Entropy and energy analysis of water/silver nanofluid flow in a microchannel by changing the angle of attack of a cam-shaped vortex generator

Abstract

Background: This study simulates the laminar forced flow of water/silver nanofluid in solid nanoparticle volume fractions ranging from 0 % to 6 % in a microchannel with vortex generators. For Reynolds numbers 100 to 800, the angle of attack of the vortex is changed from 0 to -90° Methods: The finite volume method is used for the 2D numerical study. Increasing the angle of attack leads to greater local flow mixing, which diffuses heat towards the upper parts of the flow, resulting in a favorable microchannel temperature distribution. During the movement of the fluid, the temperature difference between the surface and the fluid decreases. In addition to local friction, shear stress is also responsible for the friction factor. If the Reynolds number is high and the angle of attack is -30°, then the Nusselt number becomes significant. After passing the vortex generators, the effective flow area is higher, which is due to the higher effective flow area. Among the studied cases, the highest friction occurs for an angle of attack of -90° Significant findings: For higher volume fractions of nanoparticles (φ), the effect of fluid velocity dissipation and friction factor variations are higher. To limit entropy generation, higher Reynolds numbers and nanoparticle concentrations could be used. Changing the vortex generator angle has a limited influence on the entropy generation.

Keywords

• Microchannel
• Vortex generator
• Nanofluid
• Angle of attack
• Finite volume method