Document gb9GQyyV4jKrO6xZbdaNzGa5q

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 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 951, 1314, and 1510, a total of 3775.. The yearly total is 8721, so that during these three months the estimated consumption is: X 108,419 = 46,945 lb. 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 iio 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 83 shows actual average units for these various types. These figures are obtained from operating results in 196 buildings located in 21 different cities in 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 included in the values Table 8. Steam Consumption for Various Classes of Buildings3 ,, (Heating Season Only) Building Classification - No. OF Buildings Lifted * Steam Consumption Pounds per Degree-Dat--65 F Basis^ Per M Co Ft Per M Sq Ft Per M Btu of Heated of Radiators per Hour of Space -Surface TTfftt Lofisd Department Stores. ........................................... 16 1.78 10 1.46 12 1.32 7 1.25 10 0.96 18 0.90 6 0.90 10 0.89 7 0.88- 8 . 0.83 6 . 0.58 14 0.57 6 0.42 35 1.09 35 0.975 97.5 80.6 64.2 105.5 ,77;0" 80.6 75.0 .72.3 45.2 62.2 49.4 60.7 72.3 70.0 65.4 0.359 0.371 0.268 0.498 0.283 0.238 0.283 0.256 Includes steam for heating' domestic water for heating season only. bThe figures are a numerical--not a weighted-average for the several buildings in each class, cEquivalent steam radiator surface. dHeat loss calculated for maximum design condition (in most cases 70 F inside, zero outside). Based on zero consumption at 55 F. The Heat Requirements of Buildings, by J. H. Walker and G. H. Tuttle (A.S.H.V.E. Transactions, VoL 41, 1935, p. 171). CHAPTER 11. ESTIMATING FUEL CONSUMPTION Table 9. Building Load Factors and Demands of Some Detroit Buildings Building Classification Clubs and Lodges............................................................ Printing...................................................... ....................... Apartments...... ......................--.................. -....... ........ Retail Stores--------------------.........................................-- Auto Sales and Service. ......... .................................. Banks---------- ----------;----------- ............ ............................. Churches--------------------------------------------- .................. Department Stores.... ................................................ . Theaters............... ...... ....................................................... Load Factor 0.318 0.316 0.287 0.263 0.255 0.238 0.223 0.203 0.158 0.138 0.126 . Lb of Demand per Hour per Sq Ft op 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 given in Table 8, but in the case of office buildings, the steam for heating only is also shown. Presentation of the unit consumption in three ways permits making the estimate if either the calculated heat loss or the volume of net heated space.in the building is known. Example 8. A store in Philadelphia with a-heating system designed to maintain 70. F inside in 0 F weather has 1700 sq ft of equivalent direct steam radiator surface, .and uses only moderate quantities of hot water. What would-be the estimated average yearly steam consumption of purchased steam for heating and for hot water during the heating* season? _ Solution. According to Table 8, a store (0 to 70 F conditions) would use 80.6 lb of steam per thousand square feet of radiation per degree-day, including winter hot water. From Table 3, Philadelphia has 4784 degree-days per normal year. Inserting in Equation 2: F = 80.6 X 1.7 X 4784 = 655,504 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-thenumber 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 239