Thermal research of climbing film evaporation desalination system: Controlling attribute of the energy cascade utilization principle

Based on the pinch theory and energy cascade utilization principle, the performance of a multi-effect shipboard climbing film evaporation desalination system combined thermal vapour compression (TVC) with different preheating configuration has been analysed. The mathematical model was established for thermodynamic simulation, in which various thermodynamic losses caused by boiling point elevation and pressure drop were considered, and the effective heat transfer temperature difference and temperature difference of the hot side were used to analyse the influences of the heating steam temperature, the final effect evaporation temperature, and the concentration ratio on the thermal performance including gained output ratio, specific heat transfer area for different preheating process. The results showed that the internal average effective heat transfer temperature difference determined the characteristics of the multi-effect evaporating system, while for the system with the similar average effective heat transfer temperature, the temperature difference of the hot side was the controlling parameter. The energy cascade utilization principle showed the controlling attribute in the multi-effect evaporating thermodynamic system, as the gained output ratio was improved mainly due to utilization of the secondary energy and residual energy of the heating steam for the preheating process.