Comparative Study on Theoretical and Numerical Calculations of Mass Flow Rate through Opening of Compartment

Abstract

In this study, stratified, well-mixed, and simplified theoretical model equations and Fire Dynamics Simulator (FDS) were used to calculate the mass inflow, outflow and neutral height to determine the usefulness of previously proposed simple formulas for the calculation of the mas flow rate through openings of compartments in case of fire. The mass flow rate through the opening was evaluated for two conditions, i.e., a fire inside the compartment and no fire, with a high-temperature homogeneous mixture filled inside the compartment. The height of the neutral plane calculated using the theory and FDS under the condition of fire inside the compartment well obeyed the trend of the experiment. In particular, the FDS results for the neutral plane height and inlet air mass flow well agreed with the experiment. However, for the inlet air mass flow rate, the theoretically obtained stratified and well-mixed model equations overestimated the mass flow variation trend according to the increase in opening width. The results of the stratified model equation were the most consistent with the FDS calculation results regardless of temperature, under the condition of a uniform mixture inside the compartment. Regarding the inlet air flow rate, the difference between the theoretical equation result and FDS result was not small. In contrast, for the effluent air flow rate, the results of the simplified formula were the most consistent with the FDS results.