Air-heater sizing starts with mass airflow and required temperature rise. Fins increase surface area, but they do not eliminate the need for sufficient velocity, uniform distribution and protection against fan loss or blocked filters.
Use this guide to prepare a design review or RFQ. Final ratings depend on the complete product, installation, controls and operating environment.
Selection inputs that change the design
| Decision | Information to provide | Why it matters |
|---|---|---|
| Airflow | Mass or volumetric flow at known conditions | Sets the useful heat absorbed by the air. |
| Temperature rise | Inlet and required outlet temperature | Defines ideal process power. |
| Duct geometry | Area, heater position and bypass paths | Controls velocity and distribution. |
| Safety | Flow switch and independent high limit | Protects the element during loss of airflow. |
Calculate the process load
Use air mass flow, specific heat and required temperature rise to estimate useful power. Convert volumetric flow using the actual air density rather than assuming standard conditions at high temperature or altitude.
Add duct and process losses with stated assumptions. Avoid hiding an uncertain airflow value inside an oversized safety factor.
Design for even flow
Provide duct dimensions, upstream bends, filters, fans and obstructions. Uneven velocity creates hot areas even when average airflow looks adequate.
Use baffles or adequate straight duct length where necessary, and prevent air from bypassing around the heater frame. Confirm acceptable pressure drop.
Protect abnormal conditions
Interlock heater power with proven airflow and use an independent high-temperature limit located where reduced cooling is detected.
Stage or modulate power to avoid large temperature swings. Verify fan coast-down and shutdown sequencing so the elements do not remain energized without cooling.
Common specification mistakes
- Sizing from duct area without measured airflow
- Using standard air density for every condition
- Ignoring bypass and velocity distribution
- Relying only on the process controller for safety
RFQ checklist
- Airflow units and operating density
- Inlet and outlet temperatures
- Duct drawing, fan and filters
- Supply, stages and control method
- Flow proof and independent high limit
Review the matching Tubular Heaters product range, then send this checklist with your drawing for an engineer-reviewed quotation.
Frequently asked questions
Do fins allow operation without airflow?
No. A finned heater designed for moving air can overheat quickly when airflow is lost.
How is required power estimated?
Use mass flow multiplied by specific heat and temperature rise, then add documented system losses.
Where should the limit sensor go?
Place it where it detects the most severe credible loss-of-airflow condition without being falsely cooled or shielded.