Question

Determine the following parameters for the water having quality x=0.7 at 200 kPa:

a) the phase
compressed liquid
superheated vapor
saturated liquid
saturated vapor
saturated mixture
b) temperature (in °C)
c) specific volume, in m3/kg
d) specific energy, in kJ/kg
e) specific enthalpy, in kJ/kg
f) What is the enthalpy of 500 g of water (in kJ)?

Answer 1

Given :

Water have quality x = 0.7 (dryness fraction) at around pressure of 200 kPa

The phase diagram is provided below.

a). The phase is a standard mixture.

b). At pressure, p = 200 kPa, T =
`$T_(saturated)$`

Temperature = 120.21°C

c). Specific volume

`$v_(f)= 0.001061, \ \ v_g=0.88578 \ m^3/kg$`

`$v_x=v_f+x(v_g-v_f)$`

`$=0.001061+0.7(0.88578-0.001061)$`

`$=0.62036 \ m^3/kg$`

d). Specific energy (
`u_x`)

`$u_f=504.5 \ kJ/kg, \ \ u_(fg)=2024.6 \ kJ/kg$`

`$u_x=504.5 + 0.7(2024.6)$`

`$=1921.72 \ kJ/kg$`

e). Specific enthalpy
`$(h_x)$`

At
`$h_f = 504.71, \ \ h_(fg) = 2201.6$`

`h_x=504.71+(0.7* 2201.6)`

`$= 2045.83 \ kJ/kg$`

f). Enthalpy at m = 0.5 kg

`$H=mh_x$`

`$= 0.5 * 2045.83$`

= 1022.91 kJ