Saturated liquid water at 20 degree Celsius enters a mixing chamber at a rate of

Question

Saturated liquid water at 20 degree Celsius enters a mixing chamber at a rate of 2.5kg/s. At the same time, hot water steam at 200kPa and 150 degree Celsius enters the mixing chamber at a rate of 0.2kg/s. After mixing in the chamber, all the water leaves the chamber as saturate liquid at 60 degree Celsius. Please determine the heat loss rate of this mixing chamber. If all the heat loss to the surrounding at 25 degree Celsius, determine the rate of total entropy generation during this mixing process.

Explanation / Answer

refrence is 0 degree c
for 20 degree water let enthalpy be H1 = cdt =84kJ/kg
for 150 degree steam let it be H2 =2.76 *10^3 kJ/kg
for 60 degree let it be H3 =252k/j/kg
and mass of water leaving =2.5+0.2 =2.7 kg/s
rate of heat loss =rate of heat enering -rate of heat leaving
=2.5H1 +0.2H2 -2.7H3 = 81.6kJ/s

rate of entropy generated =81600/298 =273.83 J/K*s

(refrence for steam table is http://www.spiraxsarco.com/resources/steam-tables/superheated-steam.asp)

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