Question 6.CSGP.83: A condenser (heat exchanger) brings 1 kg/s water flow at 10 ......
A condenser (heat exchanger) brings 1 kg/s water flow at 10 kPa from 300°C to saturated liquid at 10 kPa, as shown in Fig. P6.84. The cooling is done by lake water at 20°C that returns to the lake at 30°C. For an insulated condenser, find the flow rate of cooling water.
C.V. Heat exchanger
Energy Eq.6.10: \dot{ m }_{ cool } h _{20}+\dot{ m }_{ H _2 O } h _{300}=\dot{ m }_{ cool} h _{30}+\dot{ m }_{ H _2 O } h _{ f , 10 \,kPa }
Table B.1.1: h _{20}=83.96 \,kJ / kg , \quad h _{30}=125.79 \,kJ / kg
Table B.1.3: h _{300,10\,kPa }=3076.5 \,kJ / kg , \text { B.1.2: } \quad h _{ f , 10 \,kPa }=191.83 \,kJ / kg
\dot{ m }_{ cool }=\dot{ m }_{ H _2 O } \frac{ h _{300}- h _{ f , 10 kPa }}{ h _{30}- h _{20}}=1 \times \frac{3076.5-191.83}{125.79-83.96}=69 \,kg / s
