[mossaied]

Hi
I have some confusion about how ansys calculates enthalpy in j/mol.kg
I have seen many answers that says just multiply enthalpy of a material by the its molecular weight but that simply does not make sense for me because : enthalpy is in j/kg and molecular weight is in kg/mol so the resultant dimension would be j/mol not j/mol.kg as required by ansys?
may be this naive question but I am new to ansys and fluid mechanics in general and my background is mainly in computer engineering

Thanks

[LuckyTran]

Enthalpy is indeed J/kg or J/mol. I think you are confusing J/kgmol as being kg*mol. A kgmol is not kg*mol but a type of mol.

[mossaied]

so if for example, the enthalpy is 2000 j/mol, how to convert it to j/kgmol?

[LuckyTran]

Believe it or not, 2000 J/mol is 2000 000 J/kgmol or 2000 kJ/kgmol

[Sowmiya]

Hi
Actually standard state of enthalpy of CO2 is -393.5 kJ/mol but in fluent the database value of CO2 is -3.935324e+08 J/kg mol. How this is possible??? whether the unit is correct as mentioned before?

[Vidushi]

kgmol is not kg*mol. It is like a kilo mol.
So 1kgmol = 1000 mol.

[marcoberna23]

Originally Posted by Sowmiya

Hi
Actually standard state of enthalpy of CO2 is -393.5 kJ/mol but in fluent the database value of CO2 is -3.935324e+08 J/kg mol. How this is possible??? whether the unit is correct as mentioned before?

Hi Sowmiya,

that is correct. In fact you need to multiply by a factor 1000 to go from kJ to J. Moreover, you need to divide by a factor 1000 to go from mol to kmol (let's remember that the lowercase letter 'k' means 'kilo' which is, I think, ancient Greek for 'a thousand'). Thus, being that at the denominator, you need to multiply everything by 1000.
So, 3 digits because of kJ + 3 digits because of kmol + 2 digits for scientific notation and there you go you have your e+08.
Hope it helps,
Marco

[LJA_Koers]

I'm still confused as to why Fluent adds 'kg' to indicate 1e3 instead if just 'k'. Haven't seen this anywhere but here.