Flow Boiling in Open Microchannels with Tapered Manifolds using Ethanol in a Gravity-Driven Flow

Flow boiling in microchannel heat sinks has been researched extensively for its use in the cooling of high-power electronics. Previous works have proven open microchannels with tapered gap manifolds are effective in delivering enhanced flow boiling performance, with significant reductions in pressure drop. This work explores the feasibility of employing ethanol as a dielectric fluid in an open microchannel geometry with tapered manifolds, under a gravity-driven flow. A heat flux of 217 ± 13 W/cm2 was dissipated with a pressure drop of only 8.8 ± 0.5 kPa. Parametric trends are presented regarding flow rate, taper, pressure drop characteristics, and their effect on critical heat flux, providing basic insight into designing high heat flux systems under a given gravitational head requirement. Based on the obtained results, design guidelines are developed for the manifold taper, ethanol flow rate, and imposed heat flux on the heat transfer coefficient and gravity head requirement for electronics cooling. Reducing flow instability and pressure drop, and enhancing heat transfer performance for a dielectric fluid will enable the development of pumpless cooling solutions in a variety of electronics cooling applications