The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation. A one-dimensional, non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was verified. The results demonstrate that the inlet temperature of the heat transfer fluid (HTF) had the greatest influence on each index. When the inlet temperature increased from 333 K to 363 K, exergy destruction increased threefold, effective heat storage time decreased by 67%, effective heat storage increased by 38%, and exergy efficiency decreased by 11%. The decrease of the capsule diameter had a positive effect on each evaluation index. According to the sensitivity analysis, the order of importance of each parameter within their variation range was HTF inlet temperature, HTF flow rate, PCM capsule size and PCM initial temperature.

In this study, a simplified numerical model was developed to calculate the internal thermal distribution rules and thermal performance index of a packed bed latent heat thermal storage system (PBLHTES). The accuracy of the model was verified by comparing numerical results with experimental data. The response surface method (RSM) was applied to study and optimize the thermal performance of the PBLHTES. The quadratic regression model of three response indices was established based on 130 groups of Box–Behnken design (BBD) model scheme results, and rationality was verified through analysis of variance (ANOVA). The results showed the degree of influence of single factors and interactive factors on each performance index. The combined effect of the main interactive factors was analyzed in detail. The multi-objective optimized results indicated that effective heat storage time, effective heat storage, and exergy efficiency decreased by 30.24%, increased by 39.81%, and improved by 7.50%, respectively, compared with the basic working conditions before optimization.

The addition of CaO has been used to reduce the harmful NOx precursors (NH3 and HCN) generated by the pyrolysis of municipal sewage sludge. However, the underlying reduction mechanism remains unclear. To address this issue, we systematically investigated the effects of temperature and CaO addition on the generation of NH3 and HCN during the pyrolysis of sludge protein and a model protein. With increasing temperature from 300 to 900 degrees C, the inhibitory effect of CaO on NH3 emission was observed to fluctuate, maximizing at 400 degrees C. The inhibition was attributed to the reaction of CaO with nitrogen in the produced char to form CaCxNy, resulting in enhanced fixation of the char pyridines and nitriles. The nitriles exhibited high thermal stability and inertness to CaO. The increased nitrile content at high temperatures was attributed to the formation of the species from amines and N-containing heterocycles. The CaCx produced by the thermal decomposition of CaCxNy above 700 degrees C was found to increase P-N fixation and decrease NH3 formation. The observed poor inhibitory effect of CaO on NOx precursor formation at 650 degrees C was attributed to the production of NH3 via HCN hydrolysis. Because HCN directly reacted with CaO, the inhibition of HCN formation was highest at 650-900 degrees C, preventing the conversion of char nitriles into HCN. (C) 2019 Elsevier Ltd. All rights reserved.

The technology of latent heat storage in packed bed is widely used in solar energy utilization and heating ventilation air conditioning. Due to the complex transient characteristics and high experimental cost of the latent heat storage system of packed bed under different application environments, researchers developed relevant mathematical models and adopted different numerical calculation methods to analyze the effects of different factors on the system performance. In this paper, the common numerical models of heat storage process in packed bed were classified, and the characteristics and applicability of different models were analyzed in detail. Secondly, the computational efficiency and error of the model were compared. Finally, the application characteristics of different numerical models in latent heat packed bed heat storage technology were summarized, which provides a basis for the development and application of similar models.

Using palmitic acid (PA), expanded graphite (EG), and carbon fiber (CF) as raw materials, PA/EG/CF composite phase change materials (CPCMs) with diverse CF contents were invented by melt blending approach. The effects of different ratios on thermal properties were studied by experimental characterization and testing. Scanning electron microscopy images displayed that PA was adsorbed in the pores of the EG surface, while CF was disorderly but uniformly embedded in the interior and surface of pores. The chemical stability and thermal decomposition stability of CPCM at low temperature were proved by Fourier transform infrared spectrometer and thermogravimetric analyzer results, respectively. According to the law of heat storage/release time and latent heat variation, the optimal ratio scheme was determined, and its heat storage/release time was 65% and 59% lower than pure PA, respectively. The form-stable materials were prepared by compression forming method, and thermal cycling experiment results demonstrated that the higher the content of CF, the stronger the inhibition of mass loss. Based on the experimental results, the PA/EG/CF CPCM has the advantages of stable phase transition, strong stability, and fast heat storage and release rate, so it has a marvelous application prospect in the field of low-temperature heat storage engineering.

