Combustion monitoring in large industrial furnace can be simplified to a radiation heat transfer problem within the enclosed cavity system, and precise quantification of its boundary radiation characteristic is the basis to carry out follow-up studyon the radiation inverse problem, but the coupled problem of wall radiation and media radiation need to be solved. A Monte Carlo priciple was involved to solve the radiation heat transfer equation in the enclosed cavity, and to decouple the shares of wall radiation and media radiation in the boundary detection information. The influence of temperature distribution and radiation properties on the share of wall radiation were discussed, at last the experiment verifies the feasibility of using the radiation information of boundary detection to retrieve the wall source term. This study will provide a reference to the exploration of physical field detection method of wall surface in industrial furnace.

A Printed Circuit Heat Exchanger (PCHE), with straight channels and semi-circle cross section, was fabricated and experimental studies on heat transfer and fluid flow were conducted, during which the flow regime was transition flow, water was working fluid, and flow rate of water was various. The results obtained from correlations of macro circular tubes had obvious deviations from the experimental results. Specifically, the f factor obtained from experiments are larger, and the changes of the overall heat transfer coefficient were more complex with various Reynolds number. The heat transfer and flow correlations in transition zone of PCHE was calibrated within corresponding application ranges. In order to obtain the heat transfer correlations, a numerical method was introduced to obtain one-sided average convective heat transfer coefficients under transition flow. The results showed that the average deviations of the overall heat transfer coefficient obtained from average convective heat transfer coefficients was 8.5% comparing to experimental results, while the maximum deviation reached 17.2%. However, in spite of that, a correlation to predicted the overall heat transfer coefficients through average convective ones still can be obtained, and the deviations comparing with experimental results was within 10%. It is recommended that obtaining one-sided average convective heat transfer coefficient with numerical method is feasible especially when it was transition flow in PCHE.

The exhausted heat losses in the PRC and inefficiency in medium and low heat source applications are significant challenges affecting the application of supercritical carbon dioxide Brayton cycle for renewable energy sources. To achieve efficient utilization, a precooler-free power/cooling combined system with superior heat source adaptability is proposed and analyzed. Integrating with the precooling-heating coupled module and the absorption power/cooling module instead of the PRC, the waste heat from the LTR is completely recovered, moreover, multiple operating modes ensure that the system performance unaffected by ambient temperature and seasonal changes. Parametric studies indicate that the TUR2 inlet temperature, the WHE1 outflow overheat degree, and the hot end temperature difference have significant effects on the Split Ratio, energy outputs, and the coupling relations among modules. Moreover, due to the improvement of irreversibility and the decrease of exergy losses, the three-largest exergy destructions occur in the IHE, the TUR1, and the RET+GEN, which account for 56.1%, 6.9%, and 5.2% respectively. Furthermore, the optimized cases exhibit optimal η_thermal, η_exergy, c_P,total, and W_net of 84.2%, 74.1%, 9.48 dollars/GJ, and 397.4 MW respectively.

Self-recirculation casing treatment can significantly improve the aerodynamic performance of the supercritical carbon dioxide centrifugal impeller in small flow rate region, but the improvement is not obvious near the large flow rate region. Therefore, the coupling effect between the self-recirculation casing treatment and the key parameter of the impeller is considered, and the coupling optimization of the casing treatment geometry and the impeller blade sweep angle is carried out to achieve a comprehensive improvement of the impeller performance. After the coupling optimization, the efficiency of the impeller is increased by 3.51%, 2.60% and 4.43% respectively under the large flow rate condition, the design condition and the small flow rate condition. The mechanisms of the coupling optimization for stability and efficiency enhancements are as follows. Under the large flow rate condition, the flow incidence angle of impeller is improved, the subcritical zone inside the impeller is reduced, then the condensation is suppressed and the flow capacity of the impeller is improved. Under the design condition, the recirculation flow of casing treatment is increased, more low-energy fluid near the shroud tip is removed, and the flow field structure downstream of the impeller is improved. Under the small flow rate condition, the internal blockage of the impeller is effectively reduced, the flow stability of the impeller is enhanced, and the mixing loss caused by the recirculation flow is improved, so the impeller efficiency is improved.

For enhancing the film stiffness of supercritical CO₂ (S-CO₂) hydrodynamic dry gas seal and reducing the additional power consumption due to the installation of heater in the seal inlet line, a new structure of S-CO₂ hydrostatic-dynamic dry gas seal with the heating of the ring body at the back of the static ring is proposed. Based on the conjugate heat transfer model, the pressure and temperature distribution of dry gas seal were simulated utilizing commercial software Fluent. The steady-state performance and flow field distribution of S-CO₂ hydrodynamic seal, hydrostatic seal and hydrostatic-dynamic seal were compared and analyzed, and the flow and heat transfer characteristics and power consumption of S-CO₂ hydrostatic-dynamic dry gas seals under different heating modes and heat temperatures were discussed. The results show that the film stiffness of the hydrostatic-dynamic dry gas seal is improved more than doubled compared with the hydrodynamic dry gas seal, while the leakage rate increased significantly by 35% at the same time. The power consumption under ring heating mode is 44% lower than that under direct gas heating mode, leading to better operating economy. It provides a new idea for the structure design and auxiliary system improvement of compressor dry gas seal in S-CO₂ power generation system.

