Tray hydraulics: for otherwise identical operating conditions, which tray type typically exhibits the HIGHEST pressure drop?

Introduction / Context:
Pressure drop across trays affects compressor duty, column diameter, and operating costs. Different tray internals create different vapor–liquid contacting resistances. This question compares common tray types under identical conditions.

Given Data / Assumptions:

• Same vapor and liquid rates, physical properties, and tray spacing.
• Geometry optimized within typical ranges for each tray type.
• Focus on intrinsic pressure drop characteristics.

Concept / Approach:
Bubble-cap trays force vapor to flow up risers and laterally beneath caps before bubbling through slots, creating a larger hydraulic resistance and ensuring a liquid seal. Sieve trays are perforated plates without moving parts and generally have the lowest pressure drop. Valve trays sit between sieve and bubble-cap trays, with adjustable openings that increase resistance somewhat but not as much as bubble caps.

Step-by-Step Solution:
List relative pressure drops: sieve < valve < bubble cap.Identify highest among options: bubble-cap tray.Select option (d) accordingly.

Verification / Alternative check:
Empirical correlations for dry tray and aerated head confirm greater head losses on bubble-cap designs due to multiple flow turns and slot restriction beneath the cap skirts.

Why Other Options Are Wrong:
Sieve: usually lowest drop.Valve: intermediate drop due to throttling across valves.Counterflow: not a standard tray type designation; pressure drop depends on specific design but is not recognized as higher than bubble-cap here.

Common Pitfalls:
Comparing trays at different turndown or froth regimes; ignoring weeping/entrainment limits that change effective drop.

Final Answer:
Bubble-cap tray