Material drying pretreatment plays an important role in the oil shale retorting process. In this study, the drying process of particulate oil shale in a spouted bed was simulated using computational particle fluid dynamics numerical schemes. This study analyzes the effect of the draft tube and inlet air temperature on the drying rate and drying uniformity, and establishes a new insight into the drying process and multi-phase flow characteristics inside the spouted bed. The results indicate that using an ordinary cylindrical spouted bed results in a poor drying uniformity, which causing by a large number of the annulus-region particles fall into the spout region from the height of approximately 150 mm and resulting in a stirless area usually observed at the height of 50-150 mm near the wall. Inserting the draft tube and reducing the drying temperature can improve the uniformity of the drying process, and the former is more efficient than the latter. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

采用离散元数值模拟法对多元颗粒在不同偏心距工况下进行数值模拟,研究偏心滚筒对全部大颗粒的运动初始阶段、稳定阶段的平均速度波动的影响.结果表明:在不同偏心距的偏心滚筒中,同粒径颗粒的平均速度波动不同;偏心滚筒中颗粒平均速度曲线在每个运动周期都会出现波峰和波谷现象,且偏心距越大,该现象越明显;在颗粒运动的初始阶段,大粒径颗粒平均速度波动范围大,偏心距为20 mm的滚筒中所有大颗粒平均速度波动范围最大;在颗粒运动的稳定阶段,随着时间的延长,粒径对于颗粒平均速度的影响不明显.

With the further development of China's energy reform, it puts forward higher requirements for the subject of energy and power professional personnel training based on traditional energy sources. This paper proposed to carry out the "13th Five-Year" education planning idea, of which the modern educational technology and virtual reality technology will be introduced into practice teaching of energy and power undergraduates. In order to enhance the dynamic balance between the demand of electric power industry and personnel training, it's necessary to reform the practice teaching mode and teaching methods, what's more, constructing virtual practice teaching platform. Cultivating the compound talents with solid theoretical foundation and collaborative innovation ability, in order that providing strong support for the development of China's energy and electric power industry.

采用焓-多孔介质模型对高温蓄热堆积床蓄热单元相变过程进行模拟,探讨不同的封装材料、相变材料、熔化温度和运动粘度对相变材料熔化过程的影响.结果表明:当封装材料的导热系数远大于相变材料的导热系数时,封装材料对相变的影响非常小,可忽略不计;通过对比不同相变材料的熔化时间和蓄热能力可知NaNO3、KNO3、LiNO3的完全相变熔化时间相差不大;高粘度的相变材料在相变过程中自然对流较弱,低粘度有利于相变材料熔化过程中的自然对流;熔化温度范围越小,越有利于相变材料的熔化.

生物质与煤共气化可解决生物质不易稳定流化及气化气焦油含量高的问题。基于流化床反应器的松木屑与褐煤共气化试验,研究松木屑掺混比例对合成气及未反应碳的值和效率的影响,并将试验值和理论值进行分析比较。结果表明,各成分气体对合成气值的贡献关系是:CH 4 ＞C 2 H 4 ＞CO＞H 2 ,松木屑气化有更好的能量利用效率;合成气值和效率的试验值均高于计算值,而未反应碳值和效率的试验值均低于计算值;在生物质掺混比例为50%的工况下,松木屑与褐煤共气化协同作用最显著,表现为一种更好的气化方式。

The rapid development of high-speed railway brought tremendous opportunity for the quick transport of goods development. Great efforts to build high-speed rail not only release the existing railway transport capacity, but also provide a new choice to the quick transport of goods. This paper choose some factors to analysis which will influence the express transport, using time series forecasting prediction and gray combination forecasting method to predict results of the 2020 Express Freight shipments. By selecting the integrity, economy, efficiency, convenience, punctuality, service and environmental friendliness those seven Utility Index, established Logit cargo flow rate balancing model, to concluded that high-speed fast freight volume in 2020, which provide references for high-speed rail fast cargo transportation organization.

An AC-linked large scale wind/photovoltaic (PV)/energy storage (ES) hybrid energy conversion system for grid-connected application was proposed in this paper. Wind energy conversion system (WECS) and PV generation system are the primary power sources of the hybrid system. The ES system, including battery and fuel cell (FC), is used as a backup and a power regulation unit to ensure continuous power supply and to take care of the intermittent nature of wind and photovoltaic resources. Static synchronous compensator (STATCOM) is employed to support the AC-linked bus voltage and improve low voltage ride through (LVRT) capability of the proposed system. An overall power coordinated control strategy is designed to manage real-power and reactive-power flows among the different energy sources, the storage unit, and the STATCOM system in the hybrid system. A simulation case study carried out on Western System Coordinating Council (WSCC) 3-machine 9-bus test system for the large scale hybrid energy conversion system has been developed using the DIgSILENT/Power Factory software platform. The hybrid system performance under different scenarios has been verified by simulation studies using practical load demand profiles and real weather data.

According to the exergy efficiency analysis of circulating fluidized bed (CFB) boiler, various exergy loss rates are discussed in this paper. Combustion exergy loss and heat transfer exergy loss are the major losses of CFB boiler, accounting for more than 45% of the fuel chemical exergy by CFB boiler exergy analysis method. For 300MW and its below assembling unit, the exergy efficiency of CFB boiler is generally less than 50%. The boiler exhaust exergy loss rate is about 1%, which is much less than heat loss rate calculated by heat balance method, but there is still a great potentiality to be reduced. As far as CFB boiler is concerned, chemical incomplete combustion exergy loss rate and radiating exergy loss rate are both too small to be negligible. Unburned carbon exergy loss should be focused on due to its high energy quality. CFB boiler slag has a higher proportion of coal ash. Therefore, it is important to reduce the slag physical exergy loss for improving CFB boiler efficiency.

Experiments were conducted to study the factors which affect motion state of particles in a circular eccentric drum,and the effects of two offsets,four filling rates and four rotating speeds on the motion model were analyzed. Rotating speed and filling rate were the main factors affecting the change of the motion model of particles in a circular eccentric drum,while offset had no effect. Filling rate did not have an impact on the motion model of particles at rotating speed of 15r/min and 25r/min. But when rotating speed was 5r/min,the motion model of particles varied from slumping mode to rolling mode accordingly when filling rate increased from 1/6 to 1/3,and when rotating speed was 40r/min, the motion model of particles varied from rolling mode to cascading mode accordingly when filling rate increased from 1/6 to 1/3. With increasing offset,vortex core generated in the process of movement deviated more from the center of the drum. Increasing rotating speed resulted in the change of the upper surface of particle group and the arc of the falling particle group on both ends. The effect of filling rate on the motion model of particles occurred only at low and high rotating speeds.

The TG-FTIR anaylsis technology was applied to analyze the co-gasification process and gasification products of pine sawdust, lignite and their mixtures. The influence of mixing ratio, heating rate and reaction atmosphere on the co-gasification process was also studied. The results show that the pine sawdust can improve the reactivity of samples. As the mixing ratio of pine sawdust is increasing, the mass loss rate of gasification decreases, and the beginning temperature and the peak area of CO formation have a decreasing tendency. It is found that the lower heating rate is advantageous to the formation of CO and CH4. With increasing the heating rate, the DTG curves move to higher temperature ranges, the maximum weight loss rate increases, and the pine sawdust peak disappears. The effect of CO2 atmosphere on the weight loss of devolatilization is not significant. The two peaks of devolatilization are corresponding to the volatile combustion and fixed carbon combustion in air, and the coke gasification is not significant in the atmosphere of air.

Waste heat of circulating water emitted to the environment causes huge thermal pollution and los-ses lots of thermal energy.Thus,absorption heat pump is applied to recycle the heat.Taking a certain 200 MW extraction condensing unit and its heating system as the example,the Aspen Plus software was employed to establish the single/double effect lithium bromide absorption heat pump model.Moreover, comparative analysis for the system under variable conditions was performed.The results indicate that, with an increase in the heat pump outlet heating network water temperature or the heat pump driven steam source,the coefficient of performance (COP)of both the single and double effect cycle heat pump declined. For the same heating temperature,the double-effect cycle can save steam by about 30% more than the sin-gle-effect cycle.When the temperature of heat pump outlet heating network water exceeded 90 ℃,the heat-ing network return water can be heated to about 90 ℃ by heat pump first,and then to the required temper-ature by spike heater,thus to ensure the stable operation of system.

To obtain a performance model for the adjustable blades axial flow fan, the performance surface of fan was fitted using binary polynomial fitting method, and the coefficients matrix was solved with QR decomposition. By comparing the fitting results show that the fitting effect is good when the 5 order polynomial was used to fit the performance surface of the fan and the 6 order polynomial was used to fit the boundary of performance surface. The accuracy of the obtained model can meet the requirements of the engineering application and scientific research.

The mixing mechanism and mixing quality of three-component particles in rotary cylinder were studied by using MATLAB image processing, Lacey index and comprehensive method. The results show: diffusion mixing is most obvious during the process of three-component particles mixing, and plays an important role in all three stages, i,e, convective mixing stage, both convective mixing and shear mixing working stage and shear mixing stage; the big particles are distributed as petal shaped, the type and the quantity of the petal shape is concerning with filling rate, dip angle and rotating speed of the rotary cylinder. The particle mixing quality with each factor changes showing regularity, and it is different from the regular of particle mixing degree. A favorite mixing condition achieves at 16.7% vessel filling, 0 degree dip angle and 3.4 r/min rotating rate.