Table of Contents
- Face velocity is the approach speed of air entering the core face: face_velocity = volumetric_flow / core_face_area It is measured in metres per second (m/s).
- For HVAC air-to-air cores, face velocity usually sits between 1.5 and 3.5 m/s. Lower is gentler on the core and the fan; higher packs more flow into a smaller core.
- Doubling face velocity roughly quadruples the pressure drop across the core, which raises fan power. But a smaller core is cheaper and fits tighter casings. Selection is a balance: pick the face area that meets effectiveness at an acceptable fan penalty. This is the same lever discussed for plate exchangers and their pressure-drop budgets.
- Is higher face velocity ever good? Only when space is tight and fan energy is cheap; otherwise lower velocity wins on lifecycle cost. Does face velocity equal duct velocity? Not exactly - it is referenced to the core opening, which may differ from the connecting duct. Need help specifying the right air-to-air heat recovery for your project? Contact the QIYU engineering team - WhatsApp +86 157 5335 5505, or email kuns913@gmail.com. Frequently Asked Questions What is face velocity? Face velocity is the volumetric airflow divided by the frontal area of the core; it is the speed of air entering the exchanger face. Why does face velocity affect pressure drop? Pressure drop rises roughly with the square of face velocity, while effectiveness improves only marginally; lowering face velocity with a larger core is the usual way to cut fan energy.
Face velocity is the approach speed of air entering the core face:
face_velocity = volumetric_flow / core_face_area
It is measured in metres per second (m/s).
For HVAC air-to-air cores, face velocity usually sits between 1.5 and 3.5 m/s. Lower is gentler on the core and the fan; higher packs more flow into a smaller core.
Doubling face velocity roughly quadruples the pressure drop across the core, which raises fan power. But a smaller core is cheaper and fits tighter casings. Selection is a balance: pick the face area that meets effectiveness at an acceptable fan penalty. This is the same lever discussed for plate exchangers and their pressure-drop budgets.
Is higher face velocity ever good? Only when space is tight and fan energy is cheap; otherwise lower velocity wins on lifecycle cost.
Does face velocity equal duct velocity? Not exactly - it is referenced to the core opening, which may differ from the connecting duct.
Need help specifying the right air-to-air heat recovery for your project? Contact the QIYU engineering team - WhatsApp +86 157 5335 5505, or email kuns913@gmail.com.
Frequently Asked Questions
What is face velocity?
Face velocity is the volumetric airflow divided by the frontal area of the core; it is the speed of air entering the exchanger face.
Why does face velocity affect pressure drop?
Pressure drop rises roughly with the square of face velocity, while effectiveness improves only marginally; lowering face velocity with a larger core is the usual way to cut fan energy.