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# Viscosity of gases

Wed 1 Oct, 2014 04:29 am
Nowadays, i am studying and analyzing about the Viscosity of gases at different different conditions and situation. So i need the Viscosity of different gases at NTP conditions(=1 atm pressure and 273.15 kelvin temperature).If anybody knows about information , then please you can help me. Note that result obtained or data of gases Viscosity must be result from experiment( May be from previous ) And not resulted from Sutherland's formula or according to it.

You can also help me by suppying the Viscosity of different gases at same temperature and pressure conditions.
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engineer

1
Wed 1 Oct, 2014 05:09 am
@krishna basnet,
Just search for the "viscosity of gases." You will find all the information you need.
krishna basnet

1
Wed 1 Oct, 2014 05:32 am
@engineer,
Almost all times, i find that Viscosity of gases is mainly calculated as function of temperature but in all data for Viscosity of gases, pressure is keeping constant or not during changing the temperature is not clearly justified.Furthermore if we heat the gases in open clinder than decrease in density of gases decreases the Viscosity of gases but if we heat the gases by compression than increase in density increases the Viscosity of gases.
Further more in internet and Google search, it was not clearly tell that temperature is increases by heating of gases system or by compression of gases system.

So, i am totally confused that normally in fluid, Viscosity decreases on heating but in case of gases it was found to be increasing from Google datas.
Please if you have any information, give me the datas for Viscosity of gases at NTP or STP state of gases.
engineer

1
Wed 1 Oct, 2014 05:54 am
@krishna basnet,
krishna basnet wrote:

... but if we heat the gases by compression than increase in density increases the Viscosity of gases.

Heating of a gas in a closed container does not increase the density. Density is mass per unit volume and neither of those change.
krishna basnet

1
Wed 1 Oct, 2014 06:53 am
@engineer,
I think that You cannot clearly understand about that. i cannot say like that.You just considered that on case of heating the gases, cylindrical vessel is not closed ie hole is made on the cylindrical vessel so that expanding air can pass through it to outside sourronding.

further more, can you imagine that if you heat the gases in closed cylindrical vessel, than increase in temperature also increases the pressure of gases even density is constant.Due to this combination of both change in pressure and temperature makes difficult to think about the Viscosity of gases.So please just only considered about the heating of gases on the open cylindrical vessel.
timur

1
Wed 1 Oct, 2014 07:50 am
@krishna basnet,
Well, all the information you need is out there on the internet.

Just try googling with the appropriate keywords.

You can find things like this (I left the image in its original size on purpose): But you can also find the viscosity of different gases on this calculator:

Gas Viscosity calculator

This one is made with the Sutherland's formula but you find others with different formulas..
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Miller

0
Wed 1 Oct, 2014 09:06 am
@krishna basnet,
Why don't you use your textbook? When I studied physics and physical chemistry, we students didn't have Google. We had textbooks and we had the library.

Why not use the library and your textbook.
engineer

1
Wed 1 Oct, 2014 09:08 am
@Miller,
The Internet is the library these days and that's not a bad thing. I don't understand why you would ask strangers when you could just search for the information directly.
Miller

0
Wed 1 Oct, 2014 09:16 am
@engineer,
I don't know either. I do know that while the internet & google serve an important tool, there is much misinformation out there and for the young student, it could be hard for them to evaluate what they are reading.

0 Replies

krishna basnet

1
Wed 1 Oct, 2014 01:04 pm
Problem is like that it was really difficult to find the Viscosity of gases with increase in temperature of gases.I'm try to findout the new methods for Viscosity of gases but according to Maxwell formulae, Viscosity of gases is proportional to half power of absolute temperature but by Sutherland's formulae , Viscosity is proportional to one and half power of absolute temperature. This two concepts makes really difficult to think that how Viscosity of gases depends upon temperature.Furthermore in which conditions , which is applicable is not really justified in Google.So i need the experimental datas for analysis but it was not easier to find the Viscosity of gases at NTP state (choose this conditions as during this all gases have same volume and pressure for same mole ). Furthermore it was not easier to experiment on Viscosity of gases as my country as those required material are not easily available in market.So i want to collect experimental datas for of Viscosity of gases by Google.
0 Replies

Miller

0
Wed 1 Oct, 2014 01:17 pm
@engineer,
engineer wrote:

krishna basnet wrote:

... but if we heat the gases by compression than increase in density increases the Viscosity of gases.

