Polytropic Process: Finding Final Pressure and Volume

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Homework Help Overview

The discussion revolves around a thermodynamics problem involving a polytropic process of an ideal gas (hydrogen) within a piston-cylinder setup. The initial conditions include pressure, temperature, and volume, with the final volume specified. Participants are tasked with finding the mass of the gas and the final pressure and volume.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss relevant equations for the polytropic process, particularly the relationship PVn = constant. There are inquiries about how to determine the final volume and pressure based on the given parameters.

Discussion Status

Some participants have reported finding answers for part of the problem, while others express confusion about the next steps. Guidance has been offered regarding the application of the polytropic equation, but there is no explicit consensus on the overall solution.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can provide or seek. There is a focus on understanding the implications of the polytropic process and the relationships between pressure, volume, and the polytropic index.

Mohd17
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Homework Statement



A frictionless piston cylinder contains ideal gas hydrogen , R = 4.125 KJ/Kg.K , initially at p1=100 Kpa , t1 = 765 C , V1 = 0.35 m3 . The gas undergoes a polytropic process with n = 1.22 until the final volume becomes V2=8.0 m3

Cp = 14.3338 , Cv= 10.2043 , [URL]http://www.taftan.com/thermodynamics/GAMMA.GIF[/URL] = 1.4

Find :
a) Mass of the ideal gas
b) Final pressure and volume of the gas
 
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You need to post your attempt.

What relevant equations do you think are needed here?
 
the problem how can i get the volume of the gas !

already i get the answers for part a and the final pressure
 
Mohd17 said:
the problem how can i get the volume of the gas !

already i get the answers for part a and the final pressure

You should know for a polytropic process PVn = constant.
 
sorry but i didin't understand ...
now what's the answer ?
 
Mohd17 said:
sorry but i didin't understand ...
now what's the answer ?

PVn = constant means that

P1V1n = P2V2n

You were given P1, V1, n and you found P2.
 

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