Process Design
Residence Time Calculator
Hydraulic residence time (also called retention time) is the average time a fluid element spends inside a vessel. It is the ratio of vessel volume to volumetric flow rate. This calculator solves for any one of the three variables when the other two are known.
TypeInteractive calculator — separate from unit conversions
Calculator
Result
Residence time5 h
Formulas
Residence time
τ = V / Q
Volume
V = τ × Q
Flow
Q = V / τ
Diagram
Worked example
A vessel has an effective volume of 10 m³. The volumetric flow rate is 2 m³/h. What is the residence time?
- 01τ = V / Q
- 02τ = 10 / 2
- 03τ = 5 h
Result
The hydraulic residence time is 5 hours.
FAQ
Does this include reactor kinetics or conversion?
No. This calculator computes hydraulic residence time only. Reactor design, kinetics, and conversion calculations are not implemented.
Does this account for dead volume?
No. You should enter the effective volume. If the vessel has significant dead zones, reduce the volume input accordingly.
Can I use this for a CSTR or PFR?
You can use it to calculate the mean hydraulic residence time for either. But it does not model the residence time distribution, mixing, or conversion.
Does this handle multiphase flow?
Only if you specify the volume and flow for a single phase. Multiphase residence time distribution is outside scope.