Numerical simulation of flow in an array of in-line blunt boards: mass transfer and flow patterns

The airflow patterns around an array of in-line truncated boards and the su blimation process of thin naphthalene layers over the in-line boards have b een simulated numerically. The simulation used the renormalization group k- epsilon turbulence model and the two-layer zonal model for the near-wall tr eatments. When only one of the in-line boards is coated with naphthalene, a s in the experiments by previous authors, the predicted local mass-transfer coefficients over that board show a substantial increase at the leading ed ge of the board and are in good agreement with the measurement data. Howeve r, when all the in-line boards are naphthalene coated, the calculated mass- transfer coefficients decrease in an approximately asymptotic manner from a maximum value near the leading edge of the first board. These results indi cate that the small gaps between in-line boards have an insignificant effec t on the mass-transfer coefficients. Vortex shedding from in-line boards se parated by small gaps has also been investigated numerically. It is shown t hat in a wind tunnel with a single layer of boards, all the recirculating f low eddies at different locations around the in-line boards are characteriz ed by vortex shedding, in agreement with the experimental observations by p revious authors, while in a kiln stack with multiple layers of in-line boar ds, only the eddies in the near wake of the stack are formed periodically. (C) 2001 Elsevier Science Ltd. All rights reserved.