介质物态变化对超低温阀门降温效果的影响.

In-depth research on key technologies of ultra-low temperature valves has far-reaching impact on improving special valve technologies in China. When the temperature distribution of the ultra-low temperature valve was simulated, the analysis method used ignored the heat transfer between the low-temperature gas and the valve after the low-temperature medium absorbed the heat and underwent phase change. Therefore, taking Class300-DN65 ultra-low temperature cut-off valve as an example, the influence of medium state change and low temperature gas produced by phase change on valve cooling effect during steady-state operation was studied. Firstly, computational fluid dynamics（CFD） simulation of the medium flow process under adiabatic condition was performed, and a heat transfer model was established to explain the heat transfer process. Then, when heat transfer occurred, the internal clearance of the valve cover and the media distribution law of the flow field inside the valve were studied. Finally, the temperature distribution of the valve was analyzed by steady-state flow-thermal coupling. The research results show that the low temperature gas generated by evaporation and vaporization of LNG will flow at the bottom of the internal cavity of the valve cover, and constantly cool down the valve cover and stem by convective heat exchange, and the bottom temperature of the stuffing box is 10.6 ℃ when the effect of low temperature gas on the temperature field of the valve structure is not considered; but the bottom temperature of the stuffing box is only-0.2 ℃ when the low temperature gas is considered. Therefore, when designing the ultra-low temperature valves, it is necessary to consider the effect of cryogenic gas on the cooling of the valve, which otherwise may lead to seal failure. [ABSTRACT FROM AUTHOR]