Question

Determine the temperature and quality (if defined) for water at a pressure of 300kPa and at each of these specific volumes: Correct Value: T=379.9 degrees

Explain Why this is a superheated vapor. Is it because the volume of 1.0 is greater than the Vf and vg values of saturated liquid, .00107, and .6058. or for another reason. What if the volume was lower than .00107 ( vf of saturated liquid at given pressure of 300kpa (3 bar). What could be concluded from that. That it is a compreessed liquid perhaps, or something else. Please address this.

B) 1.0m³/kg

Answer 1

From the saturated steam table it can be found that for a pressure of 300 kPa the temperature would be 133.53 C

This is called superheated vapor. We know that under normal atmospheric pressure of 1 bar , the boiling point of water is 100 C after which it turns into vapor. But with the increase of pressure with minor increase in temperature we can keep the liquid form to be stable.Here the liquid is in equilibrium with the vapor at the saturated vapor pressure. However, the critical point so defined is 374 C.

Vf is the specific volume at saturated temperature for liquid

Vg is the specific volume at saturated temperature for steam/ gas.

It cannot be concluded that it is a compressed liquid as water is almost incompressible below 300 C so the physical properties such as mass, volume , density is not much affected by the increase in pressure.