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Thermal management of heat in the temperature range of 20-100° Celsius is a problem encountered in a variety of situations and is particularly problematic for high-flux heat and in volume and weight constrained environments. Conventional methods of thermal management such as heat rejection, heat conversion, and heat storage are generally insufficient to manage this low-grade or low quality and/or high-flux heat.
High-quality heat is generally understood to mean that the operational temperature of the entity requiring cooling is significantly higher than the temperature of the heat sink to which the thermal energy is transferred. In contrast, low quality heat occurs when the fluid or object requiring cooling is close in temperature to the heat sink. Low-grade waste heat generated from machinery, electrical equipment, and electronic devices presents a significant problem as most equipment and electronics must operate in a temperature range of about 20-100° C.
In response to the above, Air Force researchers have developed a thermal management system utilizing ammonium carbamate for efficient management of thermal loads. Formation of ammonium carbamate is exothermic, while its decomposition into ammonia and carbon dioxide is highly endothermic, making it ideal thermal energy storage or rejection material to manage heat under a variety of conditions. The system is particularly useful for the management of low quality or high flux heat loads, including thermal loads in the 20-100° C. temperature range. It may have further benefit for the management of heat in volume- and weight-constrained environments.
Applications include on-demand heat rejection, thermal energy storage, and cooling. The technology may be further leveraged to provide a source of ammonia for a variety of applications including ammonia-powered engines, ammonia fuel cells, as well as reduction of NOx gases produced by combustion and industrial processes. In an ammonia source application, ammonium carbamate is an attractive alternative to liquid ammonia because it does not require high-pressure storage systems, nor does it present the health hazards that liquid or gaseous ammonia present upon accidental release.
This patent is related to U.S. Patent 9,863,725.
- Ammonium carbamate provides a gravimetric thermal energy density an order of magnitude (~10x) greater than many conventional thermal management materials
- Ammonium carbamate or slurries tolerate storage well, provided that they are sealed and prolonged temperatures above 30° C. are avoided
- Ammonium carbamate is also commercially available and safely managed in large industrial quantities in its role as an intermediate in the production of urea
- Businesses can commercialize the technology by licensing U.S. Patent 9,677,817 from the Air Force