Thermal equilibrium in open systems

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SUMMARY

An open system can reach thermal equilibrium under specific conditions, such as when mass flows in and out at the same temperature, exemplified by a system where a flow at T=400K enters and exits while undergoing isothermal compression. In this scenario, thermal equilibrium is maintained despite work being done. However, if the system is adiabatic and work is performed, the enthalpy of the gas increases, leading to a temperature rise, which complicates the definition of thermal equilibrium. Thus, while thermal equilibrium is achievable, it depends on the balance of heat removal and work done within the system.

PREREQUISITES
  • Understanding of open systems in thermodynamics
  • Knowledge of isothermal processes
  • Familiarity with adiabatic systems
  • Basic principles of enthalpy and temperature relationships
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  • Study isothermal and adiabatic processes in thermodynamics
  • Explore enthalpy changes in gas compression
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PT12
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Is it possible for an open system to reach thermal equilibrium? why/why not?
 
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PT12 said:
Is it possible for an open system to reach thermal equilibrium? why/why not?
Can you provide an example of what you are alluding to?
 
You could define an system in which a flow at T=400K goes in, a flow at T=400K goes out, while inside it is compressed isothermally, couldn't you? It remains in thermal equilibrium while work is done, and it's an open system since there is mass flow in and out.
 
oobgular said:
You could define an system in which a flow at T=400K goes in, a flow at T=400K goes out, while inside it is compressed isothermally, couldn't you? It remains in thermal equilibrium while work is done, and it's an open system since there is mass flow in and out.
If you have an open system (fixed control volume) operating at steady state, and shaft work is being done to compress the gas, if the system is adiabatic (insulated), then the enthalpy per unit mass of the gas at the exit is higher than at the entrance. So the temperature of the gas increases. If heat is being removed from the control volume as the gas passes through, such that the heat removed is equal to the shaft work, then the inlet and outlet enthalpies per unit mass are the same, and the temperatures are the same. But, I'm not sure you would call this thermal equilibrium.
 

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