Boiler Efficiency

[Mark31]

This one should separate the men from the boys.....

When calculating boiler efficiency (chemical heat or fuel efficiency), you can account for a steam coil airheater by either adding a credit to the loss account or by increasing the reference temperature. Both make sense except they give different answers for efficiency...why?

 

[Cormoran]

Mark, please send your calcs.
Alfredo

 

[Mark31]

Alf,

Have you experiance with SCAH credits or do you just want to see if I have made a mistake?
The calculations are done by my boiler simulation program, there is no error in the calculation. There must be a reason why increasing the reference temperature doesnt work.

Essentially, the heat credit that is calculated from the temperature rise in combustion air is less than the differences in dry gas loss, etc....

Mark