Burner Sizing | Rasert™
Bulletin 4748 Page 6
HEAT FLUX and BURNER SIZING
Each RASERT configuration must be individually quoted. Information required to quote burners includes the quantity and firing rate of each burner, radiant tube diameter and length, furnace wall thickness (drawings preferred) and furnace temperature. Contact a North American Sales Representative or our Cleveland Office for more information. ORDERING INFORMATION temperature distribution on the radiant tube, the more heat can be transferred to the furnace load without over-firing the tube. In a 1500°F furnace heat flux should generally be kept under 85 Btu/hr/in 2 . As the furnace temperature increases the maximum heat flux that can be applied to the tube decreases. At a furnace temperature of 1850°F the heat flux should be no higher than 50 Btu/hr/in 2 . radiant tube determines the material selection. The combustion tube on a 4748 RASERT will run approximately 125°F hotter than the radiant tube temperature. The more uniform the
There are a number of important considerations when matching a 4748 RASERT to a radiant tube. The most obvious is the diameter of the burner and the I.D. of the radiant tube, but it is also important to not over fire the tube. The heat flux of the tube is the amount of heat that is being transferred through the tube. It is often expressed as Btu/h HHV transferred per square inch of effective tube surface area (Btu/ hr/in 2 ). The total amount of heat transferred through the tube can be found by multiplying the burner input by the available heat. (example: 140 cfh gas 1,000 Btu/cf 68% available heat = 95,200 Btu/h HHV) The effective tube surface area is simply the area of the radiant tube inside the furnace, and does not include tube surface inside the walls. ( Example : 7.56 p 58" = 1378 in 2 .) So for this example tube and firing rate: 95,200 Btu/hr/1378 in. 2 = 69.1 Btu/hr/in 2 . The maximum heat flux possible is dependent on a number of factors including maximum tube temperature, tube uniformity, and inner and outer tube material. The peak temperature on a
WARNING: Situations dangerous to personnel and property may exist with the operation and maintenance of any combustion equipment. The presence of fuels, oxidants, hot and cold combustion products, hot surfaces, electrical power in control and ignition circuits, etc., are inherent with any combustion application. Components in combustion systems may exceed 160°F (71°C) surface temperatures and present hot surface contact hazard. Fives North American Combustion, Inc. suggests the use of combustion systems that are in compliance with all Safety Codes, Standards, Regulations and Directives; and care in operation.
CONTACT fna.sales@fivesgroup.com T +1 800 626 3477 - F +1 216 373 4237
Fives North American Combustion, Inc. 4455 East 71st Street - Cleveland, OH 44105 - USA www.fivesgroup.com
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