Thermodynamic Correlation between Actual Temperature and Cryogenic Flow Rate in an Empty Cryosauna

Abstract

The objective of this study was to monitor the actual temperature in an empty partial body cryotherapy cabin throughout the cooling phase that precedes the cryotherapy session. It was shown that after 9 minutes of cooling, the minimum temperature recorded inside the empty cryosauna was −66 °C while the temperature was set to −140 °C. To further investigate the relationship between the use of nitrogen as a cryogenic fluid and the actual temperature inside the cabin, we used a numerical method and modeled the convective heat transfer for 3 different flow rates (0.01, 0.03 and 0.05 kg/s). According to the simulations, a temperature of about −100 °C may be reached after 3 minutes with a flow rate of 0.05 kg/s against 5 minutes with a flow rate of 0.03 kg/s. With the lowest flow rate, it would be possible to reach −60 °C after 10 minutes. A key assumption is that a too low nitrogen flow does not provide a thermal gradient able to induce the drop in skin temperature required to achieve therapeutic effectiveness.