Chapter 3

T-v graph

(constant P)

P-v graph

(constant T)

 

A:Compressed Liquid

B: Saturated Liquid

C: Saturated Liquid-Vapor

D: Saturated Vapor

E: Superheated Vapor

BD: Latent Heat of Vaporisation

when a substance exists as part liquid and part vapor at saturation conditions, its quality (x) is defines as

 

 

Example 1:

Refer Table A-5:

at pressure 200kPa,      T_sat=133.52°C      V_f=0.001073 m³/kg     V_g=0.60582 m³/kg

let x=0.7

Solution:

v= v_f + xv_fg

  =0.001073 + 0.7(0.60582 - 0.001073)

  =0.4634 m³/kg

 

 

Example 2:

A vessel of volume 0.04m³ contains a mixture of saturated water and saturated steam at a temperature of 250°C. The mass of the liquid present is 9kg. Find the pressure, the mass, the specific volume, the enthalpy and the internal energy.

Solution:

 

Example 3:

 Steam initially at 0.3MPa, 250°C is cooled at constant volume

a.    At what temperature will the steam become saturated vapour?

b.    What is the quality at 80°C?

c.    What is the heat transferred per kg of steam in cooling from 250°C to 80°C

Solution: