Document ZnzEqvR36Qm3rM2vNQXkkXG9Z

270 CHAPTER 14 1946 Guide - HentineLoad 271 retained in the room if the product being manufactured is not removed ' until its temperature is the same.as the room temperature. If power is transmitted to the machinery from the outside,-then only ' the heat equivalent of the brake horsepower supplied is used. In the _ ,, Motor horsepower . first case the Btu supplied per hour = Effidencyof m3tor X 2546, and in the second case Btu per hour = bhp X 2546, in which 2546 is the Btu equivalent of 1 hp-hr. In some mills this is the chief source of heating and it is frequently sufficient to overheat the building even in zero weather, thus requiring cooling by ventilation the year round.. The heat (in Btu per hour) from electric lamps is obtained by multi plying the watts per lamp by the number of lamps and by 3.413. One cubic foot of producer gas gives off about 150 Btu; one cubic foot of manufactured gas about 535 Btu; and one cubic foot of natural gas about 1000 Btu. A Welsbach burner averages 3 cu ft of gas per hour arid ' a fish-tail burner, 5 cu ft per hour. For information concerning the heat supplied by persons, refer to data given in Chapter 12. INTERMITTENTLY HEATED BUILDINGS In the case of intermittently heated buildings additional heat is required for raising the temperature of the air, the building, materials and the material contents of the building to the specified inside temperature. The rate at which this additional heat must be supplied depends upon the heat capacity of the structure and its material contents and upon the time in which these are to be heated 7. This additional heat may be figured and allowed for as conditions re quire,, but inasmuch as the heating system proportioned for taking care of the heat losses will usually have a capacity about 100 per cerit greater than that required for average winter weather, and inasmuch as most buildings iriay either be continuously heated or have more time allowed for heating-up during the few minimum temperature days,- no allowance is usually made except in the size of boilers or furnaces. For churches, auditoriums and other interfiiitieritly. heated buildings, additional capacity should be provided. RESIDENCE HEAT LOSS PROBLEMS Example 6. Calculate the heat loss of residence shown in Fig. 2 located in the vicinity of Chicago. Assume inside and outside design temperatures to be 70;F and ; --10 F respectively. The attic is unheated: Assume ground temperature to be ,50. F under basement'and garage floors, and 32 F adjoining basement walls. Estimate in filtration by crack method, assuming average wind velocity to be 12.5 mph during December, January and February, No Wall, ceiling or roof insulation is to be figured in this problem, but all first and second floor windows are to have storm sash. The building ' is constructed as follows (transmission coefficients (17) in parentheses): Walls: Brick veneer, building paper, wood sheathing, studding, metal lath and plaster (0.28). Walls of dormer over garage, same except wood siding in place of brick veneer (0.26). AUic Walls: Brick veneer, building paper, wood sheathing on stiidding'(0.42). Basement Walls:.. 10 in.concrete.(0.10). Roof: Asphalt shingles on wood sheathing on rafters (0.53). Ceiling [Second floor): Metal lath and plaster (0.69). Windows: Double-hung wood windows with storm sash (0.45).. Steel casement sash in basement (1.13). Floor [Bedroom D): Maple finish flooring on yellow pine sub-flooring;-metal lath and.plaster ceiling below (0.25).