Baking&Snack - April 2017 - 88

Combining types of heat transfer helps bakers take
advantage of the benefits of each - radiant, convection
and conduction - to improve the finished product and
achieve an efficient bake.
Baker Perkins

you get consistency with bake without
any hot spots," Mr. Bloom said.

Keeping things moving

The effectiveness of hybrids
Achieving an efficient bake starts with matching the oven
with the appropriate application. By understanding what the
product needs in the oven, bakers can choose the correct
heat transfer method, burners, air velocity and use of steam
if necessary. However, sometimes the most effective way to
achieve the final bake results desired goes beyond using just
one style of baking.
"The most efficient ovens are constructed so that the optimal proportions of radiant, convection and conduction are
applied to the products at the correct period during the baking cycle," said Shawn Moye, vice-president, sales, Reading
Bakery Systems. "By doing this we can ensure that we produce the highest quality products. For example, convection
baking is the most efficient method of removing moisture
from products but an all-convection oven may not produce
the most desirable product characteristics."
For many years, it was commonly believed that the best
crackers were produced with direct-gas-fired ribbon burner
ovens. Now, according to Mr. Moye, the best cracker ovens
are a combination of direct-fired zones and convection baking
zones. "The convection zones offer greater energy efficiency
by regulating the burner temperatures and blower speeds to
complete the baking, drying and coloring of the crackers," he
explained.
Radiant heat coming from burners above and below in
a direct gas-fired oven can be useful in situations where
humidity levels need to be high, according to Brett Cutler,
applications sales engineer, Baker Perkins, but add a little
convective air turbulence and the baking efficiency improves.
On the other hand, some products need radiant heat to deliver non-uniform coloration on the surface. For those kinds
of products, Baker Perkins offers the EM Recirc or HiCirc
ovens that combine convection and radiant heat. "The ratio
of convective to radiant heat is infinitely variable, allowing
the optimum balance between baking efficiency and product
appearance to be achieved," he said. Read more about hybrid
ovens in the upcoming September issue of Baking & Snack.

88 Baking & Snack April 2017 / www.bakingandsnack.com

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

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Baking&Snack - April 2017

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