Measurement and analytical modeling of entropy generation in microchannels

Microchannel heat-sinks, offer an innovative means of removing a large amount of heat within a small volume. Minimizing the entropy generation associated with flow in a microchannel provides and effective method for simultaneously optimizing heat transfer and viscous dissipation.

In this project, an analytical model for predicting the rate of entropy generation in a microchannel heat-sink is developed and used to determine the optimum geometry of the heat sink that minimizes the production of entropy. The results will be verified by the experimental measurement of entropy generation using a micro Particle Image Velocimetry system.

Optimization of microfluidic channels and heat sinks using entropy generation minimization

The thermal/fluid behaviour of microfluidic systems do not always agree with predictions made using conventional 'large-scale', or continuum models. Investigation of flow phenomena experimentally using MicroPIV can be useful to gain insight into this 'new physics' and, if possible, utilize these quantitative observations in the development of new theoretical and empirical models for micro-scale flow phenomena. A simple but accurate model using Entropy Generation Minimization (EGM) will be developed for the purpose of developing an optimized cooling device for microelectronics.

Hossain, M.R., Culham, J.R., and Yovanovich, M.M.,, 2007, "Influence of Bypass on Flow Through a Plate Fin Heat Sink," Symposium on Semiconductor Thermal Measurement and Management (SEMI-THERM 23), San Jose, Ca, (Submitted).

Hossain, M.R., Culham, J.R., and Yovanovich, M.M., 2007, "Design of an Optimized Plate Fin Heat Sink with Flow Bypass Using Entropy Generation Minimzation," The ASME/Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS, and NEMS (InterPACK'07), Vancouver, BC (Submitted).

Micromachining of Vapor/Compression Refrigeration Systems

The deleterious effects of heat generation and thermally-induced failures of micro/nano electronic and photonic components have necessitated the development of thermal packaging solutions at progressively smaller scales. The current trend in microelectronics is to incorporate higher operating frequencies and reduced component sizes leading to higher heat flux densities. These conditions exceed the limitations of conventional cooling technologies such as fans along with heats sinks due to their size, weight and reliability. The objective of this research is to develop of micro-scale refrigeration systems for electronics cooling that address the needs associated with high heat flux. A comprehensive theoretical analysis, in conjunction with design and fabrication of innovative Micro Refrigeration Systems (MRS) to cool thermoelectric coolers will be conducted.

Analytical Modeling of Thin Film Thermoelectric Devices

Advanced semiconductors continue to increase performance by increasing functional integration and clock speed. Not only is the total power consumption increasing, the power distribution is highly non-uniform over the die area. Continued reductions in feature size are likely to increase non-uniformities in the power density, especially as high heat flux, high-speed circuits become integrated with lower-speed circuits that dissipate little power but consume a larger die area. The high temperature of localized hot spots adversely effects product reliability, performance and yield. Thin-film thermoelectric devices mounted directly on the silicon chip or PCB can provide overall system cooling and control of localized temperature hot spots.
The topics covered in this research program include thermal measurements to characterize thin-film thermoelectric devices, development of analytical predictive tools and evaluation of potential new technologies including closed-loop microchannel systems.