Numerical modeling based on volume of fluid (VOF) method is conducted and experimentally validated for the two-phase flow and heat transfer in a loop thermosyphon for wide filling ratios. The results show that, under the 87% filling ratio, the loop is dominated by bubbly flow and sub-cooled flow boiling, with sensible heat transfer enhanced by bubble pumping effect, which is beneficial for wobbling, tilting, and mobile applications to avoid evaporator dry-out. Under the 64% filling ratio, geyser boiling instability occurs. A train of bubble-liquid intermittently passes the loop summit under the collaboration of buoyancy, gravity, viscous, and surface tension forces, causing intense flow and temperature oscillations, enhancing both latent and sensible heat transfer. Under the 38% filling ratio, the characteristic flow patterns are churn flow, mist flow, and film condensing, leading to highly efficient latent heat transfer.

The centrifugal compressor is the core component of supercritical CO₂ power cycle, and its performance and operation stability are research hotspots. However, there are few experimental studies, especially for compressors used in Mwe-scale power cycles. In this paper, based on a 1 MWe supercritical CO₂ power cycle, a single-stage centrifugal supercritical CO₂ compressor is designed with speed of 40,000 RPM, a pressure ratio of 2.5 and a mass flow of 16.3 kg/s. In order to carry out the compressor test, a general experimental platform for MWe sCO₂ compressors is built. In the test, the mass flow range is 13.5~18 kg/s and the maximum experimental pressure ratio is close to 2.0. The performance curve of the compressor of 31,000 ± 1000 RPM is obtained, and the historical curve of the experiment is given. Then, the experimental curve is compared with the design curve using a dimensionless method. The isentropic head coefficient of the experimental curve is lower than the design value, and the experimental curves shift towards the boundary of small flow coefficient. Finally, the influence of compressor inlet condensation on compressor performance and the change of operating boundary is preliminarily explained.

A hybrid cooling system consisting of both a dry section and wet section is proposed in this paper as a means to conserving energy and water by combining the benefits of both dry and wet cooling modes. A new thermodynamic coupling characteristics computing model was established to identify the best combination of dry and wet cooling subsystems in the hybrid tower throughout year-round operation based on its air thermodynamic state under the “no plume” principle. A hybrid cooling tower in Inner Mongolia, China, consisting of an elliptical tube heat exchanger with rectangular fins and counter-flow wet packing, was designed as an example under the no plume principle. The minimum number of heat exchanger units in service and the corresponding thermodynamic operating parameters were obtained under a year-round operation. The tower exhibited notable advantages in regards to water conservation compared to the traditional evaporative cooling tower at an estimated yearly savings of 3.74 × 10⁷ kg water.

An actual one-dimensional(1-D) computation method for a labyrinth seal is proposed. Relevant computation hypotheses for the 1-D method are analyzed and the specificity of internal flow in an SCO₂ (supercritical CO₂) labyrinth seal is explored in advance. Then, the experimental correlation discharge coefficient and the residual kinetic energy coefficient used in SCO₂ labyrinth seals are proposed. In addition, the speed of sound in two-phase flow is corrected in the 1-D method. All recent experimental results of the SCO₂ labyrinth seal are sorted out and the latest experimental results of a stepped-staggered labyrinth seal are proposed to verify the accuracy and applicability of the 1-D method. Finally, the sealing efficiency of the SCO₂ labyrinth seals are analyzed using the 1-D method.