Non-equilibrium two-phase refrigerant flow at subcooled temperatures in an R600a refrigeration system

A refrigeration system is typically designed such that the refrigerant reaches a subcooled state at the condenser outlet. A series of experiments are conducted to investigate the refrigerant state at the condenser outlet and the capillary tube inlet. The refrigeration system used in the present experiment is operated with R600a. The visual observations, as well as temperature and pressure measurements, demonstrate that R600a flows in a non-equilibrium two-phase state at highly subcooled temperatures. Furthermore, a set of equations is proposed for calculating the specific enthalpy of the refrigerant in a non-equilibrium two-phase state, and this calculation method is verified using experimental measurements. It is found that the thermodynamic property table does not provide an appropriate value of specific enthalpy in non-equilibrium conditions, while the enthalpy calculation method proposed in this work is in good agreement with the experimentally measured values.