Experimental Analysis of the Thermal Field and Energy Balance of a Wood-fired Bakery Oven during the Preheating Phase

Abstract

Preheating determines the amount of thermal energy stored in refractory components before baking and is therefore central to the operation of a wood-fired bakery oven. This study experimentally characterised the thermal behaviour and energy balance of an industrial wood-fired bakery oven used in Burkina Faso. Exterior wall and flue-gas temperatures were monitored during preheating after a long period of inactivity and during reheating between successive baking cycles. The exterior wall temperatures remained below 60 °C, whereas the oven openings showed greater heat dissipation. The flue-gas temperature exhibited three successive regimes: initial combustion stabilisation, progressive heat storage in the refractory materials, and a later rapid temperature increase associated with a reduction in the instantaneous capacity of the refractories to absorb additional heat. For preheating after prolonged inactivity, the energy balance showed that wall losses accounted for approximately 4% of the fuel energy and flue-gas losses for approximately 35%, while about 61% was stored in the oven. The reported storage efficiency was also approximately 61% during preheating after baking. Although a longer preheating period and greater fuel consumption were required after prolonged inactivity, the proportion of energy stored remained similar. These findings indicate that energy performance during preheating is influenced more strongly by flue-gas and opening losses than by heat transfer through the insulated walls. The results provide an experimental basis for improving preheating management and reducing avoidable heat losses.