Thermal equilibrium in open systems

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An open system can reach thermal equilibrium under specific conditions, such as when mass flows in and out at the same temperature, like a system with a 400K inlet and outlet. In this scenario, if the system is compressed isothermally, it can maintain thermal equilibrium while performing work. However, in an adiabatic process where shaft work is done, the exit enthalpy and temperature of the gas may increase, complicating the definition of thermal equilibrium. If heat is simultaneously removed to balance the work done, the inlet and outlet enthalpies and temperatures can remain equal, but this may not strictly qualify as thermal equilibrium. Overall, the concept of thermal equilibrium in open systems is nuanced and depends on the specific interactions of heat, work, and mass flow.
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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