Intro Thermodynamics Question using Steam Tables

Click For Summary
SUMMARY

The discussion focuses on determining the pressure gauge reading in psig when all liquid water in a rigid container has turned to vapor. The initial conditions include a pressure of 10.2 psig and a local atmospheric pressure of 14.8 psia, with the container holding 2 gallons of water. The solution involves using steam tables to find the saturated vapor pressure corresponding to the specific volume of 0.8 ft³/lb after heating. The key equation utilized is v = vf + x(fg), where the quality x changes from 4.8% to 100% as the water transitions to saturated vapor.

PREREQUISITES
  • Understanding of steam tables and their application in thermodynamics.
  • Familiarity with the concepts of pressure, temperature, and specific volume.
  • Knowledge of the quality of steam and its significance in phase changes.
  • Ability to interpret T-v diagrams for thermodynamic processes.
NEXT STEPS
  • Consult steam tables for saturated vapor pressure at specific volumes.
  • Learn how to construct and interpret T-v diagrams for phase transitions.
  • Study the relationship between pressure, temperature, and specific volume in thermodynamic systems.
  • Explore the implications of constant volume heating in rigid containers.
USEFUL FOR

Students and professionals in thermodynamics, mechanical engineers, and anyone involved in the study of phase changes in fluids, particularly those using steam tables for calculations.

cheme333
Messages
1
Reaction score
0

Homework Statement



A transparent rigid container is filled with 2 gallons of water. Initially the pressure is
measured to be 10.2 psig, using a gage attached to the container. The local atmospheric pressure is 14.8 psia. It is observed that the liquid water in the container occupies two percent of the container volume. The water in the container is heated. Determine the reading on the pressure gage in psig when all the liquid has just turned to vapor (all saturated vapor). Show this process on a sketch of a T-v diagram.

Homework Equations



Equatin for quality: v = vf + x(fg)

The Attempt at a Solution



I understand the concept of steam tables. And I understand exactly what this looks like on a T-v diagram. I guess I am getting too bogged down in the information given to not know what to consult the steam tables for.

I understand that the absolute pressure in the container before being heated is 25 psia, so I can get a saturated temperature reading from that, and a specific volume based on the fact the 98% of the water is steam (see above equation). But I'm not sure how to related that to the container once it's been heated. The volume stays constant and I'm left with saturated vapor, but what does that mean for the pressure?

Any help is appreciated and I'll be happy to clear up any blurry areas of my question.
 
Last edited:
Physics news on Phys.org
Condition 1: P1=25psia. T1:240 F, V1=.8 ft^3/Lb, X=4.8%

Condition 2: V2=.8 ft^3/lb, x=100% because you are saturated vapor, Vg=V2=.8 ft^3/lb

look on steam tables at Vg= .8 ft^3/lb to find P2 and T2
 

Similar threads

Replies
14
Views
4K
  • · Replies 8 ·
Replies
8
Views
5K
  • · Replies 19 ·
Replies
19
Views
4K
  • · Replies 13 ·
Replies
13
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
1
Views
3K
  • · Replies 7 ·
Replies
7
Views
6K
  • · Replies 8 ·
Replies
8
Views
5K
  • · Replies 1 ·
Replies
1
Views
8K