The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

Hot Water Suply

Principles Of Water Heating

1.Circulation of Water.—When a body of water is increased in temperature, it expands and consequently occupies ore space; when decreased in temperature, it contracts and occupies less space. The smaller the space a given weight of water occupies, the greater is the density of the water; and the greater the space the same weight of water occupies, the less dense will be the water. Suppose that the temperature of a given volume of water at the bottom of a large body of water in a vessel is raised and hence its density is decreased. Since the attraction of the earth, that is, the force of gravity, is less on a given volume of the warmed water than on the same volume of cold water, the cold water sinks to the bottom and displaces the warm water, which rises to the top. If a small volume of water near the bottom is heated continuously, the warmed water will rise in a stream and cold water will flow in continuously to take its place, become heated, and rise, in turn. This flow of water is called circulation, and since it is due to the action of the force of gravity, it is spoken of as gravity circulation; a circulation of water due to this cause is also called natural circulation, to distinguish it from a circulation induced by mechanical means, as a pump, and known as forced circulation.

2. Suppose that a vessel is partly filled with water andthat heat is applied to the center of its base by a flame, as shown in Fig. 1. Heat from the flame is absorbed by the bottom of the vessel and conducted to its inner surface, from which it is transmitted to the nearest portion of water.

This portion, being increased in temperature, becomes less dense, and consequently rises toward the surface. The water that takes its place, in turn, becomes heated and also rises. The water at the top is cooled by coming in contact with the atmosphere.