Document 71eYxn5L8KLaO4XZxV5mM657R

HEATINC VENTILATINC AIR CONDITIONING GUIDE 1941 The factors in Table 4, as corrected if necessary, are satisfactory for regions having 3500 to 6500 degree-days per heating season. In regions with less than 3500 degree-days the unit gas consumption is higher than given; where over 6500, the unit is less than given. Ten per cent addition or deduction in these cases is recommended by AGA publications. For gas heating values other than those given in Table 4, simply inter polate or extrapolate. It will also be noted that Table 4 applies only to small installations. In general the larger the installation the smaller the unit gas consumption becomes and the values in the table should be used with care, if at all, in large gas-burning installations. Example 7. Make an estimate of the gas required to heat a building located in Chicago, III., assuming that the calculated heating surface requirements are 1000 sq ft of hot water radiation based on design temperature of 0 F and 70 F. Chicago has 800 Btu mixed gas, and 6027 degree-days. Solution. Using Equation 3 and Table 4, the fuel consumption for a design tem perature of 0 F with 800 Btu gas is found to be 0.085 cu ft of gas per degree-day per square foot of hot water radiation. 0.085 X 1000 X 6027 = 512,295 cu ft. Estimating Oil Consumption Unit fuel consumption factors for oil, similar to those for gas in Table 4 are given in Table 6. The factors in Table 6 apply only to an inside design Table 4. Factors for Estimating Gas Consumption* Btc VALUE or Gas rsR Cu Ft 500 535 800 1000 Hot Wateb Cu Ft Gas per Degree-Day per Sq Ft Radiator Up to 500 8q Ft 500 to 1200 Sq Ft Over 1200 Sq Ft 0.142 0.132 0.089 0.071 0.135 0.126 0.085 0.068 0.128 0.120 0.081 0.065 Steam Warm Air Cu Ft Gas per Degree-Day per Sq Ft Radiator Up to 500 Sq Ft 300 to 700 Sq Ft Over 700 8q Ft Cu Ft Gas per Degree-Day per 1000 Btu Hourly Design Heat Loss 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 0.001 IS 0.00110 0.00428 0.00409 Abstracted from Comfort Heating, American Gas Association, 1038, Table 5. Correction Factors for Outside Design Temperatures Outside Design Temp. Deg F -20 -10 0 +10 +20 Inside Design Temp. Deg F 70 70 70 70 70 Multiplt Values in Tables 4, 6 and 7 bt 0.778 0.875 0.000 1.167 1.400 216 CHAPTER 10. HEAT AND FUEL UTILIZATION teroture of 70 F and an outside design temperature of 0 F. For other **"tside design temperatures, the constants in Table 6 must be multiplied b*1 the values in Table 5 as explained under Estimating Gas Consumption. Table 6 assumes the use of oil with a heating value of 140,000 Btu per allon. For other heating values, multiply the values in Table 6 by the ratio of 140,000 divided by the heating value per gallon of fuel being used. Example 8. What would be the estimated seasonal oil consumption of a boiler. T". un;t in Minneapolis of a building having a calculated heat loss of 192,000 Btu per Bur burning 144,000 Btu per gallon oil and operating at a seasonal efficiency of 60 60 rent if the outside design temperature for Minneapolis is -- 20 F, and the inside temperature is 70 F? Solution. From Table 6, under 60 per cent efficiency and opposite the bottom column, find the uncorrected U to be 0.00476 gal per 1000 Btu hourly heat loss. Table 5, the correction multiplier for -20 F outside design temperature is 0778 Solving, 0.778 X 0.00476 = 0.00370. Making a further correction for the heating value: 0 0037 X = 0.0036 gal per 1000 Btu per hour calculated heat loss per degree- day. From Table 3, the average degree-days for Minneapolis number 7883, and from the problem N = 192. Substituting in Equation 3: nrtnots v/ *7000 v/ iao pa an___1 Table 6. Unit Fuel Consumption* Constants for Oil*> Unit 40 Gal Oil per Sq Ft Steam Radiator.. 0.00172 EmciENCT m Peb Cent 50 60 70 0.00137 0.00114 0.00098 80 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 0.00715 0.00571 0.00476 0.00409 0.00358 Based on a beating value of 140,000 Btu per gallon. ^Abstracted by permission from Degree-Day Handbook (Second Edition, 1037), by C. Strock and C. H. B. Hotchkiss. Table 7. Unit Fuel Consumption4 Constants for Coal*> Unit 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 Emeuscr uf Peb Cent 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 beating value of 12.QQ0 Btu per pound. ^Abstracted by permission from Degree-Day Handbook, (Second Edition, 1937), by C. Strock and C. H. B. Hotchkiss. 217