For a counter current heat exchanger with Ti h = 80°C, T°c = 60°C, T°h = 50°C and Ti c = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy___________________?
Correct answer: B. d2T/dZ2 = 0
- A. d2T/dZ2 > 0
- B. d2T/dZ2 = 0
- C. d2T/dZ2 < 0
- D. dT/dZ = 0
Explanation
The endpoint temperature differences are 80 - 60 = 20°C and 50 - 30 = 20°C, so the temperature difference remains constant along the exchanger. A linear temperature profile has zero second derivative, hence d²T/dZ² = 0.
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