Unit Conversion - BTU/SCF to KJ/KG

[FAIZANYOUSUF]

Dear Experts,

I am trying to convert the unit BTU/SCF to KJ/KG for natural has having GCV 1017.08 BTU/SCF. The problem is one factor having volume unit in denominator and other having weight unit in denominator. I have given a following try. Please check and let me know am I correct?

Gas Density = 0.8 KG/Cubic /Meter
1 BUT/cubic feet = 38.26 KJ/Cubic Meter

Now if we divide right side with density we get unit KJ/KG.

 

[quark]

Yes, that simple. 1BTU = 1.055 kJ, so 1BTU/cu.ft = 37.22 kJ/Cu.Mtr, check whether extra 1kJ is significant. Check whether the density is at standard conditions or not.

 

[IRstuff]

Your gas density doesn't appear to match the temperature conditions for an SCF definition. Moreover, the density of your natural gas will depend on its exact composition.

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[poli60]

This post wouldn't pass an examination at the university (at the high school, too) :-(
- SCF is referred to volume at Standard conditions
- Standard conditions are not univoque: they have to be specifically declared
- kg is referred to a mass
- you need a Molecular mass (or a gas density referred to certain T and P) for passing from SCF to kg

This matter is discussed by wikipedia as follows:
quoted-------------------
For petroleum gases, the standard cubic foot (scf) is defined as one cubic foot of gas at 60 °F (288.7 K; 15.56 °C) and at normal sea level air pressure. The pressure definition differs between sources, but are all close to normal sea level air pressure.
[ul]
[li]A pressure of 14.696 pounds per square inch (1.00000 atm; 101.325 kPa).[2] This is the same pressure as the SI system standard pressure. Gives 1.1953 moles per scf.[/li]
[li]A pressure of 101.35 kilopascals (1.0002 atm; 14.700 psi).[2][3] Gives 1.1956 moles per scf.[/li]
[li]A pressure 14.73 pounds per square inch (1.0023 atm; 101.56 kPa).[1] This value is very close to 30 inches of mercury. Gives 1.1981 moles per scf or 0.002641 pound moles per scf.[/li]
[/ul]
The standard cubic meter of gas (scm) is used in the context of the SI system. It similarly defined as the quantity of gas contained in a cubic meter at a temperature of 15 °C (288.150 K; 59.000 °F) and a pressure of 101.325 kilopascals (1.0000 atm; 14.696 psi).[1]
Converting volume units between the standard cubic foot and the standard cubic meter is not exact, as the base temperature and pressure used are different, but for most practical situations the difference can be ignored. Comparing the same volume between the 15 °C (288.15 K) and 101.325 kPa standard cubic meter versus the 60 °F (288.71 K) and 14.73 psi (101.56 kPa) standard cubic foot gives an error of 0.04%. A standard cubic foot in the US Customary System is approximately equivalent to 0.02833 standard cubic meters in the SI system."
----------unquoted

In order to go ahead with your question:
- let's assume GCV 1017.08 BTU/SCF is referred to US Customary system: it is equivalent to 1017.08 * 0.02833 = 28.8133 BTU/scm
- from BTU to kJ multiply by 1.05506 -> GCV = 28.8133 * 1.05506 = 30.4 kJ/scm
- if your density is referred to the Standard cubic meter in SI system: GCV = 30.4 / 0.8 = 38 kJ/kg

At the end of the day, the discussions on this matter are big, the final differences are little :-(