A theoretical model of brick drying as a conjugate problem

The evaporative drying or a two-dimensional rectangular brick is studied nu merically as a conjugate problem. The conservation equations for the solid are obtained using the continuum approach. The Navier-Stokes equations have been employed for obtaining the flow field and the corresponding flow solu tions are used for predicting the drying behavior of the brick. The predict ions of temperature and moisture content show that the leading edge dries f aster compared to other sides of the solid. The full two-dimensional soluti ons differ considerably from the solutions based on heat and mass transfer through the boundary layers over the top surface. Average heat and mass tra nsfer coefficients appropriate to the conjugate problem have been defined, based on constant temperature and moisture differentials between the solid and the ambient. The corresponding Nusselt and Sherwood number values indic ate that analogy does not exist between heat and mass transfer, until the e ntire brick reaches wet bulb conditions. Free convection effects on drying are also studied for some initial period for low Reynolds number. Due to th e influence of buoyant forces imparted by gravity, the overall drying rate has improved. (C) 2001 Elsevier Science Ltd. All rights reserved.