Question

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

Answer 1

Solution :

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 $h_f = 504.71, \ \ h_{fg} = 2201.6$

   $h_x=504.71+(0.7\times 2201.6)$

        $= 2045.83 \ kJ/kg$

f). Enthalpy at m = 0.5 kg

  $H=mh_x$

       $= 0.5 \times 2045.83$

       = 1022.91 kJ