液氮灭火系统管路输送压力损失影响因素及计算方法研究

Study on the influencing factors and calculation methods of pipeline transportation resistance loss in liquid nitrogen fire extinguishing system

结合液氮防灭火工程管路实际,分析了环境温度、液氮温度、入口流速、管长、管径、出口口径对管路出口液氮含量、输送压降的影响,并结合模拟与试验分析了均相模型预测管路输送压降的计算方法。结果表明:环境温度、液氮温度对液氮含量和管路压降影响较小;管路流速越快、输送距离越长、管径越小,压降增加越显著;随管路出口口径的减小压降迅速增加。对于低干度的气液两相氮适合用于均相模型计算,提出的简化计算经验模型压降预测值与试验值吻合良好,可以预测气液两相氮的管路输送压降,为液氮输送管路的工程应用设计提供理论支撑。

Based on the actual situation of the pipeline of the liquid nitrogen fire prevention project,the influence of environmental temperature,liquid nitrogen temperature,inlet flow rate,pipe length,pipe diameter,and outlet diameter on the liquid nitrogen content and transportation pressure drop at the pipeline outlet are analyzed.The calculation method for predicting pipeline transpor⁃tation pressure drop using a homogeneous model was analyzed through simulation and experimental.The results show that the environmental temperature and liquid nitrogen temperature have little influence on the liquid nitrogen content and pipeline pressure drop;The faster the flow rate,the longer the conveying dis⁃tance,and the smaller the pipe diameter,the more significant the increase in pressure drop;The pressure drop will rapidly increase as the outlet diameter of the pipeline decreases.For low dryness gas-liquid two-phase nitrogen,it is suitable for homogeneous model calculation.The proposed simplified modified empirical model has a good agreement between the predicted pressure drop and experimental values,and can predict the pressure drop of gasliquid two-phase nitrogen pipeline transportation,thus guiding the engineering application design of liquid nitrogen transportation pipelines.