Thermodynamic System: Closed vs Controlled Volumes

In summary: A control volume is a mathematical tool used for an open system, while a closed system does not require such a tool. While some may refer to a closed system as a controlled mass system, it is not commonly accepted as the proper terminology. In summary, a closed system cannot be called a Controlled Volume system because it does not require a control volume, unlike an open system which does.
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Why a closed system can't be called as a Controlled Volume system?
 
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  • #2
"Controlled volume" is not all closed systems.
 
  • #3
Well, a control volume is a mathematical tool we set up on an open system in order to account for material flow streams (and energy flow streams, too) entering and exiting said system. Normally, we decide how to define a control volume for an open system. In a closed system, there are no materials entering or leaving the system, and the system usually has its boundaries well defined, so there's no need for us to define a control volume.
 
  • #4
I agree with mexcheme.
Control volume means a device is used to control the volume; commonly valve is used.
Closed system is used usually in refrigerant system.
 
  • #5
Well.Thanq MexchemE i got it.
Someone mentioned that we can call a Closed system as a controlled mass system and an Open system as a Controlled volume one...

Here the Truth is we are using a controlled volume in an open system and that's the point... So we can't simply call it a Controlled Volume system..
 
  • #6
holdmenow said:
I agree with mexcheme.
Control volume means a device is used to control the volume; commonly valve is used.
Closed system is used usually in refrigerant system.
This is not the conventional terminology that is used.
 
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1. What is a thermodynamic system?

A thermodynamic system is a region of space that is under study and contains a certain amount of matter or energy. It can be a single substance or a mixture of substances and is typically separated from its surroundings by a boundary.

2. What is the difference between a closed and a controlled volume thermodynamic system?

A closed system is one where neither matter nor energy can enter or leave, while a controlled volume system allows for the transfer of matter but not energy. In other words, a closed system has a fixed mass, while a controlled volume system has a fixed volume.

3. How does a closed system maintain its energy balance?

A closed system maintains its energy balance through internal processes such as heat transfer, work, and changes in internal energy. This means that the total energy within the system remains constant, but it can be redistributed among different forms.

4. Can a closed system be in thermodynamic equilibrium?

Yes, a closed system can be in thermodynamic equilibrium when the macroscopic properties of the system, such as temperature, pressure, and density, remain constant over time. This means that there is no net flow of matter or energy within the system.

5. What are some examples of closed and controlled volume thermodynamic systems?

Examples of closed systems include a sealed container of gas, a chemical reaction in a closed vessel, and the Earth's atmosphere. Controlled volume systems can be seen in devices such as pumps, turbines, and piston-cylinder arrangements used in heat engines.

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