Thermal Performance Analysis Of A Double Direct Contact Humidification-Dehumidification Desalination System

Because the advantages of low energy-consumption and low cost,humidificationdehumidification(HDH)system has been widely concerned in recent years.The research on the optimization of HDH system has always been emphasized,for the reason that the surface heat exchanger was always used as the dehumidifier,and significant pressure drop,corrosion and blocking resulting from the seawater increased the operation cost and reduced the lifetime of the desalination system.Direct contact heat and mass transfer can effectively improve the efficiency of heat and mass transfer,it was verified that such direct contact dehumidifier was a good choice to improve the general application of the HDH desalination systemby cleaning up former research.According to the theory of heat and mass transfer,a novel double direct-contact HDH system was built to solve the problems of the traditional HDH system.A mathematical model of the process was developed to obtain the characteristic curve and optimal parameters.Specific tasks accomplished including the followings:The output of fresh water and the power of electric heater increase with the increase of the amount of the seawater,but the system gained output ration(GOR)was decrease.GOR increases with the increase of the amount of sprinkler fresh water in the range of simulated working conditions.GOR of the spray fresh water amount of 0.045kg/s is 2.72 times than that of 0.025kg/s.The system GOR decreases with the increase of air flow.When the air flow is 0.013kg/s,GOR is 1.16 times than that of 0.017kg/s.The system GOR decreases with the increase of sprinkler seawater temperature in humidifier.When the sprinkler seawater temperature is 75oC,GOR is 1.14 times than that of 85oC.Specific entropy of the system also be studied,it was found that the changing trend of specific entropy and GOR is opposite.The system best operating point was get through orthogonal analysing and a platform of double direct-contact HDH system was built by the best operating point.The reliability of the numerical simulation method used in this paper is verified by a series of experiments.The air distribution in the humidifier is analyzed by CFD numerical simulation,and the gas distributor of humidifier is optimized to the experimental platform.The results show that the air distribution is beneficial to enhances heat and mass transfer capacity in the HDH system,The improved experimental system GOR can reached 1.37 and the output of fresh water can reached 9.96kg/h,which increased by 3.8% and 3.4%,respectively.