Question Bank • QB_DFE_EXP_006 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Heat and Mass Transfer

Subtopic: Working principles of heat exchangers

Question Statement:

In a plate heat exchanger, the heat capacity rates of the hot and cold fluid streams are equal ($C_{hot} = C_{cold} = C_{min} = 10.0\text{ kW/K}$). If the Number of Transfer Units $NTU = 2.0$, using the counter-flow effectiveness formula $\epsilon = \frac{NTU}{1 + NTU}$ (for $C_{min}/C_{max} = 1$), the heat exchanger effectiveness $\epsilon$ is ________ (round off to 3 decimal places).

Answer Key:

0.667

Step-by-Step Solution & Explanation

For a counter-flow heat exchanger with equal heat capacity rates ($C_r = 1.0$): $\epsilon = \frac{NTU}{1 + NTU}$ Given $NTU = 2.0$: $\epsilon = \frac{2.0}{1 + 2.0} = \frac{2}{3} \approx 0.6667 \approx 0.667$
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