Document pBOOjeByezydRqMgzrGGZpwrk

222 . Chapter 11 1945 Guide !v 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 6) 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 7 shows actual average units for Table 7. Steam Consumption of Buildings with Various Types of Occupancy3 Type of Building No. Bldgs. i Office........ ................................ ............. Office and Bank........................... ........ 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 Heated Space 1000 Cu Ft - Steam for Heating Lb per DD per 1000 Cu Ft Average Hours of Occupancy 2160 3000 1895 4950 1615 806 3400 310 865 2230 1795 1425 1240 1540 1350 656 3306 1115 3215 880 1387 . 0.685 0.577 1.230 0.412 0.617 0.786 0.385 0.624 0.588 0.459 0.990 0.962 0.482 0.202 0.808 0.532 1.194 0.592 0.587 0.390 0.479 ' 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 , 1890 0.651 .13.4 Principles'of Economical Heating,,Naiicnci Association of Building Owners and Managers. 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 7. 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 7, a store would use 0.624 lb of steam per degree-day per 1000 cu ft heated space. From Table 2, 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 mwn in Table 2--------I- V?TM nnor,hno data Table 8. Heat Consumption Record for Comparison , Heating Season 1942-43 . Col. 1 Col. 2 Col. 3 Total Consumption Consumption For Heating Oct.......... Nov......... Dec.......... Jan.......... Feb... ... Mar......... Apr. May June....... . Ttilv 337,500 834,200 1,446,600 2,176,400 2,332,200 2,131,100 2,021,900 1,241,500 672,500 258,600 188,400 IRQ, 100 13.82L000 170,500 667,200 1,279,600 2,009,400 2,165,200 1,964,100 1,854,900 1,074,500 505,500 91,600 Col. 4 AVG. Temp. 65 53 44 25 , 22 28 31 43 . 55 . Col. 5 Deg Days 65 F Base 146 339 641 1,233 1,297 1,106 1,032 647 303 50 Col. 6 .Col. 7 Lb/Deg Lb/Dbg Day/ M Cu Ft 1,170 1,966 1,990 1,630 1,670 1,775 1,799 1,660 1,670 1,830 , 0.575 0.970 0.982 0.804 0.822 0.888 0.885 0.818 0.822. 0.905 . Heating Season 1943-44 Col. 1 Col. 2 Col. 3 Total Consumption Consumption For Heating Sept......... Oct.. Nov.. 330,200 887,100 1,525,200 Dec. 2,045,500 Jan... ..... . 1,933,400 . Feb_ 1,990,200 Mar. . 1,984,100 Apr.. May June Tulv Au&. Total--. 146,200 . 703,100 1,341,200 1,861,500 1,749,400 1,806,200 1,800,100 Col. 4 Avg. Temp. 61 52 . 39 28 30 30 31 Col. 5 Deg Days Base 167 410 812 ' 1,120, 1,044 1,111 1,021 ' Col'. 6 Lb/Deg Day 875 1,718 1,653 1,660 1,670 1;624 1,760 Col. 7 Lb/Deg Day/ MCuFt 0.431 0.845 . 0.815 . 0.817 0.825 0.800 0.868 - If, for example, the heat consumption in March, 1943, is compared with that-in March, 1944, it will be found that in the latter the steam consumption is 1799 -- 1760 = 39 (b less which is a decrease of 2.2 per cent. 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. The figures in Table 8 illustrate a typical example of a method of