HHV and LHV 1

[firefastball]

Hi,

Fuel energy content are usually given in HHV and LHV. I know that by using HHV in boiler efficiency calculation assumes that water is condensed (energy is recovered) and by using LHV, energy is not recovered and is lost to the stack.

Can anyone advise on when do one use HHV or LHV to calculate boiler efficiency? Does it depend on the fuel used or the type of boiler (non-condensing or condensing)?
Why does boiler eff calculation used HHV instead of LHV in natural gas? Can it applies to diesel which have sulphur in it?

Thanks

 

[davefitz]

HHV had been historically used because it is very easy to test for a fuel's HHV at the plant's lab in a "bomb calorimeter" with no add'l calculations. LHV determination of a current fuel is a little more complicated but modern technology can estimate it in real time , so there is no longer a real need to use HHV.

LHV efficiency is best used with fuels that are either wet or which generate a lot of water during combustion, such as natural gas , wood, MSW. Characterizing and comparing different boilers based on LHV is much easier in the case where a wet fuel is being evaluated. For example , a boiler firing waste wood is much easier to review via LHV for the cases of 19% , 35%, 50% , 60% water content of the wood .

"Whom the gods would destroy, they first make mad "

 

[MortenA]

When to use HHV or LHV should not depend on your fuel type but on your boiler type (as you have identified yourself). HHV for condensing and LHV for non-condensing.

 

[MisterDonut]

The usual convention is to rate boiler efficiency on HHV basis, whether or not it is designed to operate in a condensing mode.
Combustion turbines are frequently rated on LHV basis.