Document 2q0gz24rONw88nBkZQXn8rjMR

HEATINC VENTILATINC AIR CONDITIONING CUIDE 1944 Fuel used over any period is, according to the theory of the degree-day, proportional to the number of degree-days during the period. From Table 3, the average numbers of degree-days for November, December! and January in Marquette are 927, 1306, and 1471, a total of 3704. The yearly total is 8786, so that during these three months the estimated consumption is: ' 0704 X 109,200 = 46,200 lb. 8786 Estimating Steam Consumption In estimating steam consumption the efficiency is generally assumed at 100 per cent. If for low pressure steam an average heating value of 1000 Btu per pound of steam is used no correction is necessary. In com paring values from different cities, correction should be made for design temperature (see Table 7) when the unit figures are in terms of square foot of radiator or 1000 Btu per hour calculated heat loss, but not when the values are in terms of building volume or floor space. Consideration has been given to the difference in steam utilization of different types of buildings and Table 8 shows actual average units for these various types. . These figures were obtained from operating results in 896 buildings located in all sections of the United States. Being averages, and for small groups in each type, the figures may need con siderable modification to allow for local variations. It should be especially noted that the steam used for heating hot water is not included in the values given in Table 8. Table 8. Steam Consumption of Buildings with Various Types of Occupancy3 Type of Building No. Bldgs. Office.................................................... .. Office and Bank.1.................................... Office and Printing................................ Office and Theater. .......................... Office and Stores or Shops................... Bank.............. .......... ............. ......... Department Store.................................. Stores. ............. ....................................... Loft....... -.................................................. Warehouse................................................ Hotel and Club....................................... Apartment or Residence...... .......... .. Theater........................ ............................. Garage.................................................... Manufacturing. ......................... ........... Church. ......................................... Hospital........ ............................................ School................ .... .............................. Municipal or Federal............... ,,.......... Lodge, Gym, Hall or Auditorium. .... Miscellaneous.- _______________ _ Total or Average........................... 334 49 8 7 26 16 63 73 63 24 73 51 22 13 19 9 4 8 15 12 7 . 896 Average Volume Space 1000 Cu Ft Steam for Heating Lb per DD per 1000 Cu Ft 2160 0.685 3000 - - 0.577 1895 4950 1.230 0.412 1615 0.617 806 0.786 3400 310 865 2230 1795 1425 1240 1540 0.385 0.624 0.588 0.459 0.990 0.962 0.482 0.202 1350 656 3306 1115 0.808 0.532 1.194 0.592 3215 880 0.587 0.390 1387 0.479 -- -- 1890 0.651 Average Hours of Occupancy 12.1 13.1 17.7 12.9 13.2 11.7 11.1 10.4 10.0 9.4 22.3 21.8 12.9 21.4 9.5 7.9 22.0 11.5 15.6 12.4 21.4 -- 13.4 Principles of Economical Heating, National Association of Building Owners and Managers. 234 CHAPTER 11. ESTIMATING FUEL CONSUMPTION Example 8. A store in Philadelphia with a heating system designed to maintain 70 F inside in 0 F weather has 250,000 cu ft of heated space. What would be the estimated average yearly steam consumption of purchased steam for heating? Solution. According to Table 8, a store would use 0.624 lb of steam per degree-day per 1000 cu ft heated space. From Table 3, Philadelphia has 4749 degree-days per normal year. Inserting in Equation 4: F = 0.624 X 250 X 4749 = 740,000 lb of steam. Degree-Day as an Operating Unit The use of the degree-day as a fuel predicting unit, explained in the foregoing, is perhaps the lesser of its two most used applications. It is also widely used as a unit for eliminating the weather (temperature) variable for existing plants from month to month or year to year. The degree-days given in Table 3 are normals or averages. For operating data the actual number occurring for a given month and year in a city under consideration is recorded. Since fuel consumption is proportional to the number of degree-days, plant operators frequently compute each month, the fuel burned per degree-day by the heating plant. The resulting unit figure, by eliminating the outside temperature variable, indicates whether the operating efficiency of the plant is above or below the previous month or year. MAXIMUM DEMANDS AND LOAD FACTORS In one form of district heating rates, a portion of the charge is based upon the maximum demand of the building. The maximum demand may be measured in several different ways. It may be taken as the instan taneous peak or as the rate of use during any specified interval. One method is to take the average of the three highest hours during the winter. These figures are available for a number of buildings in Detroit, as shown in Table 95. These maximum demands were measured by an attachment on the condensation meter and therefore represent the amounts of condensation passed through the meter in the highest hours, rather than the true rate Table 9. Building Load Factors and Demands of Some Detroit Buildings Building Classification Printing..................................................................-- -- Load Factor 0.318 0.316 0.287 0.263 0.255 0.238 0.223 0.203 0.158 0.138 0.126 L orb Demand per Hour S orper q Ft Equivalent Installed Radiator Surface 0.184 0.207 0.217 0.209 0.225 0.182 0.248 0.158 0.152 0.145 0.151 5The Heat Requirements of Buildings, by J. H. Walker and G. H. Tuttle (A.S.H.V.E. Transactions, Vol. 41, 1935, p. 171), 235