Oven Air Velocity
What is Oven Air Velocity?
Oven air velocity is the measurement of airflow in the oven. It can be denoted as m/sec or ft/min. Its measurement is important because, together with other oven parameters, air velocity influences the coloration and bake of the final product.
The importance of even air velocity
Even distribution of airflow is vital in maintaining the quality of product delivered by any oven system.
- In a radiant oven (e.g., ribbon burners), the airflow comes from the moving conveyor, the exhaust system, and natural combustion air currents.
- In a convection oven (e.g., air recirculation), the airflow comes primarily from the air distribution plenums. Here, airflow is particularly important because it directly controls the amount of heat delivered to the product.
Why oven air velocity is important
Air velocity profiles are useful in adjusting your process to maximize quality and reduce waste.
- An increase in air velocity causes an increase in the apparent heat transfer coefficient, convective heat flux.1
- Velocity of the circulating air can also influence baking time. The velocity of the airflow influences the percentage of convective heat in the oven chamber. Consequently, the overall heat transfer mechanism changes, and the process time is reduced considerably.
- Weight loss, browning, and firmness of baked product can be increased by increasing air velocity. For example, increases in air velocity result in a dry, cone-shaped sponge cake with dark surface color. Increases in air velocity produce a firmer sponge cake, independent of air temperature.2
- Cohesiveness and product volume are unaffected by air velocity.2
How to measure oven air velocity
Oven air velocity can be recorded by an air velocity sensor. The sensor array delivers a precise picture of airflow patterns inside an oven from side to side and end to end. The sensors collect data, at product level, as the array passes through the process. The number of sensors varies with the width of the conveyor.
An air velocity sensor array can help with spotting airflow differences between baking zones, concentrated air velocities on isolated parts of the conveyor, and unwanted air currents at the entrance or exit of the oven.
Here is an example for bread:
- Baik, O.D., et al. “Heat Transfer Coefficients on Cakes Baked in a Tunnel Type Industrial Oven.” Journal of Food Science, vol. 64, no. 4, 1999, pp. 688–694.
- Sato, Hidemi, et al. “Apparent Heat Transfer in a Forced Convection Oven and Properties of Baked Food.” Journal of Food Science, vol. 52, no. 1, 1987, pp. 185–188.