In an inclined long-tube vertical (ILTV) evaporator, the tubes are set at approximately what inclination angle to promote drainage and film flow?
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A15°
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B90°
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C45°
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D60°
Answer
Correct Answer: 15°
Explanation
Introduction / Context:ILTV evaporators are variants of long-tube vertical units where a slight inclination helps drainage, prevents flooding, and promotes film stability inside tubes. Correct inclination enhances heat transfer and avoids dry spots or back-mixing that can degrade product quality.
Given Data / Assumptions:
- Evaporation under conditions where gravity-assisted film flow is important.
- “Inclined” implies a modest angle rather than a steep slope.
Concept / Approach:Small inclinations (on the order of 10°–15°) provide enough hydrostatic head differential to assist liquid return and maintain a uniform falling film without significantly increasing floor space. Larger angles approach configurations more akin to falling-film or horizontal units and are not typical for ILTV designs.
Step-by-Step Solution:
Identify ILTV design intent—slight inclination for drainage.Select a small angle consistent with standard practice, ~15°.Reject large angles that are not considered “slight.”Verification / Alternative check:Industry examples and textbooks commonly quote inclinations near 10–15° for ILTV equipment to improve film behavior and cleaning access.
Why Other Options Are Wrong:
- 90°: Vertical; not “inclined.”
- 45° or 60°: Excessively steep for typical ILTV practice; increases footprint and changes hydraulics.
Common Pitfalls:Confusing ILTV with horizontal or steeply inclined falling-film designs; neglecting impact of viscosity and fouling which may prompt slight adjustments around the nominal angle.
Final Answer:15°