Document ymRRee5opxJJzXqZ643vk23zd

HEATING VENTILATING AIR CONDITIONING GUIDE 1940 Density of air at 95 F dry-bulb and 75 F wet-bulb for a barometric pressure of 29.92 in. is 0.07105 lb per cubic foot (Table 4, Chapter .1). ... ./ Dew-point of outdoor air is 66 F (psychrometric chart). Partial pressure of vapor is 0.64378 in. Hg. (Pressure of saturated vapor at 66 F,' Table 6, Chapter 1). W = 0.622 (-^4^) = 0.622 (29.m'^M4378) = ;0137'lb Water VaPr per; pound dry air (Formula 5 a, Chapter 1). -------- ---------- = 0.986 lb dry air per pound outside air. 1 + 0.0137 do = 0.07105 X 0.986 = 0.0699 lb dry air per cubic foot outside air. , Ha = 60 X 500 X 0.0699 X 0.24 (95-80) = 7549 Btu per hour. Total heat, H = 60 do Q {ho -- h) (Formula 5). ho = 38.46 Btu per pound dry air at 75 F wet-bulb (Table 6, Chapter 1). h = 31.51 Btu per pound dry air at 67 F wet-bulb (Table 6, Chapter 1). H = 60 X 0.0699 X 500 (38.46 -- 31.51) = 14,574 Btu per hour. Latent heat gain from outside air = 14,574 -- 7549 = 7025 Btu per hour. People Heat Gain: 50 X 225 = 11,250 Btu per hour, sensible heat. 50 X 206 -- 10,300 Btu per hour, latent heat. Light Heat Gain: 4200 X 3.413 = 14,335 Btu per hour. Summary: Component op Load Btu feb Houb Sensible 16.164 47.946 7,549: 11.250 14,335 97.244 Latent 7.025 i 10,300 17.325 - 97,244 4- 17,325 = 114,569 Btu per hour,, 156 Chapter 9 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. Oxygen, Or........ .............................................. Nitrogen, Nt........................................ Bt Volume Per Cent 20.9 79.1 Bt Weight Ppa 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 157