Based on a DC microgrid system coupled with photovoltaic power generation, lithium battery-supercapacitor hybrid energy storage, electrolysistank and hydrogen-burning micro gas turbine, a power allocation strategy that integrates the lithium battery state of charge (SOC) and hydrogen storage tank hydrogen state (LOH) is proposed. A PV-electrolysistank-micro gas turbine DC microgrid system model is constructed. The allocation logic of the power judgment module of the coordination control layer is designed, and three operation modes are given when the residual power exists in the DC network. The power allocation strategy is simulated and verified using MATLAB/Simulink software. The simulation results show that the power allocation strategy of DC microgrid system based on hydrogen energy storage can make the lithium battery charge state gradually converge to a reasonable storage interval and can improve the service life of lithium battery.

Supercritical carbon dioxide cycle has many advantages such as small turbine size, small compressor power consumption and high cycle efficiency. In order to explore the cycle configuration with the highest power generation efficiency after the power generation system of supercritical carbon dioxide cycle coupled gas turbine, four cycle layouts were proposed. The main parameters of the circulating system were optimized by genetic algorithm with the maximum circulating efficiency as the optimization objective. Among the four schemes, the gas turbine/two-turbine supercritical carbon dioxide combined cycle system has the highest cycle efficiency, which is 44.87%. And the dynamic system analysis of the scheme, with the bottom cycle input heat load as the disturbance variable, explore the dynamic response of the system after the step reduction from full load to 90% load, 80% load and 70% load respectively. The results show that the response time of parameters near the flue gas heat exchanger is faster and the response time is longer when the shadow of thermal inertia is farther away from the flue gas heat exchanger in the working medium flow. At the same position, the response time of pressure is slightly longer than that of temperature, and the drop range of parameters near the high-temperature turbine is greater than that of the low-temperature turbine.

A comparative analysis between simulation and test with roughness is carried out for a supercritical carbon dioxide (S-CO₂) axial turbine with different operating conditions, focusing on the roughness impact of the turbine performance. The results show that the numerical calculation method of wall roughness is able to assess the performance of the turbine at different load conditions accurately. Compared with test result, the maximum efficiency error is 1.82 percentage point. Wall roughness degrades the overall performance of the turbine, with a maximum efficiency drop of 2.8 percentage point at Ra1.6 roughness level during the five working condition, and the turbine stage roughness has a more obvious effect on the turbine performance. In addition, the more severe of wall roughness, the greater reduction of turbine efficiency. In non-design operating conditions, the efficiency drops by 11.6 percentage point at Ra6.3 roughness level. The wall roughness exacerbates flow separation of pressure surface, causing greater friction losses and serious affecting of turbine performance. The research can provide technical support for the design and performance simulation of S-CO₂ axial turbines.

A new combined cooling, heating and power system is proposed based on solar photovoltaic, wind power, ground-source heat pump and energy storage unit (WSSH-CCHP) to improve the efficient utilization of renewable energy resources and the entire system energy efficiency. The comprehensive evaluation indexes are developed by using the analytic hierarchy process to account for the system performance of energy efficiency, economy and environment. The mixed integer linear programming (MILP) algorithm is employed to perform the optimization on the selection of equipment types, capacity allocation and system operation stratagem. A case study on an energy center in Jinan city is conducted to explore the optimal performance and operation characteristics of WSSH-CCHP. The obtained results indicate that the proposed system comprehensive performance is much better than the separate production system, which provide useful information for the development of CCHP system with wind-solar-storage and heat pump and the study on its integrated optimization and operation characteristics.

The static corrosion behavior of 316L stainless steel and 347 stainless steel at 500 ℃ in Solar Salt (60%NaNO₃ + 40%KNO₃) was investigated via static corrosion test. Corrosion kinetic curves of 316L stainless steel and 347 stainless steel in molten salts at 500 ℃ were obtained through measuring the weight changes of the specimens at each time intervals. XRD and ICP-MS were employed to characterize the phase and component of molten nitrate salts; XRD, SEM/EDS were used to characterize the morphology, composition and microstructure of the corrosion products on the surface and the cross section of corroded specimens. Finally, combining the changes of molten salt and stainless steels, the corrosion mechanism of 316L stainless steel and 347 stainless steel in Solar Salt was discussed respectively. Results showed that the corrosion behavior of 347 SS in Solar Salt at 500 ℃ was characterized by mass gain. As time goes on, the trend of 316L stainless steel increased first and then decreased, while the trend of 347 stainless steel was on the increase. SEM/EDS showed that 347 stainless steel was more likely to be oxidized, while the chromium element in 347 was prone to dissolve, comparing to 316L stainless steel is better stability in Solar Salt, that is, 316L stainless steel is more corrosion resistant.