Document Evv6XaKdbXzem3zjJkweD6XNN

Heating Ventilating Air Conditioning Guide 1939 2 0 What factors should be taken into consideration when determining tk efficiency at which a fuel will be burned? e Manufacturers' catalogs usually give equipment efficiencies obtained under test cod ditions. These values do not allow for poor attendance, defects in installation, or pooi draft. Such efficiencies do not consider heat radiated from the outside of the equipment but in many cases this heat is utilized. Neither do they allow for the fact that the ef* ficiency under less than rated capacity is frequently lower than at the rating point 3 Make an estimate of the gas required to heat a building located in Chicago 111., assuming that the calculated heating surface requirements are 1000 sq of hot water radiation based on design temperature of 0 F and 70 F. Chicago has 800 Btu mixed gas, and 6290 degree-days. 6 Using Equation 3 and Table 4, the fuel consumption for a design temperature 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 6290 = 534,650 cu ft. 4 A building in Marquette, Mich., has an hourly heat loss at design con ditions of 240,000 Btu per hour. If the inside design temperature is to be 70 F and the outside design temperature is --10 F, what will be the estimated norm^ seasonal coal consumption for heating if 12,000 Btu per pound fuel is burned at a 50 per cent seasonal efficiency, and what part of the total will he used during November, December, and January? From Table 7, U, uncorrected, is 0.0666 lb of coal per 1000 Btu per hour heat loss. Correcting for the outside design temperature, Table 5, the corrected value of U is 0.875 X 0.0666 = 0.0583. From Table 3, D is 8693 and from the problem N is 240. Substituting in Equation 3: F = 0.0583 X 240 X 8693 = 121,632 lb. 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 number of degree-days for November, December, and January in Marquette are 960, 1302, and 1500, a total of 3762. The yearly total is 8693, so that during these three months the estimated consumption is: X 121,632 = 52,638 lb. 5 Careful estimates of the probable fuel consumption of a building in Balti more based on average degree-days as shown in Table 3 indicated that the fuel consumed should total 13,600 gal of oil in a normal year. The first heating season the building was in operation, the winter was cold and the degree-days totaled 4741 and the oil consumed totaled 14,500 gal. Was the plant performing according to the estimate or not? From Table 3, the average number of degree-days in Baltimore is 4533. During the period under consideration the degree-days were above normal, so that the calculated consumption would have been: t X 13,600 gal = 14,223 gal. Since the building consumed 14,500 gal the operating performance was slightly worse than expected after allowance was made for the severe winter. 6 # Which item may be determined more closely, the heating value of a fuel or the efficiency of its combustion? The heating values of oil, gas, and solid fuels are closely determinable, whereas the efficiency of burning depends on the particular equipment chosen and the skill used in handling it. . . Chapter 13 HEA TING BOILERS Cast-Iron Boilers, Steel Boilers, Special Heating Boilers, Gas-Fired Boilers, Hot Water Supply Boilers, Furnace Design, Heating Surface, Testing and Rating Codes, Output Effic iency, Selection of Boilers, Connections and Fittings, Erection, s Operation and Maintenance, Boiler Insulation STEAM and hot water boilers for low pressure heating work are built in a wide variety of types, many of which are illustrated in the Catalog Data Section, and are classified as (1) cast-iron sectional, (2) steel fire tube. (3) steel water tube, and (4) special. CAST-IRON BOILERS Cast-iron boilers may be of round pattern with circular grate and hori zontal pancake sections joined by push nipples and tie rods, or of rec tangular pattern with vertical sections. The latter type may be either of outside header construction where each section is independent of the other and the water and steam connections are made externally through these headers, or assembled with push nipples and tie rods, in which case the . water and steam connections are internal. Cast-iron boilers usually are shipped knocked down to facilitate hand ling at the place of installation where assembly is made. One of the chief advantages of cast-iron boilers is that the separate sections can be taken into or out of basements and other places more or less inaccessible after the building is constructed. This feature is of importance in making repairs to or replacing a damaged or worn-out boiler and should be given consideration in the original selection. Sufficient space should be pro vided iri the boiler room for assembling the boiler and for disassembling it conveniently if repairs are needed. With the outside header type of boiler a damaged section in the middle of the boiler can be removed without disturbing the other sections so side clearance should be provided. Capacities of cast-iron boilers range from that required for small residences up to about 18,000 sq ft of steam radiation. For larger loads, cast-iron boilers must be installed in multiple, or a steel boiler must be used. In most cases cast-iron boilers are limited to working pressures of 15 lb for steam and 30 lb for water. Special types are built for hot water supply which will withstand higher local water pressures. STEEL BOILERS Two general classifications may be applied to steel boilers: first, with regard to the relative position of water and hot gases', distinguished as fire -tube or water tube; second, with regard to arrangement of furnace and 249