Liquid-Adjustment Evaporator with Zeotropic Mixtures: Principle, Design and Statistical Analysis

Abstract

Zeotropic mixture has advantages of environmentally-friendly, safety and flexible thermal properties, its featured temperature glide during phase changing can match the temperature variations of heat sources, enhancing the system thermodynamic performance. It has been considered as the promising alternative candidate. However, the heat transfer coefficient of zeotropic mixture generally worse than that of its pure component, and its nonlinear temperature-enthalpy relationship leads to extra irreversible losses. To overcome these issues, liquid-adjustment is implemented to improve heat transfer capacity and irreversible losses. Firstly, the principles of liquid-adjustment for zeotropic mixture are introduced and illustrated. Secondly, a conceptual design of liquid-adjustment evaporator with counter flow for zeotropic mixture and water is proposed. Thirdly, the optimized scheme is selected and compared to the conventional evaporator. The liquid-adjustment evaporator has a 9.72% increased heat transfer capacity and a 22.4% reduced total exergy resistance. Meanwhile, its local heat transfer coefficients can be significantly increased by 111% and exergy resistance decreased by 52.5% after the first separation. Finally, statistical analysis is carried out to reveal the interactions and insights of the parameters. It is found that the vapor quality is the main influential factor in both heat transfer coefficient and local slope of T-Q curve.

Keywords: Zeotropic mixture, Liquid-adjustment, heat transfer coefficient, Irreversible losses, Statistical analysis