Entropy in isothermal expansion

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SUMMARY

The discussion focuses on calculating entropy during isothermal expansion of air, specifically from an initial state of V1=0.1 m³, P1=1 MPa, and T1=20°C to a final state of P2=0.1 MPa. The user successfully determined the final temperature T2 (20°C), mass M (1.1927 kg), final volume V2 (1 m³), and heat transfer Q (230258 J). The user clarified that entropy values s1 and s2 can be calculated using the same formula by substituting the respective pressures, with Cp set at 1000 J/kg·K and reference conditions at P0 (760 mm Hg) and T0 (273.15 K).

PREREQUISITES
  • Understanding of thermodynamic principles, specifically isothermal processes.
  • Familiarity with the ideal gas law and its applications.
  • Knowledge of specific heat capacities, particularly Cp for air.
  • Basic skills in calculating thermodynamic properties such as entropy.
NEXT STEPS
  • Study the derivation and application of the entropy formula in thermodynamics.
  • Learn about the ideal gas law and its implications for real gases.
  • Explore the concept of specific heat capacities and their role in energy calculations.
  • Investigate the T-s diagram and its use in visualizing thermodynamic processes.
USEFUL FOR

Students and professionals in thermodynamics, mechanical engineers, and anyone involved in the study of gas behavior during expansion processes.

cytr
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Air:
V1= 0,1 m3
P1= 1 MPa
T1= 20 C
After isothermal expansion P2= 0,1 MPa

I had to find T2, M, V2, L, Q and found all those (T2=20 C; M=1,1927 kg; V2=1 m3; L=Q=230258 J) but need s (enthropy) for creating illustration in T-s
I can`t find how it`s possible to calculate s1 and s2, is it possible at all or is it possible to find only delta s?
 
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I already found the solution. :)
qRqUVr.jpg

S2 with same formula, just had to change P with P2 (if finding S1, then P=P1), Cp was 1000, P0 is normal pressure (760 mm HG), T0 is normal temperature (273,15 K)
 

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