Design and Development of an Earthen Oven with Automatic Temperature Control

Abstract

The traditional earthen oven has been a staple in many cultures for drying and baking, but it lacks the ability to control and maintain a consistent temperature. This limitation can lead to uneven drying results and longer drying times, which may not meet the demands of modern drying needs. The incorporation of an automatic temperature controller to the earthen oven aimed to address this problem. The materials employed in fabricating the oven included clay, mild steel rods, mild steel angle bars, insulation fibre and so on. Other accessories were temperature controller, AC-DC inverter, 12V Battery which were acquired from the open market. The insulation layer of the oven comprised a mixture of clay and metallic straw. The methodology included testing the oven with varying air flow rates ranging from 2 to 4 m/s, heating times ranging from 10 to 30 minutes, and charcoal masses ranging from 5 to 25 kg. Linear shrinkage value of -8.9 indicated uniform heating of the oven walls, leading to effective retention of heat within the oven drying chamber. The grain size distribution, with percentages passing ranging from 93.44 to 100%, indicating finer particles that would result in cohesive and impermeable material with high strength, permeability, and thermal conductivity of the oven walls. The plastic index of 18.7% indicated a wider range of moisture content for workability to prevent cracking or collapsing during use, liquid limit of 44.5%. Liquid limit of 44.5% indicated significant improvement against cracking and crumbling of the oven clay walls. The range of temperature obtained from evaluation of the earthen oven was in the range of 280-300^oC. As the heating time increased for a fixed air flow rate of 2, 3 and 4 m/s, it was seen that longer duration of running the oven tended to result in a steadier retention of the high temperature. Higher oven temperature was observed as a function of air flow rate which acted as a catalyst to the burning charcoal. The findings provide a promising solution to inconsistent drying outcomes in traditional earthen ovens. The design and operating parameters should be optimized for different drying applications.