Thermodynamic Performance Analysis Of Solar-driven Desalination System

The shortage of pure water has become more and more serious due to several factors,including serious contaminants of fresh water,water dehydration and increase depletion clean water of the ground.Many countries in the world suffer from this phenomenon,including China.There are several of ingredients which can be used to eliminate the freshwater crisis.One effective solution to alleviate the water crisis is the desalination seawater.Due to the rapid shortage of energy and the serious environmental pollution resulting from the use of fossil fuels as a heat source for desalination,the search for new technology to desalinate water through renewable energy is the main direction for the development of desalination technology.The use of solar energy as a thermal source for desalination sea water by a multi-effect desalination technology is an important method to reduce the water crisis.In this research,a detailed theoretical study on the basic theory of seawater desalination by multi-effect desalination plant with productivity 139 kg/s of fresh water driven by parabolic trough solar collector is carried out.In this the study;four mathematical model implemented in MATLAB software are developed to simulate the performance of the multi-effect desalination plant including;evaporators,preheaters,flashing boxes,and condenser,as well as the parabolic trough solar collector.In the first model,the thermal performance of parabolic trough collector is evaluated.While,the effects of the input temperature(102-397?C)and the mass flow rate(12.59 to 50 gpm)of working fluid on the boundary layer inside the absorber tube of the parabolic trough collector are studied,in the second model.Moreover,the third model is a simplified mathematical model,in which the thermal performance parameters of the proposed desalination plant are estimated.Furthermore,a detailed analysis of steady-state multi-effect desalination plant including;the thermodynamic behavior,energy balances and heat transfer processes at each effect of the plant,is presented in the fourth model.The simulation results obtained by the first model are validated with experimental data obtained from a parabolic trough collector at the SANDIA national laboratory,and showed a good agreement with experimental results.The results also showed that the high temperature of working fluid lead to a decrease in collector efficiency due to the increase in the thermal losses and the decrease in the friction coefficient and Darcy factor.In addition,the thermal efficiency of the parabolic trough collector is found to be 72.4%,cross pending to outlet temperature of 120.75 ~oC,at mass flow rate of 12.85gpm and solar radiation of 933.7 k W/m~2,respectively.Moreover,the simulation results of the desalination plant are compared with the results obtained from the literature and also showed a good agreement between the model predictions and literature results.The results also showed that the performance ratio of the plant is increased by decreasing the top brine temperature and increasing the number of effects.Furthermore,it is also found that the performance ratio of the plant is estimated to 11.73,at a top brine temperature of 65 ~oC and a distillate product of 138 kg/s,respectively.