Subtopic: Steady state heat transfer in conduction, convection and radiation
Question Statement:
The log mean temperature difference (LMTD) correction factor is not required during heat transfer rate calculation in
Options:
(A) plate heat exchanger
(B) 1 shell pass and 1 tube pass heat exchanger
(C) 1 shell pass and 2 tube pass heat exchanger
(D) 2 shell pass and 4 tube pass heat exchanger
Official Answer Key:
B
Step-by-Step Solution & Explanation
The LMTD correction factor F (F≤1) is required whenever the flow arrangement deviates from true (ideal) counter-current or co-current (parallel) flow — e.g., multi-pass shell-and-tube configurations with cross/mixed flow components. A 1-shell-pass, 1-tube-pass heat exchanger is the ONLY configuration among the options that corresponds to true counter-current (or co-current) flow throughout, for which F=1 exactly, i.e., no correction factor is needed — the plain LMTD applies directly. Configurations with 2 tube passes, 4 tube passes, or plate exchangers with cross-flow elements generally have some counter/co-current flow deviation requiring F<1. Answer: (B).
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