Dynamic model of a transcritical CO2 ejector expansion refrigeration system

• A dynamic model of a transcritical CO2 ejector expansion cycle is developed.
• The presented model is validated against the experimental results.
• Variable ejector efficiencies are incorporated into the system dynamic model.
• The system dynamic behaviors under certain disturbances are simulated.

This paper presents a dynamic model of a transcritical CO2 ejector expansion refrigeration cycle (EERC) which is a promising refrigeration system due to its environment-benign nature and low throttling loss. The mathematical models for gas cooler, evaporator and separator are formulated by using the mass and energy conservation equations. Based on the real properties of CO2, the ejector model is developed and the variable ejector component efficiencies are taken into account because they vary with operation conditions. The compressor and expansive valve are modeled in a set of algebraic equations. The presented transient simulation results are in good agreement with the experimental data. The dynamic behaviors of the system undergoing the change of expansion valve opening and ejector area ratio are observed by the developed model, which helps to understand the characteristics of the EERC and guide the system control.