Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

Air Enthalpy Calculation


This topic has been archived. This means that you cannot reply to this topic.
3 replies to this topic
Share this topic:
| More

#1 slmn

slmn

    Brand New Member

  • Members
  • 7 posts

Posted 09 April 2012 - 02:02 PM

in gas turbine performance book , i found this equation for air enthalpy calculation
H=a(T-T0)+b(T^2-T0^2)/2-c(1/T-1/T0)
the constants a,b,c and the mass fraction of air constituents are provided
T0=273k
T=288k
i did apply in the equation as in the attached sheet

by sum the last column i got this value for enthalpy, the book says the enthalpy is 14.876 kj/kg

any idea
thanks in advance

Attached Files


Edited by slmn, 09 April 2012 - 02:18 PM.


#2 kkala

kkala

    Gold Member

  • Banned
  • PipPipPipPipPip
  • 1,939 posts

Posted 13 April 2012 - 06:40 AM

Heat capacity of air is roughly 0.24 kcal/kg, so you need 0.24*4.19*15 ~ 15 kJ to heat 1 kg air from 0 to 15 oC, which is in rather good agreement to 14.876 kJ/kg of the book.
Attached "Rev0.xls" contains the spreadsheet of enthalpy calculation, with some remarks on it. No arithmetic errors could be traced, it seems that the application of enthalpy formula for gases contains some error. Probably the units? Resulting heat capacities for gases are not realistic, as indicated in the added columns.
Check formula for enthalpy again, error cannot be specifically located by me. Hopefully tracing will be easy.

Editing note: Added "1 kg" on Apr 15th, 2012

Attached Files


Edited by kkala, 15 April 2012 - 05:48 AM.


#3 ankur2061

ankur2061

    Gold Member

  • Forum Moderator
  • 2,483 posts

Posted 13 April 2012 - 11:03 PM

slmn,

What you are looking for is psychrometric calculations for wet or humid air including the entahlpy of wet / humid air.

In such a case refer the excel spreadsheet, "Psyschro.xls" attached in the link below:

http://www.cheresour...6833#entry26833

Regards,
Ankur.

#4 slmn

slmn

    Brand New Member

  • Members
  • 7 posts

Posted 13 April 2012 - 11:17 PM

thank you fot the great help




Similar Topics