14 



CIRCULAR 4*3. U. 



DEPARTMENT of AGRICULTURE 



With a thermal efficiency of 60 percent the 

 of water will require in the neighborhood 

 quantity of heat would be supplied by 4i 

 •5.500 cubic feet of natural gas fuel. 



In practice final dilution of furnace ga; 

 aiy air inlet. This inlet is so arranged ' 

 wanned by passing over heated portions 

 bustion chamber note drawing of Dut ?h- 

 The furnace gases may be still further chit; 

 just ahead of the drier inlet although thh 



to 



poration of 3,000 pounds 

 5,500,000 B. t. u. This 

 45 gallons of fuel oil or 



;es takes place at the second- 

 hat the atmospheric air is 

 of the exterior of the com- 

 oven type of furnace, fig, 7 . 

 ted by providing an opening 

 « is not essential. 





-'- '- e- 



cn 





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FlGU&S 



i 



Furnace design may be either of the cylindrical or rectangular cross 

 section figs. 7 and S\ The rectangular cross-section furnace is 

 usually termed the Dutch-oven type and can be built more eco- 

 nomically than the cylindrical type of furnace because only the stand- 

 ard shaped firebrick are required in the combustion chamber. The 

 outer wall can be built of ordinary second-hand construction brick. 

 These two general types of furnaces are adaptable for burning either 

 oil or gas fuels. 



The problem of utilizing solid fuels in drying forage is one requiring 

 special consideration, so that the diying gases are rendered smokeless 

 and do not contain incandescent particles of hying ash. Oil- or gas- 

 burning equipment possesses advantages that place the coal- or coke- 

 burning furnace at a disadvantage for hay driers unless a mechanical 

 stoker is available. 



In order not to localize the combustion of the fuel in too small a 

 space it has been found that, with the fuel oil used at Jeanerette, from 

 1.75 to 2 pounds of oil may be fired per hour per cubic foot of com- 

 bustion space. This quantitv of oil has a heat value of about 33,000 

 B. t. u. 



In drying hay it required the combustion of a fuel capable of gener- 

 ating approximately 5.500.000 B. t.u. of heat energy to evaporate 3,000 

 pounds of water per hour. On the above basis it would require a com- 

 bustion chamber with a volume of from 165 to 175 cubic feet. For 

 practical purposes the dimensions might be as follows: Width 4 feet. 

 height to top of arch 5 feet, and length to bridge wall 10 feet. 



The combustion of gaseous fuels is relatively simple, reqtiring only 

 a suitable mixing carburetor. For oil fuels it is essential that there 

 be smokeless combustion which can be accomplished only by thorough 

 atomization of fuel. Under ordinary conditions, satisfactory results 

 are more certain if oil having a specific gravity greater than 0.03 is not 

 used. This specific gravity corresponds to 2 j.6 : American Petroleum 

 Institute' . Fuels heavier than this usually require preheating equip- 

 ment in order to insure proper combustion. 



