CSTR Space Time & Conversion Calculator
Calculate continuous stirred tank reactor space time (τ), Damköhler number (Da), fractional conversion (X), and required vessel volume.
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Frequently Asked Questions
What is space time (τ) and how does it differ from mean residence time?
Space time (τ = V / v0) is the time required to process one reactor volume of feed measured at inlet feed conditions. For constant density liquids, space time equals mean residence time. In variable-density gas systems, true residence time changes with expansion or contraction.
What does the Damköhler number (Da) represent in reactor design?
The Damköhler number is the dimensionless ratio of the reaction rate to the convective transport rate (Da = rate of reaction / rate of mass transport = k * τ for first order). When Da << 0.1, conversion is very low (<10%). When Da >> 10, conversion approaches 100% and transport limits the process.
Why does a CSTR require a much larger volume than a PFR for the same conversion?
In an ideal CSTR, complete backmixing immediately dilutes incoming reactant to the low exit concentration. Because reaction rate decreases with reactant concentration, the entire CSTR operates at the slowest possible rate, requiring a substantially larger volume than a Plug Flow Reactor.