Thermophysical Problem Research On The Concentrating Light Solar Desalination System

With the rapid social development and the population of this planet growth, safe waterdemand for various purpose, domestic, industrial and agriculture, has increasedconsiderably. Owing to the pollution, abnormal climate and intensive exploitation groundwater, the situation mentioned above will be more and more critical over the next decadesor so. Solar desalination would be an effective solution of providing potable water andirrigation water for human being. Up to now, many studies have been carried out on thesolar desalination. However, high cost and small scale have become the biggest obstaclesfor solar desalination technology, which is caused by the structural mismatch of lowefficiency of the solar collector system at high temperature and low efficiency of theseawater desalination system at low temperature.In this paper, the idea of concentrating light evaporation type solar desalination systemis proposed, by utilizing the high efficient concentrating solar system to produce highstrength solar energy and concentrate to the seawater, the high temperature and highpressure vapor can then be generated and supplied into the traditional seawater desalinationsystem to generate freshwater, in the meantime, making salt from residual brine. In order toprobe the thermophysical problem of the concentrating light solar desalination, theconcentrator performance, the performance of concentrating solar desalination system andthe heat and mass transfer mechanism in humidification-dehumidification solar desalinationsystem and tubular solar desalination system is investigated and analyzed.In this paper, a typical ideal distillation process is proposed and analyzed using thefirst and second-laws of thermodynamics to minimum work requirement for individualprocesses. The ideal operation process of solar desalination driven by solar collector istheoretical proposed. Based on the detailed analysis above, the relation of the yield andminimum work requirement is achieved.According to the design theory, a trough three reflection surface concentrator and atrough focus overlap concentrator have been constructed to meet the requirement of theconcentrating light solar desalination system. The structure curve functions are given. Thebasic sizes and the relationship between characteristic parameter of the concentrator anddeflector have been determined. A3D model of the concentrator supported with opticalanalysis software LightTools is used to analyze the performance. The influence of the incident angle and installation error of receptor has been discussed.A concept of functioned seawater is represented. In order to enhance the sun lightabsorptive capacity of the seawater, black particles are added in the seawater. The influenceof the operation parameter including beam transmission position, size of particle, waterboiling extent and particle abundance on the transparency rate from the view point of opticsis studied. Then the transparency rate of functioned seawater attenuated exponentially withthe water boiling extent. The trend of the variation of the theoretical calculation is the sameas that of the variation of experimental results, and the R2of the experimental analysisexceeds0.95.Based on the analysis results, the trough type concentrating solar desalination deviceand the dish type concentrating solar desalination device are constructed. The temperatureand water yield characteristics of the devices are got through experimental study outdoors.A dimensionless parameter of “efficiency rate” is posed in this paper, which is used toevaluate the extinction performance of the functioned seawater. Meanwhile, the economicanalysis of the concentrating solar desalination system is carried out.A novel two-stage multi-effect solar desalination based onhumidification-dehumidification process is experimental investigated. The main objectiveof this work is to study the thermophysical problem of vapor in the process of evaporationand condensation. The fresh water production of the device can reach63.55kg/h and thegained output ratio (GOR) can reach1.89, because it recycles and reutilizes latent heat andthe residual heat in the brine. A mathematical model based on mass and energy balances ineach component of the unit is developed. A serious of experiments were conducted andcompared with the simulation results to validate the developed models.Finally, a group of multi-effect horizontal tubular solar desalination devices andvertical tubular solar desalination devices have been designed and constructed. The heatand mass transfer mechanism of the operation process is analyzed. The research calculatedand analyzed the yield and the temperature value of every measured point inside the deviceunder conditions of fixed power, fixed temperature medium and negative pressure. Theeffect of different gas media on the water production rate is experimental investigated. Thesemi-empirical expression of the water production rate is given. The GOR of thethree-effect device can reach1.91when the fixed heating power was350W. The yieldperformance of a group of multi-effect vertical tubular solar desalination devices is alsostudied. The GOR of the three-effect device can reach1.89when the fixed heating power was400W.