Heating of a gas in a closed container does not increase the density. Density is mass per unit volume and neither of those change.

I think the clue is where she says heat the gases by COMPRESSION, which in a restricted, closed space would increase the density. Is this a closed space?
Miller

0
Wed 1 Oct, 2014 01:30 pm
@Miller,
Calculating gas viscosity

The viscosity of gas mixtures at one atmosphere and reservoir temperature can either be read from Fig. 2 or determined from the gas-mixture composition with Eq. 1.

Vol1 page 0236 eq 001.png....................(1)

where:

μga = viscosity of the gas mixture at the desired temperature and atmospheric pressure
yi = mole fraction of the ith component
μi = viscosity of the ith component of the gas mixture at the desired temperature and atmospheric pressure (obtained from Fig. 1)
Mgi = molecular weight of the ith component of the gas mixture
N = number of components in the gas mixture.

This viscosity is then multiplied by the viscosity ratio (from Fig. 3 or Fig. 4) to obtain the viscosity at reservoir temperature and pressure.

Note that Figs. 3 and 4 (from Carr et al.) are based on pseudocritical properties determined with Kay’s rules. It would not be correct, then, to use the methods of Sutton or Piper et al. to calculate the pseudocritical properties for use with those charts. However, Kay’s rules require a full gas composition.

If only specific gravity is known, then the pseudocritical properties would have to be obtained from Fig. 5 (or Eqs. 10 and 11 in Real gases). The inserts of Fig. 2 are corrections to be added to the atmospheric viscosity when the gas contains N2, CO2, and H2S.

Fig. 5 – Pseudocritical properties of methane-based natural gases (from Sutton).

Lee et al. developed a useful analytical method that gives a good estimate of gas viscosity for most natural gases. This method lends itself for use in computer programs and spreadsheets. The method uses the gas temperature, pressure, z factor, and molecular weight, which have to be measured or calculated; the density can be measured or calculated as well. The equations of Lee et al. are for specific units as noted below and are as follows:

Vol1 page 0237 eq 001.png....................(3)

where:

Vol1 page 0238 inline 001.png

Vol1 page 0238 inline 002.png

Vol1 page 0238 inline 003.png

Y = 2.4 - 0.2X
μg = gas viscosity, cp
ρ =gas density, g/cm3
p = pressure, psia
T = temperature °R
Mg = gas molecular weight = 28.967 γg

For the data from which the correlation was developed, the standard deviation in the calculated gas viscosity was 2.7%, and the maximum deviation was 9%. The ranges of variables used in the correlation were 100 psia < p < 8,000 psia, 100 < T (°F) < 340, and 0.90 < CO2 (mol%) < 3.20 and 0.0 < N2 (mol%) < 4.80. In using these equations, it is important either to measure the density or to ensure that the z -factor calculation has included the effect of N2, CO2, and H2S using the method of Wichert and Aziz. The equations of Lee et al. were originally written to give the viscosity in micropoise, but the modified form above gives the viscosity in the more commonly used centipoise. This viscosity unit (cp) is also easily converted to the SI unit of Pa•s by dividing by 1,000.
Example of calculating viscosity

Calculate the viscosity at 150°F (609.67°R) and 2,012 psia for the gas of the composition shown in Table 1.

Table 1

Solution (by the Carr et al. method).

First, calculate the pseudocritical properties using Kay’s rules. The charts of Carr et al. are based on pseudocritical properties determined with Kay’s rules; it would not be correct, then, to use the methods of Sutton or Piper et al. to calculate the pseudocritical properties for use with the viscosity calculation. The details are in Table 2.

