Calculator Inputs
Formula Used
Dilution Rate
D = F / V
D is dilution rate, F is volumetric flow rate, and V is working volume.
Hydraulic Retention Time
τ = V / F = 1 / D
Retention time estimates the average time fluid remains in the vessel.
Volume Exchanged Over Run Time
Vexchanged = F × t
Turnovers during the run equal exchanged volume divided by working volume.
Safety Threshold Check
Dsafe = Dcritical × (1 - SF)
SF is the safety factor entered as a decimal percentage term.
How to Use This Calculator
1. Enter Feed Conditions
Input the reactor or tank inlet flow and choose the correct unit.
2. Enter Working Volume
Use active liquid volume, not gross shell volume, for accurate dilution calculations.
3. Set Operating Time
This helps estimate how much fluid is replaced during the selected run.
4. Add Optional Design Limits
Provide a critical dilution limit and target rate for safety and sizing checks.
5. Review and Export
Read the result cards, then export the calculation as CSV or PDF.
Example Data Table
| Case | Flow Rate | Working Volume | Dilution Rate | Retention Time | Comment |
|---|---|---|---|---|---|
| Pilot bioreactor | 18 L/h | 120 L | 0.1500 1/h | 6.67 h | Moderate turnover with a comfortable residence time. |
| Blend tank | 4 m3/h | 2.5 m3 | 1.6000 1/h | 0.63 h | High dilution, suitable for fast continuous replacement. |
| Fermentation train | 18 m3/day | 2.0 m3 | 0.3750 1/h | 2.67 h | Useful for comparing productivity against washout limits. |
Frequently Asked Questions
1. What does dilution rate mean?
Dilution rate is the inlet volumetric flow divided by working volume. It shows how quickly fresh fluid replaces material inside a continuous vessel.
2. Why is retention time also shown?
Retention time is the inverse of dilution rate. Engineers often use it to understand residence time, reaction exposure, and average replacement speed.
3. Which volume should I enter?
Enter the effective liquid volume under operating conditions. Avoid total vessel shell volume if headspace, coils, or dead zones reduce usable capacity.
4. What is a critical dilution limit?
It is the maximum acceptable dilution rate before process instability, poor conversion, or biological washout becomes likely. The calculator flags when operation approaches that limit.
5. Can I use different units?
Yes. The calculator converts several common flow and volume units into a consistent basis before calculating dilution rate and retention time.
6. What are turnovers during the run?
Turnovers show how many working volumes pass through the system during the chosen operating time. It helps estimate flushing intensity or replacement completeness.
7. Why add a target dilution rate?
A target rate helps back-calculate the required flow for a fixed volume, or the required volume for an existing flow condition.
8. Are the exports suitable for reports?
Yes. CSV works well for spreadsheets and audit trails, while PDF is convenient for sharing design snapshots with teams or clients.