Open Competition 5 - Chemistry and Materials

A Novel Vapor Compression System Utilizing Carbon Dioxide

Sponsor: Thar Technologies, Inc. (formerly Thar Designs, Inc.)

• Project Performance Period: 9/1/2002 - 8/31/2005
• Total project (est.): $2,472,882.00
• Requested ATP funds: $1,902,402.00

Recent advances in computer technology have not been matched by improvements in cooling systems. As circuit elements are packed closer together and microchips operate at higher frequencies, cooling elements such as fans and heatsinks cannot always compensate for the resulting increase in heat, which degrades components and increases system volatility. More than half of electronic product failures are attributed to overheating. Thar Technologies proposes to design and build a novel miniature, low-cost vapor compression system -- a "cooler on a chip" -- to cool microelectronic devices below ambient temperatures. Thar belives the miniature cooler, which will use a natural refrigerant such as carbon dioxide, will be more cost effective and energy efficient than existing cooling methods. A standard vapor compression cycle has four stages: compression, condensation, expansion, and evaporation. The key innovation will be the addition of a novel expansion mechanism that enhances the percentage of CO2 that is in the "supercritical" (exhibiting characteristics of both a liquid and a gas) phase during the expansion part of the cycle. Supercritical CO2 has a higher refrigeration capacity, and so is more efficient. Popular as a refrigerant many years ago, CO2 is now attracting interest again for home and auto air conditioning systems. For safety and cost reasons, it is the best natural refrigerant, and recent technological advances enable the design of microchannel tubes to handle the high operating pressure. There have been problems in the past with a low coefficient of performance (COP), but certain expansion mechanisms used for "throttle control" appear to increase COP by as much as 50 percent. The company also will develop an algorithm to modify the thermodynamic cycle to optimize energy per kilowatt of refrigeration, design a high-speed microcompressor, and place microchannel heat exchangers between the cool gas and hot liquid to provide supercharging. Computational Fluid Dynamics Research Corp. (Huntsville, Ala.) will be subcontracted to perform simulations of system and component designs. Carnegie-Mellon University (Pittsburgh, Pa.) will provide consulting services. ATP support is needed because potential industrial investors have large stakes in existing technologies and are unwilling to invest in a risky and path-breaking approach. If successfully developed and commercialized, the new cooling technology can help improve computer performance, reliability, and durability and support the development of higher processor speeds and new software programs and peripherals. In addition, the technology could be used in other refrigeration systems, reducing emissions of "greenhouse" gases and reducing the costs of electricity, servicing, refrigerant certification, and other needs associated with conventional systems.

For project information:

Brian Moyer, (412) 826-3939
moyer@thartech.com

ATP Project Manager

Gerald Castellucci, (301) 975-2435
gerald.castellucci@nist.gov