Exergy analysis of a closed mechanical vapour compression desalination system by the entropy method

Corrosion is a common problem for desalination systems. To protect the compressor in a desalination system from being corroded and damaged, a novel mechanical vapour compression desalination system, denoted as a closed mechanical vapour compression desalination system, is proposed, in which the compressor does not contact the vapour produced by seawater directly. Mathematical models corresponding to the proposed system were established, and then an exergy analysis based on entropy method was achieved to investigate the performance of the system with a flow rate of 1,000 kg/h. The results showed that the total exergy loss was 29.4 kW, for which the circulating water tank accounts for 41% due to a superimposition of flashing and mixing, followed by the heat exchanger (23%), evaporator (16%), compressor (13%), preheater (5%) and pumps (1%). The exergy loss of the pumps is much smaller due to their lower power consumption.