Effect of design parameters on thermodynamic losses of the heat transfer process in LT-MEE desalination plant

• Thermodynamic losses in a large scale LT-MEE desalination plant were investigated.
• Effects of design parameters on the thermodynamic losses were analyzed.
• The operating characteristics of LT-MEE desalination plant were summarized.

Thermodynamic losses caused by the flow resistances and the boiling point elevation (BPE) in low-temperature multi-effect evaporation (LT-MEE) desalination plant were investigated. The purpose is to provide detailed considerations for the design and modeling of LT-MEE process. Design parameters were analyzed to evaluate their effects on thermodynamic losses. Results indicate that on the premise of constant distillate production, as the sequence number of evaporator/condenser increases, each flow resistance decreases first and then increases, while the variation of corresponding temperature depression always performs a rising tendency. With the increase of tube length, the proportion of saturated temperature depression caused by the in-tube condensation flow resistance increases, and that caused by the inter-tube flow resistance decreases. The tube length for the lowest temperature depression occurs when two temperature depressions are in similar proportions. The thermodynamic losses caused by the flow resistances and the BPE account for considerable percentages, especially when under smaller temperature difference. The operating characteristics of LT-MEE desalination plant are summarized based on the analysis.