Electrical power plants and ships commonly use steam to drive turbines, producing mechanical energy from the pressure of the system. The rotating turbine is connected to a generator that produces electricity. Steam enters a turbine at a high temperature and pressure and exits, still a gas, at a lower temperature and pressure. Determine the final pressure of steam that is converted from 10.0kL at 600kPa and 150C to 18.0kL at 110C.
One Response
Assuming steam, H2O(g), behaves like
an ideal gas, and no gas is lost to
surroundings, there are two states 1&2,
that form the combined gas law:
(P1 x V1)/T1 = (P2 x V2)/T2
where,
P1 = 600kPa
V1 = 10.0kL
T1 = 150ºC + 273.15 = 423.15 K
V2 = 18.0kL
T2 = 110ºC + 273.15 = 383.15 K
(temps. must be in Kelvin, while
others must be in same units)
Solving for P2:
P2 = (P1 x V1 x T2)/(V2 x T1)
Substituting numbers:
P2 = (600kPa x 10.0kL x 383.15 K)/(18.0kL x 423.15 K)
= (600kPa x 10.0 x 383.15)/(18.0 x 423.15)
= 301.824 kPa
*** Answer: 302 kPa ***
(at 3 sig. figs.)