Convection Ovens 101Sep 10
How Does A Convection Oven Work?
Natural Convection versus Forced Convection
Convection is the process by which heat is transferred through the movement of air, steam, or liquid, resulting in changes in temperature. It is through Convection that food cooks in ovens.
In Natural Convection, hot air naturally rises, and cooler air sinks. In an oven, there is a constant movement of air as the heat source—electric elements or gas burners— works to maintain a designated temperature. This process can be accelerated, however through Forced Convection.
In Forced Convection ovens, air is the heating medium, and the air is forced to circulate throughout the oven with fans, causing the heat to be transferred faster. As the hot air circulates around the food, it cooks faster. Generally, the faster the air moves, the faster the food will cook.
Heat Transfer Methods
Convection ovens are heated through gas burners or electric elements. In most electric convection ovens, the elements are placed around the fan. As the fan moves air past the elements, it pulls the heat from the surface of the elements and circulates hot air around the compartment.
In a gas oven, there are at least three methods used.
Indirect method – The gas burners are placed under the oven liner, or cooking compartment. The flames are directed at a heat deflector mounted just below the liner. Through the deflector, the bottom, sides and rear of the oven are heated. The convection fan pulls heat from the surface of the hot liner and moves the heat throughout the compartment, transferring heat to the food. The products of combustion are vented at the top rear of the oven and do not come in contact with the food.
Direct method – Gas burners are mounted in the rear or on the side of the oven liner. The heat is drawn into the compartment through a fan which also circulates the hot air throughout the cooking compartment. The direct method is more efficient than the indirect method, because the heat is brought directly into the compartment, rather than depending on a heat transfer surface to deliver the heat into the oven.
Dual method - The most common method used in gas convection ovens is a combination of the direct and indirect methods. The burners are underneath the liner, and the hot air is pulled into the compartment. This dual method is the most energy efficient.
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