Simple Method of Design for the Natural Circulation System in the Boiler

Abstract

Recent years, pressure and capacity of steam generating units have been rapidly increased with the improvement of efficiency of the power plant. In such a high pressure, it will become difficult to obtain adequate circulation of water without the suitable method of design. On the several assumption, the author applied "Bernoullis' theorem" to the simple evaporating circuit and introduced a practical formula obtaining the number "n" of uprisers to downcommer, giving the boiler pressure, heat absorption rate, top dryness of the upriser, friction coefficient, diameter of the tube and height of the boiler, and also, to obtain rapidly "n", introduced a graphie chart from this formula. Using these theories, we discussed about many factors affecting circulating velocity, number "n" and economics of the circulation system, and especially recognized that it is economically advantageous to use few downcammers having large diameter, as the boiler becomes larger.