3 replies to this topic

[Sherif Morsi]

Hi,

 

I am trying to estimate the Methanol/Water liquid mixture viscosity for Methanol Injection Package. The mixture is 90%vol Methanol and 10%vol water.

 

I found Refutas Equation for estimation mixture viscosity, the steps are as follows:

 

(1)   

where ν is the kinematic viscosity in centistokes (cSt). It is important that the kinematic viscosity of each component of the blend be obtained at the same temperature.

(2)   

where x_X is the mass fraction of each component of the blend.

(3)   

where VBN_Blend is the viscosity blending number of the blend.

 

My questions are: What are the limitations to this equation (temperature, pressure....etc)? Is there any other method that would calculate a round figure?

 

Thanks,

Sherif

[PingPong]

The viscosity of that methanol/water mixture will be so low that it really does not matter for the design or selection of the injection package. You could just use 1 centiPoise (= 1 mPa.s).

 

If you want it more accurate then you need to use literature data, such as Table 3 and Figure 9 in following:

http://repository.ku...cjpnv49p059.pdf

 

Refutas is meant for mixtures of hydrocarbons, specifically fuel oil blending of residue with kerosene or gasoil.

It is not suitable for polar fluids, as these have a tendency to exhibit minima or maxima in a graph of viscosity versus concentration.

Edited by PingPong, 23 May 2014 - 12:21 PM.

[Sherif Morsi]

Thanks for replying, however the said table and figure are limited to 10 C while I am looking for -10 C. Any idea how to reach this? 

[PingPong]

You have 2 options:

 

1) google until you find the data you need

 

2) look at Figure 9 and estimate for x = 0.8 what the mixture viscosity would be at -10 ^oC. I guess something between 1.5 and 2 mPa.s so if you take 2 mPa.s it will be safe enough. It really makes no difference for the injection package whether it is 1.0 or 1.5 or 2.0 mPa.s