Closed System

Definition

A closed system is a type of thermodynamic system that does not exchange matter with its surroundings but can exchange energy in the form of heat or work. This means that while the mass within the system remains constant, energy can flow in and out, influencing the internal state of the system. Understanding closed systems is crucial for analyzing various engineering principles, particularly in relation to mass conservation, material balances, and energy transformations.

5 Must Know Facts For Your Next Test

1. In a closed system, the total mass remains constant because there is no input or output of material, which is fundamental to understanding mass conservation.
2. Material balance calculations often assume closed systems to simplify analysis by focusing only on energy changes rather than mass changes.
3. The first law of thermodynamics applies to closed systems by stating that the change in internal energy equals the heat added to the system minus the work done by the system.
4. Heat transfer in a closed system can occur through conduction, convection, or radiation without affecting the amount of substance present.
5. Closed systems are common in many engineering applications, including engines and refrigeration systems, where control over mass flow is essential.

Review Questions

• How does a closed system relate to the conservation of mass and what implications does this have for material balance calculations?
  • In a closed system, since there is no exchange of matter with the environment, the principle of conservation of mass dictates that the total mass remains unchanged. This allows for straightforward material balance calculations because engineers can focus solely on the energy changes without needing to account for mass flows into or out of the system. This simplification helps facilitate analysis and design in various engineering scenarios.
• Discuss how energy transformations in a closed system adhere to the first law of thermodynamics.
  • The first law of thermodynamics states that energy cannot be created or destroyed; it can only change forms. In a closed system, when heat is added or work is done on the system, the internal energy changes according to this law. For example, if heat enters a closed system while doing work on its surroundings, the internal energy of the system will increase proportionally to these energy transfers. This relationship is crucial for understanding how energy behaves within such systems.
• Evaluate the role of closed systems in engineering design and their impact on energy efficiency.
  • Closed systems play a vital role in engineering design by allowing precise control over energy transformations while maintaining constant mass. This characteristic enables engineers to optimize processes such as combustion engines or heat exchangers, improving overall energy efficiency. By analyzing energy inputs and outputs without accounting for mass loss or gain, engineers can identify opportunities for minimizing waste and maximizing performance in various applications.

Related terms

Open System:

An open system can exchange both matter and energy with its surroundings, allowing for the continuous flow of substances in and out of the system.

Isolated System:

An isolated system does not exchange either matter or energy with its surroundings, effectively being completely self-contained.

Energy Conservation:

The principle stating that energy cannot be created or destroyed, only transformed from one form to another within a closed or isolated system.