Thermal and hydraulic study of mini-channel with irregular surface topology

Abstract

The present study aims at identifying the critical Reynolds number for transition from laminar to turbulent in irregular shaped mini-channels. Numerical study including conjugate heat transfer and axial conduction is carried out using commercially available software ANSYS Fluent®. The channel of length 105 mm, width 4.5 mm, and height 2 mm is fabricated in an aluminium substrate of length 114 mm (L), width 15 mm (W), and height 6.3 mm (H). Water is used as working fluid. Average hydraulic diameter (Dh) of mini-channel is 2.86 mm, and cross-section area varies non-uniformly from 10 mm2 to 18 mm2 along the length. Problem is set up with mass flow rate and outflow boundary condition at inlet and outlet, respectively. Bottom wall is given with uniform heat flux (q) of 200 watts thus incorporating conduction in solid wall of channel. Temperature difference between the inlet and outlet is compared with experimental measurement and found to be in good agreement. It is observed that the heat transfer coefficient as well as pressure drop both increases with increase in mass flow rate; however, increase in pressure drop is found larger compared to increase in heat transfer coefficient. Further, we also found the axial conduction in the solid wall. It is interesting to note that the transition from laminar to turbulent is observed at lower Reynolds number. Present work provides platform to study thermal and fluid flow behaviour of the irregular shaped mini-channels.