Abstract
The hot gas spurting from a window of a burning concrete house has a tendency to flow from horizontally to vertically because of its buoyancy due to higher temperature than that of surroundings. The position of central axis of jet gives considerable influence upon the temperature of rising hot current ; when the hot air current rises apart from a wall above a window, it diffuses more widely than the current rising closely to the wall. In the former case, therefore, the temperature of the current is lower than that in the latter.
The position of a rising hot gas in various window shapes is discussed in this paper.
Results are as follows :
1. When the space above a window is free.
Using the velocity at a window as an initial condition, the equation of trajectory of the spurting gas can be obtained from the equation (1) and (6), where the upward acceleration due to the buoyancy is given.
Assuming that the rising air current is spurting from a line source placed at xo inside a window plane, the trajectory shows a cubic parabola expressed in the equation (10) ; the parabola depends upon the window height, but has little connection with the air temperature in a burning room.
The parameter xo was obtained from model experiments.
The above results were confirmed in model and full-scale experiments.
2. When a wall is above a window.
In this case the rising air current comes nearer to the wall than in the former case 1, depending upon the ratio of window width to window height ; when the window width is greater than the window height, the spurting air current comes nearer to the wall, and its temperature is higher, even if the spurting heat quantity per unit time is equal.
