Prediction of steady-state two-phase flow of nitrogen + extinguishant in the pipeline and a correlation for mass flow rate

Nitrogen used for pressurization of a fire extinguisher could be partially dissolved in the fire extinguishing agent, forming a binary mixture accompanied by a phase change while flowing inside the pipeline. Notwithstanding the widespread use of fire extinguishing system, few effective methods have been considered to predict two-phase flow performance of nitrogen + extinguishant in the pipeline. This paper presents the study on the performance of the steady-state two-phase flow of extinguishant in the pipeline, including C₃HF₇ (HFC227ea), CF₃I, and C₂HF₅ (HFC125). The average viscosity of mixture was calculated using six quoted methods (VM-1–VM-6). The corresponding prediction models (STFM-1–STFM-6) for large mass flux nitrogen + extinguishant in a fire extinguishing pipeline were developed based on the VM-1–VM-6. In comparison with previous experimental and theoretical data, the applicability and accuracy of the proposed mathematical models was examined from mass flow rate and pressure drop. The results indicated that both models STFM-2 and STFM-3 could accurately predict for mass flow rate and that STFM-2 could predict for pressure drop. Finally, new correlations for mass flow rate and pressure drop have been established accurately based on the predicted data, respectively. This work contributes to a good theoretical approach on the analysis of two-phase flow of nitrogen + extinguishant.