In a heat exchanger, the temperature and pressure of fluid varies along its flow channels. For a residential heat
pump system that uses supercritical carbon dioxide (CO2), the CO2 temperature changes from more than 100 C at the inlet to less than 30 C at the outlet.
The corresponding CO2 pressure is 9–12 MPa, and the critical point of CO2 is 7.4 MPa at 31 C.
Therefore, CO2 in the heat exchanger of the heat pump system passes the pseudo-critical point.
portrays the specific heat of CO2 around the critical temperature.
Not only specific heat but also all other fluid properties change rapidly around the pseudo-critical point.