Thermally Conductive Porous Element-Based Recuperators

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Schematic of an exemplary recuperative heat exchanger according to an embodiment of the inventionDepiction of heat transfer between a heat transfer pair comprising pair of open cell porous elements, according to an embodiment of the invention
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Researchers
Louis Chow, Ph.D.
Jian-Hua Du, Ph.D.
Jayanta Kapat, Ph.D.
Yeong-Ren Lin
Wei Wu
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Andrea Adkins
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Patent Protection

Thermally conductive porous element-based recuperators

US Patent 8,322,406 B2
Publications
Design and Experiment of Compact and Effective Carbon Foam Recuperative Heat Exchangers
Journal of Thermophysics and Heat Transfer, Vol. 23, No. 2, 2009.

A compact and lightweight heat exchanger with embodiments of heat exchangers based on thermally conductive carbon foam materials to achieve an enhancement in heat transfer and reduction in size and weight

Heat exchangers have one very simple purpose, to raise or lower a fluid’s temperature by adding or removing thermal energy. While there are many different sizes, levels of sophistication, and types of heat exchangers, they all use a thermally conductive element generally in the form of a tube or plate that separates two fluids, such that one can transfer thermal energy to the other during the process of heat transfer. Recuperative heat exchangers separate flow passages which are provided for the hot and cold fluid. Conventional recuperative heat exchanges often utilize aluminum or copper and are generally large in size and heavy, making it very undesirable for many applications. Moreover, these heat exchangers lack scalability, modularity and also fail to provide high-effectiveness. The effectiveness of the heat exchanger is a performance measure of the degree of heat exchange between the hot and cold streams. An effectiveness of 100% indicates that there is complete heat exchange between the two streams, which is the ideal situation in order to maintain a high operational coefficient of performance (COP).

Technical Details

The present invention is able to achieve overall effectiveness beyond 98% by employing a highly thermal conductive material known as carbon foam, allowing significant heat transfer enhancement and greatly reducing the size of the recuperator. The low density of carbon foam also leads to a significant weight reduction for the system. This new and unique development has size and weight advantages, and can be easily scaled up for larger heat transfer requirements. There are numerous applications for heat exchangers according to embodiments of this ingenious invention, based on the combination of light-weightedness, compactness and high effectiveness. Exemplary applications include a recuperative heat exchanger for cryocoolers for space exploration or high temperature superconductors, micro or mini turbines, thermal management in hybrid automobiles and environmental control for fuel cells.

Benefits

  • Highly effective, reaching beyond 98%, by minimizing the axial conduction along the fluid flow direction, thereby maintaining a high operational coefficient of performance
  • Compact modular counter flow design for scalability, allowing easy scaling up for larger heat transfer requirements
  • Use of carbon foam for significant heat transfer enhancement between the fluid streams, thus greatly reducing the size and weight of the recuperator
  • The material choice and configuration design offers reduction of the axial conduction, thereby increasing the effectiveness of the recuperative heat exchanger

Applications

  • Thermal and moisture management in fuel cells
  • Mobile power generation systems based on Brayton engines,
  • Heat recovery for solar and other renewable energy systems
  • Micro or mini turbines
  • Compact cryo-coolers used by the aerospace, medical, and military sectors