High-voltage electric heating for large-scale molten salt thermal energy storage is fundamentally constrained by the trade-off between dielectric strength and heat transfer capability in conventional heating tubes. To address this challenge, a metal powder-ceramic electric heating tube is proposed and systematically investigated. The electrical characteristics of the metal powder are first analyzed, revealing that its resistance is strongly dependent on particle size and powder type, with a wide resistance range. Due to the oxide layers between particles, significant contact resistance exists, and the intrinsic resistance can be effectively manifested only under high radial voltage breakdown. Experimental results demonstrate the feasibility of the proposed heating tube, showing a uniform temperature distribution and no observable local hotspots under steady-state conditions. Compared with conventional electric heating tubes, the ceramic tube exhibits superior insulation and thermal conductivity. At 5 kV and room temperature, the leakage current of the ceramic heating tube is only 13.8
With the rapid development of renewable energy in recent decades, China’s power system faces dual challenges of carbon emission reduction and grid stability. As the largest CO2 emission source and the most important flexibility provider supporting grid stability, coal-fired power plants will have to adopt CO2 capture units and simultaneously operate at partial loads frequently in the future. This paper simulates the characteristics and performance of coal-fired power plants equipped with post-combustion capture units under partial load conditions via EBSILON and Aspen Plus. This research reveals the mechanism behind the partial load operation of CO2 capture units. The trade-off between the flue gas’s decarbonization duty and the solvent’s absorption capability in the absorption process, and the correlation between the regeneration duty and the heat supply to the reboiler in the desorption process, are the two crucial relationships deciding the partial load performance of the CO2 capture unit. Moreover, the combination of the liquid-to-gas ratio (L/G) and the heat supply to the reboiler will affect this relationship. As the electrical load decreases, the L/G and the heat supply should be correspondingly reduced. And if the magnitude of this reduction is insufficient, it may lead to “under-absorption” within the absorption column or “over-desorption” in the desorption column, which can be explained by deviations in lean and rich loadings of the solvent. Correspondingly, an operating rule can be obtained, which is to maintain both lean and rich solvent loadings at their design values, thereby ensuring that the absolute value and position of the effective loading remain unchanged. A shortcut calculation method for solvent circulation flow rate and heat supply under different power loads is given to quantify the rule. The case results indicate that, over the 30
Shrouded centrifugal compressors have advantages in effectively suppressing tip leakage within the impeller and hence have received much attention in the research area of compressor components in the sCO2 Brayton cycle. However, the related research mainly focused on numerical simulation, with little experimental research available. In this paper, experimental tests are carried out for an in-house designed shrouded sCO2 centrifugal compressor with a highly integrated electrical motor. The design idea of the compressor-motor integrated equipment, the construction of the experimental platform, and the compressor aerodynamic performance test methods are elaborated in detail. Based on these works, the aerodynamic performance experiment of a 100 kW-class shrouded sCO2 centrifugal compressor was completed. The test results provide experimental data that can support the research and development of the shrouded sCO2 centrifugal compressor.
Although the supercritical carbon dioxide (SCO2) power cycle can efficiently utilize nuclear energy, a large amount of waste heat remains unused in its gas cooler. To address this issue, this paper proposes a novel multi-generation system that integrates the SCO2 cycle, Kalina cycle, absorption refrigeration cycle, and multi-stage flash desalination to achieve synergistic production of electricity, cooling, and fresh water, thereby promoting cascade utilization of nuclear energy. A comprehensive evaluation model is established based on energy, exergy, economic, and environmental dimensions. Key parameters are identified through sensitivity analysis, and multi-objective optimization is employed to balance thermodynamic performance and environmental impact. Sensitivity analysis shows that the SCO2 turbine inlet temperature, split ratio, compressor inlet temperature, and the ammonia concentration in the Kalina cycle have the most significant influence on the overall system performance. Under the design condition, the system achieves an energy efficiency of 52.76 EM_ CO_2 ) of 119.94×104 t. Among the four optimization schemes, the first two mainly reduce EM_ CO_2 ; Scheme 3 achieves a significant reduction in LCOE (2.30 EM_ CO_2 ; Scheme 4 brings comprehensive improvements in thermo-economic performance. Overall, the proposed system shows promising potential for sustainable and environmentally friendly energy utilization.
Marine vapor-compression air-conditioning systems depend on liquid refrigerants and may experience leakage, oil-return problems, and severe efficiency penalties at high heat-rejection temperatures. This study proposes a refrigerant-free open-cycle reverse Brayton cycle (ORBC) for ship cabins that combines a high-pressure dehumidifying cooler (DHC), recuperation, controllable bypass mixing, alternative fresh-air routing, and spray-assisted intake conditioning. A steady-state moist-air model, expressed per unit mass of dry air, is used for eight configurations. The term optimization refers to a constrained grid-based parametric search rather than a global numerical optimizer. The implementation was checked against analytical ideal-gas relations: the compressor- and expander-outlet temperatures differed by only 0.2°C and 0.1°C, respectively, and the predicted minimum pressure ratio for dehumidification at a 40°C DHC outlet was 3.88. The baseline sensible-cooling case at a total compressor/expander pressure ratio (Rc) of 1.4 gives a coefficient of performance (COP) of 0.717; dehumidification at 40°C requires Rc≥3.88. For the simple cycle, the maximum COP occurs at Rc≈1.4–1.8, depending on ambient temperature. Spray conditioning increases representative COP from about 1.58 to 1.98, and recuperation raises it further to about 2.28. Under the combined high-load cases, COP increases from 3.526 to 3.669. Direct cabin delivery of a larger fraction of outdoor air reduces the compressor penalty. The results define feasible pressure ratio, heat rejection temperature, turbomachinery efficiency, and ventilation control ranges for refrigerant-free marine HVAC.
