Document Exzpzn7YOn7ed7O4Mp0XGw6Nn

HEATING VENTILATING AIR CONDITIONING CUIDE 1940 gas passages must not be so small as to cause excessive resistance to the flow of gases where natural draft is employed. Inserting baffles so that the heating surface is arranged in series with respect to the gas flow increases boiler efficiency and reduces stack temperature and increases the draft loss through the boiler. Heat Transfer Rates Practical rates of heat transfer in heating boilers will average about 3300 Btu per sq ft per hour for hand-fired boilers and 4000 Btu per sq ft per hour for mechanically fired boilers when operating at design -load. When operating at maximum load1 these values will run between 5000 and 6000 Btu per sq ft per hour. Boilers operating under favorable conditions at the above heat transfer rates will give exit gas temperatures that are considered consistent with good practice. TESTINC AND RATING CODES The Society has adopted-four solid fuel testing codes, a solid fuel rating code and an oil fuel testing code. A.S.H.V.E. Standard and Short Form Heat Balance Codes for Testing Low-Pressure Steam Heating Solid Fuel Boilers--Codes 1 and 2--(Revision of June 1929)*, are intended to provide a method for conducting and reporting tests to determine heat efficiency and performance characteristics. A.S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers--Code No. 3--(Edition of 1929)* is intended for use with A.S.H.V.E. Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers*. The object of this test code is to specify the tests to be conducted and to provide a method for conducting and reporting tests to determine the efficiencies and performance of the boiler. The A.S.H.V.E. Standard Code for Testing Steam' Heating Boilers Burning Oil Fuel* is intended to provide a standard method for con ducting and reporting tests to determine the heating efficiency and per formance characteristics when oil fuel is used with steam heating boilers. In 1938 the Society adopted a Standard Code for Testing Stoker-Fired Steam Heating Boilers6 which is intended to provide a test method for determining the efficiency and performance characteristics of any stoker or boiler combination' burning any type of solid fuel such as anthracite or bituminous coal. The Steel Heating Boiler Institute has adopted a method for the rating of low pressure boilers based on their physical characteristics and ex pressed in square feet of steam or water radiation or in Btu per hour as given in Table 2. The detailed requirements of this code were outlined in Chapter 13 of The Guide 1939. The Institute of Boiler and Radiator Manufacturers has also adopted a method of rating cast-iron heating boilers based upon performance obtained under tests. This code became effective August 1, 1939 for sectional boilers of 20 in. width grate or less, but the Institute intends eventually to expand the code to apply to all For definitions of design load and maximum load see page 246. See A.S.H.V.E. Transactions. Vol. 35, 1929, pp. 322 and 332. See A.S.H.V.E. Transactions. Vol. 36, 1930, p. 42. See A.S.H.V.E. Transactions. Vol. 37, 1931.- p. 23. See A.S.H.V.E. Transactions. Vol. 44, 1938, p.*366. 244 CHAPTER 13. HEATING BOILERS Table 2. Steel Heating Boiler Standard Ratings3 Hand-Fired Rating Mechanicallt-Fibed Rating Steam Radiation SqFt Catalog Water Radiation SqFt Btu per Hour in Thou sands Net Load Steam Radiation SqFt Heating Surface SqFt | Grate Area SqFt Steam Radiation SqFt Catalog Water Radiation Sq Ft Net Load Furnace Vol Btu per ume, Oil, Gas Steam * or Bituminous Hour in Radiation Coal Cu Ft Thousands Sq Ft 1,800 2,200 2,600 3,000 3,500 4,000 4,500 5,000 6,000 7,000 8,500 10,000 12,500 15,000 17,500 20,000 25,000 30,000 35,000 2,880 432 3,520 528 4,160 624 4,800 720 5,600 840 6,400 960 7,200 1,080 8,000 1,200 9,600 1,440 11,200 1,680 13,600 2,040 16,000 2,400 20,000 3,000 24,000 3,600 28,000 4,200 32,000 4,800 40,000 6,000 48,000 7,200 56,000 8,400 1,389 1,702 2,020 2,335 2,732 3,135 3,540 3,945 4,770 5,608 6,885 8,197 10,417 12,500 14,584 16,667 20,834 25,000 29,167 129 158 186 215 250 286 322 358 429 500 608 715 893 1,072 1,250 1,429 1,786 2,143 2,500 7.9 8.9 9.7 10.5 11.4 12.2 13.4 14.5 16.4 18.1 20.5 22.5 25.6 28.4 30.9 33.2 37.4 41.2 44.7 2,190 2,680 3,160 3,650 4,250 4,860 5,470 6,080 7,290 8,500 10,330 12,150 15,180 18,220 21,250 24,290 30,360 36,430 42,500 3,500 4,280 5,050 5,840 6,800 7,770 8,750 9,720 11,660 13,600 16,520 19,440 24,280 29,150 34,000 38,860 48,570 58,280 68,000 525 643 758 876 1,020 1,166 1,312 1,459 1,749 2,040 2,479 2,916 3,643 4,372 5,100 5,829 7,286 8,743 10,200 1,695 2,089 2,461 2-,853 3,335 3,830 4,330 4,834 5,850 6,885 8,490 10,125 12,650 15,183 17,708 20,242 25,300 30,359 35,417 15.7 19.2 22.6 26.1 30.4 34.8 39.1 43.5 52.1 60.8 73.8 86.8 108.5 130.2 151.8 173.5 216.9 260.3 303.6 Adopted by the Steel Heating Boiler Institute in cooperation with the Bureau of Standards, United States Department of Commerce Simplified Practice Recommendations R 167-36. sizes of boilers. Methods of testing hand-fired and oil-fired, boilers are specified and are referred to as IBR testing codes. BOILER OUTPUT Boiler output as defined in A.S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers (Code No. 3) is the quantity of heat available at the boiler nozzle with the boiler normally insulated. It should be based on actual tests conducted in accordance with this code. This output is usually stated in Btu and in square feet of equivalent heat ing surface (radiation). According to the A.S.H.V.E. Standard Code for Rating Steam Heating, Solid Fuel Hand-Fired Boilers, the performance data should be given in tabular or curve form on the following items for at least five outputs ranging from maximum down to 35 per cent of maxi mum: (1) fuel available, (2) combustion rate, (3) efficiency, (4) draft tension, (5) flue gas temperature. The only definite restriction placed on setting the maximum output is that priming shall not exceed 2 per cent. These curves provide complete data regarding the performance of the boiler under test conditions. Certain other pertinent information, such as grate area, heating surface and chimney dimensions is desirable also in forming an opinion of how the boiler will perform in actual service. The output of large heating boilers is frequently stated in terms of boiler horsepower instead of in Btu per hour or square feet of equivalent radiation. 245 10