Issues related to the physical properties parameters of supercritical fluids!

Thread Content

1. The issue of specific heat capacity of supercritical fluids? Taking nitrogen as an example, the critical temperature is -147°C and the specific heat capacity is 42.19 kj/(kg*K). So what should be used as the specific heat capacity when the pressure and temperature exceed these critical values? Supercritical fluids are neither gases nor liquids; of course, there is no liquid state in a supercritical state! Is it selected based on the gas parameters? 2. What is the density of supercritical fluids? The density of supercritical fluids is determined either by referring to pressure-enthalpy diagrams or based on physical properties! Is it chosen based on the density of the gas? 3. A high-pressure heat exchanger for liquid nitrogen evaporation is currently being designed, with an operating pressure of 15 Mpa ； The inlet flow is pumped in by a plunger pump; the inlet pressure of this pump is 2.5 Mpa, corresponding to a saturated liquid temperature of -153.3°C. The flow entering the heat exchanger has a pressure of 15 Mpa and a temperature of -153.3°C (heat absorption along the way is ignored for now) ； The outlet temperature after heat exchange is -120℃ ； Liquid nitrogen flows in the tube side, while the heated water with an inlet temperature of 40°C and an outlet temperature of 20°C flows in the shell side ； The required heat exchange power is 100 kW ； Since the parameters after heat exchange in the heat exchanger far exceed those of nitrogen at 3.39 Mpa and -147.13°C, and the latent heat during the phase transition of a supercritical fluid to a gas is almost zero, the calculation is divided into two stages: 1. Heat calculation under supercritical conditions at the inlet ； 2. Supercritical state – outlet temperature! Could everyone please help check if the approach is correct? Also, please ask an expert member to help analyze it! I would be extremely grateful if you could share any information or examples related to supercritical fluid heat exchangers!