Estimation of Water Vapor Density in Adiabatic Mixing of Cryogenic Gas and Moist Air

Abstract

Concentration distribution is essential for the emergency disposal of cryogenic fuel leakage. In the dispersion process of cryogenic gas, its concentration is greatly influenced by the atmospheric water vapor. The authors have presented an adiabatic mixing model to derive the concentration of the cryogenic gas, in which the value of water vapor density is obtained by referring to the NIST database continuously. However, it is difficult to achieve fast system response times for real-time monitoring systems when calling NIST. Thus, a simple algebraic model of water vapor density with high calculation efficiency is necessary. Based on the detection of temperature and the solution of water vapor partial pressure, a calculation model was developed. For a given initial ambient temperature and relative humidity, the dew point could be solved by Qian’s correlation. By temperature comparisons of the mixture cloud, dew point, and triple point, the water vapor partial pressure can be calculated by the Goff–Gratch formulation. Then, the water vapor density during the temperature declining process can be derived via EOS. The results show that the model has high estimation accuracy, and has a close mean deviationof 0.08%to the IAPWS 95 of 0.03%. The increase in the computation efficiency was confirmed as +67% under nine testing points. The model facilitates the engineering utilization of the adiabatic mixing model for cryogenic fuel leakage monitoring.