Document pB6MZxmrRYG199eKboo7YzEB

HEATING VENTILATING AIR CONDITIONING GUIDE 1940 vapor pressure which is constant, as long as the' total heat loss from the' sphere is of the desired rate." If the BET becomes too high'for" comfort, a greater vapor pressure results from the smaller heat loss from the sphere, acts on a diaphragm, and turns down the supply of heat to the room. With falling. BET, the reverse action occurs. For testing work, the globe thermometer is a very useful instrument. It tonsists of an ordinary, mercury thermometer, with its bulb placed in the center of a. sphere from 6 to 9 in. in diameter, usually made of thin copper and painted black. The temperature thus recorded is termed the radiation-convection-temperature. REFERENCES ' / '1 Panel Warming, by L. J. Fowler (A.S.H.V.E. Transactions, Vol.-36, 1930, p. 287). Room Warming by Radiation, by A. H. Barker (A;S.H.V.E. Transactions, VoK 38, 1932, p. 331). What W.iU be the Future Development of Heating and Air Conditioning, by W. H; Carrier {Healing, Piping and Air Conditioning, January,. 1933, p, 16). American Practice in Panel Heating, by L. L. Munier (Heating, Piping and Air Conditioning, June, 1937, p. 424). .. .. r... . Panel Heating in the British Embassy, by Alfred L. Jaros, -Jr. and Richard A. Wolff (Heating and Ventilating, May and June, 1930). Calculations for Radiant Heating, by T.' Napier Adlam (Heatingand Ventilating, October, 1931). y ., .... ; Notes on" Electric Warming with Special Reference to Low. Temperature Panel Systems, by R. Grierson (Proceedings of The Institution of Heating and Ventilating Engineers, London, Vol. 28, 1929). Notes on the Theory of Radiant Heating, by C. G. Heys Hallett (Proceedings of The Institution of Heating and Ventilating Engineers, London,'Vpl. 29, 1930). Radiant Heat, by A. F. Dufton (Proceedings of The Institution of Healing and Ven tilating Engineers, London, Vol. 30,1931). .." Panel Heating, by C. M. Oates (Proceedings of The Institution of Heating and Ventila ting Engineers, London, Vol. 30, 1931). Principles of Calculation of Low Temperature Radiant Heating, by A. H. Barker (Proceedings of The Institution Of Heating and Ventilating Engineers, London, Vol. 30; mi). ' ' ` Radiant Heat, by A. F. Dufton (Proceedings of The Institution of Heating and Ven tilating Engineers, London, Vol. 31, 1932). -V . ,i 727 .Chapter 43 DISTRICT HEATING . Steam Distribution Piping, Selection of Pipe Sises, Provision for .Expansion, Capacity of Returns with Various Grades, Conduits for Piping, Pipe Tunnels, Inside Piping, Steam. Re quirements, Fluid Meters and Metering, Rates, Utilisation, Automatic Temperature Control THOSE phases of district heating which frequently fall within' the province of the heating engineer are-outlined here with data and information for solving incidental problems in cohnection with institutions and factories. Some data are included to cover the piping-peculiar to heating.systems which are to be supplied with purchased steam. A com plete district heating installation should not, be attempted without a thorough study of the entire, problem by. men competent and experienced in that industry. ; . STEAM DISTRIBUTION PIPING The methods used in district heating work for the distribution of steam are applicable to any problem involving the supply of steam to a group of buildings. The first step is to establish the route of the pipes, and in this matter the local conditions so fully control the layout that little can be said regarding it. Haying established the route of the pipes, the next step is to calculate the pipe sizes. In district heating work it is common practice to design the piping system on the basis of pressure drop. The initial pressure and the minimum permissible terminal pressure are specified and the pipe sizes are so chosen that the required amount of steam, with suitable allowances for future increases, will be transmitted without exceeding this pressure drop. The steam velocity is therefore almost disregarded and may reach a very high figure. Velocities of 35,000 fpm are not con sidered high. By the use of this method the pipe sizes are kept to a minimum with consequent savings in investment. The steam flowing through any section of the piping can be computed from a study of the requirements of the several buildings served. In general a.condensation rate of 0.25 lb per hour per square foot of equiva lent heating surface is a safe figure. This allows for line condensation which, however, is a small part of the total at times of maximum load. Miscellaneous steam requirements such as laundry, cooking, or process should be individually calculated. The steam requirements for water heating should be taken into account, 725