Boiler Surface and Radiation loss calculation

Yep. Carry out an energy balance calculation on the boiler:

• One knows the fuel calorific value
• One knows the fuel flowrate
• One knows the steam flowrate
• One knows the temperature of the water coming from the hotwell
• One knows the flowrate of water coming from the hotwell
• One knows the steam conditions, from which its energy content is found in Steam Tables
• One knows the steam flowrate
• One knows the flowrate of gases up the stack
• One knows the conditions of the gases fowing up the stack
• One knows the composition of gases flowing up the stack.

Assuming the air is coming in at ambient temperature, the rest is arithmetic.

Well, you can get a rough estimate if you know the surface temperature of the boiler vessel. The heat radiation is approximated fairly well by the Stephen Boltzmann law which says the the radiated heat = Emissivity x area x Stephan-Boltzmann constant x (T_surface ^4 - T_amb ^4).

The emissivity can be found from reference books and depends on the type of material it is. Again, the surface may be insulated to reduce the effect of the radiative heat loss.

What about the convected heat, though?

If one measures, why is there a need to calculate?

Do you actually have a boiler, or just the desire to know?

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Dear Mr. gauravsharma

You have not given details about the quality of Insulation/Lagging, Skin Temp., Ambient Temp. Wind/Air Velocity over the Boiler surface.

Pl. go to Engineering Tool Box and refer there. You can get much more details there.

DHAYANANDAN.S