What Happens When Water Vapor Cools at Constant Pressure?

Click For Summary
SUMMARY

The discussion centers on the behavior of water vapor in a closed system as it cools at constant pressure, specifically transitioning from state d to state 2 on a T-v diagram. The cooling process from state 1 to state d occurs at constant pressure, but the movement from d to 2 involves a decrease in temperature and an increase in volume, which does not maintain constant pressure. The final transition to state 3, where the system reaches a saturated liquid state, occurs at constant pressure and temperature despite a reduction in volume through piston compression.

PREREQUISITES
  • Understanding of T-v diagrams in thermodynamics
  • Knowledge of phase changes in water vapor
  • Familiarity with the concepts of saturated vapor and saturated liquid
  • Basic principles of closed systems in thermodynamic processes
NEXT STEPS
  • Study the principles of phase transitions in thermodynamics
  • Learn about the implications of constant pressure processes in closed systems
  • Explore the use of T-v diagrams for analyzing thermodynamic cycles
  • Investigate the behavior of moist air and its properties under varying conditions
USEFUL FOR

Students and professionals in thermodynamics, mechanical engineers, and anyone studying the behavior of gases and phase changes in closed systems.

princejan7
Messages
93
Reaction score
0

Homework Statement



This is a diagram T-v diagram for a closed system consisting of a sample of moist air that is cooled at constant pressure
can someone explain what happens for the state of the water vapor to move from d to 2? if its cooling at constant pressure, why does it not stay on the pv1<pg1 curve

Homework Equations


http://postimg.org/image/93qb4figj/

The Attempt at a Solution

 
Physics news on Phys.org
Going from d to 2 is not at constant pressure. It's constant pressure from 1 to d. From the graph it looks like temperature is further dropped while the volume is simultaneously increased, always so as to keep the fluid at saturated vapor. That would get you to point 2. After that, you reduce the volume (by pressing on the piston) until you reach point 3 which is saturated liquid. In this last stage pressure (and temperature) stay constant even though you're pushing on the piston to reduce the volume.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 27 ·
Replies
27
Views
5K
Replies
4
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
2
Views
2K
  • · Replies 44 ·
2
Replies
44
Views
6K
  • · Replies 13 ·
Replies
13
Views
7K
Replies
35
Views
6K
  • · Replies 12 ·
Replies
12
Views
7K
  • · Replies 1 ·
Replies
1
Views
2K