Intro Thermodynamics Question using Steam Tables

In summary, the problem involves a transparent rigid container filled with 2 gallons of water at an initial pressure of 10.2 psig and an atmospheric pressure of 14.8 psia. The water occupies 2% of the container volume. The task is to determine the pressure reading on the gage when all the liquid has turned to vapor, represented on a T-v diagram. The steam tables are consulted to find the saturation temperature and specific volume at the initial condition, and then again at the saturated vapor condition. The resulting values are used to find the pressure and temperature at the final condition.
  • #1
cheme333
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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.
 
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  • #2
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
 

FAQ: Intro Thermodynamics Question using Steam Tables

1. What is thermodynamics?

Thermodynamics is the branch of science that deals with the study of energy and its transformation between different forms, such as heat, work, and internal energy. It also examines the relationships between these different forms of energy and how they affect the behavior of matter.

2. What are steam tables?

Steam tables are a set of tables containing thermodynamic properties of water and steam, such as temperature, pressure, specific volume, and enthalpy. These tables are essential tools for engineers and scientists working with steam systems, as they provide valuable information for designing and analyzing thermodynamic processes involving water and steam.

3. How are steam tables used in thermodynamics?

Steam tables are used in thermodynamics to determine the thermodynamic properties of water and steam at a given temperature and pressure. This information is then used to calculate other properties, such as heat transfer and work, and to analyze and design thermodynamic processes involving water and steam.

4. What are the units used in steam tables?

The units used in steam tables depend on the specific table being used. However, the most common units are temperature in degrees Celsius (°C), pressure in kilopascals (kPa), specific volume in cubic meters per kilogram (m3/kg), and enthalpy in kilojoules per kilogram (kJ/kg).

5. How do I read a steam table?

To read a steam table, you must first locate the desired temperature and pressure values on the table. Then, you can read the corresponding values for specific volume and enthalpy. These values can be used in equations to calculate other properties or can be plotted on a diagram to visualize thermodynamic processes.

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