Isobaric Process - Entropy in Terms of Pressure and Volume

 

Isobaric Process - Entropy in Terms of Pressure and Volume Formula
\( S  \;=\;  \Delta S \cdot ( - n \cdot R ) \cdot  \left( n \cdot \dfrac{ p_f }{ p_i } \right)  \) 
Symbol English Metric
\( S \) = Entropy \(Btu \;/\; lbm-R\) \(kJ \;/\;kg-K\)
\( \Delta S \) = Entropy Change \(Btu \;/\; lbm-R\) \(kJ \;/\;kg-K\)
\( n \) = Number of Moles \(dimensionless\) \(dimensionless\)
\( R \) = Molar Gas Constant \(lbf-ft \;/\; lbmol-R\) \(J \;/\; kmol-K\)
\( ln \) = Natural Logarithm \(dimensionless\) \(dimensionless\)
\( p_f \) = Final Pressure \(lbf \;/\; in^2\) \(Pa\)
\( p_i \) = Initial Pressure \(lbf \;/\; in^2\) \(Pa\)

Isobaric process is a thermodynamic process where the pressure is kept constant, \(\Delta p = 0\).                

Isobaric Process - Entropy in Terms of Pressure and Volume Formula
\( S  \;=\;   \Delta S \cdot  ( n \cdot R ) \cdot  \left( ln \cdot \dfrac{ V_f }{ V_i } \right) \) 
Symbol English Metric
\( S \) = Entropy \(Btu \;/\; lbm-R\) \(kJ \;/\;kg-K\)
\( \Delta S \) = Entropy Change \(Btu \;/\; lbm-R\) \(kJ \;/\;kg-K\)
\( n \) = Number of Moles \(dimensionless\) \(dimensionless\)
\( R \) = Molar Gas Constant \(lbf-ft \;/\; lbmol-R\) \(J \;/\; kmol-K\)
\( ln \) = Natural Logarithm \(dimensionless\) \(dimensionless\)
\( V_f \) = Final Volume \(in^3\) \(mm^3\)
\(V_i \) = Initial Volume \(in^3\) \(mm^3\)

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