Viscosity blending of liquids

[mbeychok]

Calculating the viscosity of a blended liquid consisting of two or more liquids having different viscosities is a three step procedure. The first step involves calculation of the Viscosity Blending Index (VBI) of each component of the blend using the following equation (known as a Refutas equation):

 

(1) VBI = 14.534 × ln[ln(v + 0.8)] + 10.975

 

where v is the viscosity in centistokes and ln is the natural logarithm (Log_e).

 

The second step involves using this blending equation:

 

(2) VBI_Blend = [w_A × VBI_A] + [w_B × VBI_B] + ... + [w_X × VBI_X]

 

where w is the weight fraction (i.e., % ÷ 100) of each component of the blend. In using the above blending equation, it is necessary that all viscosities are determined at the same temperature, for example, 100 ^oC.

 

The third and final step is to determine the viscosity of the blend by using the invert of equation (1):

 

(3) v = e^{e(VBI - 10.975) ÷ 14.534} − 0.8

 

where VBI is the Viscosity Blending Index of the blend and e is the transcendental number 2.71828, also known as [[Euler's number]].

[DrDNA]

Wow. This is almost as interesting as your air pollution conversion factors. I think I'll visit your site to learn more (NOT).

[Bignose]

Is there something you want to discuss about this? Because, otherwise, what is the point in posting some formulas that no one asked about? It's about a much use as if I'd posted a "how to add numbers to sum to 4" post and told everybody that you can add 2+2, or 1+3, or 0+4, or even -1+5 to get 4. Yay!

 

So, if you want to discuss something about this, discuss away. However, just posting this stuff without any questions or even comments on it is a waste.

[DrDNA]

I think he is trying to drum up business for his book. Not very good at it though.

[Mr Skeptic]

He has almost as many threads as posts, too.

[John Cuthber]

Not only is it an odd post, I don't think it's correct. A lot of mixtures give rather odd viscosities when mixed. For example a mixture of methanol and water is rather more viscous than its components.

Here is some data for methanol and a few other things, there's a clear maximum.

http://journals.tubitak.gov.tr/physics/issues/fiz-02-26-3/fiz-26-3-12-0006-28.pdf

The components of the mix have nearly the same viscosity (if you don't like the "nearly" bit then use the solution with the same viscosity as water its near 70% mole fraction methanol) so if you were to calculate the "VBI" for each of them you would get the same number for methanol or water, linear combinations of these would also give the same number and reversing the calculation to get back to a viscosity would also give the same answer.

In other words the equations above predict that any mixture of methanol and water will have the same viscosity; in fact they don't.

 

I haven't checked; is the rest of his site and/or book equally helpful?