Windows,Android apps for Engineers/ Students / Educational / Sports / Health personnel etc.
DIFFUSIVITIES GAS-LIQUID
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Allows for the prediction of gas and liquid diffusivities . The prediction is based upon the group contributions of each individual component of the compound
GASES :
The Diffusivity of gases can be predicted using the Fuller et al
equation.
Equation :
Dv = (1.013x10^-7(T^1.75)(1/Mb +
1/Mb)^1/2)/(p[((sum(Via))^1/3 + (sum(Vib))^1/3)]^2)
Dv = diffusivity, m^2/s
T = temperature, K
Ma, Mb = molecular weights of
components a and b.
P = total pressure, bar
Sum(Via), Sum(Vib) = Summations of
the special diffusion volume coefficients for components a, b.
The program calculates these values.
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Method of use :
Determine the structure of the gas components. Enter the relevant
number of times each component occurs in the structure, ie. if
Nitrogen, N, occurs 4 times enter a 4 to the text box next to the N
label. Click the Contribution A buttonto determine the
contribution of component A. Enter the values to determine the
Contribution of component B, (click Contribution B button)
Once the Component contributions have been determined, enter the
molecular weights of the components, pressure and temperature of the
gas. Calculations are made with each value change, the Diffusivity
will be calculated and displayed.
Example :
Methanol in Air
Pressure 1.013 bar
Temperature 25 o C
Element Contribution
Number Total
C 16.50
1 16.50
H 1.98
4 7.92
O 5.48
1 5.48
Total contribution of A 29.90
Total contribution of Air , B 20.1
Hence using the equation the
Diffusivity of Methanol = 16.2 x 10^-6 m^2/s
LIQUIDS:
Allows for the prediction of liquid heat capacity of a compound at
20 Degrees Celsius . The prediction is based upon the group
contributions of each individual component of the compound.
The Diffusivity of Liquids can be predicted using the Wilke and
Chang equation.
Equation :
DL = (1.173 x 10^-13(@M)^0.5T)/(uVm^0.6)
DL = Liquid diffusivity, m^2/s
@ = association factor of the solvent
example : 2.6,2.26 for water, 1.9 for methanol, 1.5 for ethanol,
1.0 for unassociated solvents.
M = molecular weight of solvent.
u = viscosity of solvent, mNs/m^2
T = temperature, K.
Vm = molar volume of the solute at its boiling point, m^3/kmol.
The program calculates these values.
Method Of Use:
Determine the chemical groups of the compound which the
diffusivity needs to be determined for.
Select the contribution value of each group by selecting relevant
group structure buttons. I.e. if the compound contains Atomic
elements click the Atomic/Molecular button.
Once the button is selected a form will be displayed showing all
the structures available. For each structure enter the number of
times it appears in the compound, in the associated text box .i.e. if
the compounds has two carbon atoms enter a 2 in the associated text
box. Click the okay button of each form to enter the
contribution value of the structure for the compound.
Once the contribution has been determined enter the viscosity of
the component, molecular weight, temperature, and the association
factor.
Calculations are made with each value change.
Example :
Predict, diffusivity of phenol in ethanol.
Temperature20 oC
Viscosity of ethanol at 20 o C 1.2 mN s/m^2
Molecular Weight of phenol = 46.
Contribution value :
Atom Volume
Number Totals
C 0.0148
6 0.0888
H 0.0037
6 0.0222
O 0.0074
1 0.0074
Ring -0.015
1 -0.015
0.103
m^3/Kmol
Hence using the equation the Diffusivity = 8 x 10^-10 m^2/s