Liquid water as a compressed liquid at 65 degree F and 20 ps

Liquid water (as a compressed liquid) at 65 degree F and 20 psia is heated in a chamber by mixing it with saturated water vapor at 20 psia. If both streams enter the mixing chamber at the same mass flow rate, determine the exiting stream: (a) specific enthalpy (kJ/kg), (b) temperature in deg F and (c) the quality in %. Assume that the pressure is constant throughout the device and that the device is well-insulated (see picture below).

Solution

SOLUTION:

1) given-

first stream of cold water at 65 farenhite or 18.33 degree celsius has property as

t1=18.33+273=291.33 degree kelvin

C_pa=1.005 and x1=dryness fraction=0,Hliq1=1.005*291.33=292.78 KJ/Kg

second stream of vapor has property as

DBT=100 degree celsius and Hliq2=456.47 KJ/Kg and Hg2=2689.31 KJ/Kg and x2=1 from steam table

2) condition of mixture of vapor and liquid turn to steam, hence enthalpy at exit is given as

m1*Hliq1+m2*Hg2=m3*H3

AS m1=m2,hence

m1+m2=m3 on arranging we get,

H3=(Hliq1+Hg2)/2=1491.04 KJ/Kg

3) temperature at exit is given as

m1*t1+m2*t2=m3*t3

t3=(t1+t2)/2=65+212/2=138.5 degree farenhite

4) condition at exit is given as

m1*x1+m2*x2=m3*x3

x3=(x1+x2)/2=(0+1)/2=.5

hence dryness fraction of steam would be 0.5 or .5 kg of vapor in kg of wet steam