Question

In a parallel flow heat exchanger, the NTU is calculated to be 2. The highest possible effectiveness for this heat exchanger is _____

• A. 49. 08%
• B. 86.5%
• C. 67.67 %
• D. 98.16%

Answer 1

The correct option is B 86.5%

$(ϵ{)}_{parallel}=\frac{1-e^{-(1+C)NTU}}{1+C}$
For maximum possible effectiveness, C = 0
$e=\frac{1-e^{-NTU}}{1}=\frac{1-e^{-2}}{1}$
= 1-0.135 = 0.864 $\approx$ 86.5%