How to calculate initial pressure and temperature - adiabatic process

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SUMMARY

The discussion focuses on calculating work in an adiabatic process where the initial pressure and temperature are unknown. The relevant equation mentioned is the adiabatic relation $$PV^{\gamma}=Constant$$, with a specific heat ratio of 5/3. The final values provided include a final volume of 0.37, final pressure of 276,000 Pa, and final temperature of 297.273 K. The calculated work for the process is -63,000 J, but the participants express confusion about how to derive this result without initial conditions.

PREREQUISITES
  • Understanding of adiabatic processes in thermodynamics
  • Familiarity with the equation $$PV^{\gamma}=Constant$$
  • Knowledge of the ideal gas law, $$PV=nRT$$
  • Concept of specific heat ratios, particularly for diatomic gases
NEXT STEPS
  • Study the derivation of work done in adiabatic processes using initial and final states
  • Learn how to apply the adiabatic equations to find unknown initial conditions
  • Explore the relationship between pressure, volume, and temperature in thermodynamic systems
  • Investigate the implications of specific heat ratios on gas behavior during adiabatic transformations
USEFUL FOR

Students and professionals in thermodynamics, mechanical engineers, and anyone involved in calculating work in adiabatic processes.

JoeyBob
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Homework Statement
Ratio from specific heats = 5/3

Initial volume = 0.814, final volume = 0.37, final pressure = 276000, final temperature is 297.273 K

Find Work
Relevant Equations
PV=nRT
Im confused on working backwards so to speak to find adiabatic work.

To find work for this adiabatic process, I either need to know the change in temperature OR the initial pressure (I think?).

The issue is that I don't know either the initial temperature nor the initial pressure so I am not sure how to calculate the work using the adiabatic eqns that require these values.

I know the answer to this problem is -63000 J, just not sure how to get there.
 
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When you say adiabatic equations, what do mean?
 
Are you familiar with the equation $$PV^{\gamma}=Constant$$
 
JoeyBob said:
The issue is that I don't know either the initial temperature nor the initial pressure so I am not sure how to calculate the work using the adiabatic eqns that require these values.
The adiabatic equations you pointed me to don't involve temperature. Can you find the value of ##K##?
 
JoeyBob said:
Homework Statement:: Ratio from specific heats = 5/3

Initial volume = 0.814, final volume = 0.37, final pressure = 276000, final temperature is 297.273 K

Find Work
Relevant Equations:: PV=nRT

Im confused on working backwards so to speak to find adiabatic work.

To find work for this adiabatic process, I either need to know the change in temperature OR the initial pressure (I think?).

The issue is that I don't know either the initial temperature nor the initial pressure so I am not sure how to calculate the work using the adiabatic eqns that require these values.

I know the answer to this problem is -63000 J, just not sure how to get there.
Check very carefully what you are given at final state.
 
Chestermiller said:
Are you familiar with the equation $$PV^{\gamma}=Constant$$
So I use final volume and pressure for this? I treid that and it didnt give the right answer for me.
 
JoeyBob said:
So I use final volume and pressure for this? I treid that and it didnt give the right answer for me.
Show us what you did.
 

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