Question

The log mean temperature difference (LMTD) correction factor is not required during heat transfer rate calculation in:

• 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

Hint:

Correction factor is essential in multipass and cross-flow exchangers. Only in pure counter-flow or parallel-flow (like 1–1 heat exchangers) it is not required.

Answer 1

The Correct Option is B

Step 1: Recall LMTD formula. The log mean temperature difference method is used in heat exchangers: \[ Q = U \cdot A \cdot \Delta T_{lm} \] where \(\Delta T_{lm}\) is the log mean temperature difference.

Step 2: Role of correction factor. When the flow arrangement is not strictly counter-flow or parallel-flow (such as multipass heat exchangers), a correction factor \(F\) is used: \[ Q = U \cdot A \cdot F \cdot \Delta T_{lm} \]

Step 3: Special case. For a single-pass shell and a single-pass tube heat exchanger (true counter-flow or parallel flow), the correction factor \(F = 1\). Hence, no correction factor is required. \[ \boxed{\text{Option (B)}} \]