Around the globe, there has been a growing interest in using sCO₂ power cycles to recover waste heat from various heat sources. This paper will focus on the case of a supercritical CO₂ compander designed, built, tested, and supplied by the authors’ company.

The compander is applied in a Brayton cycle to recover waste heat from a gas engine providing the output power to a generator connected to a gear box via a coupling. To design the heatrecovery cycle with the highest possible efficiency, a lowoperation temperature at the compressor inlet was required. At the given pressure, this leads to a subcooled fluid.

With support from the client and additional internal studies, it was confirmed that this suction condition at the compressor inlet will lead to the lowest power consumption on the compression side. This, in turn, results in the highest cycle efficiency, in addition to a small machinery footprint. Therefore, the solution fits into marine applications or other projects which face space constraints.

During the compression process, a phase change of the CO₂ from the subcooled to the supercritical state occurs with a low temperature and density change. CFD simulations of the compression process were performed in advance, considering the real fluid behavior near the critical point.

This paper presents the test results and a comparison with the CFD analysis.