Radiant Heat Transfer of Fire in a Concrete House

Abstract

In this paper I tried to estimate the quantity of radiant heat transfer from flame to wall and the curve of flame temperature rise in a burning concrete house which had the definite wall space and burning condition as shown in Table 1.
The method used in this paper is based upon Yagi and Kunii’s theory concerning radiant heat transfer in an industrial furnace. Applying this theory to a burning concrete house, I obtained the quantity of a radiant heat transfer, which was the important factor in this problem.
Epitome of the Method
I assumed that the inside of the burning concrete house is completely covered with flame of fire, the wall surface of the concrete house are all absorbing planes for radiation with emissivity ε_c and the outside from open parts of the wall (or window plane) are black body at outdoor temperature t₀°C as Fig. 1. Then, quantities of radiant heat exchange (q_ij) between planes (B,C) and flame are expressed in Eq. (1)
q_ij=A_iφ_ij(E_i-E_j) …………(1)
where, A_i, φ_ij and E_i are area of surface i, over-all interchange factor and emission power of black body, respectively.
Next, I considered the income and outgo of quantity of heat in the burning concrete house.
These relations are as follows.
(a) on the calorific value by fire and heat loss,
Q_H =q_GC＋q′_GC＋q_GB＋Q_L
(b) at the wall surface
Q_W =q_GC＋q′_GC
where, Q_H is calorific value of combustion of fuel in the concrete house, q_GC and q_GB are quantities of radiant heat transfer from flame to plane B and C. Q_L is quantity of heat carried away with the combustion gas, q′_GC is heat quantity by convection between flame and wall.
(c) temperature distribution in the wall estimated by Schmidt’s graphical solution for nonsteady heat conduction.
Results
I calculated above relations (a) to (c) under observed results obtained in two fire tests. Curves obtained are given in Fig. 2 and 3. In these figures flame temperature rises calculated by this method agree with practical rises at the climax time of fire (about 30 min. after the ignition). In fire test (I), about 40% of the heat quantity created by the combustion (G_H), is transferred from flame to the wall by radiation and 5% by the convection.