Table 2

Calculating the pseudocritical properties using Kay’s rules yields:

Vol1 page 0249 eq 001.png

These parameters are then used to determine the viscosity at 1 atm. First, the viscosity for Mg = 20.079 at p = 1 atm and T = 150°F is read from Fig. 2. This gives μga = 0.0114 cp, but a correction is needed for the nitrogen. The correction for 15.8% N2 is 0.0013 cp. Hence, this gives μga = 0.0127 cp.

Next, the ratio of μg/μga is read from Fig. 4 using the pseudoreduced properties calculated above, which gives μg/μga = 1.32.

Hence, μg = (1.32) (0.0127) = 0.0168 cp. This represents a 2.5% error from the experimentally determined value of 0.0172 cp.

Solution (by the Lee et al. method).

In this method, the z factor is required; this is most accurately determined with the Piper et al. method, the details of which are in Table 3.

Table 3

The calculations are:

Vol1 page 0250 eq 001.png

Look up the chart of Fig.2 from Real gases, which gives a value of z = 0.91; then,

Vol1 page 0251 eq 001.png

This method gives a value that is 5.5% less than the experimentally determined value of 0.0172 cp.
Nomenclature
K1 = parameter in the Lee et al. viscosity, cp
Mg = average molecular weight of gas mixture
N = number of components in the gas mixture
p = absolute pressure, Pa
ppc = pseudocritical pressure of a gas mixture, Pa
R = gas law constant, J/(g mol-K)
T = absolute temperature, K
Tpc = corrected pseudocritical temperature, K
X = parameter used to calculate Y
yi = mole fraction of component i in a gas mixture
z = compressibility factor (gas deviation factor)
ρg = density of gas, kg/m3
γg = specific gravity for gas
μ = viscosity, Pa•s
μg = viscosity of gas, Pa•s
μga = viscosity of gas mixture at desired temperature and atmospheric pressure, Pa•s
References

↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Carr, N.L., Kobayashi, R., and Burrows, D.B. 1954. Viscosity of Hydrocarbon Gases Under Pressure. J Pet Technol 6 (10): 47-55. SPE-297-G. http://dx.doi.org/10.2118/297-G
↑ 2.0 2.1 2.2 Sutton, R.P. 1985. Compressibility Factors for High-Molecular-Weight Reservoir Gases. Presented at the SPE Annual Technical Conference and Exhibition, Las Vegas, Nevada, USA, 22-26 September. SPE-14265-MS. http://dx.doi.org/10.2118/14265-MS
↑ 3.0 3.1 3.2 Piper, L.D., McCain Jr., W.D., and Corredor, J.H. 1993. Compressibility Factors for Naturally Occurring Petroleum Gases (1993 version). Presented at the SPE Annual Technical Conference and Exhibition, Houston, 3–6 October. SPE-26668-MS. http://dx.doi.org/10.2118/26668-MS
↑ 4.0 4.1 4.2 Lee, A.L., Gonzalez, M.H., and Eakin, B.E. 1966. The Viscosity of Natural Gases. J Pet Technol 18 (8): 997–1000. SPE-1340-PA. http://dx.doi.org/10.2118/1340-PA
↑ Wichert, E. and Aziz, K. 1972. Calculate Z's for Sour Gases. Hydrocarbon Processing 51 (May): 119–122.
↑ Kay, W. 1936. Gases and Vapors At High Temperature and Pressure - Density of Hydrocarbon. Ind. Eng. Chem. 28 (9): 1014-1019. http://dx.doi.org/10.1021/ie50321a008
↑ 7.0 7.1 Lee, A.L., Gonzalez, M.H., and Eakin, B.E. 1966. The Viscosity of Natural Gases. J Pet Technol 18 (8): 997–1000. SPE-1340-PA. http://dx.doi.org/10.2118/1340-PA

Noteworthy papers in OnePetro

Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro

Real gases

Gas properties

Calculating gas properties

Gas formation volume factor and density

Vapor pressure

PEH:Gas Properties

SOURCE: Petrowiki.org/gas....<Has several examples/calculations
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