toohotforme
Mechanical
Is there a source that provides detailed boiler efficiency calculations that shows how a boiler efficiency value is derived from the standpoint of the combustion side data.
This gets most confusing when the values are intermingled to suit whoever the seller is!
e.g. a firetube boiler fired on natural gas has CO2 of 10.5% with stack temp. of 220 degrees celcius at full load and ambient of 30C. The fuel has a higher calorific value of 40MJ/m3 and a lower calorific value of 34 MJ/kg at stp. (The stoichiometric CO2 is 11.9% and the stoichiometric air fuel ratio is 9.26)
We have a formula such as 100-(K * stack temp(C) - air temp(C))/CO2(%) where K = 0.54
so the above equation looks like this
=100-(220-30)*0.54/10.5 = 90.23% boiler efficiency.
It is apparently based on the 'Hassanstad' formula(?)
So,
1) where does the K factor originate? and
2) where does the fuel gross or net calorific value finds its way in? and
3) what does the efficiency mean in practice? e.g. if we burned 100kg of the above fuel of 40MJ/kg = 4GJ heat in the furnace - how much of that find its way in to the water / steam? (90.23% ? - with the balance being e.g. stack losses, radiation, latent heat of water vapour?)
This gets most confusing when the values are intermingled to suit whoever the seller is!
e.g. a firetube boiler fired on natural gas has CO2 of 10.5% with stack temp. of 220 degrees celcius at full load and ambient of 30C. The fuel has a higher calorific value of 40MJ/m3 and a lower calorific value of 34 MJ/kg at stp. (The stoichiometric CO2 is 11.9% and the stoichiometric air fuel ratio is 9.26)
We have a formula such as 100-(K * stack temp(C) - air temp(C))/CO2(%) where K = 0.54
so the above equation looks like this
=100-(220-30)*0.54/10.5 = 90.23% boiler efficiency.
It is apparently based on the 'Hassanstad' formula(?)
So,
1) where does the K factor originate? and
2) where does the fuel gross or net calorific value finds its way in? and
3) what does the efficiency mean in practice? e.g. if we burned 100kg of the above fuel of 40MJ/kg = 4GJ heat in the furnace - how much of that find its way in to the water / steam? (90.23% ? - with the balance being e.g. stack losses, radiation, latent heat of water vapour?)