Question

Which one of the following statements is correct for a superheated vapour?

Options :

  1. Its pressure is less than the saturation pressure at a given temperature.

  2. Its temperature is less than the saturation temperature at a given pressure.

  3. Its volume is less than the volume of the saturated vapour at a given temperature.

  4. Its enthalpy is less than the enthalpy of the saturated vapour at a given pressure

Show Answer

Answer :

Its pressure is less than the saturation pressure at a given temperature.

Solution :

If the temperature of the fluid is greater than its saturation temperature corresponding to its pressure, the fluid is called superheated vapour.

Other characteristics of the superheated vapour are:

  • Lower pressures (P < Psat at a certain T)
  • Higher temperature (T > Tsat at a certain P)
  • Higher specific volumes (v > vg at a certain T or P)
  • Higher internal energies (u > ug at a certain T or P)
  • Higher enthalpies (h > hg at a certain T or P)

Mistake Point: If the pressure of a liquid is greater than the saturation pressure corresponding to its temperature, the liquid is said to be compressed liquid.

If the temperature of a liquid is less than the saturation temperature corresponding to its pressure, the liquid is in a subcooled liquid state.

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