How to heat air to 500+ degrees

can air be heated

Dear friends.
We need atmospheric air to be heated up to 500+ degrees celsius for an industrial application. But as per our various experiments since 2-3 years, we have seen the coil and the enclosure may heat more than 700+ degrees celsius but the air that is blown out just measures not more than 280 degrees celsius. I wanted to know is there any way to heat air for the specified temperature?

specific heat capacity air 500 deg c

pranam77 said:

Dear friends.
We need atmospheric air to be heated up to 500+ degrees celsius for an industrial application. But as per our various experiments since 2-3 years, we have seen the coil and the enclosure may heat more than 700+ degrees celsius but the air that is blown out just measures not more than 280 degrees celsius. I wanted to know is there any way to heat air for the specified temperature?

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you are right
as you blow out air using a small nozzle, the hot air cools down immediately.
you could watch the temp od air comming out of your own mouth, by 'Fooooo" for cool air and "Haaaa" for Hot air

Perhaps this should give a clue that they way you release HOT air should be fom a wider aperture and NOT Narrow Nozzle.

Please try out.

heated out of a can

Thanks Sarma ji for the reply. In fact this set up is to burn CO (Carbon monoxide) released by a company through the exhaust pipe which is more than 2.5 meters in diameter and we are now usiing LPG to increase the temperature and burn off CO. CO will burn off if the temerature rises beyond 550 degree celcius. Thus we are now trying to use electricity and save LPG. But despite all our experiments, we are unable to increase the Air temperature. Thus i also expecting some one to reply who has already done such job or experiment.

air heated experiments

Can air be heated?

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Yes!

as you blow out air using a small nozzle, the hot air cools down immediately.

Click to expand...

I don't think that this is generally correct. There may be different opinions about the meaning of "small", if it's e.g. 10 mm or 1 mm diameter, or even less. But you can get hot air tools that achieve 500 °C even with really small nozzles.

A technical thermodynamics text book contains all necessary formulas and material properties to analyze your heater construction and would help you to design a working version.

Basic properties that have to be considered are heat capacity and heat conductivity of air. Also you should understand convective heat exchange in case of forced flow.

The first question is, if you actually achieve a sufficient air temperature at the outlet of your heater "coil". This should be checked with a thin wire thermocouple.

The second question is, if the hot air possibly cools down too fast, e.g. because the nozzle is kept cool.

As a third point, the hot air of course mixes with cold air, depends on where you are measuring the outlet temperature.

Finally, your temperature measurement method may be inappropriate, e.g. using a thick temperature probe.

But as most hot air blowers from a DIY market can achieve 500 °C, the problem seems solvable anyway.


P.S.: Considering the additional information, you gave in your second post:

You mainly have to know the exhaust air mass flow to calculate the required heating power. Most likely, you simply don't apply sufficient power.

Using an electric heater rather than a LPG burner can simplify the construction, but increases energy costs (I don't know your local prizes, of course).

Normally, thermal treatment of exhaust air in an industrial scale is required to use heat exchangers for energy recovery, if the energy costs shall be affordable. Unfortunately, the plant investment is respectively high.

As another comment, did you consider catalytic oxydation of the exhaust gas?

Re: Can air be heated?

FvM said:

Can air be heated?

Click to expand...

Yes!

as you blow out air using a small nozzle, the hot air cools down immediately.

Click to expand...

I don't think that this is generally correct. There may be different opinions about the meaning of "small", if it's e.g. 10 mm or 1 mm diameter, or even less. But you can get hot air tools that achieve 500 °C even with really small nozzles.

......

As another comment, did you consider catalytic oxydation of the exhaust gas?

Click to expand...

Thanks, what i meant was, as the hot air coming out of a narrow nozzle, to a open atmosphere, it cools down. I agree heating and maintaining the nozzle end helps.
your catalytic oxidation appears a promising approach.
Sarma