Thermal performance and exergy analysis of a thermal vapor compression desalination system

A thermodynamic analysis based on the first and second laws is conducted to evaluate the performance of a thermal vapor compression (TVC) desalination system. The performance of the analytical model is compared with operational data obtained from tests performed on a four-effect, low temperature TVC desalination system with performance ratios of 6.5-6.8, located in the U.A.E. The effect of the process variables on the plant's performance ratios is investigated. The exergy losses due to irreversibilities in different subsystems of the TVC system are evaluated and compared with those of the conventional multi-effect boiling (MEB) and mechanical vapor compression (MVC) desalination systems. The TVC system yields the least exergy destruction among the three systems. Subsystem exergy analysis shows that most of the exergy destruction in the TVC system occurs in the first effect and in the thermo-compressor. Overall exergy losses can be significantly reduced by increasing the number of effects and the thermo-compressor entrainment ratio, and by decreasing the top brine and heating steam temperatures.