Finned wafer baking plates for heat transfer and distribution

Abstract

Wafer baking is a recognized process in food industry, and there is a large worldwide demand to develop wafer baking equipment for the current trends, namely, high-productivity, high quality with lower wastes and lower energy expenditure. This work deals with the thermal design of the heating side of flat wafer baking plates in gas ovens seeking less heat, less baking time and better quality control. The key feature under study is the thermal interaction between the gas flames and the baking plates. Heat flows mostly by thermal radiation to the back of the baking plates which design is under study. Heat then reaches the opposite side where the batter (dough) is duly baked. The flames are modelled as a radiant solid surface with fixed geometry and uniform equivalent mean temperature. Steady, 2-d, heat conduction within the baking plate determines the superficial temperature field of the baking side. All the physics is modelled mathematically and solved in a commercial finite-element software. The method of Constructal Design is employed in order to explore possible designs of the back surface of the baking plates with the goal of providing uniform temperature heating at the baking side. We explored, for instance, the possibility of extended surfaces for a given volume of material. Variable rectangular, trapezoidal and parabolic straight long fins were considered. They varied in number and geometry. Results showed the baking plate with 17 fins provides a better heat distribution and increase of near 20°C from the plate with 3 fins. This means an overall gain of approximately 10%. In sum the new designs provide better heat transfer that in turn decreases the baking time, and it also improves heat distribution that in turn warrants product quality. Furthermore, the new designs provide the same mechanical resistance with less 17% material.