Question Bank • QB_DFE_HMT_005 MSQ • 2 Marks

Section 7: Dairy and Food Engineering

Heat and Mass Transfer

Subtopic: Working principles of heat exchangers

Question Statement:

Which of the following operational advantages are provided by Gasketed Plate Heat Exchangers (PHE) compared to Shell-and-Tube heat exchangers in dairy processing?

Options:

  • (A) Exceptionally high overall heat transfer coefficients ($U = 3000\text{--}5000\text{ W/(m}^2\cdot\text{K)}$) due to corrugated chevron plate turbulence
  • (B) True counter-current flow yielding very close temperature approaches (
    lt; 1^\circ\text{C}$)
  • (C) Ease of sanitation, complete dismantling for visual inspection, and flexible surface area modification by adding or removing plates
  • (D) Capability to safely handle operating pressures exceeding $150\text{ bar}$ without gasket blow-out

Answer Key:

A, B, C

Step-by-Step Solution & Explanation

PHEs offer high $U$ values (A), close approach temperatures (B), and modular sanitary maintainability (C). Statement D is INCORRECT because elastomeric gaskets limit PHE operating pressures to typically
lt; 15-25\text{ bar}$, whereas shell-and-tube exchangers withstand high pressures.
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