Heat Exchanger Testing for Closed, Brayton Cycles Using Supercritical CO2 as the Working Fluid

by Patrick M. Fourspring & Joseph P. Nehrbauer
Bechtel Marine Propulsion Corporation / Knolls Atomic Power Laboratory

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Heat exchangers are an enabling technology for efficient power generation with a closed, recuperated Brayton cycle using supercritical CO2 as the working fluid. The heat exchangers impact the overall system efficiency (operating cost) and size (installation cost). The heat exchanger designs must balance between heat exchanger effectiveness and pressure drop to achieve the desired tradeoff between system efficiency and system size. This tradeoff between system efficiency and system size will vary for a given application of the energy conversion system.

To begin to explore various compact heat exchanger options for use in such a cycle, a shell-and-tube heat exchanger using low-finned tubes with supercritical CO2 on the shell side and water on the tube side was tested.

The shell-and-tube heat exchanger using lowfinned tubes on the shell side successfully cooled supercritical CO2 using water. For the specified design conditions of this heat exchanger, the additional area provided by the low-finned tubes on the shell side was effective. Therefore, the use of low-finned tube can reduce the size of the heat exchanger. Finally, the design methods, commonly used for analyzing shell-and-tube heat exchanger, are applicable with the use of supercritical CO2 on the shell side.