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390 CHAPTER. 20 > 1948 Guide ' Table 2: Unit Fuel Consumption Constants (U) for Gas Based onO F Outside Temperature, 70 F Inside Temperature, and 8-Hour Reductionto 60 F. Hot Water Heating Value or Gas Btu per Cu Ft Cu Ft Gas per Degree-Day per Sq Ft Badiator Up to 500 . Sq Ft 500 to 1200 Sq Ft . Over 1200 8q Ft 500 535 800 1000 0.142 0.132 0.089 0.071 0.135 0.126 0.085 0.068 0.128 6.120 0.081 0.065 Stbam . Warm Axb Cu Ft Gas per Degree-Day per Sq Ft-Raoiator Cu Ft Gas per Degree-Day per 1000 Btu Hourly Design Heat Loss Up to 300 Sq Ft 300 to Over 700 700 1 Sq Ft - ' Sq Ft Gravity Fan Systems 0.242 0.226 0.151 0.121 0.231 0.215 0.144 0.115 0.220 0.206 0.137 0.110 0.855 0.800 0.534 0.428 . 0.820 0.766 0.513 0.410 1 Therm 100.000 Btu Gas Consumption in Therms per Degree-Day 0.000708 0.000675 0.000642 0.00121 0.00115 0.00110 0.00428 0.00409 Abstracted from Comfort Heating, American Gas Association, 1938. Table 3. Unit Fuel Consumption Constants (U) for OiLb Based on 0 F Outside Temperature, 70 F Inside Temperature, and 8-Hour Reduction to 55 F Untto EmcisNCT vh Per Cent 40 50 60 70 80 Gal Oil per Sq Ft Steam Radiator.. 0.00172 0.00137 0.00114 0.00098 0.00086 Gal Oil per Sq Ft Hot Water Radiator. .......... ............................... 0.00108 0.00086 0.00072 0.00062 0.00054 Gal Oil per 1000 Btu per Hour Heat Loss... _ ........... .................. 0.00715 0.00571 0.00476 0.00409 0.00358 aBased on a beating value of 140,000 Btu per gallon. ^Abstracted by permission from Degree-Day Handbook (Second Edition, 1937). by C. Strock and C. H. B. Hotchkiss. cper degree-day. Table 4. Unit Fuel Consumption3 Constants (77) for CoALb Based onO F Outside Temperature, 70 F Inside Temperature, and 8-Hour Reduction to 55 F. Unttc 40 Lb Coal per Sq Ft Steam Radiator.. 0.0200 Lb Coal per Sq Ft Hot Water Radiator 0.0125 Lb Coal per 1000 Btu per Hour Heat Loss_____________ __ ______ 0.0825 PeaEtiicibrct in Cbnt 50 0.0160 60 0.0133 70 0,0114 0.0100 0.0084 0.0072 0.0666 0.0550 0.0471 80 0.0100 0.0063 0.0412 .Based on a heating value of 12,000 Btu per pound. ^Abstracted by permission from Degree-Day Handbook (Second Edition, 1937), by C. Strock and C. H. B. Hotchkiss. ' .Per degree-day. Estimating Fuel Consumption for Space Heating 391 Example 5. Estimate the gas required to heat a building located in Chicago. 111., which has 6282 degree-days and a gas heating value of 800 Btu per cubic foot. The calculated heating surface requirements are 1000 sq ft of hot water radiation based on design temperature of --10 F and 70 F. Solution. From Table 2, the fuel consumption for a design temperature of 0 F with 800 Btu gas is found to be 0.085 cu ft of gas per (degree-day) (square foot of hot water radiation). From Table 5. the correction factor is 0.875 for --10 F outside design tem perature, hence 0.875 X 0.085 = 0.07438. By Equation 4, F = 0.07438 X 1000 X 6282 = 467,255 cu It. Estimating Oil Consumption Unit fuel consumption factors for oil, similar to those for gas in Table 2, are given in Table 3. The factors in Table 3 apply only to an inside design temperature of 70 F and an outside design temperature of OF. For other outside design temperatures, the constants in iTable 3 must be multiplied by the values in Table 5 as explained under Estimating Gas Consumption. Values given in Table 3 assume the use of oil with a heating value of 140.000 Btu per gallon. For other heating values, multiply the values in Table 3 by the ratio of 140,000 divided by the heating value per gallon of fuel being used. Example 6. Estimate the seasonal oil consumption of an oil-fired boiler in a building located in Minneapolis having a calculated heat loss of 192,000 Btu per hour, burning 144.000 Btu per gallon oil and operating at a seasonal efficiency of 60 per cent. The out side design temperature for Minneapolis is --20 F, and the inside design temperature is 70 F. Solution. From Table 3, under 60 per cent efficiency and opposite the bottom column, the value of V is found to be 0.00476 gal per 1000 Btu hourly heat loss for 0 F outside temperature. The correction factor for --20 F outside design temperature from Table 5 is 0.778. Solving, 0.778 X 0.00476 = 0.00370. Making a further correction for the heating value: 140 000 0.0037 X 144 000 " 0.0036 gal per 1000 Btu per hour calculated heat loss per degree- day. From Table 1, the normal degree-days for Minneapolis are 7966. Since V is ex pressed in 1000 Btu, N is equal to 192. Substituting in Equation 4: F = 0.0036 X 7966 X 192 = 5506 gal. Estimating Coal or Coke Consumption Coal or coke consumption estimates are made in exactly the same procedure as for oil. Values of U are given in Table 4 which only apply to an inside design temperature of 70 F and an outside design temperature of 0 F. A correction must be made for other conditions by use of the mul tiplying factors in Table 5. Data in Table 4 are based on 12,000 Btu per Table 5. Correction Factors for Outside Design Temperatures3 Outside Design Temp. F Deg___ Correction Factor__ ____ __ -20 0.778 -10 0.875 0 1.000 + 10 1.167 20 1.400 "The multipliers in Table 5, which are'high for mild climates and low for cold regions are not in error as might appear. The unit figures in Tables 2, 3, and 4 are per square foot of radiator or thousand Btu heat loss per degree-day. For- equivalent buildings and heating seasons, those in warm climates have lower design heat losses and smaller radiator quantities than those in cold cities. Consequently, the unit figure m quantity of fuel per (square foot of radiator) (degree-day), is larger for warm localities than for colder regions. Since the northern cities have more radiator surface per given building and a higher seasonal degree-day total than cities in the south, the total fuel per season will be larger for the northern city.