Maejo Int. J. Sci. Technol. 2014, 8(02), 207-220 Maejo International Journal of Science and Technology ISSN 1905-7873 Available online at www.mijst.mju.ac.th Full Paper Single-phase and multiphase models for temperature and relative humidity calculations during forced convection in a rubber-sheet drying chamber Racha Dejchanchaiwong 1, 2 , Yutthana Tirawanichakul 1, 3 , Supawan Tirawanichakul 1, 2 and Perapong Tekasakul 1, 4, * 1 Energy Technology Research Centre (ETRC), Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand 2 Department of Chemical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand 3 Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand 4 Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand *Corresponding author, e-mail: perapong.t@psu.ac.th Received: 29 August 2013 / Accepted: 4 August 2014/ Published: 25 August 2014 Abstract: Computational fluid dynamics modelling of single-phase and multiphase flows was used to simulate the temperature and relative humidity at various locations in an empty rubber-sheet drying chamber. In all planes, unlike the single-phase model, the multiphase model’s temperature distribution is relatively uniform, and the temperature deviations are 0.01-4.73°C in the bottom plane, 0.02-4.05°C in the middle plane, and 0.01-3.84°C in the top plane. The single-phase model results in temperature deviations of 0.55-6.63°C, 0.02-6.02°C and 0.36-3.89°C in the bottom, middle and top planes respectively. Thus, the multiphase model is deemed superior. The inclusion of water vapour in the multiphase model increases the agreement between model and experimental temperature data. The largest temperature deviations occur at the centre-frontal positions of all planes owing to the turbulence of the hot gas at the inlet. In all planes the relative humidity is almost uniform, except near the centre-frontal area of the bottom plane. Clearly, the multiphase model is more appropriate for simulating chambers containing rubber sheets, though the diffusion of moisture from rubber sheets needs to be considered as well. Keywords: natural rubber, rubber-sheet drying, multiphase model