Distillation Condenser & Subcooling Duty Calculator
Calculate total condensing and sensible subcooling heat duty, cooling water circulation rate, and the cold reflux internal reflux ratio amplification.
Overhead Vapor Flow & Properties
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Condenser Duty & Reflux Impact
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Frequently Asked Questions
Why does subcooled reflux increase the internal reflux ratio?
When liquid reflux is returned to the top tray colder than its bubble point, sensible heat from the ascending vapor heats the liquid up to boiling. In absorbing this sensible heat, a fraction of the vapor condenses onto the top tray, adding to the descending liquid traffic and magnifying the effective internal reflux ratio (L_int/V_int).
Why is moderate subcooling deliberately designed into reflux drums?
Subcooling prevents cavitation and vapor lock in the reflux pumps by providing net positive suction head (NPSH) margin above the liquid vapor pressure. It also stabilizes the reflux drum pressure and prevents flash-evaporation in pump discharge piping.
How is cooling water requirement calculated for condensing services?
Cooling water flow is computed via Q = m * Cp * ΔT. In imperial engineering units, 1 GPM of water with a 10°F temperature rise absorbs 5,000 BTU/hr (or 500 BTU/hr per 1°F rise). Dividing the total condenser heat duty (BTU/hr) by 500 × ΔT_cw gives the exact cooling water GPM required.