Section 8.8CALCULATION OF FUGACITY (LIQUIDS)±8.8CALCULATION OF FUGACITY (LIQUIDS)Example S8.1 Vapor and Liquid Fugacities using the Virial EquationDetermine the fugacity (MPa) for acetylene at: (a) 250K and 10 bar; (b) 250K and 20 bar. Use thevirial equation and the shortcut vapor pressure equation.Solution:From the back flap of the text for acetylene: Tc= 308.3 K, Pc= 6.139, ω= 0.187, Zc= 0.271.For each part of the problem, the fluid state of aggregation is determined before the method ofsolution is specified. At 250 K, using the shortcut vapor pressure equation, Eqn 8.11, the vaporpressure is Psat= 1.387 MPa. We anticipate the need to calculate the virial coefficient at 250K using Eqns. 6.8-6.9:Tr= 250/308.3 = 0.810, Bo= −0.5071, B1= −0.2758, B = -233.3 cm3/mol.(a) P= 1 MPa < Psatso the acetylene is vapor. Using Eqn 6.10 to evaluate the appropriatenessof the virial equation at 1 MPa, Pr= 1/6.139 = 0.163, and 0.686 + 0.439Pr= 0.76 and Tr=0.810, so the correlation should be accurate.Using Eqn 8.29,f= ϕP= 0.894 (1) = 0.894 MPa(b) P= 2 MPa > Psatso the acetylene is liquid. For a liquid phase, the only way to incorporatethe virial equation is to use the Poynting Method, Eqn 8.36. Using Eqn 6.10 to evaluate the
This is the end of the preview.
access the rest of the document.