This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ... misconception of the laws which govern the movements of air that so many ventilation schemes fail. The forces tending to move the air in a room are the wind and the difference in temperature between the outside and the inside of the building. That is to say, provided sufficient inlets and outlets are furnished the ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ... misconception of the laws which govern the movements of air that so many ventilation schemes fail. The forces tending to move the air in a room are the wind and the difference in temperature between the outside and the inside of the building. That is to say, provided sufficient inlets and outlets are furnished the movement of air will be directly proportional to the force of the wind and the difference in temperatures, which latter is, by-the-hy, the principal agent in natural ventilation. The wind is, therefore, a strong factor, but unfortunately it acts principally in cold weather, when to open windows or ventilators without warming the incoming air causes unbearable draughts. In warm weather with a warm breeze good ventilation may be obtained, but on a still day in hot weather, with stagnant air, when its frequent change is required, ventilation is wanting. Wind is, moreover, such an uncertain agent that it is not advisable to allow any ventilation scheme to depend upon it. Natural principles of great importance are that the specific gravity of cold air is greater than that of hot air of equal purity, and that air when heated expands and rises. Air expands 002, or 5 of its bulk, for every degree Fahrenheit it is heated, so that if the air be heated 5 degrees above the external air it will be increased in bulk-th, and is, therefore, lighter in proportion. Cold air when introduced into an apartment has a natural tendency to fall, unless properly warmed. As we shall show, this must be done if a ventilation scheme is to be of any use, otherwise in cold weather the inlets are soon closed because of the draught brought about by the introduction of the cold air, because cold air being heavier than hot air a cold draught descends from what should be the outlet ...
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