Definition
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).
Typical range
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.
The core-size vs pressure-drop trade-off
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.
Frequently asked questions
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.
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.
Specify the right heat exchanger
Our engineers size the core to your airflow, temperature and pressure-drop budget, and select plate, rotary or heat-pipe recovery by application. Read the heat exchanger guide or contact us for a specification.
Related products
Plate, wheel or pipe recovery for HVAC and ventilation.
Stationary, high-surface-area cores for air and liquid.
High-effectiveness energy recovery for large airflows.
Passive, fully separated streams for clean applications.