Thermodynamics-heating water in piston help

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SUMMARY

The discussion focuses on a thermodynamics problem involving a cylinder/piston arrangement containing water at 105°C and 85% quality. The system is heated until the piston compresses a spring, with the final pressure reaching 200 kPa. The calculations involve determining the force on the spring, the displacement of the spring, and the final state of the water/vapor mix using saturation tables. Key equations include F/A = pressure and F = K*d, which are essential for solving the problem.

PREREQUISITES
  • Understanding of thermodynamic properties of water and steam
  • Familiarity with the ideal gas law and phase change concepts
  • Knowledge of spring mechanics and Hooke's Law
  • Ability to use steam tables for quality and saturation calculations
NEXT STEPS
  • Study the use of steam tables to determine properties of water at various pressures and temperatures
  • Learn about the relationship between pressure, volume, and temperature in thermodynamic systems
  • Explore the concept of constant entropy processes in thermodynamics
  • Investigate the application of Hooke's Law in mechanical systems involving springs
USEFUL FOR

This discussion is beneficial for students and professionals in mechanical engineering, particularly those studying thermodynamics, fluid mechanics, and mechanical systems involving springs and pistons.

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Homework Statement


A cylinder/piston arrangement contains water at 105 C, 85% quality with a volume of 1L.
The system is heated, causing the piston to rise and encounter a linear spring. At this
point, the volume is 1.5 L, piston diameter is 150 mm, and spring constant is 100 N/mm.
The heating continues, so the piston compresses the spring. What is the cylinder
temperature when the pressure reaches 200 kPa.


Homework Equations


F/A=pressure
F=K*d


The Attempt at a Solution


From what I stated with. I solved for the Force on the spring.
F/(pi/4)(.150^2)mm=200,000 Pa
F=3534.29N

Then I found out the displacement of the spring.
3534.39=100*d
d=35.3439mm

That is where I am stuck at. What I tough might work is to find the volume after the spring is compressed. That is just over 1.5L and comparing that to the saturation tables it is above the saturated vapor. So it would be a gas. But I don't think that is correct. If anyone can help straighten me out and point me in the right direction. Thanks.
 
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The expansion from 1 L to 1.5 L is done at constant pressure with heat input. So the final state (ie: quality) of the water/water vapor, can be found from the tables. Do you know how to do that?

Once the water/vapor mix begins pushing against the piston, it is doing work and follows a line of constant entropy. If you can find the state at 1.5L above, then you can find the entropy at that state from the tables. Follow the line of constant entropy up to the pressure specified to find the final state.
 

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