Document 6Bprpk6vmERqGDrM2OX5Jdg24

448 CHAPTER 18 1955 Guide from Table 3 is 0.875. Solving 0.875 X 0.00383 = 0.00335. Making a further cor rection for the heating value, 0.00335 X = 0.00328 gal per 1000 Btu per hr calculated heat loss per degree- 144>l)UU day. From Table 2, the total normal degree-days for Toledo are 6269. Since U is expressed in 1000 Btu, N is equal to 240. Substituting in Equation 4 .. . F = 0.00328 X 6269 X 240 = 4930 gal. Estimating Coal or Coke Consumption Coal or coke consumption estimates are made by following exactly the same procedure as for oil. Values of U are given in Table 6 which only apply to an inside design temperature of 70 F and an outside design tem perature of 0 F. A correction must be made for other conditions by use of Table 4. Unit Fuel Consumption Constants (U) for Gas* Based on 0 F Outside Temperature, 70 F Inside Temperature Hot Wateb Heatino Value op Gas Btu per Cu Ft Cu Ft Gaa per Degree-Day per Sq Ft EDR Up to 500 Sq Ft 500 to 1200 Sq Ft Over 1200 Sq Ft 500 535 800 1000 0.149 0.139 0.094 0.075 0.142 0.132 0.087 0.071 0.134 0,126 0.085 0.068 Steam Wabu Air Cu Ft Gas per Degree-Day per Sq Ft EDR Cu Ft Gas per Degree- Day per 1000 Btu Hourly Design Heat Loss Up to 300 Sq Ft 0.254 0.237 0.159 0.127 300 to 700 Sq Ft 0.242 0.226 0.151 0.121 Over 700 Sq Ft 0.231 0.216 0.144 0.116 Gravity 0.896 0.840 0.560 0.449 Fan Systems 0.861 0.805 0.538 0.431 1 Therm Gas Consumption in Therms per Degree-Day 100,000 Btu 0.000743 0.000709 0.000675 0.00127 0.00121 0.00116 0.00450 0.00430 Abstracted from Comfort lirating, American Goa Ascociotion, 1938 and 5 percent added tor operation without night reduction of temperature. the multiplying factors in Table 3. Data in Table 6 are based on 12,000 Btu per lb coal, and for other heating values of coal they must be multiplied by the ratio of 12,000 divided by the heating value of fuel used. Example 6: A building in Scranton, Pa. has a calculated heat loss of 240,000 Btu per hr based on an inside design temperature of 70 F and an outside design temper ature of --10 F. What will be the estimated normal seasonal anthracite or coke consumption for heating if 13,000 Btu per lb fuel is burned in a hand-fired boiler, with automatic control, at a seasonal efficiency of 80 percent, and what part of the total will be used during November, December, and January? Solution: From Table-6, U is 0.0444 of coal or coke per 1000 Btu per hr heat loss per degree-day. Correcting for the outside design temperature of --10 F from Table 3, the value of U is 0.875 X 0.0444 = 0.0389. From Table 2, D is 6218 and from the problem, N is 240. Substituting in Equation 4, F = 0.0389 X 240 X 6218 = 58,100 lb. Fuel used over any period is, according to the theory of the degree-day, propor tional to the number of degree-days during the period. From Table 2, the average numbers of degree-days for November, December, and January in Scranton are 717, 1074, and 1162 respectively, a total of 2953. The yearly total is 6218, so that during these three months the estimated consumption is 2953 X 58,100 6218 27,600 lb. Estimating Fuel Consumption for Space Heating 449 Table 5.- Unit Fuel Consumption* Constants (U) fob Oil1 Based on 0 F Outside Temperature, 70 F Inside Temperature ' Unit0 Gal Oil per Sq Ft Steam Radiator............................. EmciENCT in Percent 70 0.00105 80 0.00092 Gal Oil per Sq Ft Hot Water Radiator................. 0.00066 0.00058 Gal Oil per 1000 IJtu per Hour Heat Loss. . 0.00437 0,00383 Based on a heating value of 141,000 Btu per gallon. b Abstracted by permission from Degre+Day Handbook {Second Edition, 1937), by C. Strode and C. H. B. Hotchkiss. Seven percent added for operation without mgbt reduction of temperature and change to beat^ mg value o! 141,000 Btu per gallon. 0 Per degree day. Estimating Steam Consumption In estimating steam consumption the efficiency is generally assumed at 100 percent. If for low-pressure steam an average heating value of 1000 Btu per pound of steam is used, no correction is necessary. In comparing values from different cities, correction should be made for design tempera ture (see Table 3) when the unit figures are in terms of heat loss but not when the values are in terms of building volume or floor space. Where the heat loss is calculated in Btu per (hour) (degree difference in temperature) the simple Equation 5 may be used: where H X 24 X D 1000 (5) F = pounds of steam required for estimate period. H = calculated heat loss, Btu per (hour) (degree difference) 1 24 = hours in one day. D = number of degree-days for the period of estimation. 1000 = Btu delivered per pound of steam condensed. In this method the number of degree-days automatically takes care of average inside and outside temperature difference.. When degree-days are taken from Table.2, an average inside temperature of approximately 70 F is assumed throughout the period. If an average inside temperature other Table 6. Unit Fuel Consumption* Constants ({/) fob Coal* Based on 0 F Outside Temperature, 70 F Inside Temperature Unit0 40 al per Sq Ft Steam Radiator.... 0.0216 *1 per Sq Ft Hot Water Radiator.. 0.0135 I*b Co^al per 1000 Btu per Hour Heat Epficienct in Percent 50 GO 70 0.0172 0:0143 0.0123 0.0108 0.0091 0.0078 80 0.0108 0.0068 Q ft heating value of 12,000 Btu_per pound. H iV'r^fcr&cted by tnctikitt. Eight permission from Degree-Day Handbook {SecondEdition, 1937), byC. Strock percent added for operation without night reduction of temperature. and C. H. B. ,Per degree-day.