100 kg of steam is enclosed in a piston-cylinder device, initially at 300°C and 5 bar. It expands
and cools to 200°C and 1 bar.
A) What is the change in internal energy of the steam in this process?
To calculate the change in internal energy of the steam in this process, we need to consider the initial and final states of the steam.
The change in internal energy (ΔU) can be determined using the First Law of Thermodynamics equation:
ΔU = Q - W
where ΔU is the change in internal energy, Q is the heat transfer, and W is the work done.
1. Calculate the heat transfer:
The heat transfer is given by the equation:
Q = m * (u2 - u1)
where Q is the heat transfer, m is the mass of the steam, and (u2 - u1) is the difference in specific internal energy between the initial and final states.
To find the specific internal energy values, we can use the steam tables. The specific internal energy values for the initial and final states can be determined by looking up the properties of steam at the respective temperatures and pressures.
2. Calculate the work done:
The work done can be determined using the equation:
W = P * (V2 - V1)
where W is the work done, P is the pressure, and (V2 - V1) is the difference in specific volume between the initial and final states.
Again, you can use the steam tables to find the specific volume values for the initial and final states.
3. Substitute the values into the equation for ΔU:
ΔU = Q - W
By substituting the calculated values for Q and W, you can find the change in internal energy (ΔU) of the steam during the process.