scfh to Nm3h
scfh to Nm3h
(OP)
Can you tell me how to convert from scfh to Nm3h? Thanks
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RE: scfh to Nm3h
There are many different sets of temperature and pressure used to define scfh and to define Nm3h. The best way to convert any gas volume from one set of temperature and pressure conditions to another set of temperature and pressure is to use the combined gas law as given below. It does not matter what you call each volume (scfh, Nm3h or anything else) ... all that matters is the temperature and pressure of each volume:
V2/V1 = (Z2/Z1)(P1/P2)(T2/T1)
where:
V = gas volume
P = pressure
T = temperature
Z = gas compressibility factor
In most cases, the gas compressibility factors are not needed unless you want extreme accuracy.
As for the many different temperature and pressure reference conditons used to define "standard" or "Normal" volumes, read this online Wikipedia article:
http://
Whenever you use a term like "scfh" or "Nm3, you must state the temperature and pressure that applies to that term.
Milton Beychok
(Visit me at www.air-dispersion.com)
.
RE: scfh to Nm3h
Then also remeber never take anything for granted! Always state your standard conditions (typically 60 def F 0 psig or 0 deg C, 1 atm). But these may vary. Event the US units!
If you have 1 SCF (60 deg F, 0 psig) then you have 0.0269 Nm3
Best regards
Morten
RE: scfh to Nm3h
MortenA forgot to say that 1 scf at 60 deg F and 0 psig equals 0.0269 Nm3 only when the Nm3 is defined as being at 0 deg C and 1 atmosphere (absolute).
As stated in the Wikipedia article that I referred to earlier, there is no universally accepted set of reference temperature and pressure for scf or Nm3 or any other named volume.
As emphasized by both MortenA and myself, you must always define your reference conditions of temperature and pressure for scf, Nm3, acf, icf, etc., etc.
Milton Beychok
(Visit me at www.air-dispersion.com)
.
RE: scfh to Nm3h
Best regards
Morten
RE: scfh to Nm3h
RE: scfh to Nm3h
See thats the problem! Nver take anything for granted! Even though SCF is defined at 60 def F=15.667 deg C - the SM3 is usually defined at 15 deg C!
Do you think im wrong? Check out this reference at wikipedia:
ht
As you can see - ISA,ISO 13443, EEA and EGIA prefers the 15 deg C! But SPE apperanely now recommends 1 bar as the reference pressure where most other prefers 0 barg or 1.01325 bar!
Best regards
Morten
RE: scfh to Nm3h
RE: scfh to Nm3h
Firstly, the combined gas law equation that I gave in my first response above includes compressibility factors Z.
Secondly, it depends on what you mean by "no good". What degree of accuracy do you define as "no good"? In my experience, using the combined gas law equation can be used up to 1000 psig or more and worked fine in the design of refinery process units that operated at those pressures. Where did you come up up with that cap of 60 psig?
Milton Beychok
(Visit me at www.air-dispersion.com)
.
RE: scfh to Nm3h
First, "atmosphere" is a local phenomena that defines the abaolute pressure when a gauge reads zero (where I live the atmospheric pressure ranges from 11.2 psia to 12.5 psia depending upon which hill or valley you're in). For standard conditions I've seen 1 bara (100 kPa, 14.5 psig), or 101.325 kPa (14.696 psi), but "atmosphere" is meaningless. Second, the multiplier you gave only works if both reference pressures are the same. If for example, the scf reference uses 14.73 psia (which is the reference recommended by GPA and API in the hydrocarbon measurement standards) and the nm3 reference uses one bar then the multiplier increases to 0.0272. Not a huge change, but it is over 1% error.
The real key to this is that the only place that the "standard" conditions are laid out clearly and unambigiously is in gas-sales contracts. If you are dealing with gas sales then you had better read the contract. If you are doing a plant balance then as long as you are consistent then you can pick your own values (within reason).
Man I wish it were that simple. I've gotten data in nm3 that referenced 0C, and data that referenced 16C and data that referenced 15C. Same with sm3. Pressures are just as far over the map. When I'm dealing with SCF, I assume the Oil & Gas "standard" of 14.73 psia, but a couple of states mandate 15.025 psia and my "assumption" bites me in the butt (you can't do velocity calcs on SCF). When I'm dealing with nm3 or sm3 I don't assume anything.
I've found that you are reasonably safe using the ideal gas law (without the "Z") up to about 2 atmospheres (call it 36 psia where I live, 44 psia by the seashore) with pretty good quick and dirty results. Going all the way to 60 psig is just too much error on real gases.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: scfh to Nm3h
While there seems to be more confusion re. the "metric" definition it appears that even for SCF there exists deviations.
Jest remember that at the end of the day the std volume is just another word for a number of moles.
Best regards
Morten
RE: scfh to Nm3h
How could that last sentence be any clearer??
And if everyone would only read that Wikipedia article in detail!!
Milton Beychok
(Visit me at www.air-dispersion.com)
.
RE: scfh to Nm3h
Best regards
Morten
RE: scfh to Nm3h
Doug
RE: scfh to Nm3h
SCFH or Nm3h-1, thank God we don't need to set standards for hour [H or h]!
RE: scfh to Nm3h
RE: scfh to Nm3h
The 60 psig rule of thumb is just that. I got it from Campbell. It works fine for oil patch work, for the gases I deal with every day (HC gas mixtures with high CO2 fractions) within an 'acceptable' margin of error. It produces results that correlate well with field data read from store-bought pressure gauges as well as pressure transmitters calibrated on Friday afternoon by oil patch instrumentation techs who are on their way out of town to go hunting or 4x4'ing. If 44 psia works for you, right on brother.
RE: scfh to Nm3h
David
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem