为提升热电联产系统中蒸汽引射器性能,对引射器不同结构参数进行优化研究.以某典型2×350 MW热电联产机组为例,确定引射器设计参数并建立数值模型,采用单参数结构优化分析混合腔直径、喉嘴距和入口倾角等结构参数对引射性能的影响,通过正交试验进行多参数结构优化,得到各结构的敏感性分析结果和引射性能相对最优的结构组合,在此基础上分析热电联产机组变工况条件下引射器适用性及运行策略.结果表明:多参数结构优化可进一步提升引射系数至0.945,较初始设计引射器增幅达18.7％,引射性能明显提升;热电联产机组变工况下引射器动力蒸汽压力和出口背压需控制在合理范围以维持较高引射系数,实际运行中通过增大吸入蒸汽压力提升引射器性能的效果不明显.

为满足空气源热泵冬季集中供热的需求,该文采用新型工质将空气源热泵的制热温度提高至90℃以上.首先建立高温空气源热泵的数学模型并对该系统进行理论计算,进而搭建高温空气源热泵试验台,分别在环境温度为0、5、10℃时对模拟结果进行实验验证,当热水进口温度为80℃时,系统实际COP分别较理论结果低5.9%、5.3%和1.7%.该空气源热泵相比现有技术提升制热温度40℃以上,因此具有较好的市场应用前景和推广意义.

The energy utilization efficiency and the flexibility enhancement of the combined heat and power (CHP) plant can promote both decarbonization and renewable energy integration. In this research, we proposed a novel CHP cascade heating system by integrating it with the electric heat pump (EHP). The integration of EHP can consume power generation load and bear part of the heat load, which improves the flexible peak regulation ability of the novel heating system. Based on the detailed simulation model of a typical 2 x 300 MW subcritical CHP plant, the reference and novel systems are compared in thermodynamic and peak-load regulation performance to present the benefits of the EHP design. The results showed that, under the design condition, the heating capacity in the novel system had an increment of 6.02 % to that in the reference system, bringing out a 4.51 % improvement in electricity generation efficiency. Correspondingly, the average standard coal consumption rate for generating of the novel system reduced by 9.53 g/kWh. Under the same heat load, the peak shaving lower limit of the novel system is 59 MW lower than the reference system on average, and the load rate is reduced by 10 % of the rated power generation capacity on average. In the case study, under the typical day operation of the regional electric -thermal integrated energy system, the wind power curtailment ratio of the novel system is 10.75 % lower than that of the reference system. Meanwhile, with further waste heat recovery, the daily standard coal consumption of the novel system can be saved by 231.81 t, equivalent to a reduction of 607.34 t of CO2 emissions.

Increasing the share of renewable energy in the future electricity market requires measures to maintain the stability of the grid, owing to the volatility and intermittency of renewable energy. For a combined heat and power (CHP) plant, molten salt thermal energy storage (TES) can be added to improve the flexibility to meet the needs of peak shaving. This paper proposed a novel cascade reheat steam extraction system to adjust the elec-trical load by using EBSILON software applied to thermal simulation and thermal analysis. A 350 MW super-critical CHP plant was used as an example to analyze the thermal and peak shaving performance under variable operating conditions. Meanwhile, through the static simulation, the change in the load and the efficiency of TES can be calculated during the charging and discharging cycle. The results show that the efficiency of TES is 40-51 %. With an increase in the load, the efficiency of TES is reduced, and the exergy loss range is from 4 MW to 12.4 MW mainly due to the throttling process and the molten salt heat transfer process. Moreover, the thermal ef-ficiency and exergy efficiency of the novel system are higher than those of the traditional CHP plant below 60 % turbine heat acceptance, so it is relatively economical to run for peak shaving under low loads. Finally, depending on the corresponding operating strategy, a reduction of the minimum load by up to 1 % of the rated output electrical load during charging and an increase of the maximum load by up to 2 % of the rated output electrical load during discharging are possible. Overall, the proposed system provides a feasible method for the flexibilization of CHP plants alongside new renewable systems.

