Document 4vpBKKzzq8VjJnVYGVnJoD8dN

Heating Ventilating Air'-Conditioning Guide 1938 It should be noted that the-figures in Table d are for the heating season only and include steam for heating dome&tlfc water. / Example 1 solved by the degree-yay method aUd using7values -taken from Table 3 would show a higher steam consumption. `v . a-dc Example S. Factor .for steam consumption for a manufacturing building per M.^Btu per hour heatloss per degree-day. = 0.283; total number of degree-days per year (Table 1) = 4855; heat loss = 500,000 Btu per hour. '' . ' *v Solution.. 0.283' X 4855 X -500 = 686,982 lb of steam per year. This calculation results in an estimate 45 per cent higher than the previous calculation and one which would be more nearly correctffor actual practice. . Chapter 12. Heat and Fuel Utilization unit, the consumption should be assumed as from .10 to 20 per cent greater. One reason for this difference in steam consumption is that district steam is a metered service, and building managers are therefore more conscious of their heating costs, which generally results in better maintained heating systems. Also, the district steam service is usually installed with ther mostatic control which reduces overheating to a minimum. Fig. 2 shows the amount of coal or oil that may be estimated when the steam consumption is known. Assuming the steam consumption that CU FT OF GAS PER DEGREE DAY PER UNIT Fig. 2. Curve for Estimating Fuel Consumption for Various Known Steam Consumption3 This curve is based on heating efficiencies of 60 to 70 per cent for coal and oil. respectively, a calorific value of coal of 13.000 Btu per pound, a calorific value of oU of 140,000 Btu per gallon. In case the heat loss figure is not known this method of estimating heat or steam consumption can also be applied if the net heated space figure is available. ' " ' ; :! calculation of fuel consumption : After the heat and steam consumption of the building have been calcu lated, the corresponding'/fuel ^requirements may also bR, estimated by assuming the correct boiler and 'furnace efficiencies. If the building is to be supplied with steam from a district heating company, the stea.m con sumptions as calciilated-by the two Methods are generally assumed to be correct. However, if thesteam is to be supplied from an individual boiler 236 Fig. 3. Chart Giving Gas Requirements per Degree-Day for Various Calorific Values of Gas and for Different Heating Systems3 This chart Is based on an inside temperature of 70 Fiand an outside temperature of zero. If the radia tion is installed on the basis of any other temperature difference, multiply the result obtained from this chart by 70, and divide by the actual temperature difference. From Industrial Gas Series House Heating {third edition) published by the American Gas Association. was calculated in Example 2, 686,982 lb, the corresponding coal con sumption, from the curve, is 44 tons and the. oil consumption 6006 gal. Fig. 3 indicates the average gas consumption per degree-day for various heat contents. While the fuel consumption in individual cases may vary-somewhat from the curve values, these average values are sufficiently accurate for estimating purposes and give satisfactory results. The value generally used in the' manufactured gas" industry for resi dences is 0.21 cu ft per degree-d^.y per .square foot of equivalent steam radiation (240 Btu) based on. the theoretical requirements. A correction for warmer climates is necessary and/it is .customary to gradually increase, the relative fuel consumption below 30Q0 degree-days to about 20 per pent: . more at 1000 degree-days.' 237