Oil enters a counterflow concentric heat exchanger at120°C,20 kg/min; water enters the opposite end at30°C,50 kg/min. Specific heats are oil1.9 and water4.2 kJ/(kg °C), effectiveness0.7. Find water exit temperature in °C.
Capacity rates are Ch=20×1.9=38 and Cc=50×4.2=210 kJ/(min K). Qmax=Cmin(Th,in−Tc,in)=38(90)=3420 kJ/min. Actual Q=0.7×3420=2394. Therefore water rise=2394/210=11.4°C, giving41.4°C, B.