Modeling, numerical simulation and validation of a convective dryer in steady conditions: case study of tropical woods

ABSTRACT

This paper presents a modeling and a numerical study that allows following the variation of the moisture content, temperature, drying rate and heat and mass transfer coefficients of four African tropical woods coming from Douala Cameroon. Experimental setup was developed in order to verify the drying curves and calculation of mass and heat transfer coefficients for both moisture content gradient and temperature gradient. The thermophysical properties were selected after performing an exhaustive literature review linked to the tested materials. The drying conditions were 25°C, 33.5°C and 0.25 m/s, representing wet temperature, dry temperature and air velocity, respectively. Wood thickness ranged between 22 and 25 mm. According to modeling and simulation results, the predicted moisture content shows an average relative error on each drying curve less than 10% compared to the experimental results. Mass and heat transfer coefficient evolutions are physically explained with satisfaction. Mass transfer coefficients for temperature gradient can be neglected in steady drying conditions as compared to the other transfer coefficients. Water permeability and brake factor of diffusivity of the air vapor in wood are determined using an inverse method. The presented drying model can be used to simulate in particular the tropical woods drying.

KEYWORDS:

• Tropical woods
• drying model
• non-hygroscopic and hygroscopic domain
• steady conditions

Acknowledgments

S.-T. Merlin acknowledges Dr-Hab Romain Rémond and Mr Tristan Stein for the sampling collection of our woods and the setting of apparatus measures.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the International Tropical Timber Organization (ITTO) [grant number 011/11A], [grant number 012/15A].

Notes on contributors

Merlin Simo-Tagne

Merlin Simo-Tagne holds his Ph.D in Energetic and Environment. He has a Specialized Professional Master in Electric, Energetic and Renewable Energies Engineering, also a High School Teacher's Diploma. He has make two post-doctorates at University of Lorraine, France, financed by the ITTO, Tokyo, Japan. He teaches and researches in the sustainable energies domain (thermal storage, solar dryers, laboratory characterization) using numerical modeling (Fortran language) and industrial experiments. He has more than 30 papers published in international scientific journals.

Lyes Bennamoun

Lyes Bennamoun is a research professional at University of New Brunswick, Fredericton, New Brunswick, Canada, since 2013. His main axes of research are mathematical modeling of the woody biomass supply chain management, heat treatment including pyrolysis and convective and microwave drying of several biomass. From 2011 to 2013, Dr. Bennamoun was working at the Department of Applied Chemistry, University of Liège, Belgium, as foreign fellow, where he performed experimental and modeling studies related to convective and conductive drying of thermos-sensitive and rheologically complex products, such as wastewater sludge and yeast. In 2008, Dr. Bennamoun was postdoctoral fellow at Food Research and Development Centre, St-Hyacinthe, Quebec, Canada. His main study in the research centre was the characterization and extraction of fibers from canola residues. Dr. Bennamoun is also working on the thermal conversion of solar energy and its applications. He has published 90 publications in international journals, chapter and edited books and international conferences. He is member of the editorial board of 9 international journals linked to renewable and green energy, energy conversion and processing.

Angélique Léonard

Angélique Léonard obtained her Chemical Engineering degree (1998) and PhD in Applied Sciences (2003) from University of Liège. She was appointed by the Belgian Fund for Scientific Research (FNRS) from 1998 to 2009. She then became Professor within the Department of Chemical Engineering at the University of Liège, in the chair “Chemical processes and sustainable development”. She is the head of this Department since 2011. She obtained the "Frédéric Swarts Prize" of the Division of Sciences of the Royal Academy of Belgium, 33rd two-year period, 2002-2004 and the "Award for the Best Scientist under the age of 35 years" given by the "World Forum for Crystallization, Filtration and drying" during IDS2008 - 16th International Drying Conference, Hyderabad, India, November 9-12, 2008. She is member representative for Belgium of the EFCE Working Party on Drying and of the International Drying Symposium advisory board. She organized in 2008 the first edition of the European Conference on Sludge Management at University of Liège. Her research interest are: convective drying of deformable porous materials (including sludge), sludge treatment (dewatering and drying), X-ray microtomography as a tool to characterize the texture of porous materials. She also leads a Life Cycle Assessment (LCA) team with more than 10 years expertise. LCA related works includes environmental product declarations (EPDs), LCA of processes, training in various fields: chemical and energy industry, waste management, biofuels, agrofood sector, building materials, batteries. She has authored/ co-authored over 60 refereed research publications and about 120 conference proceedings. She cooperates as Referee for about 15 international scientific Journals.

Yann Rogaume

Yann Rogaume is Professor of the University of Lorraine and Head of the LERMaB Laboratory situated in Epinal, France. He obtained his PhD in 1999 on thermal degradation domain. He works now in Combustion, gasification and pyrolysis domain mainly, but also in another domain such as drying and thermal comfort. Until now, he directed 6 theses, was jury president for 5 theses, has been rapporteur for 6 theses and was a jury member for 1 thesis. He has more than 80 papers published in international scientific journals.