Question 6.CSGP.91: A two fluid heat exchanger has 2 kg/s liquid ammonia at 20°C......
A two fluid heat exchanger has 2 kg/s liquid ammonia at 20°C, 1003 kPa entering state 3 and exiting at state 4. It is heated by a flow of 1 kg/s nitrogen at 1500 K, state 1, leaving at 600 K, state 2 similar to Fig. P6.85. Find the total rate of heat transfer inside the heat exchanger. Sketch the temperature versus distance for the ammonia and find state 4 (T, v) of the ammonia.
CV: Nitrogen flow line, steady rates of flow, \dot{ Q } \text { out and } \dot{ W }=0
Continiuty: \dot{ m }_1=\dot{ m }_2=1 \,kg / s ; \quad \text { Energy Eq: } \quad \dot{ m }_1 h _1=\dot{ m }_2 h _2+\dot{ Q }_{\text {out }}
Tbl. A.8: h _1=1680.7\, kJ / kg ; \quad h _2=627.24 \,kJ / kg
\dot{ Q }_{\text {out }}=\dot{ m }_1\left( h _1- h _2\right)=1(1680.7-627.24)= 1 0 5 3 . 5 k \,W
If Tbl A.5 is used: Cp =1.042 \,kJ / kg K
\dot{ Q }_{\text {out }}=\dot{ m }_1 Cp \left( T _1- T _2\right)=1 \times 1.042(1500-600)= 9 3 7 . 8 \,k W
CV The whole heat exchanger: No external \dot{ Q } , constant pressure in each line.
