Question

In shell and tube heat exchanger, external cleaning of the tubes is easy in case of

• A. Equilateral triangular pitch arrangement of tube layout
• B. Right angle triangular pitch arrangement of tube layout
• C. Square pitch arrangement of tube layout
• D. Hexagonal pitch arrangement of tube layout

Hint:

Square pitch in shell and tube heat exchangers facilitates external tube cleaning due to straight, accessible paths, unlike triangular pitch which is more compact but harder to clean.

Answer 1

The Correct Option is C

Step 1: Understand tube layouts in shell and tube heat exchangers.
In a shell and tube heat exchanger, tubes are arranged in a specific pattern (pitch) to optimize heat transfer, pressure drop, and maintenance. Common tube layouts include:
Triangular pitch (including equilateral triangular): Tubes are arranged in a triangular pattern, providing a compact arrangement with high heat transfer due to increased turbulence on the shell side.
Square pitch: Tubes are arranged in a square pattern, with tubes aligned in rows and columns.
Hexagonal pitch: A less common layout, often a variation of triangular pitch.
Step 2: Analyze the ease of external cleaning.
External cleaning refers to cleaning the outside of the tubes (shell side), where fouling may occur due to the fluid flowing over the tubes.
Triangular pitch: The staggered arrangement makes it difficult to access the tubes for cleaning. Brushes or cleaning tools cannot easily pass through the tight, offset spaces between tubes.
Square pitch: Tubes are aligned in straight rows and columns, creating clear, straight paths between the tubes. This allows cleaning tools (e.g., brushes or jets) to pass through easily, making external cleaning more straightforward.
Hexagonal pitch: Similar to triangular pitch, the staggered arrangement hinders cleaning access.
Step 3: Evaluate the options.
(1) Equilateral triangular pitch arrangement of tube layout: Incorrect, as the staggered triangular arrangement makes external cleaning difficult due to limited access. Incorrect.
(2) Right angle triangular pitch arrangement of tube layout: Incorrect, as this is not a standard term, but even if interpreted as a triangular pitch, it would still hinder cleaning. Incorrect.
(3) Square pitch arrangement of tube layout: Correct, as the aligned rows and columns in a square pitch allow easy access for external cleaning of the tubes. Correct.
(4) Hexagonal pitch arrangement of tube layout: Incorrect, as the staggered arrangement (similar to triangular) makes cleaning difficult. Incorrect.
Step 4: Select the correct answer.
In a shell and tube heat exchanger, external cleaning of the tubes is easy in the case of a square pitch arrangement of tube layout, matching option (3).