A heat pump-driven mechanical vapor compression desalination system and its operating characteristics

Abstract

The converter valve of ultra-high-voltage direct current grid requires a large amount of cooling water for heat dissipation. Considering the generated waste heat, this study proposes a heat pump-driven mechanical vapor compression (HP-MVC) desalination system based on traditional power-driven mechanical vapor compression (MVC). Using the scaling-endoreversible thermodynamic model, the analytical solutions of the structural equation and operating boundary of the proposed HP-MVC system were derived, which is the innovation of this study. The effects of different component parameters on the thermodynamic characteristics and operation boundaries of the HP-MVC were determined. The results revealed that the HP-MVC system alternately exhibited heat-drive dominant and power-drive dominant modes, in which the specific power consumption was lower in the former. When the recovery ratio was 0.3, with an increase in the pressure ratio from 1.15 to 1.50, the heat supplemented by the heat pump decreased by 31.9 %, and the specific power consumption increased by 63.1 %. The analytical solutions of the structural equation provide a theoretical basis for the efficient operation of the system, and the operation boundaries demonstrate the difference between HP-MVC and traditional MVC. The HP-MVC reduces heat dissipation requirements and results in a more energy-efficient desalination system, which is a typical mutually beneficial design and worth promoting.