ASB technical session breaks down energy transfer in the oven
March 6, 2017
by Charlotte Atchley
Richard Starke, director, Reading Thermal.
With the help of some equations, graphs and heat sensor, bakers can better understand the baking profile of their ovens in an effort to better control the their products’ baking characteristics. At this year’s American Society of Baking BakingTech conference, Richard Starke, director, Reading Thermal, illustrated how understanding heat flux and total heat can benefit bakers in his technical session “Energy Transfer in Commercial Baking Ovens.”
While some might obsess over measures such as temperature and humidity when tweaking an oven profile, heat flux and total heat actually give bakers the information they are looking for. “Everyone measures temperature, but temperature is an input to this system,” Mr. Starke said. “It’s energy transfer that’s doing the baking. So critical to understanding finished product characteristics are knowing the total heat experienced by the product and the component quantities of the radiant and convection heat fluxes.”
Heat flux refers to the amount of energy passing through an imaginary surface of a specific cross-sectional area per unit of time, in other words, Btus per hour per sq ft. Total heat is the amount of energy experienced or collected over a period of time, Btus per sq ft. Mr. Starke simplified heat flux and total heat with the imagery of a bucket catching rain. Heat flux measures the rain as it passes through the entrance to the bucket. Total heat is the rain collected at the bottom of that bucket.
Energy is transferred to the product in the oven by three different components bakers are familiar with: conduction, convection and radiation. “Every product has its own mix of these three heat components,” Mr. Starke said. “There’s not one heat flux profile that fits everything. It’s unique to the product and the type of oven you’re using that’s delivering the energy.”
Heat flux sensors can show bakers the heat flux profile of their ovens and the total heat collected by their products at each point in the oven. Armed with this information, bakers can better understand what is happening within their ovens. “It’s often used when you’re trying to produce the same product on two different lines or trying to transfer product from one line to another,” Mr. Starke said. “When heat flux profiles are matched between two lines, they should produce the same product.”
When increasing tonnage and reducing dwell time, it’s important to know how much energy needs to be transferred in order to achieve the same quality product. Heat flux profiles can also help the R&D department successfully scale up a new product from pilot plant to full scale production.