Question

In a heat exchanger, if the temp of one of the fluid remains constant, the effectiveness of counter flow heat exchanger is

• A. $\frac{1-e^{-NTU}}{2}$
• B. $\frac{1}{(1+C)}$
• C. $1-e^{-NTU}$
• D. $1-e^{-2NTU}$

Answer 1

The correct option is C $1-e^{-NTU}$

If the temperature of one fluid is remains constant that means the heat exchange will be either condenser or evaporator.

In this case

$C=\frac{C_{min}}{C_{max}}=\frac{C_{min}}{\infty }=0$

C = 0

$\text{Efficiency}(ϵ{)}_{\text{counter}}=\frac{1-e^{-(1-e,)NTU}}{1-C\times e^{-(1-e)NTU}}$

When C = 0

$(ϵ{)}_{\text{counter}}=1-e^{-NTU}$