Advanced Heat Exchangers for Dry Cooling Systems

Dry cooling systems are currently the only option for industrial and utility power plants that are unable to obtain permits for cooling water or where cooling water is unavailable. Available dry cooling systems are more expensive and less efficient than wet cooling systems, so significant improvements in efficiency are needed to make them economically viable. Ultramet is designing, fabricating, and testing heat exchangers based on high thermal conductivity, high-permeability open-cell foams. The high surface area of the foams, combined with their high conductivity and low pressure drop, enables them to achieve high efficiency while simultaneously reducing the size of the heat exchanger. In Phase I, subscale graphite foam heat exchangers were designed, fabricated, and tested. The results demonstrated that the foam increased heat transfer by a factor of four compared with the no-foam case. A correlation was developed between the Nusselt number and the Reynolds number. In Phase II, Ultramet will work with Advanced Thermal and Environmental Concepts (ATEC), an affiliate company of the University of Maryland, to scale up the technology so that it can be implemented in a power plant. This will involve more detailed thermohydraulic modeling and the fabrication and testing of larger-scale heat exchanger modules. A full-scale system would comprise a series of these modules. Commercial applications and other benefits: Large-scale commercial applications include industrial and utility power plants. Smaller applications include heat exchangers used by the military in desert environments (e.g. air conditioners, environmental control units, heat exchangers for radars, etc).