Complex implicit expressions and many intermediate parameters are not conducive to the application of entropy generation optimization to the performance of thermal and energy systems from component and system perspectives. In this paper, we derived matrix heat transport equations of three primary heat exchanger networks according to the heat current method. Based on the matrix equations, we established the matrixed model of a typical heat supply system and obtained the corresponding matrix equation reflecting the power topology structure of the system. Moreover, we derived and reconstructed a single heat exchanger's entropy generation rate expression based on the standard thermal resistance, which was only related to inlet temperatures, structural parameters, and operating parameters. The total system entropy generation rate was then derived and minimized by the Lagrange multiplier method. The optimization results provided the optimal distribution of the mass flow rate of each fluid. Besides, the influence of the heat transfer rate and outer loop inlet temperature on the optimization results revealed that local equipment parameters and conditions could affect the system's minimum entropy generation. The total entropy generation rate decreases by 17.5% when the outer loop inlet temperature was increased from 274 to 280 K. In conclusion, the matrixed modeling and entropy generation analysis are feasible for thermal system modeling and optimization.

Under the background of auxiliary heat supply of ejector, in order to study the characteristics of ejector under variable working conditions, the calculation methods of ejector at home and abroad are investigated, the ejector calculation model is established and coupled with the high back pressure unit. Moreover, the effects of working steam, ejected steam, ejector back pressure, and ejector opening on the performance of the ejector under variable working conditions are obtained. The results show that, when the working fluid pressure of the ejector changes from 0.25 MPa to 0.45 MPa, the mass flow of the working fluid first increases and then decreases, and the ejector has the best performance at the design working steam pressure. The critical back pressure increases with the steam injection pressure. The pressure of the mixed fluid after injection will not only affect the work of the ejector but also the work of the condenser. Compared with the back pumping unit, the minimum cooling flow of the low pressure cylinder of the high back pressure coupling injector unit can be reduced by 140 t/h and the power supply range can be increased by 43 MW.

大型汽轮机组采用高背压方式供热可以充分利用乏汽余热,提高燃料利用效率,已经有越来越多火电厂进行高背压供热改造.为确保高背压机组运行经济性,针对某电厂330 MW高背压热电联产机组建立Ebsi-lon模型并进行全工况模拟,根据低压缸最小冷却流量确定了机组的理论负荷区间,针对其实际热负荷条件建立了热网数学模型,结合热网供回水温度分析其在不同环境温度条件下的背压运行方式和电负荷范围,确定了优化背压后机组的实际运行边界;并针对热网回水偏离理想值时的经济性进行分析,确定了机组高背压投运策略.结果表明:机组采用高背压乏汽余热供热方式可以有效提高供热能力约80 MW,但是其环境温度适应性较差,环境温度较高时,采用抽背方式供热的经济性要明显优于抽凝方式,采用优化后的背压运行方式最高可降低标准发电煤耗约34 g/kW·h;另外,热网回水温度严重影响高背压机组的经济性,在不同的供水温度下,其高背压投运的边界回水温度也相应改变.

Flexibility enhancement of coal-fired combined heat and power units is an essential approach for improving the wind power accommodation and a significant low-carbon way to achieve clean urban heating. To consume excess wind power, this paper proposed a novel combined heat and power system integrated with the various flexible technologies. The EBSILON software was applied for modeling the proposed thermal systems and analyzing the thermal performance under different operating conditions. On this basis, the mechanism of their heating compensation and wind power consumption was revealed and the indicator, the heating compensation capacity, was presented considering from both peak shaving and coal-savings perspectives. Compared with the conventional system, the wind power accommodation rate of the novel system had a maximum increment of 31.7% and the standard coal consumption had a maximum reduction of 14.3%. Meanwhile, by adding dynamic payback period and internal rate of return, the techno-economic performances were more reasonable and precise. The results showed that the heating compensation capacities of absorption heat pumps, low-pressure cylinder of turbine removal and thermal energy storage with extracted steam from turbine are 0.29 t/MWh, 0.26 t/MWh, and 0.25 t/MWh, respectively, which are better than that of other technologies. The net annual revenue of thermal energy storage system could reach 3.87 M$, 0.57 and 0.37 M$ higher than that of low-pressure cylinder of turbine removal and absorption heat pumps, respectively. It can be concluded that thermal energy storage can be the best to balance the peak shaving demand and techno-economic performance. In all, the proposed systems provided a promising method for the flexibilization of coal-fired combined heat and power units alongside new renewable systems.

The multi-scale, multi-component, multi-process, and multi-parameter characteristics increase intermediate variables and complexity of modeling and analysis of solid oxide fuel cell cogeneration systems. This paper applied the standard thermal resistance for constructing the heat current model to analyze the overall heat transfer performance of the external heat exchangers. On this basis, the research introduced the equivalent electric circuit for presenting the internal electrochemical process and then proposed the overall cross-scale modeling of the solid oxide fuel cell cogeneration system from the internal heat and mass transfer and electrochemical processes to the various external heat exchangers. Moreover, considering the internal and external multi-processes, the system's overall constraints were derived. The simulation results show that the total energy utilization rate of the solid oxide fuel cell cogeneration system is 79.12 %. Besides, the influences of water-to-carbon ratio, excess air coefficient, thermal conductances of each heat exchanger, and ambient temperature on the system performance were developed. The optimal operation parameters are given for improving the maximum net power generation of the system. Finally, the proposed cross-scale modeling method is feasible and convenient for analyzing and improving the solid oxide fuel cell cogeneration system.

In directly irradiated solid particle solar receivers (SPSRs), the performance of the heat transfer and thermal energy storage medium is a hot research topic. Herein, the thermophysical properties, thermal stability, surface morphology, element compositions and absorptivities of 16 kinds of candidate particles are studied and evaluated. Considering that the performance of homogenous particles as heat transfer medium (HTM) is not ideal, a novel concept of multi-component mixed particle systems with different mass ratios is proposed for the first time. To explore the effect of the particle systems on the receiver performance, a quartz tube falling receiver numerical model is applied. The results indicate that the absorption performance of the particle systems have increased with the addition of dark colored materials, but this effect becomes less obvious with the amount of additives, especially for quartz sand-silicon carbide particle systems. A quartz sand-silicon carbide particle system with a mass ratio of 7:3 may be the optimal choice for achieving both high receiver outlet temperature and low mass flow rate. Compared to the pure silicon carbide particle system, it has a 64.47% reduction in the material cost with only a 4.11% reduction in receiver thermal efficiency. This work provides ideas for the design of multi-component particle systems, which may open a significant development for next-generation concentrated solar power station.

The intelligent heating system can improve heating efficiency and promote renewable energy accommodation that positively affects the realization of the dual-carbon strategy. This paper dynamically modeled the key components based on the standardized thermal resistance defined by the inlet temperature difference and constructed the overall dynamic heat current model of the heating system from the heat source to the user. The dynamic model simultaneously and comprehensively reflects the heat transfer, storage, and delay characteristics of the heat exchanger, piping, and building. On this basis, an iterative method is proposed and used to develop various heating strategies for the hourly quality regulation of the primary heating network. The proposed user-following heating strategy has the greatest energy-saving potential of 25.27% compared with the all-day heating strategy. Moreover, based on the user-following heating strategy, we proposed five different heating strategies, namely all-day constant heating type, inverted triangle type, stair-step type, trapezoid type, and parabolic type, to achieve energy-saving operation of the heating system for the actual application. The trapezoid type has the highest energy-saving ratio of 9.41% compared to the all-day constant heating type. In all, this standardized thermal resistance-based dynamic modeling method and the proposed heating strategy provide a new theoretical basis and solutions for the intelligent heating system.

为兼顾供热节能和负荷调节灵活性,构建低品位余热与抽汽耦合的高效灵活供热系统,确定评价供热和调峰的性能指标,并利用Ebsilon软件进行热力建模;针对案例地区研究系统设计工况和变工况热力性能,得到不同供热负荷下的电负荷可调范围,研究同时满足热、电需求下的系统灵活运行调控策略及能耗特性.结果表明:系统通过能质匹配,降低比当量电耗,实现了低能耗供热,设计工况供热煤耗率为13.3 kg/GJ;调峰容量比最大为48.1％,比抽背模式提高24.3％;电热负荷变化时,背-抽-切方式间切换,供热煤耗率区间为8～14.7 kg/GJ;供热煤耗率随电负荷率降低而增加;系统充分发挥低品位余热供热的节能优势,且在一定范围内热电解耦,兼顾了"节能"与"灵活"运行.

High-efficiency heating in the combined heat and power (CHP) system is considered a promising strategy for energy conservation and emission reduction with the explosion of the heating demands. To recover the excessive waste heat from the exhaust steam and reduce the exergy destruction of the heating supply, we proposed a novel CHP cascade heating system integrated with a steam ejector and carried out research about ejector comparative designs and optimizations. Three methods were applied for the ejector designs in a CHP system and the software Fluent was used for numerical simulation to analyze and compare the performance and internal flow characteristics of the ejector. The ejector designed with the optimized thermodynamic method yielded the largest heating capacity and the highest system heating exergy efficiency of 212 MW and 71.0%, thus offering greater strengths for designing ejectors in the CHP cascade heating systems. On this basis, the thermodynamic performance of the designed ejector was further optimized by adjusting the structure of the mixing chamber based on the exergy analysis. The ejector entrainment ratio maximally increased by 11.4% and 6.4% through optimizing the inlet angle and the length of the contraction section of the mixing chamber. Compared with the existing ejector in the CHP heating system, the entrainment ratio of the designed ejector had a significant increment of 24.9% with a higher pressure lift ratio. Meanwhile, the heating capacity of the designed ejector and system heating exergy efficiency improved by 19 MW and 6.1%, respectively. This work provided an applicable method for the ejector designs and optimizations in a CHP system.

To improve the utilization rate of industrial waste heat, a novel cogeneration waste heat recovery heating system coupled with a steam ejector was proposed. This model allowed part of the low-temperature exhaust steam to be injected into the extraction steam and used as an intermediate heat source to cascade heating water in the heating network. Considering the energy matching characteristics of the steam ejector, taking a 350 MW cogeneration unit as a case, the operation parameters of the ejector were determined through variable calculated working conditions and the cascade heating system integration was completed. Based on this simulation, the thermodynamic system model was established and the research on the thermodynamic performances and applicability of variable working conditions was analyzed. Results show that compared with the case system, the new system has acquired an extra 12.15% of exhaust steam utilization rate under designed heating condition, an increase of 4.64% in the average power generation thermal efficiency, and a reduction of 8.50 g/（kW·h） in the standard coal consumption rate. The flexibility of load regulation is also improved, when the heating load rate reaches 80%, the peak capacity ratio of the new system can be increased to 27.26%, which is 5.78% higher than that of the case system.

Pumped thermal electricity storage (PTES) is suitable for large-scale energy storage applications because of its low cost and no geographical constraints. In this study, the performance of PTES system for adjusting the net power output of the heat engine cycle to meet the load demand variation, is investigated. Based on the off-design condition models of turbomachinery and heat exchangers, the heat engine cycle dynamic model of a 5 MW PTES system is established. The disturbance simulation of the user-side load is carried out, and the dynamic response results are obtained. The inventory control strategy of working fluid is proposed to control the net power output to follow the variations of the load demand. The traditional PI controller is used in the two control processes of 50% ramp-down in load demand and a typical day load demand in Zhangbei District of north China. The results indicate that the net power output of the heat engine cycle can follow the variation of load demand in time. With the inventory control strategy, the heat engine cycle mode of PTES system can adjust the net power output to meet changes in load demand.

