Calculating CV of Fuel/Air Mixture @ 25°C

In summary, the fuel gas consists of 75% butane (C4H10), 10% propane (C3H8) and 15% butene (C4H8) by volume. It is to be fed to the combustion chamber in 10% excess air at 25°C, where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate 5 bar steam from water at 90°C.
  • #36
That's the incorrect number of total mols in the mix, total ,mols is 33.8 > 34 Mols
 
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  • #37
OK. So 2580/33.8=76.3 kJ/mole

The volume per mole is 0.0245 m^3/mole

So, 76.3/0.0245 = 3115 kJ/m^3 of fuel mixture = 3.12 MJ/m^3 of fuel mixture
 
  • #38
OK. So 2580/33.8=76.3 kJ/mole

The volume per mole is 0.0245 m^3/mole

So, 76.3/0.0245 = 3115 kJ/m^3 of fuel mixture = 3.12 MJ/m^3 of fuel mixture
 
  • #39
Chestermiller said:
OK. So 2580/33.8=76.3 kJ/mole

The volume per mole is 0.0245 m^3/mole

So, 76.3/0.0245 = 3115 kJ/m^3 of fuel mixture = 3.12 MJ/m^3 of fuel mixture

It doesn't look right that the CV is 3.12 MJ / m^3 as the gross CV is 108.1 MJ M^3, my calculated NET CV of 103.2 MJ M^3 looks more realistic?
 
  • #40
Andy86 said:
It doesn't look right that the CV is 3.12 MJ / m^3 as the gross CV is 108.1 MJ M^3, my calculated NET CV of 103.2 MJ M^3 looks more realistic?
The stream is diluted by a factor of 33,9
 
  • #41
Chestermiller said:
The stream is diluted by a factor of 33,9

Meaning?
 
  • #42
Andy86 said:
Meaning?
You have 1 mole of actual fuel and 32,9 mioles of nitrogen and oxygen that dilute the heating value. Just take your 100MJ and divide by 33.9. What do you get?
 
  • #43
NET CV BY VOL = 103.2MJ / M^-3

103.2 / 33.8 = 3.05MJ / M^-3
 
  • #44
Andy86 said:
NET CV BY VOL = 103.2MJ / M^-3

103.2 / 33.8 = 3.05MJ / M^-3
Pretty close, huh?
 
  • #45
VERY! :-)

So.....

NET CV BY MASS

n = PV / RT = 100000 * 1 / 8.314 * 298 = 40.3 MOL = 0.0403 KMOL

CV = MK M^-3 / KMOL
= 3.05 MJ M^-3 / 0.0403 KMOL
= 75.6 MJ KMOL^-1

?
 
Last edited:
  • #46
Andy86 said:
VERY! :-)

So.....

NET CV BY MASS

n = PV / RT = 100000 * 1 / 8.314 * 298 = 40.3 MOL = 0.0403 KMOL

CV = MK M^-3 / KMOL
= 3.05 MJ M^-3 / 0.0403 KMOL
= 75.6 MJ KMOL^-1

?
You're going in a circle. You already had the CV per mole.
 
  • #47
Andy86 said:
VERY! :-)

So.....

NET CV BY MASS

n = PV / RT = 100000 * 1 / 8.314 * 298 = 40.3 MOL = 0.0403 KMOL

CV = MK M^-3 / KMOL
= 3.05 MJ M^-3 / 0.0403 KMOL
= 75.6 MJ KMOL^-1

?
You're going in a circle. You already had the CV per mole.
 
  • #48
Ok Great, thanks for all your help Chester I really appreciate it.

Andy
 
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