Two-phase choking conditions of real gases flow at their critical stagnation temperatures and closely above

Abstract

Homogenous flow choking conditions as pressure, temperature, speed of sound, and the consequent mass flux are derived for stagnation temperatures at the vicinity of the critical temperature and for a broad range of stagnation pressure (from 0.1 and up to 30 times the critical pressure). Results are presented and studied as relative as well as absolute deviations from the ideal gas predictions. It was found that there is a broad domain of isothermal stagnation states for which the corresponding choking states are of single-phase at saturated conditions. However, there is a narrow domain of stagnation states for which choking occurs inside the two-phase dome. For this domain, the homogenous flow choking is compared to that of the slip flow. Mass fluxes are discussed in view of the principle of corresponding states. On the basic level, a quite unified presentation is obtained by the proper normalization of the choked mass flux. The principle is refined by the observation that the remaining deviation may be organized according to the magnitude of the acentricity factor of each gas. Some practical examples are listed for demonstrating the relevance of results for Joule–Thomson cryocooling.