Performance Research On The Concentrating Light Tubular Solar Brackish Water Desalination System

With the scarcity of fresh water resources and the depletion of fossil fuels in the world,using solar concentrating technology to collect heat to drive brackish water desalination device to generate fresh water will be one of the effective ways to reduce the shortage of fresh water.Especially the economic prospects of using solar energy for brackish water desalination in remote areas where low population density,low rainfall,abundant sunny will be more meaningful.In view of the multistage flash or multi-effect distillation desalination system are more applicable to the market demand of the large-scale operation,this paper presents a concentrating light tubular solar desalination system which can be used in small scale and distributed application.The system is simple in structure and easy to maintain,which can satisfy the needs of distributed fresh water.In this paper,the structure and working principle of the concentrating light tubular brackish water desalination system were introduced.A trough-type compound multi-surface concentrator suitable for the brackish water desalination device was designed,and the equations in the concentrator were given.Meanwhile,parameters that affect the performance of the concentrator,such as receiver shape,incident angle,installation error were analyzed and simulated by optical simulation software,the tracking accuracy requirements of the concentrator were given.At the same time,the trough compound multi-surface concentrator test set-up was designed,the performance of the plate solar cell with the cooling device was tested.The results showed that the overall performance efficiency was 69.88% when the mass flow rate of water was 2.41g/s under the 2 times the condenser ratio conditions.The heat and mass transfer process in the tubular solar desalination device was analyzed,and the calculation method of freshwater production was given.The tubular solar brackish water desalination experimental set-up was built,and the experimental study on the water absorption thickness and brackish water flow rate were carried out.At the same time,water production and temperature of the device was tested at fixed power heating process.The results indicated that the maximum optimal performance coefficient of the unit was 0.80.In order to improve water production of concentrating light tubular solar brackish water desalination system,the methods of enhancing heat and mass transfer process in the unit were explored.The freshwater production and the evaporation and condensation temperature of the device were studied and analyzed when the device under regenerative operating state,negative pressure operating state,air-cooling negative pressure operating state and water-cooling negative pressure operating state.The results showed that the fresh water yield increased by 43% when the operating temperature was 50 oC and the operating pressure decreased from 100 kPa to 75 kPa.Under the water–cooling and negative pressure operating conditions,when the operating temperature was 70 oC,the operating pressure of 75 kPa,the water production of the device with water cooling was 683.8g/h,which was 289% higher than that of the water production in the same operating condition.The results showed that improving of the heat and mass transfer process could be achieved by increasing temperature difference between evaporation surface and condensation surface and reducing the content of non-condensable gas inside the device,thus effectively the fresh water production of the device was improved.