- #1
maserati1969
- 24
- 3
- Homework Statement
- A cylinder fitted with a piston has a volume of 0.1 m3 and contains 0.5 kg of steam at 0.4 MPa. Heat is transferred to the steam until the temperature is 300 °C, while the pressure remains constant. Determine the heat transfer and work done for this process. Neglect the change in kinetic and potential energies.
- Relevant Equations
- Q-W = Delta U
Q = m(h2 - h1)
h = hf + (x.hfg)
I found the specific volume to be 0.2 m^3/kg (0.1 / 0.5), this gives me a dryness fraction (x) of 0.4311
Then I can use Q = m(h2 - h1)
h2 is just enthalpy for superheated steam at 400kPa and 300 Celsius = 3066.8 kJ/kg
but for h1 do I now use:
h = hf + (x.hfg)
or do I use
h = x.hg + (1-x).hf
I get a different enthalpy value for each and not sure which to use?
Thanks in advance for any help
Then I can use Q = m(h2 - h1)
h2 is just enthalpy for superheated steam at 400kPa and 300 Celsius = 3066.8 kJ/kg
but for h1 do I now use:
h = hf + (x.hfg)
or do I use
h = x.hg + (1-x).hf
I get a different enthalpy value for each and not sure which to use?
Thanks in advance for any help