Heat exchangers involving plain tubes in crossflow are widely employed in various industrial applications. Detailed studies have established relations between the heat transfer coefficient and the arrangement of tubes within the tube bank. Most of the data available in the literature concern with the tube bank heat transfer under forced convection conditions at relatively high Reynolds numbers, exceeding 103. However, the buoyancy effects become significant or even dominant under low-flow-rate conditions. Today reliable data for low-Reynolds-number regimes could be obtained using advanced Computational Fluid Dynamics techniques. The current contribution deals with a buoyancy-induced flow through a staggered tube bundle. Two-dimensional unsteady convection in a tube bank of 24 rows is computed. The tube walls are assumed to be at a uniform temperature. The buoyancy effects are described with the Boussinesq’s approximation. The computations have been performed for the Prandtl number of 6.09 and the Reynolds numbers in the range of 102-103. Development of unsteady flow and temperature fields along the flow path as well as variations of the heat transfer coefficients from tube to tube are analyzed. As a general result of the present parametric computations, the effects of the transverse and longitudinal pitches on the heat removal rate have been investigated.

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