Question Bank • QB_EXP_DFE_HEX_013 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Heat Exchangers: LMTD & NTU-Effectiveness Methods

Subtopic: Counterflow heat exchanger LMTD calculation

Question Statement:

A counterflow plate heat exchanger with the temperature profile shown transfers $120\text{ kW}$ of heat. If the overall heat transfer coefficient $U = 2400\text{ W/(m}^2\cdot\text{K)}$ and $LMTD = 25.0^\circ\text{C}$, compute the required heat transfer surface area $A$ in $\text{m}^2$ (round off to one decimal place).

Answer Key:

2

Step-by-Step Solution & Explanation

$Q = U A (LMTD) \implies A = \frac{Q}{U \times LMTD} = \frac{120000}{2400 \times 25.0} = \frac{120000}{60000} = 2.0\text{ m}^2$.
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