Shell-and-tube heat exchanger practices: pick out the statement that is WRONG.
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AClearance between shell–baffle and tube–baffle should be minimal to reduce bypassing, yet sufficient for tube-bundle removal.
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BBaffles are supported by tie rods and spaced by baffle spacers, independently of the tubes.
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CTie rods are fixed at one end in the tube sheet using blind holes; minimum four rods of at least 10 mm diameter are provided.
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DBracket supports are used for a horizontal shell, while saddle supports are used for a vertical shell.
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EBaffles promote crossflow and enhance heat transfer while providing tube support.
Answer
Correct Answer: Bracket supports are used for a horizontal shell, while saddle supports are used for a vertical shell.
Explanation
Introduction / Context:Shell-and-tube exchangers must be mechanically supported and internally baffled to achieve target heat-transfer coefficients while limiting bypass and vibration. Understanding correct mechanical practices is critical for safe installation and operation.
Given Data / Assumptions:
- Conventional horizontal shell-and-tube exchanger with removable tube bundle.
- Standard baffle-and-tie-rod construction as found in industry.
- Focus is on correctness of statements about supports and baffles.
Concept / Approach:Horizontal vessels are normally mounted on saddle supports, not brackets. Vertical vessels frequently use brackets or lugs welded to the shell for support at structural beams. Baffles are carried on tie rods with spacers and must fit closely to limit shell-side bypass while still allowing assembly/removal.
Step-by-Step Solution:Evaluate each statement against standard practice.(a) Minimal but adequate clearances: correct.(b) Tie rods and spacers support/locate baffles: correct.(c) Details vary by design; multiple tie rods of adequate diameter are used—practice is plausible.(d) Reversed support types for orientations—this is wrong; horizontal shells use saddles.(e) Purpose of baffles stated correctly.
Verification / Alternative check:Manufacturer drawings and standards (e.g., TEMA practices) show horizontal shells on saddles; vertical units often on brackets/lugs or skirts (for towers).
Why Other Options Are Wrong:
- (a) Accurate; excessive clearance causes bypass.
- (b) Accurate; baffles are not supported by tubes themselves.
- (c) Acceptable practice; the essence (use of multiple tie rods) holds.
- (e) Accurate description of baffle function.
Common Pitfalls:Assuming identical supports for all orientations; ignoring maintenance needs when setting clearances.
Final Answer:Bracket supports are used for a horizontal shell, while saddle supports are used for a vertical shell.