Thermodynamics conceptual question(for advanced people)?

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SUMMARY

The discussion focuses on the thermodynamic principles governing the behavior of a monoatomic perfect gas during compression in a piston. The key equation for adiabatic compression is identified as T_fV_f^{\gamma-1} = T_iV_i^{\gamma-1}, indicating that the product of temperature and volume raised to the power of the heat capacity ratio (γ) remains constant. Additionally, the first law of thermodynamics is applied to relate changes in internal energy (ΔU), heat flow (ΔQ), and work done (W) on the gas, expressed as ΔU = nC_vΔT = ΔQ - W. The discussion also raises questions about the ratio of energy transformed into heat versus pressure during compression.

PREREQUISITES
  • Understanding of the first law of thermodynamics
  • Familiarity with adiabatic processes in thermodynamics
  • Knowledge of monoatomic perfect gas behavior
  • Concept of heat capacity ratio (γ)
NEXT STEPS
  • Study the derivation of the adiabatic process equations for ideal gases
  • Explore the implications of the first law of thermodynamics in various thermodynamic processes
  • Investigate the concept of heat capacity at constant volume (C_v) for different gases
  • Learn about the practical applications of gas compression in engineering systems
USEFUL FOR

This discussion is beneficial for advanced students of thermodynamics, mechanical engineers, and researchers focusing on gas dynamics and energy transformation processes.

StarDust563
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If you compress a gas in a piston(a monoatomic perfect gas for instance), what is the equation that gives you the temperature of the gas or amount of heat introduced in the gas vs the volume of the gas?
And what is the ratio of energy that is transformed into heat vs into pressure? Is it constant through compression?

thanks a lot
 
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StarDust563 said:
If you compress a gas in a piston(a monoatomic perfect gas for instance), what is the equation that gives you the temperature of the gas or amount of heat introduced in the gas vs the volume of the gas?
And what is the ratio of energy that is transformed into heat vs into pressure? Is it constant through compression?
If this is an adiabatic compression (no heat flow into or out of the gas), then:

[tex]T_fV_f^{\gamma-1} = T_iV_i^{\gamma-1} = \text{Constant}[/tex]

If heat is added, you have to know the heat flow and the work done by/on the gas and use the first law:

[tex]\Delta U = nC_v\Delta T = \Delta Q - W[/tex] where W is the work done by the gas (which is the negative of the work done on the gas - ie. in compressing the gas)

AM
 

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