Plug Flow Reactor Volume & Sizing Calculator
Calculate tubular PFR reactor volume, space time, fractional conversion, and compare volume requirements directly against a continuous stirred tank.
Process Operating Conditions
Target Conversion & Tube Sizing
PFR Sizing & Comparison
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Frequently Asked Questions
Why does the CSTR-to-PFR volume ratio explode at high conversions (X > 90%)?
For a first-order reaction, V_PFR scales as ln(1 / (1 - X)), whereas V_CSTR scales as X / (1 - X). At 99% conversion, ln(1 / 0.01) = 4.6, but 0.99 / 0.01 = 99. The CSTR requires over 21 times more volume than a PFR because its entire volume is stuck at 1% of the starting reactant concentration.
How does tube diameter affect PFR performance and pressure drop?
Smaller tube diameters provide superior heat transfer surface area per unit volume (critical for highly exothermic reactions) and maintain high Reynolds numbers for plug flow turbulence. However, smaller tubes rapidly increase frictional pumping pressure drop (proportional to 1/D^5).
When is a CSTR preferred over a PFR despite the larger volume requirement?
CSTRs are preferred when reaction mixtures contain heavy slurries or precipitate solids that would foul or plug narrow tubular reactors, when reaction temperature must be tightly thermostatted via internal cooling coils, or in autocatalytic reactions where backmixing accelerates reaction initiation.