Analysis On Flooded Evaporator Applied In CO₂ Transcritical System

The natural refrigerant CO₂ is an environmentally friendly refrigerant, and possesses a good application prospect in the refrigeration substitution. This study mainly focused on the improvement of CO₂ trans-critical system, combining theoretical analysis on different styles of CO₂ trans-critical system and computational numerical simulation on flooded evaporator, to provide references to improve the system efficiency.This study made theoretical analysis on CO₂ trans-critical systems by establishing calculation models of different styles of CO₂ system from thermodynamic prospective, and analyzed the optimal application of single-stage cycles and two-stage cycles. After comparing them, it was found that the system with the regenerator and expander had the highest efficiency.On the basis of the experimental data, several heat transfer correlations were analyzed, and an empirical correlation was proposed to show the relationship between the heat transfer coefficients with heat flux and reduced pressure. According to the experimental system of CO₂ heat pump water heater, the flooded evaporator applied in CO₂ trans-critical system was designed, and analysis of heat transfer coefficients of tube bundle pool boiling was presented.In this study, the temperature field, pressure field and velocity field of water in tube side of the flooded evaporator were analyzed by CFD software to lay the foundation for optimization of flooded evaporator used in CO₂ trans-critical system.