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

Abstract

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 lm), ratios of pitch to microcylinder diameter (1.5, 2 and 2.5) and ratios of microcylinder 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 microcylinder-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.Pressure difference between inlet and outlet (Pa) qHeat flux (W/m 2 ) S Micro-cylinder pitch ratio (m) S w Distance between the first row and the wall (m)

Numerical Simulation of Flow and Heat Transfer Characteristics in Non-Closed Ring-Shaped Micro-Pin-Fin Arrays

“…Mohammadi et al [13,14] explored flow and heat transfer in staggered and in-line micro-pin-fin arrays numerically, and found that the vertical split ratio had a significant effect on pressure drop, friction coefficient, thermal performance index and Nusselt number, while the diameter ratio, horizontal pitch ratio and minimum flow area of liquid exerted a lesser influence. Similar conclusions were also reached by Guan et al [15,16]. Hithaish et al [17] compared the thermal-hydraulic features in triangular micro-pin-fin arrays with different fin height and rotation angles through numerical simulation, and found that the pressure drop and frictional resistance increased with fin height.…”

Hybrid Nanofluids—Next-Generation Fluids for Spray-Cooling-Based Thermal Management of High-Heat-Flux Devices

“…Presently, the main heat dissipation methods in high-heat-flux devices include natural and forced air cooling [38,39], fluorochemical liquid-forced convection and fluorochemical liquid-boiling heat transfer [40], forced water convective cooling [41], water boiling cooling [42], jet impingement [43][44][45][46], microchannel cooling [47][48][49][50] and spray cooling [51,52]. Figure 1 shows that air cooling cannot remove a heat dissipation flux above 100 W/cm 2 and therefore cannot meet the heat dissipation requirement of the high-heat-flux devices.…”

Influence of heating load on heat transfer characteristics in micro-pin-fin arrays

“…The authors designed micro pin-fin heat sinks with different pin fin shapes and dimensions and investigated the flow and heat transfer characteristics in previous studies [5][6][7][8]; it is found that the heating load may affect the convective heat transfer characteristics apparently. In order to explore the change of convective heat transfer with different heating load and the mechanisms, the present investigation is experimentally and numerically carried out to obtain the Nu in micro pin-fin arrays with different heating load, and then the influence of thermal physical properties of working fluid is inspected.…”