory,increasing the velocity to improve the performance of closed heat source tower was not economical,because the increase of the velocity field will produce excess wind waste in specific solution flow.The numerical model of closed heat source tower under spraying condition had high reliability,which could be used to simulate the performances of closed heat source tower;Under spraying condition,using the lewis relation would underestimate the ability of the latent heat transfer under the low temperature and high humidity conditions,and the maximum deviation of the heat absorption efficiency was about 10.6%,the heat mass analogy was recommended to calculate the numerical model to improve simulation accuracy.Within the scope of the experiment,the value of lewis factor was about 0.77～0.86.