Thermal Compression + Expansion Index

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Discussion Overview

The discussion centers on the concepts of compression and expansion in thermodynamics, particularly in relation to calculating work done by heat engines. Participants explore the definitions, applications, and theoretical background of these processes.

Discussion Character

  • Technical explanation, Conceptual clarification, Homework-related

Main Points Raised

  • One participant asks about the purpose of compression and expansion in thermodynamics and their notation in formulas.
  • Another participant explains that compression is used to increase the pressure of the working fluid, requiring work input, while expansion reduces pressure and generates work output, with isentropic processes being ideal.
  • URLs are provided for further theoretical background and online calculators related to compression, expansion, and simple power cycles.
  • A later reply indicates that the provided resources were helpful in understanding the concepts and completing related calculations.

Areas of Agreement / Disagreement

Participants generally agree on the definitions and roles of compression and expansion in thermodynamics, but the discussion does not delve into competing views or unresolved issues.

Contextual Notes

The discussion does not address specific mathematical formulations or assumptions underlying the calculations of work done by heat engines.

Who May Find This Useful

Individuals interested in thermodynamics, particularly students or professionals working with heat engines and power cycles.

EngNoob
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Could anyone tell me what the compression and expansion is used for in a Thermodynamics situation?

What is the notation for Compression and Expansion in a formula?

I am trying to calculate work done by a heat engine.

Thanks
 
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Hi there:

In general, compression is used to compress the working fluid, increase the pressure -- pressurized the working fluid. Work and/or power input are required to do so. In an ideal case, isentropic compression is used.

In general, expansion is used to expand the working fluid, reduce the pressure -- expand the working fluid. Work and/or power output are generated. In an ideal case, isentropic expansion is used.

Here are two URLs when dealing with compression and expansion.

Theoretical background information on compression and expansion:
http://members.aol.com/engware/components.htm

Online calculators dealing with compression and expansion:
http://members.aol.com/engware/calc4.htm

In order to get the full meaning of compression and expansion with respect to the operation of simple power cyles, here are two more URLs dealing with simple power cycles (Carnot, Brayton, Otto and Diesel).

Theoretical background information on simple power cycles:
http://members.aol.com/engware/cycles.htm

Online calculators dealing with simple power cycles:
http://members.aol.com/engware/calc3.htm

Here are two plots regarding the compression power input and expansion power output.

Slide58.GIF


Slide185.GIF


I do hope that the provided URLs will be useful to you when dealing with theoretical background and doing related basic engineering calculations.

Thanks,

Gordan
 
Last edited by a moderator:
Thanks for those urls, they have done the trick, I have read, understood, and now completed, so thanks for all the help, most appreciated...
 
EngNoob:

No problem.

Thanks,

Gordan
 

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