Flame radiation in fire tube 1

[Jeko]

I would like to calculate the heattransfer in a firetube of a boiler. I know how to calculate the H20/CO2 gas radiation to the wall in an ideal stirred vessel.
I assume that the area of the firetube in which the flame is present should be calculated otherwise. As far as I know should direct flame radiation be calculated as cylindrical gaseous body surrounded by a concentric tube. I got stuck when calculation the emmisivity of the flame (gaseous body).
It concerns a natural gas flame.

I am not sure if I am on the right track.

- Who can tell me more about this subject.
- Are there example calculations to be found on the internet?
- What literature is best to read about this subject?

>>> Any help is welcome <<<

JeKo

 

[athomas236]

JeKo,
The main form of heat transfer from the flame is luminous radiation and consequently radiation from CO2 and H2O tends to be ignored.

Furnace temperature calculations are based on empirical/test data and a simple heat balance around the furnace as follows:

Heat in fuel and air to furnace = Heat in flue gas leaving the furnace + Heat transfered to furnace walls.

Heat in fuel and air to furnace = (Fuel flow rate kg/s * NCV kJ/kg ) + Air flow rate kg/s * Enthalpy kJ/kg

Heat in flue gas leaving the furnace = Flue gas flow kg/s * Enthalpy kJ/kg

Heat transfered to furnace walls
=5.673/100000000*Em*((Tf+273.15)^4-(Ts+273.15)^4)*Furnace area m^2

Tf = furnace gas temperature C
Ts = temperature of furnace walls C
Em = emissivity of flame based on test data and fuel fired
typically 0.85-0.90 for oil

Hope this helps

Regards,
athomas236

 

[jehar]

Hi Jeko,
You may find material that you will find useful at

http://www.wargaboiler.com/extras.html,

which is a firetube boiler site. Also, design formulas and helpful material can be found at

http://www.HRSGdesign.com,

even though this is a water tube boiler design site versus a firetube design.
Jack Hardie

 

[lucyphill]

Jeko
A good text book on the subject is as follows
'Process Heat Transfer' by D Q Kern isbn 0-07-085353-3

 

[22082002]

You can search for

http://www.heaterdesign.com,

they have online program, and, of course, check Kern, they have a dedicated chapter for heater