Jet A LHV

[rnordquest]

I think this is a better forum than where I first posted.

Does LHV for a tank of Jet A change with time? If so, how much? What LHV accuracy should I expect when I send a sample to a lab to be tested?

We get LHV value when the fuel is delivered and we check it once a month. Would we be better off checking it within a day or two after every delivery? This would allow for the new fuel to mix with the old.

Thanks,

Roger

 

[dcasto]

Heating value is only constant for a single molecule. Since Jet A is a mixture of hundreds of molecules, it will change.

If you want to see less variability in your measurements, have the lab record the LHV in BTU/lb. You'll see smaller variations and you can use the density to see the LHV in each batch.

 

[rnordquest]

We get LHV in BTU/lb now. How contant is it over time? We also get specific gravity every day. Both of those go into the calculations for engine performance.

 

[dcasto]

look up the LHV/lb on NIST worksite. Hydrocarbons have a relatively constant LHV/lb.