Numerical investigation on heat transfer of liquid flow at low Reynolds number in micro-cylinder-groups

Heat transfer of de-ionized water over in-line and staggered micro-cylinder-groups have been numerically investigated with Reynolds number varying in the range from 25 to 150. A 3-D incompressible numerical model is employed to investigate the vortex distributions and the influences of the vortices on heat transfer characteristics at low Re numbers in micro-cylinder-groups with different geometrical parameters, including micro-cylinder diameters (100, 250 and 500 mu m), ratios of pitch to micro-cylinder diameter (1.5, 2 and 2.5) and ratios of micro-cylinder height to diameter (0.5, 1, 1.5 and 2). The vortex distributions, the temperature fields, and the relationships among them are investigated by solving the numerical model with the finite volume method. It is found that the vortex number become more with the increase of pitch ratio and the change of flow rate distribution affects the heat transfer characteristics apparently. Meanwhile, the local heat transfer coefficients nearby the locations of vortices greatly increase due to the boundary layer separation, which further enhance the heat transfer in micro-cylinder-groups. The new correlations which to Nusselt number of de-ionized water over micro-cylinders with Re number varying from 25 to 150 have been proposed considering the differential pressure resistance and the buoyancy effect basing on numerical calculations in this paper.