FUSION TECH / 11
10 / OVEN BREAKPOINT GUIDE
Design Factors that Affect the Breakpoint
Supply Duct Design and Depth The design of the supply duct plays a large role in enhancing or degrading the breakpoint. The typical cone design found in most ovens allows the high and low velocity airstreams to bounce around the cabinet, resulting in overcooking product on the edges and bottom of the cart. A knife-point design with a width of around 1” keeps the high and low velocity air- streams along the oven walls to maintain velocity and make the breakpoint stronger when the airstreams collide.
There are five main factors that help create and allow you to control a strong breakpoint throughout the oven: • Angle of where the wall hits the floor • Supply duct design and depth • Shape of the return duct • Design and placement of the oven trucks • Damper positioning
When all five factors are applied correctly, you are able to control the location and duration of the breakpoint to optimize your cook cycle and increase product consistency and yields.
Wall to Floor Design Angle The design of how the side walls and floor meet will either enhance or degrade the velocity of the air streams, resulting in either a stronger or weaker breakpoint, respectively. Many oven manufacturers use a 90° or 45° angle between the walls and floor, which results in the air stream degrading once hit hits those angles.
Shape of Return Duct A study sponsored by the National Institute of Food and Agriculture, found when one supply slot was fully open and the other was closed, the Venturi effect actually pulled the air across the cabinet with only a slip-stream pulled up into the return duct. This discovery led them to develop a re-designed return duct that extended the duct down into the cabinet to reduce the Venturi effect. The new extended return duct not only reduced the pull of the Venturi, it also unexpectedly produced the most uniform, highest velocity airflow of all the test runs. The anemometer and fog machine data showed that the extended return duct favored pulling air through the historically “cold-spot” that exists at the top-center of conventional designs -- gener- ating the most uniform airflow and higher velocity air through all areas of the cabinet, including the “cold-spot.” Using the extended-return duct in combination with the variable-width supply slots created much more uniform air velocities through the “cold-zone” at the top-center of the cabinet than conventional designs. Also, when used in further combination with the new high-volume air kit, the air velocities were measurably more uniform and almost double those of conventional designs.
A radius, or cove, design along the bottom of the walls gently pushes the airstream along the floor, maintaining the air stream velocity and resulting in a stronger breakpoint to make it across the rack and evenly cook product.
FTIINC.ORG/OVENS
FTIINC.ORG/OVENS
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