Keeping things moving
With all that heat preserved inside the baking chamber, it’s important to use it as effectively as possible. In ovens that use convection heat, controlling airflow can help improve efficiency without hiking up temperature.
“You can speed up the heat transfer just by blowing air over the product,” Dr. Nikel said. Without the air movement, the cooler product keeps the air around it cool, hindering the baking. “Even though you have 450°F air in the baking chamber, the product is say 150°F in the baking chamber, so there’s going to be a very thin layer of air around the product that’s going to be 200°F,” he said. “If you are blowing the air, you disrupt that layer and heat up the product faster.”
J4 ovens achieve this with Duotherm technology, which allows bakers to add a convection component to their ovens. Dr. Nikel described one application in his experience where a baker wanted to get a lot of moisture out of the product but couldn’t heat it up too much, so Topos Mondial applied this technology to achieve the desired bake characteristics. “You can run the oven at a relatively low temperature, and you just impinge a lot of air over the product,” he explained.
Variable frequency drives on the fans allow bakers to have ultimate control on the speed of the air movement. “We can vary the speed of the fan based on the temperature of the air so we’re delivering the proper amount of air with the least amount of energy,” Mr. Morabito said.
Airflow can provide uniform temperature throughout the baking chamber when handled correctly. In its Rototherm Green oven, WP Bakery Group USA optimized the air flow system to direct air accurately on the product over the entire jet wall, according to Ms. Kennedy. This ensures every point on the baking rack is even. This uniformity shortens the baking time while also retaining moisture in the final product.
Control over airflow direction and speed helps achieve baking uniformity as well as improving efficiency. Gemini Bakery Equipment’s indirect-fired tunnel ovens feature a turbulence system with variable-speed airflow that is reversible from top-to-bottom or bottom-to-top. “This results in a uniform hearth product bake,” Mr. Johnson said.
Air movement can also help manage energy usage in heating the oven. Mr. Stockton credited the efficiency of Babbco’s air impingement ovens to the air recirculation and the high-impact velocity. “Using air circulation, the air returns through the burner at an elevated temperature, which reduces the amount of energy required to increase the air to the baking temperature,” he said. “The high-velocity air lowers the air temperature required to bake the product due to its ability to deliver that energy to the product.”
Read more to learn how humidity affects oven efficiency.