Supercritical carbon dioxide (sCO2) Brayton cycles hold great promise as they can achieve high efficiencies — in excess of 50% — even at relatively moderate temperatures of 700–800 K. However, this high performance is contingent upon high-effectiveness recuperating and heat rejection heat exchangers within the cycle. A great deal of work has gone into development of these heat exchangers as they must operate not only at elevated temperatures and very high pressures (20–30 MPa), but they must also be compact, low-cost, and long-life components in order to fully leverage the benefits of the sCO2 power cycle.
This paper discusses the mechanical design and qualification for a novel plate-fin compact heat exchanger designed for sCO2 cycle recuperators and waste heat rejection heat exchangers, as well as direct sCO2 solar absorber applications. The architecture may furthermore be extended to other very high pressure heat exchanger applications such as pipeline natural gas and transcritical cooling cycles. The basic heat exchanger construction is described, with attention given to those details which have a direct impact on the durability of the unit. Modeling and analysis of various mechanical failure modes — including burst strength, creep, and fatigue — are discussed. The design and construction of test sections, test rigs, and testing procedures are described, along with the test results that demonstrate that the tested design has an operating life well in excess of the 100,000 cycles/90,000 hour targets. Finally, the application of these findings to a set of design tools for future units is demonstrated.
Geometry and orientation effects in non-uniformly heated microchannel heat exchangers using supercritical carbon dioxide
