Ventilation
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-253
2025-11-22
21
the need of renewing the air* in order to support combustion. It also shows that this renewal is secured by means of convection currents. A room is ventilated, more or less, by convection currents through chimneys, windows, and crevices in floor and walls, whenever the temperature in the room differs from that outside.
In a house that is heated by a hot-air furnace, good ventilation is secured by bringing the air to be heated from outside the house. The distribution of the heated air takes place in convection currents. The difficulty with this method of heating is that it is affected by the direction of the wind, the hot air going most freely into the rooms situated on the opposite side of the house from the direction of the wind; into the south rooms if the wind is from the north, for instance. Figure 1 shows how fresh air can be secured when hot water or steam heating is used.
Figure 1
-----------------------------------------------------
* Demonstration.-Set a short piece of candle in a saucer and light it. Set over it a chimney from a student lamp. Pour water into the saucer to prevent air going into the chimney from the bottom, and the candle will soon go out. Why? Cut a piece of tin of the shape shown in (a) in Fig.2, and put it down the chimney with the wide part resting on the top. Light the candle again, and it will keep on burning. Why? Examine the air on both sides of the tin, by the smoke from touch paper.
الاكثر قراءة في الديناميكا الحرارية
اخر الاخبار
اخبار العتبة العباسية المقدسة
