Grant: Discovery Grants Program - Individual

In this proposal, our objective is to establish a comprehensive fundamental and practical understanding of liquid jet impingement heat transfer, which is the prime cooling process used in industry as it achieves high cooling coefficients. We plan to develop theoretical, numerical and experimental methodologies to examine factors that affect liquid jet impingement cooling of nanofluids on micro-textured and moving targets, as well as on surfaces of variable topography. Liquid jets have many valuable industrial uses. As a recent trend in automotive engine design is to increase power density to improve fuel economy, oil-jet technology has found applications in automotive engines, to accommodate the increased thermal load due to the temperatures of combustion chamber components. The high cooling performance of liquid jet impingement is attributed to the thinning of the liquid film spreading on the target surface, thus reducing the thermal resistance between the surface and the impinging flow. As the liquid spreads, a hydraulic jump forms due to viscous effects, with a significant drop in velocity and heat transfer. We shall examine the impingement on a porous layer, with relevant industrial applications in heat transfer from metal foams and boiling heat transfer, as well as the transient impinging flow on moving surfaces given its importance in the cooling of moving components. In addition to water, nanofluids are also effective coolants. A > 1% concentration of nanoparticles can result in a > 40% increase in thermal conductivity. Textured target surfaces will also be examined, where an air layer is trapped in the micro- and nanoscale cavities of the solid target, thus changing the hydrodynamic and thermal conditions. Textured surfaces can enhance local cooling by up to 50% compared to smooth target surfaces, because of the turbulence induced by the surface roughness element. Depending on our progress, multiple jets will be envisaged. In many applications, large areas need to be cooled, and the spatial variation of heat transfer observed with a single jet is not ideal. To overcome this, multiple jets are used in many applications to achieve, or approach, uniform cooling. In collaboration with colleagues at Western, we will build a precision experimental facility to provide critical measurements to support the theoretical research proposed here. The simple experimental setup to measure the film profile includes laser-based flow diagnostic techniques at our disposal here at Western. The effect of heat transfer is already planned in collaboration with two French institutions where more elaborate and larger scale experiments are carried out. Finally, the research is of great fundamental significance as it will clarify the intricate mechanisms behind jet cooling of complex liquids. It is also of significant industrial impact as it helps enhance cooling processes for the ever increasing demand for energy efficiency and miniaturization.