Enhanced Performance Carbon Foam Heat Exchanger for Power Plant Cooling

72731-Thermoelectric power plants account for 39% of the fresh water withdrawn from streams and lakes in the United States, second only to agriculture. 3.3 billion gallons daily are lost to evaporation and 190 billion returned as warm water discharge. The link between adequate supplies of low-cost energy and freshwater is clearly recognized in President Bush¿s National Energy Policy. The demands placed upon increasingly limited sources of fresh water could be reduced if more efficient power-plant cooling systems were to developed. This project will develop heat exchangers made from high thermal conductivity carbon foam, which have demonstrated performance at 1.5 to 3.5 times that of metal fins. The approach will address the low strength problems, which prevented the previous industrial implementation of carbon foam heat exchangers. During Phase I, ceramic coatings were applied to the high thermal conductivity carbon foam using a variety of raw materials and processing conditions, and the samples evaluated. Several compositions demonstrated more than double the compressive strength with a minimal impact upon thermal conductivity, making the foam sufficiently strong for implementation. Phase II will model and evaluate the heat transfer performance of various enhanced strength carbon foam configurations, and refine the strength enhancement, bonding, and machining technologies. A pilot-scale, steam-condenser heat exchanger will be produced and its performance determined by an industry partner. An economic assessment of the carbon-foam heat exchanger fabrication will be performed. Commercial Applications and Other Benefits as described by awardee: Higher efficiency heat transfer systems, fabricated from enhanced strength carbon foam, should reduce fresh water consumption in power plants and industrial chillers. In addition, the reduction in system sizes should increase the acceptance of distributed energy systems such as microturbines and fuel cells, reduce the volume of aerospace heat exchangers and solar radiators, increase the efficiency of electronics cooling systems, and reduce the radiator size in vehicles.