Magnetogasdynamic natural convection in a long vertical microchannel

Abstract

● Original study: There were no studies on microscale magnetogasdynamic natural convection. ● New finding—Velocity: Results show that a greater magnetic force would result in a flatter velocity profile. ● New finding—Thermal-flow characteristics: Results reveal that magnetic force results in decreases in thermal-flow characteristics. ● New finding—Enhanced magnetic effects: These effects could be further enhanced with higher by increasing gas rarefaction. ● Potential benefits of the present study: This study could benefit the designs of magnetically controllable microfluidic devices. Since the transport behavior of ionized gases at the microscale could be influenced by an applied magnetic field with ease, microscale magnetogasdynamics (MGD) promises to be particularly advantageous for magnetically controllable microfluidic devices. The purpose of this study is to investigate how magnetic force affects the MGD natural convection within a long asymmetrically heated vertical planar microchannel. The fully developed solutions of the thermal-flow fields and their characteristics are analytically derived on the basis of the first-order slip and jump boundary conditions and then presented for the thermophysical properties of ionized air at the standard reference state flowing through the microchannel with complete accommodation. The calculated results reveal that magnetic force plays a damping role in flow and results in decreases in flow rate, average flow drag, and average heat transfer rate. In addition, it is interesting that because the flow near the core is suppressed and the shear stress on the wall surface is reduced by the magnetic effects, a flatter velocity profile could be achieved by a greater magnetic force. These magnetic effects could be further magnified by increasing gas rarefaction or increasing cooler wall temperature.