Algebraic Equations for Calculating Surface Flame Spread and Burning of a Cubical-Shaped Polyurethane Foam Block

Abstract

This work presents a simple algebraic method for calculating heat release rate (HRR) considering the three-dimensional flame spread and burning over a cubical-shaped polyurethane foam block. Flame spread area is calculated by flame spread velocity toward multiple directions over top and side surfaces. Burnt-out area is calculated by projected area of the burnt-out portion onto original top and side surfaces. Mass burning rate per burning area is calculated by radiation from flame to each burning surfaces. HRR is calculated by multiplying burning area with mass burning rate and heat of combustion. The calculated results were compared with experiments. In cases of the cubical shape or wide shape, HRR is predicted fairly well until peak HRR. In case of tall blocks, the calculated peak HRR was smaller than experiments due to HRR per unit area over vertical surface was under estimated.