Calculating Boiler Capacity and Steam Properties

[lindsey4]

Homework Statement

An electric generating plant boils water to produce high pressure steam. The steam spins a turbine that is connected to the generator.
a) how many liters of water must be boiled to fill a 5.0 m^3 boiler with steam at 50 atm and 400 degrees Celsius.
b) The steam has dropped to 2.0 atm at 150 degrees Celsius as it exits the turbine. How much volume does it now occupy?

Homework Equations

pv=nRT (not sure...but think you have to use some sort of ideal gas equation)

The Attempt at a Solution

Can you somehow find moles of the steam and then convert that to the liquid state somehow... do you use stochiometry?

 

[Ibix]

I'd assume an ideal gas unless you've been told to do otherwise.

If you can calculate the number of moles of water you need, then you can calculate the mass of water you need. Then just look up the density of water to get the volume.

 

[RTW69]

Do not use the ideal gas law. You are dealing with superheated water vapor. Use steam tables and find the specific volume of the steam at the indicated pressure and temperature. Since you know the volume you can determine the mass of the water vapor.

 

[Ibix]

My advice would be to follow RTW69's advice, not mine.

 

[Nickie]

I would like to clarify that the ideal gas equation (pv=nRT) is not applicable in this scenario as steam is not an ideal gas. Instead, we can use the steam tables or steam property calculator to determine the properties of steam at different conditions.

a) To calculate the amount of water needed to fill a 5.0 m^3 boiler with steam at 50 atm and 400 degrees Celsius, we need to use the steam tables or steam property calculator to determine the specific volume of steam at these conditions. Once we have the specific volume (in m^3/kg), we can then calculate the mass of steam needed to fill the boiler using the formula: volume = mass/specific volume. From there, we can convert the mass to liters using the density of water.

b) To determine the volume of steam at 2.0 atm and 150 degrees Celsius, we can use the same method as above. We would first calculate the specific volume of steam at these conditions and then use the formula: volume = mass x specific volume. From there, we can convert the mass to liters using the density of water.

In summary, to accurately calculate boiler capacity and steam properties, it is important to use the appropriate equations and tools, such as steam tables or steam property calculators, rather than assuming steam behaves like an ideal gas.