Hi Marc Schenker ,

I couldn't find i-hexadecane in the Aspen databank. However, Aspen does include many C16H34 components such as:

2-methylpentadecane

tetradecane,-2,3-dimethyl-

tridecane,-7-propyl-

which are all i-hexadecanes. Therefore, the easiest way to fix your issue is to use one (or a combination) of these components to represent all i-hexadecanes. I believe the same is true for i-octadecane (i-C18H38) and i-eicosane (i-C20H42).

Cheers, Rick

Hi Richard Sherritt,

thanks for your answer. I totally aggree, unfortunately I have implemented i-hexadecane already as 2-methylpentadecane. I also checked for 2,3-Dimethyltetradecane, but the QVALNET is also 0. So, unfortunately it does not solve the problem, but thanks for your input.

Hi Marc Schenker ,

From the HELP, QVALNET is calculated from HCOM (heat of combustion) and RATES (mole fraction) of each component.

QVALNET = SUM(-HCOM(i) x RATES(i))

I checked ASPEN parameters (see attached screenshot), and the HCOM for 2-methylpentadecane is blank, which results in using zero in the calculation. However, ASPEN does give the DHFORM (heat of formation) of 2-methylpentadecane as -90.7614 kcal/mol.

The correct HCOM can be calculated from the heat of formation and entered into the REVIEW-1 table under Methods/Parameters/Pure Components.

Hope that helps.

Hi Richard Sherritt ,

thanks a lot for your help. Manually calculating HCOM and providing the values as you showed works fine, now I get reasonable results for my diesel fraction. Thanks a lot for your expertise!!