Air Cooled Electronics

1.

Evaluation and optimization of the thermal performance of heat sinks using entropy generation minimization (EGM) techniques. Heat sinks evaluated using these methods include plate fin and pin fin heat sinks, including both round and elliptical pins. Recent publications include:

Culham, J.R., and Muzychka, Y.S., 2001, "Optimization of Plate Fin Heat Sinks Using Entropy Generation Minimization," IEEE Transactions CPT, Vol. 24, No. 2, pp. 159-165.

Khan, W.A., Culham, J.R. and Yovanovich, M.M., 2005, "Optimization of Pin Fin Heat Sinks Using Entropy Generation Minimization," IEEE Transactions on Components and Packaging Technologies, Vol. 28, No. 2, pp. 247-254.

2.

Measurement and modeling of flow bypass for plate fin heat sinks, including the effects of relative duct and heat sink sizes and geometries. The analytical expressions developed to describe flow bypass will be incorporated into an model that uses EGM to predict local air cooling limits for components located in larger systems. Recent publications include:

Leonard, W., Teertstra, P., Culham, J.R., and Zaghlol, A.,, 2002, "Characterization of Heat Sink Flow Bypass in Plate Fin Heat Sinks," Proceedings of IMECE 2002, International Mechanical Congress and Exposition, New Orleans, Louisiana, November 17-22.

3.

Fundamental research into analytical modeling techniques for natural and forced convection heat transfer for finite body shapes, such as spheroids, cuboids, and rectangular plates, enclosures, and cross flow heat exchangers and tube banks. Recent publications include:

Khan, W.A., Culham, J.R. and Yovanovich, M.M.,, 2005, "Fluid Flow Around and Heat Transfer From an Infinite Circular Cylinder," ASME Journal of Heat Transfer, Vol. 127, No. 7, pp. 785 - 790.

Teertstra, P., Yovanovich, M.M. and Culham, J.R.,, 2004, "Analytical Modeling of Natural Convection in Concentric Spherical Enclosures," Paper No. AIAA2004-0496, 42nd AIAA Aerospace Sciences Meeting and Exhibit, January 5-8, 2004, Reno, NV.

Liquid Cooled Heat Sinks

Design and testing of high capacity heat sinks developed specifically for use in power electronics, where high power dissipation rates preclude the use of conventional air cooled heat sinks.  This research has involved:

1. Experimental testing of liquid cooled heat sink prototypes for a variety of flow conditions.
2. Development of an analytically-based design tools that will allow an engineer to quickly and accurately design a heat sink for a particular application.

Recent publications include:

Zugic, M.J., Culham, J.R., Teertstra, P., Horne, K., Knapp, E. and De Palma, J.-F., 2005, "Experimental and Analytical Investigation of Compact Liquid Cooled Heat Sinks," ASME International Mechanical Engineering Congress, Anaheim, CA, November 13-19.

Heating and Ventilation Models for Automotive Seating Applications

Development of simple and accurate models and algorithms for heat transfer and fluid flow in ventilated and heated car seats for the automotive industry. These models will provide the computational engine for CAD tools being developed in a joint project with NRC (London, ON)   This research has involved:

1. Analytical modeling of heat transfer and pressure drop in seat materials
2. Experimental testing of cooling and heating performance of prototype systems, including ergonomic tests to evaluate passenger comfort.
3. Detailed numerical modeling of heat transfer and fluid flow in ventilated seat system.
   

Recent publications include:

Karimi, G., Chan, E.C. and Culham, J.R.,, 2005, "Thermal Modeling of Driver/Seat Interfaces in Automotive Applications," Paper No. 2004-01-2143, SAE Transactions Journal of Materials and Manufacturing.

Karimi, G., Chan, E.C. and Culham, J.R.,, 2004, "Experimental Study and Thermal Modeling of an Automobile Driver with a Heated and Ventilated Seat," Journal of Passenger Cars - Electronic and Electrical Systems, Vol. 112, No. 7, SAE 2003 Transactions, pp. 682-692.

Heat Sealing of Flexible Plastic Packaging

Analytical and experimental characterization of impulse sealing of heat-sealed polymer films. The process is widely used in the packaging of food products, medical supplies, etc.   This research has involved:

1. Design and construction of a test apparatus that evaluates seal quality as a function of a variety of input conditions, including jaw pressure and temperature, speed, duration, and film type.
   
   
2. Development of analytical models for the impulse sealing process that predict temperatures and resulting seal quality, to be used in the set-up and control of new sealing machines.
   

Thermal Contact Resistance for Microelectronics Applications

The current work in progress at the MHTL can be broken down into the following topics: This research has involved:

Interfacial Materials: Through experimental testing and physically based analysis, models for overall joint conductance based on measurable physical properties of the interface materials will be developed for commonly used materials, such as thermal grease, compliant material layers and phase change materials. One of the key features of this research study is the measurement of thickness of the material as a function of load, temperature and surface conditions using a laser micrometer.

Recent publications include:

Savija, I., Yovanovich, M.M., Culham, J.R, and Marotta E.E.,, 2003, "Thermal Joint Resistance Model for Conforming Rough Surfaces With Grease Filled Interstitial Gaps," AIAA Journal of Thermophysics and Heat Transfer, Vol. 17, No. 2, Apr.-June, pp. 278-282.

Smith, R.A. and Culham, J.R, 2005, "In-Situ Thickness Method of Measuring Thermo-Physical Properties of Polymer-Like Thermal Interface Materials," Twenty First Annual IEEE Semiconductor Thermal Measurement and Management Symposium (Semi-Therm), San Jose, CA, March 15-17, pp. 53 - 63.

Effective Thermal Conductivity of Composite Thermal Interface Materials

Particle-laden polymers are the latest Thermal Interface Materials (TIMs) being investigated for the minimization of thermal joint resistance in microelectronics applications. A fundamental problem which remains to be addressed is how to predict the effective thermal conductivity of these materials.

Analytical models were developed using upper and lower bound solutions for heat transfer. The models were based on the effects of the volume fraction of the dispersed phase, particle geometry, distribution, and orientation. The models were verified with numerical and experimental results.

Recent publications include:

Karayacoubian, P., Yovanovich, M.M. and Culham, J.R., 2006, "Thermal Resistance-Based Bounds for the Effective Conductivity of Polymeric Thermal Interface Materials," Semi-Therm 2005, March 14-16, Dallas, Texas.

Karayacoubian, P., Bahrami, M., and Culham, J.R.,, 2005, "Asymptotic Solutions of Effective Thermal Conductivity of Particle-Laden Polymers," Paper No. IMECE2005-82734, ASME IMECE, Orlando, Florida, November 5-11.

Thermal Contact Resistance of Polymer-Polymer Joints

When heat flows through a contact formed at a polymer/polymer interface there is a temperature drop as a result of the thermal contact resistance (TCR) resulting from the imperfect contact.

This study looked at experimentally determining the TCR of a polymer/polymer joint under various interface contact pressures. Experimental data was then be compared to existing TCR models (both plastic and elastic). This entails having both the micro-hardness and the surface roughness of the polymer, both of which were looked at in detail. To experimentally determine the TCR of a polymer-polymer joint a minimal amount of heat must be used or the polymer samples will be permanently deformed. To ensure the polymer remains in a stiff, glassy state a polymer with a high glassy temperature must be used. Polycarbonate was selected for this reason and was the primary polymer used for this study.