Development of a Scroll Expander for the CO2 Refrigeration Cycle

In this study, a scroll expander was developed to recover the throttling loss in CO2 cycles. In cycles with an intercooler, the expander drives the second-stage compressor using the energy recovered from the expansion process. To carry out this function, a back-to-back scroll mechanism was applied to the expansion and subcompression processes. A prototype of the expander/subcompressor was designed by calculating the gas pressure in the chambers and estimating the gas forces. The prototype was built and tested. According to the experimental results of the prototype device, the subcompressor increased the pressure by 1.30 MPa (188.5 psi), while the pressure drop between the inlet and outlet of the expander was 3.19 Mpa (462.7 psi). Based on the gas state at the expander inlet, the volumetric efficiency was about 104%.