9 replies to this topic

[alokranjan2]

hi

can anyone suggest a method 4 determining the viscosity of a mixture of fluids..does it follows the universal rule like that of avg mol wt...?

thanks

[MrShorty]

The Properties of Liquids and Gases by Poling, Prausnitz, and O'connel has a section on estimating mixture viscosities. I might suggest that you start there.

[kkala]

can anyone suggest a method 4 determining the viscosity of a mixture of fluids..does it follows the universal rule like that of avg mol wt...?

Viscosity of a gas mixture is estimated through more complex procedures, as advised by MrShorty's post (mentioning "The Properties of gases and liquids" book). The formula using viscosity, molar fraction & molecular weight of each component seems to be the most common, valid for non polar gases up to about 10 atma. For higher pressures corresponding state theory can be adopted, after estimating the critical mixture viscosity as the molecular average of critical viscosity of components. Critical viscosity can be estimated through corresponding states too. For polar gases (e.g. H2O, NH3, CH3OH), and mixtures containing some of them, you had better search for experimental values.
I. E. Idelcik (Memento de pertes de charge, Eyroles 1979) reports Mann's formula: 1/N=x1/N1+x2/N2+x3/N3+..., N=mixture viscosity, Ni=component viscosity, xi=component volume fraction.
Viscosity of a liquid mixture should be measured experimentally. For ideal binary mixtures N^(1/3)=x1*N1^(1/3)+x2*N2^(1/3), rough estimate, x1, x2 are molar fractions (my University book says molar concentrations for x1, x2).
I. E. Idelcik presents a formula as for gases above , but placing weight fraction in lieu of volume fraction. It must be for liquid mixtures, but it is not written specifically on the page. I think some lines were omitted due to apparent error (advice on the formula for liquids welcomed!).

Edited by kkala, 14 March 2010 - 03:34 AM.

[breizh]

Hi ,
Let you try this link :
http://www.cocosimul...A/viscosity.htm

hope it helps

Breizh

[ankur2061]

hi

can anyone suggest a method 4 determining the viscosity of a mixture of fluids..does it follows the universal rule like that of avg mol wt...?

thanks

alokranjan2,

An important correlation for finding natural gas mixture viscosities has been proposed by Lee, Gonzalez & Eakin. The beauty of this correlation is that it does not require the gas composition or the pseudo- critical pressure / temperature (P_pc / T_pc) of the natural gas to calculate the viscosity. All it needs is the pressure, temperature, molecular weight & density of the gas to calculate the viscosity. The viscosity data is fairly accurate within the temperature range of 100-340 degF & pressure range of 14.7-8000 psia. The all important input data required is the molecualr weight of the natural gas which can be calculated if the relative density of the gas is known.

Regards,
Ankur.

[kkala]

An important correlation for finding natural gas mixture viscosities has been proposed by Lee, Gonzalez & Eakin. The beauty of this correlation is that it does not require the gas composition or the pseudo- critical pressure / temperature (P_pc / T_pc) of the natural gas to calculate the viscosity.

You can see the formula of mentioned correlation for natural gas at https://www.e-education.psu.edu/png520/m19_p4.html.

Note: Searching the WWW for "natural gas viscosity", we see that almost all articles request a fee, few are free (e.g. from [url]http://jsciences.ut.ac.ir , accessible through the search engine). For instance [url]http://www.springerlink.com/content/l0683804n5308870, assessing four natural gas viscosities (not including mentioned one), asks for $ 34 .

Edited by kkala, 02 April 2010 - 05:46 AM.

[ankur2061]

kkala,

A better reference on the www for the correlation I mentioned is:

http://www.aimehq.or...237/237-040.pdf

I used the above article to develop a spreadsheet for natural gas viscosity.

Hope this helps.

Regards,
Ankur.

[kkala]

A better reference on the www for the correlation I mentioned is:
http://www.aimehq.or...237/237-040.pdf
I used the above article to develop a spreadsheet for natural gas viscosity.

Thanks, ankur, for the useful reference. Most practical formula is understood to be No (6), being:

μ = K*exp(X*ρ^(y)), where

K = (9.4+0.02*M)*T^1.5 /(209+19*M+T)
X = 3.5 + 986/T +0.01*M
y = 2.4 - 0.2*X

μ = viscosity in micropoise
ρ = density at real conditions in g/cm3
Μ = molecular weight
T = temperature in oR

Can you please correct any errors on the above? Scanning is not very clear in some points and even a +/- can be critical when the formula is applied.

Note formula of K edited for a more correct value. Values still uncertain .

Edited by kkala, 03 April 2010 - 11:50 AM.

[ankur2061]

A better reference on the www for the correlation I mentioned is:
http://www.aimehq.or...237/237-040.pdf
I used the above article to develop a spreadsheet for natural gas viscosity.

Thanks, ankur, for the useful reference. Most practical formula is understood to be No (6), being:

μ = K*exp(X*ρ^(y)), where

K = (9.4+0.02*M)*T/(209+19*M+T)
X = 3.5 + 986/T +0.01*M
y = 2.4 - 0.2*X

μ = viscosity in micropoise
ρ = density at real conditions in g/cm3
Μ = molecular weight
T = temperature in oR

Can you please correct any errors on the above? Scanning is not very clear in some points and even a +/- can be critical when the formula is applied.

The equations in the article I have used are eqns. 2,3,4 & 5 which give an error within +/-5% which is sufficiently accurate for calculating other parameters such as Reynolds number (fully turbulent flow) of the natural gas flow in a pipe.

Regards,
Ankur.

[kkala]

The equations in the article I have used are eqns. 2,3,4 & 5 which give an error within +/-5% which is sufficiently accurate for calculating other parameters such as Reynolds number (fully turbulent flow) of the natural gas flow in a pipe.

Thanks, Ankur. Formulas (2) to (5) are legible enough in http://www.aimehq.or...237/237-040.pdf.

There are also formulas (6) to (8) as an alternative, which do not seem legible in some points; e.g. in the expression of K (formula 7) exponent of T is 1.5? I have edited this point in my previous post, containing all formulas (6) to (8) (and units involved) according to my interpretation. It would be useful if someone could check formulas written in mentioned post against the original document; but this may not be possible since only the scanned copy is certainly available at http://www.aimehq.or...237/237-040.pdf .

Edited by kkala, 03 April 2010 - 01:18 PM.