Question

Water at 20 C and 100 kPa is brought to 100kPa and 1500 C. Find the change in the specific internal energy, using the water tables and ideal gas tables. When answering, can you walk me through which tables you use and how you use them?

Answer 1

you won't be using the ideal gas tables in this problem, but what you will do is look up the temperature at 1 bar (=100kpa) in table A-3. The temperature is 99.63 degrees. Look up the pressure corresponding to 20 degrees C. It is 0.02339 bar. Since 1 bar is much greater than 0.02339 bar, we can treat the H20 as a compressible liquid, meaning u ~ uf. You just look up the uf value at 20 degrees C, and that is your initial specific internal energy. In regards to the 1500 degrees C, I don't see that on a table, but if anywhere, you should look for specific internal energy at 1500 degrees C in the superheated table.