Specific Gravity for gases
Specific Gravity for gases
(OP)
I want to know how can we express specific gravity for gases at actual conditions.
Is it density of gas/density of air at STP
or
Is it density of gas/density of air at that pressure and temperature
Please clarify.
Is it density of gas/density of air at STP
or
Is it density of gas/density of air at that pressure and temperature
Please clarify.





RE: Specific Gravity for gases
David
David Simpson, PE
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RE: Specific Gravity for gases
Molecular Weight / Gas sg = 21/0.73
Pressure Temperature Density
psig °F lb/ft3
635 53 3.1 dew point
570 49 2.7 dew point
300 70 1.2
300 26 1.4 dew point
50 -32 0.31 dew point
25 -48 0.19 dew point
8 -64 0.11 dew point
RE: Specific Gravity for gases
I know the density of gas at 100 Psig = 0.67 lb/ft3
Density of air at STP is = 0.0749 lb/ft3
So, actual specific gr. is = 0.67/0.0749 = 8.94
The gas is so heavy!
RE: Specific Gravity for gases
Density of air at 14.696 and 60f = .076313.
You didn't give us the temperature at 100 psig, but solving backwards, the temperature would be about 400 F to give you a density of .67 lb/ft^3 at 100 psig. Of course compressibility will kick in, but we'd have to know the gas species to adjust for that.
RE: Specific Gravity for gases
cherry123,
be sure the SG of the gas referenced applies the above definition or uses the criteria defined above to determine SG.
in nearly all cases i have observed, SG is defined by the ratio of a gas moleweight to that of air.
good luck!
-pmover
RE: Specific Gravity for gases
RE: Specific Gravity for gases
This is really simpler than you think.
If you use air at MW=29, and the mol weight of your gas is proportinal to the densidy of air, then it's a simple ratio. Using dcasto's density of .076313, the mol weight is your gas is:
29 * 2.94/.076313 = 1117.24
I have a little trouble believing that your density at STP is really that high. I've never heard of a gas that heavy.
Regards,
Speco