In the previous post, I discussed about a method called Chapman & Enskog, while also mentioned about another method called Yoon & Thodos. So in this part I will discuss the second method which is also apllicable for polar & non-polar gases both but still at low pressure say till 5 atm.
First method of Chapman Enskog is available Here or at the end of this post.
Viscosity by Yoon & Thodos correlation
There are two things to remember - 1 Polar Gas, 2 Non Polar Gas.
So for Non Polar Gas the equation is -
Vis * zeta = 4.610 * Tr^0.618 - 2.04* exp(-0.449 * Tr)+ 1.94 * exp(-4.058 Tr) + 0.1
Here
Tr = Reduced temperature with its usual definition i.e Tr = T / Tc
zeta is given by the following equation.
zeta = [Tc ^ (1/6)]/ [ M ^ 0.5 * Pc ^ (2/3) ]
So its more simpler than first method of Chapman & Enskog.
Now for Polar Gases there are two parts. One is for Tr Hydrogen bonding & second is non hydrogen bonding. The equations are -
For Hydrogen bonding gases, the applicability is Tr < 2.0
Vis x zeta = (0.755 Tr - 0.055 ) * [Zc ^ (-1.25)]
For Non Hydrogen bonding gases, the applicability is Tr < 2.5
Vis x zeta = [(1.90 Tr - 0.29 )^0.8 ] * [Zc ^ (-2/3)]
Zc = Compressibility factor at critical point, usually available.
zeta = is already given above.
Yes again the unit of viscosity here is micropoise.
List of other property estimation methods on this Blog.
First method of Chapman Enskog is available Here or at the end of this post.
Viscosity by Yoon & Thodos correlation
There are two things to remember - 1 Polar Gas, 2 Non Polar Gas.
So for Non Polar Gas the equation is -
Vis * zeta = 4.610 * Tr^0.618 - 2.04* exp(-0.449 * Tr)+ 1.94 * exp(-4.058 Tr) + 0.1
Here
Tr = Reduced temperature with its usual definition i.e Tr = T / Tc
zeta is given by the following equation.
zeta = [Tc ^ (1/6)]/ [ M ^ 0.5 * Pc ^ (2/3) ]
So its more simpler than first method of Chapman & Enskog.
Now for Polar Gases there are two parts. One is for Tr Hydrogen bonding & second is non hydrogen bonding. The equations are -
For Hydrogen bonding gases, the applicability is Tr < 2.0
Vis x zeta = (0.755 Tr - 0.055 ) * [Zc ^ (-1.25)]
For Non Hydrogen bonding gases, the applicability is Tr < 2.5
Vis x zeta = [(1.90 Tr - 0.29 )^0.8 ] * [Zc ^ (-2/3)]
Zc = Compressibility factor at critical point, usually available.
zeta = is already given above.
Yes again the unit of viscosity here is micropoise.
List of other property estimation methods on this Blog.
- Calculate Diffusion Coefficient in Gases
- Calculate Diffusion Coefficient in Liquids
- Heat Capacities of dissolved solids & organic solutions - Quickest methods
- Heat capacities with dissolved solids
- Kinematic viscosity of air Vs Temperature
- Thermal Conductivity of air Vs Temperature
- How to calculate viscosity of liquid mixtures
- Surface Tension
- Viscosities of Pure Gases at Low Pressure - 1
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