Development of advanced energy transmission fluids

The DHC system being studied by the U.S. Department of Energy are frequently comprised of long runs of piping (sometimes miles in length) which convey the working fluid (in the heating or cooling mode) between the heat sources and sinks of the system. Furthermore, these systems often operate with small temperature differences, so that large volumes of fluid must be pumped and large heat exchangers must be used to satisfy load demands. If the pressure drop or frictional losses associated with pumping these fluids and hence the pumping power can be reduced significantly and the heat transfer occurring at the heat exchangers and the energy per pound of circulating fluid can be increased, cost reductions in the operation of these systems can be realized. These reductions can also manifest themselves in the form of upfront capital equipment cost reductions through the use of smaller pipes, pumps, heat exchangers and storage tanks when new DHC system designs employing the improved energy transmission fluids are utilized. These fluids also hold promise of improving the performance of existing systems (i.e., retrofit). The efforts to develop improved transmission fluids are based on an ANL feasibility study connected in FY-85 which highlighted two concepts and on earlier ANL studies associated with the use of phase change slurries as the working fluid in thermal systems in general