Commissioning and preliminary testing of the NextORC facility

Turboexpanders are recommended for medium- and low-temperature organic Rankine cycle applications as they can handle large enthalpy drops thus achieving high pressure ratio across a single stage with high efficiency but they have a low degree of reaction where most of the enthalpy rise occurs in the stator section. The requirement for compactness and operational flexibility intersects with challenges posed by a low compressibility factor, and non-ideal gas effects. Several numerical models have been developed to investigate the non-ideal effects that occur, however, experimental data is still insufficient. Within this paper, progress in the development of the NextORC experimental facility, which includes a converging-diverging nozzle representative of a nozzle guide vane within a turbo-expander, is presented. The test facility is designed to provide an enhanced understanding of supersonic flow dynamics through the nozzle with outlet Mach number of 2. This paper outlines the setup, functionality, and initial experiments conducted at the test facility which is designed to operate at pressures up to 15 bar, temperatures reaching 120 °C, and compressibility factor down to 0.75. The results from initial commissioning tests are detailed, which demonstrate that steady-state conditions can be achieved for seven different inlet total conditions with pressures from 7 to 13 bar. Although supersonic flows were not established, the subsonic flow pressure distributions were recorded during the commissioning phase.