Document ykKYdy8kJv1Q66Qj47mpY9rm6

HEATING VENTILATING AIR CONDITIONING GUIDE 1941 Summary: Component of Load TotaL ..................................................................................... ............................... Bxu per Hour 21,413 5,993 18,965 14,410 21,550 14,335 96,664 Latent Heat: Outside air 6.03 lb water per hour. Occupants 9.95 lb water per hour. 15.98 lb water per hour. 15.98 X hfs = 15.98 X 1062.7 = 16,980 Btu per hour. 142 Chapter 7 COMBUSTION AND FUELS Principles of Combustion, Classification of Coals, Firing Methods for Coals, Firing Methods for Coke, Dustless Treat ment of Coal, Classification of Oils, Combustion of Oil, Classi fication of Gas, Combustion of Gas THE data given in the first part of this chapter are of general appli cation to the various fuels used in domestic heating which are coal, coke oil and gas. The choice of fuel is a question of dependability, cleanliness, fuel availability, economy, operating requirements and control. FUNDAMENTAL PRINCIPLES OF COMBUSTION Combustion may be defined as the chemical combination of a substance with oxygen with a resultant evolution of heat. The rate of combustion depends partly upon the specific rate of reaction of the combustible substance with oxygen and partly upon the rate at which oxygen is supplied and the surrounding conditions as they define the temperature. Complete combustion is obtained when all of the combustible elements in the fuel are oxidized with all of the oxygen with which they can combine. All of the oxygen supplied may not be utilized. Perfect combustion is defined as the result of supplying the required amount of oxygen for combination with all of the combustible elements of the fuel and utilizing all of the oxygen so supplied. The oxygen required for the process of combustion is obtained from air which is a mechanical mixture of oxygen, nitrogen and small amounts of carbon dioxide, water vapor and inert gases. These inert gases are generally included with the nitrogen, and for engineering purposes the values given herewith may be used. Bt Volume Per Cent Oxygen, Oj......... ............................ ............... Nitrogen, 1V2._.......................................................................................... 20.9 79.1 Bt Weight Per Cent 23.15 76.85 . The combination of oxygen with the combustible elements and com pounds of a fuel is in accordance with fixed laws. In the case of perfect combustion the reactions and resultant combinations are shown in Table 1. The most important condition governing the process of combustion is temperature. It is necessary to bring a combustible substance to its 143