Air flow
Also known as: air volume, air flow rate
Short definitionThe volume of air the evaporator fans move per hour, in m³/h. It decides how evenly the cold spreads through the room and how fast the product cools.
The evaporator collects heat from the air, and the fans are what pass the air over its surface. Air flow is 1,000–3,000 m³/h for small room evaporators and 20,000–40,000 m³/h for large warehouse units. American catalogues use CFM; 1 CFM is about 1.7 m³/h. Air flow divided by room volume gives the number of air changes per hour.
A storage room calls for 30–60 air changes per hour and a blast freezing room for more than 100; in blast freezing an air speed of 3–5 m/s over the product is wanted. For unwrapped meat and for fruit and vegetables, too much speed dries the product. Air throw is checked along with air flow: if one unit cannot reach the back wall of a long room, a second evaporator is fitted. The stack must not block the front of the evaporator.