Dynamic modeling study for a solar evaporator with expansion valve assembly of a transcritical CO2 heat pump

• We performed an investigation of the solar evaporator and expansion valve assembly of a CO2 heat pump.
• We modeled the behavior of the solar evaporator and expansion valve under transient and steady conditions.
• Validation is realized by comparing simulation results and experimental data.
• The model is a tool for analysis and simulation of different operating conditions.

Recently, there has been an increased interest in natural fluids from industry and scientific community who see it as one of the most promising alternatives to replace the traditional CFCs and HCFCs, especially in heat pumps for residential water heating. This work presents an investigation of the behavior of the solar evaporator and expansion valve assembly of a transcritical CO2 heat pump in transient and steady conditions. The dynamic behavior of systems using CO2 as a refrigerant is significantly influenced by the dynamics of the heat transfer mechanisms. The solar evaporator model is based on the equations of conservation of mass, momentum, and energy. The model validation is realized by comparing simulation results and experimental data. The model is a useful tool for analyzing the behavior in transient and steady conditions simulating various operating conditions of the heat pump including solar radiation, ambient temperature, wind speed and atmospheric conditions.