Coffee Airflow/Fan Speed Calculator
Created by: Olivia Harper
Last updated:
Estimate roast-phase airflow and fan-speed targets for steadier momentum and cleaner cup outcomes.
Coffee Airflow/Fan Speed Calculator
CoffeePlan phase-specific fan control from live roast trajectory
Related Calculators
What is a Coffee Airflow/Fan Speed Calculator?
Balancing heat transfer and exhaust control
A coffee airflow and fan speed calculator helps roasters choose practical exhaust settings by roast phase, momentum, and equipment class. In production, airflow decisions shape heat transfer, smoke evacuation, and cup cleanliness. Having a repeatable baseline reduces guesswork and improves profile transfer between operators.
This tool combines phase-specific airflow targets with live trajectory inputs like current rate of rise (ROR) and desired ROR. It then recommends a fan-speed adjustment that supports smoother transitions through drying, Maillard, and development. Rather than chasing noisy data point-to-point, you get a stable directional decision.
Use the result as a control reference, not a hard rule. Every roaster platform behaves differently, so final settings should be validated through roast logs, sensory results, and consistency metrics over multiple batches.
How the Airflow Recommendation Works
Directional control logic
Recommended Fan % = Phase Base + Roaster Offset + ROR Correction + Damper Correction
The phase base reflects typical airflow intensity by roast stage. Roaster offset adjusts for machine scale. ROR correction increases or reduces airflow depending on whether current momentum is above or below target. Damper correction accounts for how open or restrictive the current exhaust path is.
Output values are clamped to safe operational ranges so the recommendation remains practical for production use.
Example Calculation
Maillard phase correction case
Suppose you are in Maillard on a small production roaster with current fan at 52%, damper at 60%, current ROR at 11.5°C/min, and target ROR at 10.0°C/min. Because momentum is elevated, the model recommends a moderate fan increase to remove more energy and improve trajectory control before first crack.
If the same batch were running below target ROR, the recommendation would shift toward reduced fan intensity to preserve thermal momentum. This directional guidance helps prevent over-corrections and creates more repeatable phase behavior.
Common Applications
Standardization and transfer
These use cases are most effective when paired with consistent roast logging. Documented airflow plans improve reproducibility across operators and shifts.
- Standardizing operator airflow decisions during shift handoffs.
- Improving profile transfer from sample to production scale.
- Reducing smoky cup outcomes in dense or high-chaff lots.
- Smoothing ROR decline into first crack and development.
- Creating baseline control recipes for new coffees.
Tips for Better Airflow Control
Practical adjustment cadence
Make one meaningful adjustment at a time, then observe at least 30-60 seconds before the next move. Keep burner and fan changes logged separately so you can isolate cause-and-effect. Revisit your airflow baselines when ambient weather shifts or when moving between crop years with different moisture and density behavior.
Frequently Asked Questions
Why adjust airflow across roast phases?
Airflow controls convective heat transfer, smoke removal, and bean-surface cleanliness. Different phases need different balances between heat retention and exhaust flow.
Can higher fan speed flatten ROR?
Yes. Increasing fan speed can lower environmental heat and reduce momentum, often flattening ROR if burner or power input is unchanged.
Is there one perfect fan profile?
No. The best profile depends on roaster geometry, batch size, bean density, and flavor goals. Use this as a repeatable baseline, then calibrate from cupping.
Should I change airflow and heat at the same time?
Small coordinated changes are normal, but large simultaneous moves can make diagnosis difficult. Log each step so future adjustments stay intentional.
How often should I re-check my airflow plan?
Re-check when changing lot density, moisture, ambient conditions, or target profile style. Periodic review keeps production consistent through seasonal shifts.
Sources and References
- Scott Rao, The Coffee Roaster’s Companion, profile control and airflow strategy chapters.
- Specialty Coffee Association, roasting education resources on heat transfer and quality control.
- Manufacturer roast-operations guides for exhaust and airflow management in drum roasters.