Enhanced heat transfer in a microchannel with pseudo-roughness induced by Onsager-Wien effect

•Heat transfer enhancement by Onsager–Wien effect in a microchannel is investigated.•Electric-field-induced Onsager–Wien effect generates vortices near bottom wall.•These vortices induce a pseudo-roughness effect and disrupt the boundary layers.•Depletion of the laminar boundary layer enhances heat transfer.•Onsager–Wien effect enhances heat transfer with minimal power consumption. A three-dimensional numerical analysis of flow and conjugate heat transfer in a microchannel in the presence of the electric-field-induced Onsager–Wien effect is performed. A novel design is proposed to induce a pseudo-roughness effect in the microchannel and thereby increasing the heat transfer. A series of thin plate electrode pairs are flushed along the bottom wall of the microchannel. The electric-field-enhanced dissociation of ions induces the Onsager–Wien effect, and generates small flow vortices near the bottom wall of the channel. These flow vortices with sharp local velocity gradients effectively disrupt the viscous and thermal boundary layers, and thus, introduce a pseudo-roughness effect. This disruption of the boundary layers improves the heat transfer between the channel wall and the working fluid. The thermal and hydraulic performances in the microchannel are quantified as a function of the flow Reynolds number Re and electric Reynolds number ReEL. In general, the performance factor PF is higher when the flow and electric Reynolds numbers are higher. However, the associated pressure drop penalty reduces the PFPF