4. Use excel to solve the Peng-Robinson Eos and find the liquid and vapor specif

Question

4. Use excel to solve the Peng-Robinson Eos and find the liquid and vapor specific volumes of saturated n-butane at -40 oc, 10 oc, and 60 oc. The following are useful properties of n-butane: Mw 58.123 g/mol, 0.2, Tc 425.1 K, P 37.96 bar, vc 255 cm3/mol. Print a table of T, P vu, vvap and V NT where V NT s the intermediate root of the equation; also print one example of your excel work sheet at 10 oC. Notes: a) You will need to choose different initial estimates for each root of the equation. When choosing your estimates note that the parameter "b" is the minimum possible molar volume, so your initial liquid volume estimate should be slightly larger than b. Think what could be a good initial estimate for the vapor phase volume. b) Using the solver "add-in" and the Peng-Robinson Eos in its regular pressure explicit SAT form and solving for v when PR 0 gives better results than the equations in Appendix A. 7. You can use Appendix A.7 and get a good vapor volume, but the liquid volume will only be approximate

Explanation / Answer

Answer:

It requires to calculate a, b values.

Calculate 'a' and 'b' values from following.

a = 27 RTc2
b = R Tc/8Pc

Then use 'a' and 'b' values in the reduced ideal gas equation to get value of volume.

(P+an2/V2)(V-nb) = nRT

In-order to get specific volume, the obtained Volume has to devided with mass of molecule.

Specific volume (v) = V/m

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