Performance Comparison of Two Solar Kiln Designs for Wood Drying Using a Numerical Simulation

Abstract

The predicted performances of the two different timber-drying solar kiln designs (Oxford and Boral kilns) have been compared by using the climatic and geographical conditions of Brisbane (27.46°S) in Australia. The dimensions of the original Boral kiln have been scaled down in order to compare the kilns’ performances on the basis of same load capacity. The comparison was made in terms of the key performance indicators, including drying rates, drying qualities (i.e., the level of strains developed within the timber boards during drying), energy gains, and major elements of the energy losses (i.e., the convection and radiation losses) while drying timber from an average initial moisture content of 53% (dry basis) to a final moisture content of 15% (dry basis) in both kilns. The relative performances for the two designs were discussed in more detail by using the typical climatic conditions (spring season 2013), when the days and nights are of approximately equal length. Finally, an analysis of the seasonal effects on the kiln performances was also carried out in this article. More effective orientation of the solar absorbers with respect to sun, together with faster heat transfer rates between the circulating air and the timber stack for the Oxford design, were likely to give consistently better predicted performance for the Oxford design than for the Boral kiln throughout the year.