Isobaric Process - Entropy in Terms of Pressure and Volume

Written by Jerry Ratzlaff on . Posted in Thermodynamics

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

 

Isobaric process - entropy in terms of pressure and volume Formulas

\(\large{ S  =  \Delta S \; \left( - n\; R \right) \; \left[ ln \left( \frac{p_f}{p_i}  \right) \right] }\)   
\(\large{ S  =  \Delta S \; \left( n\; R \right) \; \left[ ln \left( \frac{V_f}{V_i}  \right) \right] }\)   

Where:

 Units English Metric
\(\large{ S }\) = entropy \(\large{\frac{Btu}{lbm-R}}\) \(\large{\frac{kJ}{kg-K}}\)
\(\large{ \Delta S }\) = change in entropy \(\large{\frac{Btu}{lbm-R}}\) \(\large{\frac{kJ}{kg-K}}\)
\(\large{ R }\) = molar gas constant \(\large{ \frac{lbf-ft}{lbmol-R} }\) \(\large{ \frac{J}{kmol-K} }\)
\(\large{ ln }\) = natural logarithm \(\large{dimensionless}\)
\(\large{ n }\) = number of moles \(\large{dimensionless}\)
\(\large{ p_f }\) = final pressure \(\large{\frac{lbf}{in^2}}\) \(\large{Pa}\)
\(\large{ p_i }\) = initial pressure \(\large{\frac{lbf}{in^2}}\) \(\large{Pa}\)
\(\large{ V_f }\) = final volume \(\large{in^3}\) \(\large{mm^3}\)
\(\large{ V_i }\) = initial volume \(\large{in^3}\) \(\large{mm^3}\)

 

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Tags: Pressure Equations Volume Equations Entropy Equations