Piston question to find temperature and pressure

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SUMMARY

The discussion revolves around a thermodynamics problem involving a vertical cylinder with a frictionless piston containing air at an initial pressure of 0.21 MPa and temperature of 430°C. The key equations referenced include the ideal gas law and the principle that PV remains constant during the cooling process. However, a critical error is identified: if PV is constant, the temperature cannot change, contradicting the cooling scenario. The problem requires clarification on the piston stops' positions to proceed with calculations.

PREREQUISITES
  • Understanding of the ideal gas law and its applications
  • Knowledge of thermodynamic principles, specifically PV=constant
  • Familiarity with specific heat and its role in gas behavior
  • Basic algebra for solving equations related to pressure and temperature
NEXT STEPS
  • Review the ideal gas law and its implications in thermodynamic processes
  • Study the concept of constant volume and its effects on temperature and pressure
  • Learn about specific heat ratios and their significance in gas behavior
  • Examine real-world applications of piston-cylinder systems in thermodynamics
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Students studying thermodynamics, engineers working with pneumatic systems, and anyone interested in the behavior of gases under varying temperature and pressure conditions.

Nightlord
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Homework Statement


Air is contained in a vertical cylinder fitted with a frictionless piston and a set of stops. The cross sectional area of the piston is 0.05m^2. The air, which is initially at 0.21 MPa and 430 C, is cooled as result of heat transfer to the surroundings. Assuming that during the decrease in volume PV=constant find (a) the temperature of the air inside the cylinder when the piston reaches the stops and (b) the pressure inside the cylinder if cooling continues until the temperature is 70 C. Assume the air behaves as an ideal gas with constant specific heat with k=1.4
The piston is 1.2m in length, stops are placed halfway of the piston, dividing the piston in two parts of 0.6m.The attempt at a solution
Cant understand where to start
 
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Hi Nightlord and welcome to PF. Please follow the rules of this forum and use the template when you seek help with homework. Show us the relevant equations and tell us what you tried and what you think about the problem. We just don't give answers away.
 
Nightlord said:
Assuming that during the decrease in volume PV=constant
There is a problem with this question. If PV=constant, then temperature would be constant (since we assume it is an ideal gas). So PV cannot be constant during a cooling process.

Also, if you are supposed to actually answer a) we would have to know where the stops are.

Please provide the entire question and show us what you have done.

AM
 

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