天然气锅炉排烟温度较高,烟气中含有较多的水蒸气潜热,具有显著的热量回收价值,目前常采用新型工质电动热泵回收天然气烟气余热加热热网回水,助力"双碳"目标的实现.为提升电动热泵的循环性能系数,研究不同工况下新型工质电动热泵适配混合工质的性能,对机组运行中R134a+R245fa,R152a+R245fa,R227ea+R245fa,R134a+R142b,R152a+R142b,R227ea+R142b共6种混合工质的循环性能进行计算分析.针对锅炉房实际运行参数,对比冷凝器热水进出口温度为50/65℃,蒸发器冷水进出口温度为40/35℃及40/30℃工况下各混合工质的热力学性能,得出在该工况下R134a+R245fa(摩尔分数比为0.41∶0.59)为较佳工质.采用所筛选工质对烟气余热回收排烟温度进行优化,分析了不同排烟温度的经济性,对比余热回收收益及电动热泵运行成本,揭示了烟气余热回收最优化温度变化规律,指导余热回收系统设计与应用.

Aiming at the technical problem of limited temperature range in the application of conventional heat pump in the field of industrial waste heat utilization，this paper studies the production of about 130 ℃ hot water or steam by a compression-absorption coupled heat pump systems under the condition of large temperature rise. In this paper，the operation principle of coupled heat pump cycle is introduced，and the complete thermodynamic model of coupled heat pump is constructed. Through the optimization function calculation of EES software，it is found that the lower the absorption side pressure is，the better the cycle COP is. At the same time， under the constraint conditions that the temperature of concentrated solution at the outlet of solution heat exchangers is 10℃higher than the crystallization temperature and the range of solution steam discharge is 5.0%-5.5%，taking an industrial waste heat recovery condition as the design condition，the results show that the inlet and outlet temperature of waste heat hot water is 90/75℃，the flow rate of residual hot water is 30 kg/s，the inlet and outlet temperature of high temperature hot water is 100/125℃，the optimal pressure values of absorption and generation side are 40 kPa and 2.2 kPa respectively，and the COP of the corresponding coupled heat pump is 9.8. In the same way，the cycle performance of the system with different outlet temperature of waste heat hot water and high temperature hot water outlet is analyzed，and it is verified that the cycle still has good virtual performance coefficient at high heating temperature.

The pumped thermal electricity storage (PTES) based on reversible Brayton cycle can effectively absorb the instability and periodic fluctuations of renewable energy. The dynamic model of heat pump cycle in 5 MW PTES system is established and the disturbance characteristics of the electric power input are obtained. The results indicate that the thermal energy storage temperature drops by 16.52K and the specific exergy loss of molten salt is 6.67% when the electric power input ramps down by 7%. Affected by thermal inertia, the variation trend of thermal energy storage temperature is obviously lagging behind the disturbance signal of electric power input. Inventory control strategy is employed to maintain the thermal energy storage temperature of the heat pump cycle, thereby maintaining energy quality of the thermal energy storage. During the 50% ramp-down progress of electric power input, the variation range of thermal energy storage temperature is within 1.87K and the specific exergy loss of molten salt is within 0.71% by the PI controller to adjust the total amount of working fluid inventory in the cycle. As the daily output of wind power plant is used as the electric power input of system, the variation range of thermal energy storage temperature is within 1.71K and the specific exergy loss of molten salt is within 0.65%, which further verifies the feasibility of the control strategy.

相对于光滑表面，微柱结构表面可以显著强化核态沸腾，强化机理主要有增大换热面积、增大核化密度、减小气泡脱离直径等，对于微结构内部的导流强化作用鲜有深入研究。本文利用多相流体积分数（VOF）三维模型，定义了微结构表面单气泡沸腾重要的几何、时间无量纲参数，通过对速度场和压力场的分析，讨论了沸腾过程中气泡、微柱与周围液体的相互作用。结果证明：微结构的间隙有利于液体的回流，在气泡底部的气液界面与基底之间建立的流动通道内导流作用明显，液体流速被显著提高，有效促进气泡脱离，强化了单气泡换热。同时，微结构的导流作用促使在微柱结构底部及侧壁面产生了高压薄液膜；底部的薄液膜具有毛细引流能力，维持了气泡内部微柱根部的液相区域；同时，侧壁面上的薄液膜取代了原来的干烧区域，传热面积增大、换热效率显著提高。