An experimental and theoretical analysis of the dynamic response of solar drying in natural convection under rainy month of Maroua (Cameroon) of three tropical wood species

Abstract

ABSTRACT This work aims to study and characterize the drying kinetics, the heat mass transfer coefficients, the densities, the thermal effusivities, the thermal diffusivities and Young’s modulus of three tropical kinds of wood: ayous (triplochiton scleroxylon), sapelli (Entandrophragma cylindricum) and iroko (Milicia excelsa). A comparison has been doing between drying using a low expensive solar dryer in natural convection and drying using open-air conditions. The novelty of this work is to use an experimental study during the rainiest period in the city of Maroua, one city in Cameroon with a hard climate. Densities are influenced by the origin of the samples in the plank and increase linearly with the moisture content. At 30&per; of humidity (d.b), average densities of sapelli, iroko, and ayous were equal to 1000, 760 and 600 kg/m3 respectively. Thermal effusivities and thermal diffusivities increase linearly with the moisture content. Thermal diffusivities of the three kinds of wood are very near (2 × 10−7 m2/s at 30&per; of humidity (d.b)) and thermal effusivities increase with the wood densities with values located from 560 to 620 J/(K.m2.s0.5) at 30&per; of humidity (d.b). The heat mass transfer coefficients are influenced by the night and day and vary from 1.5 × 10−8–1.8 × 10−7 m/s for the global mass transfer coefficients, and from 1.8–6.5 W/(m2K) for the heat transfer coefficients. According to the variations of the values of young’s modulus and the drying kinetics, drying in open-air conditions is more rapid and not recommended than one in the solar dryer. The equilibrium humidity of all samples is near 10&per; (d.b).