Calculate the change in enthalpy of a superheated steam at 700 psia and 680°F is expanded at constant entropy to 140 psia.
To calculate the change in enthalpy of a process involving superheated steam being expanded at constant entropy, you can use the steam tables. These tables provide the thermodynamic properties of water and steam at different temperatures and pressures.
Here are the steps to calculate the change in enthalpy:
Step 1: Find the initial state properties
Look up the properties of superheated steam at the initial pressure and temperature of 700 psia and 680°F in the steam tables. Specifically, you need to find the enthalpy (h1) and entropy (s1) values.
Step 2: Find the final state properties
Next, locate the properties of steam at the final pressure of 140 psia. Find the enthalpy (h2) and entropy (s2) values at this pressure.
Step 3: Calculate the change in enthalpy
Finally, calculate the change in enthalpy (ΔH) using the following equation:
ΔH = h2 - h1
Make sure to use the units provided in the steam tables for temperature, pressure, and enthalpy to ensure accuracy.
Note: If the properties you need are not directly listed in the steam tables, you can perform interpolation to estimate the values between the given values. The steam tables often provide interpolation formulas or guidelines on how to do this.
By applying the above steps, you should be able to determine the change in enthalpy for the given superheated steam expansion process.