Which is better heat transfer?

Ricwall

Which transfers more heat inside a water tube boiler furnace. The flame, or the combustion gases generated by the flame?

  Assume the flame is not impinging any water tube.

    Would appreciate a short explanation why.  Thank you



 

Tom Blackwell_2

It depends...

It depends on the amount of radiant and convective heat transfer components in the flue gas stream. Radiant surface accepts the radiant heat from the flame; whereas convective heat transfer takes place in areas of the furnace that are shielded from the radiant energy of the flame. A flue gas economizer for example is 100% convective and sees no radiant heat. For a more detailed explanation, see the B&W steam book. The design of the boiler takes into consideration the flame characteristics-whether it is oil, gas, or solid fuel, and optimizes the ratio of heat transfer characteristics to produce a cost effective boiler assembly with the required efficiency. Hope this helps...