Adaptive Surface Microprofiling for Microfluidic Energy Conversion

Abstract

Adaptive microprofiling is a newly proposed technique of embedding open microchannels within a surface to take advantage of resulting slip-flow behavior and drag reduction. The objective of this paper is to predict the optimal geometrical profiles of such microchannels, particularly for minimizing entropy production in convective heat-transfer problems. A theoretical slip-flow formulation (within microchannels) is developed for Knudsen numbers between about 0.02 and 0.07. These values fall within the range governed by the Navier-Stokes equations with slip-flow boundary conditions. Numerical results show that a fourth-order geometrical profile yields lower entropy production than a linearly diverging microchannel. With rapid advances in micromachining technology, it is viewed that adaptive microprofiling can become a useful alternative technique of drag reduction, while increasing heat-transfer effectiveness. These combined objectives can be realized through the newly formulated approach with entropy-based microprofiling, which establishes the optimal microgroove patterns by minimizing entropy production over the surface