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Serious Heat Extraction!!

Serious Heat Extraction!!

Serious Heat Extraction!!

I have a 400kW heat source (H2/O2 flame) and I need to remove the heat from it.  The flame is about 5metres below roof level.  I estimate that if I have a flow of 1 cubic metre/sec of ambient air then I will need to extract air at a temperature of around 400 degC.  To me there seem to be three ways of extracting the heat:
1)  Install a chiney adequately sized to give an updraught of 1 m3/s.  I have no idea how big this would need to be.
2)  Install a "small" diameter trunking with a bifurcated fan and achieve the air flow with a high extractionvelocity
3)  Install a "large" diameter trunking with a bifurcated fan and achieve the air flow with a low extraction velocity

My primary concern is to have a fan that survives and also to minimise the running costs.  Obviously the chimney will be cheapest if it can work.

RE: Serious Heat Extraction!!

Can you afford to use inside air, or will you need to bring in outside air to help vent this?

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

RE: Serious Heat Extraction!!

The facility is actually in Singapore so using ambient air (constantly around 25-30degC) is no problem.  The operation runs with all the windows and doors open anyway!

RE: Serious Heat Extraction!!

Describe the process

1m3/sec for a 400kW load seems small

how big is the process area (where the flame is)

Is it a naked flame?

I would try to build a hood over the process and maintain a face velocity over it to capture the heat. The exhaust temp would still be high, but possibly not as high as 400C.

You can also draw fumes and mix room air into the extract system to dilute the fumes and cool them down.

400C is not particularly difficult to handle. Go to Woods Fans or NuAire Ltd. (Uk companies)

Friar Tuck of Sherwood

RE: Serious Heat Extraction!!


You could spray water into it.

About 350 l/min at modest pressure will cool it quickly.

Much smaller water flows can be effective, if you can get the water where it needs to be and increase its surface area.

Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

RE: Serious Heat Extraction!!

Hi MikeHalloran

It's interesting that you should mention using water spray.

I used to work for a fan company that made fire rated fans. The intersting thing was that they made fans rated at 300C, 400C and 800C. The 800C fan had a spray washer in it (a simple sprinkler head unit). It worked really well.

Friar Tuck of Sherwood

RE: Serious Heat Extraction!!

I admit I didn't just conjure it up out of the blue; it's what I do for a living these days.  We make parts for 'wet' exhaust systems, where seawater that's been used to cool boat engines is injected into the exhaust stream to cool it.

Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

RE: Serious Heat Extraction!!

Typically, a slower and larger blower wheel will give you the best efficiency and least noise. Same goes for larger ductwork.

Spend the extra money and use large ductwork and a large diameter blower wheel. You will save money in the long run.

However, I would go for the smaller wheel and duct if what I am doing is using the waste heat to run a waste heat boiler for process steam or to run a small steam turbine.

RE: Serious Heat Extraction!!

If the plant does not operate under a negative condition because of process exhaust, an open flame will create enough draft to exhaust through a duct or flue.  ACGIH's manual 'Industrial Ventilation' will provide you with the methods to design a hood to contain the fumes and heat from the flame.

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