INVESTIGATION OF UTILIZATION OF NATURAL STONES AS HEAT STORAGE MATERIALS FOR INDUSTRIAL WAFER OVENS

Industrial wafer ovens typically contain 40–120 baking dies, where thermal balance and temperature homogeneity govern product quality and energy consumption. This study presents a numerical transient finite-element heat-transfer analysis evaluating the feasibility of integrating natural stones (marble, granite, basalt, and fire brick) into a conventional GG-25 cast-iron wafer die. The thermal responses of the metallic and stone-reinforced (composite) dies are compared for the warm-up stage and the subsequent production (sleep) mode. The metallic die reaches the typical operating temperature of about 140 °C in approximately 1 h, whereas stone-containing dies require longer warm-up times. When wafer batter at about 10 °C is introduced, a larger surface-temperature drop occurs on the metal die than on the composite die, indicating improved thermal buffering. Composite dies are disadvantageous for short runs but become favorable as the production period increases; they are more energy-efficient for working periods of about 3 h and above, whereas the metallic die remains preferable for less than 1 h of operation. A cost and carbon-footprint assessment indicate that increasing the stone fraction reduces both metrics; assuming about 25% of the die geometry is replaced by natural stone, a 20–25% reduction in both cost and carbon footprint is achievable.