Liquid jet fire: The impact of rainout on the predicted hazard

Abstract

Although jet fires may pose a major hazard in the chemical processing industry, they are typically modeled with semi‐empirical models that were developed based on experimental results of natural gas. In most semi‐empirical models, it is typically assumed that all liquid is instantly vaporized upon discharge and combusted fully in the jet. In reality, depending on discharge fuel momentum, elevation, temperature, and liquid fuel properties, a significant percentage of liquid fuel may fall to the ground and burn as a pool rather than contribute to the jet fire. As a result, such a model may predict overly conservative results when used to model liquid spray jet fires. In this study, a computational fluid dynamic (CFD) model previously proved to be able to predict a subcooled liquid jet fire flame shape, length, rain out condition, and thermal radiation level was used to investigate how some key factors affect the percentage of liquid fuel that could combust in jet fire. Results were used to adjust semi‐empirical jet fire models to take account of rainout effect. Examples are given for rainout jet fire cases predicted with this revised semi‐empirical model.