节流前过冷度和压力对液氮节流特性的影响

Effects of inlet supercooling and pressure on throttling behavior of liquid nitrogen

节流在普冷领域应用广泛。其在基于林德循环、克劳德循环等低温液化循环、焦汤氦制冷系统、低温推进剂热力排气系统中也都有涉及。为了深入揭示低温流体相比室温气体的节流特殊性,设计并搭建了一套低温流体气液两相节流可视化试验系统。针对渐缩渐扩管型的节流元件,分析了节流前过冷度和压力对液氮节流特性的影响。研究表明:节流前压力一定,节流后温降及气相质量分数随节流前过冷度增加而增加;节流前过冷度一定,节流后温降及气相质量分数随节流前压力增大而增大;增大节流前压力,减小节流前过冷度,会减少节流后流体的单位质量制冷量。

Throttling is widely used in refrigeration,and is also involved in cryogenic liquefaction cycles such as Linde cycle,Claude cycle,J-T helium refrigeration cycle,and cryogenic propellant thermodynamic vent systems.In order to reveal the particularity of throttling effect of cryogenic fluids compared to ambient temperature gases and refrigerants,an experimental setup was designed and established to visualize two-phase cryogenic fluid throttling process.Taking a Laval nozzle as the testing element,the effects of inlet subcooling and pressure on throttling behavior of liquid nitrogen were investigated.The study showed that at given certain inlet pressure,the temperature drop and gas mass fraction increase with the inlet subcooling degree;at given certain inlet subcooling,the temperature drop and gas mass fraction increase with inlet pressure;higher inlet pressure and lower subcooling lead to lower refrigerating capacity.