The Research On The Performance Of Solar-driven Humidification-Dehumidification Desalination System

Desalination has been one of the most effective ways to solve the global fresh water shortage. Conventional seawater desalination technology could not solve the problem of fresh water shortage in remote and scattered areas and consume a large amount of fossil fuel, which means costly production and environmental problems. Humidification-dehumidification(HDH) desalination system is easy to use and suitable for small-scale scattered devices. Furthermore, the stable performance, low-cost maintenance and availability to high salinity make it a promising desalination technology.This paper introduces the solar-driven humidification-dehumidification(HDH) desalination system. Detailed discussion is made on application of small scale desalination, classifications of solar desalination and some major methods of desalination. This paper reviews the documents about renewable energy desalination technology domestic and foreign, and introduces the theory and classifications of HDH solar energy in detail. Based on the laws of energy and mass conservation, the physical and mathematical models of solar-driven HDH desalination system are established, which includes collector mathematical model, thermal storage tank mathematical model, humidifier and dehumidifier mathematical model, heat exchanger mathematical model, and the system models are programmed and solved by utilizing MATLAB.The operation of the HDH desalination system with one to three stages has been studied. All the data are calculated in Dalian on September 15th and December 10th. The results show that temperature of the inlet water and air of the humidifier can be controlled by accommodating the mass flow rate of the water and air of the humidifier which ensured the operation of the system continuously.The heat capability of the HDH desalination system with one to three stages has been compared and analyze on September 15th. It is found that two stage system has a higher gained-out ratio (GOR), specific water production, recovery ratio and a relatively lower heat exchange area, so the two stage system has better property than the other one.The effect of inlet seawater, air temperatures and size of collector on the capability of the two stage on September 15th had been studied. In the two stage system, enlarging the area of the collector will increase water production. The GOR and the specific water production will increase and then decline with the increasing of the inlet temperature of the humidifier, and it will always increase with the increasing of the inlet air temperature. The GOR and the specific water production will increase with the increasing of the inlet air temperature of the first stage, while the result will on the contrary if the inlet air temperature of second stage is increased. The recovery ratio(RR) will increase with the increasing of the inlet water temperature of the humidifier, and decrease with the increasing of the inlet air temperature. It is found that, GOR is easily affected by the change of the collector area and the specific water production id mostly affected by the temperature of the inlet temperature of the water and air.In this paper, two stage system has a relatively higher GOR and specific water production than the results in the other works when running at peak performance, so the system has some advantages.