vacguy
Mechanical
- May 13, 2002
- 4
Good Morning All-
We are a manufacturer of industrial heating equipment, mostly metallurgical heat treating furnaces.
We build a small furnace for a customer that uses two ribbon-type burners mounted in a small enclosure that is used to heat an area measuring 6-8" wide by 60" long on a sheet of 1/8" mild steel plate. The burners are located above and below the steel being heated and are rated at 900,000 Btuh each (1.8 million total). They produce a sheet of flame down their length that impinges directly on the steel sheet.
We have a total of 45 seconds to heat the steel. Using the burners at their rated input, we can achieve a temperature of around 1550F in that amount of time.
During testing, we overdrove the burners to almost 3,000,000 total (something we don't want to do in production)and were able to get to 1700F in the 45 sec. Doubling he input only gained us around 150F.
I think what was happening is that the flame temperature of the (stoichiometric) natural gas flame was staying essentially the same at the higher input, so the delta T between the flame and the work was staying the same. All we were doing is changing the film coefficient at the surface with the higher velocity flame. Most of the added heat was just going up the flue.
Our customer is happy with the current performance at the rated input of the burners, however, he has an application that requires that the steel temperature reaches 1800F in the same 45 seconds, still using natural gas.
Apologies for the length of the post, but does anyone have any suggestions as to how to get to 1800?
TIA,
Rich R.
We are a manufacturer of industrial heating equipment, mostly metallurgical heat treating furnaces.
We build a small furnace for a customer that uses two ribbon-type burners mounted in a small enclosure that is used to heat an area measuring 6-8" wide by 60" long on a sheet of 1/8" mild steel plate. The burners are located above and below the steel being heated and are rated at 900,000 Btuh each (1.8 million total). They produce a sheet of flame down their length that impinges directly on the steel sheet.
We have a total of 45 seconds to heat the steel. Using the burners at their rated input, we can achieve a temperature of around 1550F in that amount of time.
During testing, we overdrove the burners to almost 3,000,000 total (something we don't want to do in production)and were able to get to 1700F in the 45 sec. Doubling he input only gained us around 150F.
I think what was happening is that the flame temperature of the (stoichiometric) natural gas flame was staying essentially the same at the higher input, so the delta T between the flame and the work was staying the same. All we were doing is changing the film coefficient at the surface with the higher velocity flame. Most of the added heat was just going up the flue.
Our customer is happy with the current performance at the rated input of the burners, however, he has an application that requires that the steel temperature reaches 1800F in the same 45 seconds, still using natural gas.
Apologies for the length of the post, but does anyone have any suggestions as to how to get to 1800?
TIA,
Rich R.
