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

Abstract

The airflow patterns around an array of in-line truncated boards and the sublimation process of thin naphthalene layers over the in-line boards have been simulated numerically. The simulation used the renormalization group k– ε turbulence model and the two-layer zonal model for the near-wall treatments. When only one of the in-line boards is coated with naphthalene, as in the experiments by previous authors, the predicted local mass-transfer coefficients over that board show a substantial increase at the leading edge of the board and are in good agreement with the measurement data. However, 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 indicate that the small gaps between in-line boards have an insignificant effect on the mass-transfer coefficients. Vortex shedding from in-line boards separated by small gaps has also been investigated numerically. It is shown that in a wind tunnel with a single layer of boards, all the recirculating flow eddies at different locations around the in-line boards are characterized by vortex shedding, in agreement with the experimental observations by previous authors, while in a kiln stack with multiple layers of in-line boards, only the eddies in the near wake of the stack are formed periodically.