Experimental Investigation on the Effects of Wall Chamber Insulation on Nusselt Number and Heat Loss Reduction in a Natural Convection Oven

Abstract

The main aim of this study was to investigate the effect of oven wall chamber insulation on the Nusselt number and heat loss reduction in a direct-fired natural convection oven. Three sets of experiments, namely uninsulated and insulation with each of the two insulation materials were performed and a data acquisition system was used to continuously monitor temperature and environmental changes from the oven's four sides, ambient, and inside using a heat temperature sensor and a thermocouple. The temperature profiles, the Nusselt number, the Rayleigh number and the heat transfer coefficient were used to assess the heat transfer characteristics of the oven. Within the range of the Raleigh numbers studied, the average Nusselt number is highest for the uninsulated and higher for the insulated with aluminum-reinforced fiber and least for the insulated with fiberglass. Based on the findings, installing thermal insulation materials in oven walls could reduce heat loss, appreciably. The average percentage reductions in heat loss as a result of insulation were 3.8% and 16.7% for the fiber reinforced aluminum and fiberglass, respectively. The least-square correlation of the Nusselt numbers and the Rayleigh numbers gave high values of adjusted R-square values, which are recommended for optimization of natural convective heat transfer for uninsulated and insulated ovens.