flame radiant energy 2

[curve3104]

I am trying to determine the quantity of thermal radiation from a flame. Also, more importantly, I'm trying to determine the radiant load as a function of distance from an object (i.e. don't want to burn up something near the flame). Does anyone know the relationship between thermal radiation and distance to the source? Obviously the closer to the source, the hotter it feels...

Thanks!

 

[ivymike]

any beginning heat transfer text will cover that. perhaps an internet search would help.

 

[curve3104]

Found it. Relation between intensity and distance is the inverse of the distance squared.

Any clues for the emisivity factor for a flame? Would it depend on the fuel?

Thanks.

 

[insult2injury]

The emissivity will depend on the gaseous products of combustion. If you are close enough to the flame you will also have to account for conduction effects.

I2I

 

[curve3104]

Ok, I'm no chemist, but I'm burning natural gas and fuel oil. Any ideas?

 

[insult2injury]

Any thermo or combustion book should cover the stoichiometry. The products of combustion will be a function of your A/F ratio and whether you're completely burning the fuel. Typically, you will have a mixture of carbon dioxide, water vapor and nitrogen for sure, but depending on your specific operating conditions, you may have oxygen, carbon monoxide, NOX, any trace elements/impurities in gas/fuel supply, as well as unburnt hydrocarbons. You will need to run through the calculations for your operating conditions. Incidentally, this is also how you will find the adiabatic flame temp.

I2I

 

[insult2injury]

Here are a couple links if you don't have a thermo book handy.

http://me.queensu.ca/courses/MECH435/5. Combustion Theory.ppt

http://www.engr.colostate.edu/~allan/thermo/page1/page1f.html

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http://www.engr.colostate.edu/~allan/thermo/page9/Combustion/combustion.html

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http://www.engr.colostate.edu/~allan/thermo/page12/adia_flame/Flamemain.html

I2I

 

[IRstuff]

see thread610-140748

Note that the emissivity is highly dependent on the depth of the flame itself as well. A small flame has effectively low emissivity, while a thicker flame has a higher effective emissivity.

TTFN

 

[Zapster]

Review API_RP_521 In the fourth edition the section of interest should be, 4.4.2.3

 

[25362]

The following threads may be of some help:

thread610-50077
thread633-56974
thread391-43136