3D Thermal Packaging

Thermofluid Aspects of Two Phase Microgap Channels
Avram Bar-Cohen – PI
Bongtae Han – Co-PI
Ilai Sher – Co-PI
Peter Rodgers – Co-PI
Emil Rahim – Graduate Research Assistant

Objective:

Recent Publications:

Peter Rodgers, Valerie Eveloy, Emil Rahim, and David Morgan. Thermal performance and reliability of thermal interface materials: A review. Proceedings of EuroSIME 2006, April 23-26, Milan, Italy.

A. Bar-Cohen, I. Sher, E. Rahim.  “On the Application of Macro-Pipe Two-Phase Heat Transfer Correlations and Flow Regime Maps to Mini-Channels.” Proceedings of the International Conference on Nanochannels, Microchannels and Minichannels.  Limerick, Ireland, 2006. 

Abstract: The present study is aimed at evaluating the ability of conventional “macro-pipe” correlations and regime transitions to predict the two-phase thermofluid characteristics of mini-channel cold plates. Use is made of the Taitel-Dukler flow regime maps, seven classical heat transfer coefficient correlations and two dryout predictions. The vast majority of the mini-channel two-phase heat-transfer data, taken from the literature, is predicted to fall in the annular regime, in agreement with the reported observations. A characteristic heat transfer coefficient locus has been identified, with a positive slope following the transition from Intermittent to Annular flow and a negative slope following the onset of partial dryout at higher qualities. While the classical two-phase heat transfer correlations are generally capable of providing good agreement with the low-quality annular flow data the quality at which partial dryout occurs and the ensuing heat transfer rates are not predictable by the available macro-pipe correlations.

Avram Bar-Cohen and Emil Rahim. Modeling and prediction of two-phase refrigerant flow regimes and heat transfer characteristics in microgap channels. Proceedings of ASME ICNMM 2007, June 18-20, 2007, Puebla, Mexico.

                  Abstract: This keynote lecture will open with a brief review of the primary two-phase flow regimes and their impact on thermal transport phenomena in tubes and channels. The Taitel and Dukler flow regime mapping methodology will then be described and applied to the two-phase flow of refrigerants and dielectric liquids in microgap channels. The effects of channel diameter, as well as alternative transition criteria, on the prevailing flow regimes in microgaps will be explored along with available criteria for microchannel behavior.  Available microgap data will then be shown to reflect the dominance of annular flow and to display a characteristic heat transfer coefficient curve in such configurations.  It is found that the heat transfer coefficients in the low-quality annular flow segment of this locus can be predicted by available, microtube correlations, but that the moderate-quality transition to the axially-decreasing segment occurs at substantially

Dae W. Kim, Emil Rahim, Avram Bar-Cohen, and Bongtae Han. Thermofluid characteristics of two-phase microgap coolers. Proceedings of IPACK 2007, July 8-12, Vancouver, British Columbia, Canada.

                  Abstract: The thermofluid characteristics of a chip-scale microgap cooler, including single-phase flow of water and FC-72 and flow boiling of FC-72, are explored. Heat transfer and pressure drop results for single phase water are used to validate a detailed numerical model and, together with the convective FC-72 data, establish a baseline for microgap cooler performance.  Experimental results for single phase water and FC-72 flowing in 120 μm, 260 μm and 600 mm microgap coolers, 31mm wide by 34mm long, at velocities of 0.1 - 2 m/s are reported. “Pseudo-boiling” driven by dissolved gas and flow boiling of FC-72 are found to provide significant enhancement in heat transfer relative to theoretical single phase values.

Thermal Management of 3-D Electronic Microsystems
Avram Bar-Cohen – PI
Jungho Kim ­– Co-PI
Chris Bachmann – Graduate Research Assistant

Objectives:
This project focuses on various aspects of cooling three-dimensional electronic
Microsystems, including:
1) effective property determination,
2) direct liquid cooling,
3) hotspot remediation. 
Due to small feature sizes and complex interconnect paths, effective thermal property determination becomes important in the development of global numerical simulations.  Also, the effectiveness of direct internal liquid cooling has been investigated since this approach is potentially well-suited to manage the high heat fluxes found in some electronic microsystems.  Further, localized high fluxes can lead to hotspots, and remediation of these hotspots through the implementation of anisotropic thermal interface materials has been explored.