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In a concentric counter flow heat exchange, water flows through the inner tube at 25°C and leaves at 42°C. The engine oil enters at 100°C and flows in the annular flow passage. The exit temperature of the engine oil is 50°C. Mass flow rate of water and the engine oil are 1.5 kg/s and 1 kg/s, respectively. The specific heat of water and oil are 4178 J/kgK and 2130 J/kgK, respectively. The effectiveness of this heat exchange is
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- 0.666
- 0.777
- 0.555
- 0.444
Correct Option: A
Tc,i = 25°C;
Tc,o = 42°C;
mc = 1.5 kg/s;
Cc = 4.178 kJ/kg.k
Th,i = 100°C;
Th,o = 50°C;
mh = 1 kg/s;
Ch = 2.130 kJ/kg.k
mcCc = 1.5 × 4.178
= 6.267 kW/°C = Cmax
mhCh = 1 × 2.130
= 2.130 kW/°C = Cmin
| effectiveness = ε = | Cmin(Th,i - Tc,i) |
| = | = 0.666 | 100 - 25 |
