Vent Condensers

Chapter from the Heat Exchangers Design Guide.

VENT CONDENSER APPLICATIONS & DESIGN

Vent Condenser Purpose & Applications

A vent condenser is a secondary condenser located on the overhead vapor outlet of a vessel (typically a reflux drum or accumulator) to recover condensable vapors before they reach the vent or flare system.

Applications:
• Reflux drum vent: recover HC vapors, reduce flare load
• Atmospheric tank vent: reduce emissions, recover product
• Vacuum system: condense vapors before ejector/LRVP
• Storage tank: breathing losses recovery

Types:
• Shell-and-tube (vertical, vapor on shell side)
• Air-cooled (small package units)
• Plate-fin (compact, low ΔP applications)

Design Considerations

Parameter	Guideline	Basis	Impact if Wrong
Cooling Medium	25°F approach to coolant inlet	Heat transfer economics	Oversized if too conservative, undersized if aggressive
Non-condensable Handling	Must accommodate N/C gas flow	Blanketing gas, air ingress	Vapor binding if not vented properly
Condensate Drainage	Gravity drain back to drum	Elevation and line sizing	Liquid accumulation blocks vapor flow
Pressure Drop	Minimize — often <1 psi	Back-pressure on drum	Increased drum pressure, reduced recovery
Fouling Factor	0.001-0.003 hr·ft²·°F/BTU	Service-dependent	Under-design causes rapid performance decline
Orientation	Vertical preferred (condensate drains)	Gravity-assisted drainage	Horizontal may trap condensate

Source: Heat_Exchangers_Design_Guide_v1.xlsx · sheet “Vent Condensers”

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