基于D_S证据理论的煤粉细度融合诊断

针对电厂煤粉细度在线测量难的问题,提出利用数据融合技术识别煤粉过细、煤粉正常、煤粉过粗。在分析与煤粉细度相关的多个运行状态参量基础上,根据历史运行数据,确定煤粉细度的典型样本,然后对各状态参量应用D—S融合规则得到结果。而对于D—S证据理论应用中基本概率赋值难以确定问题,应用正态分布曲线构造相似度函数．继而得到基本概率赋值,减少了方法的主观性。根据运行数据验证,该方法能够有效诊断煤粉细度,且具有较好的鲁棒性,具有工程实用价值。     

双进双出钢球磨煤机特性及优化调整

文章介绍了双进双出钢球磨煤机的技术特点和煤粉细度调整优化试验。该型磨煤机运行稳定、可靠性高、响应负荷变化速度快、调节范围宽、对煤种适应性强、系统布置紧凑。但在某电厂的运行中发现,煤粉细度偏粗,导致煤粉燃烧不充分,锅炉的效率低。通过对磨煤机的试验调整,降低了煤粉细度,提高了锅炉效率。     

中速磨煤机直吹式制粉系统特性对锅炉运行的影响分析

根据中速磨煤机直吹式制粉系统设计及运行参数的特性,分析了磨煤机的风量、煤粉分配均匀性、磨煤机负荷率、煤粉细度、煤质变化等因素对大型煤粉锅炉燃烧系统的影响。在锅炉运行中,需根据制粉系统的特性优化调整锅炉的运行参数,达到制粉系统与锅炉燃烧系统的耦合匹配。     

高风温点火燃烧器中煤粉气流的着火规律

针对一种新型电站锅炉使用的高风温直接点火的煤粉燃烧器,在现场实验和数学模型的基础上详细讨论了煤粉浓度、煤粉气流速度、热风速度和温度等因素对煤粉气流着火的影响规律,为燃烧器的设计与运行参数的选择提供指导.     

运行参数对锅炉煤粉着火燃烧和飞灰含碳量影响的数值研究

为了达到锅炉的优化运行以保证煤粉气流及时着火和充分燃尽，采用IPSA两相流动模型和煤粉燃烧综合模型，在不同的一次风率和煤粉细度的工况下，对1台350MW锅炉煤粉燃烧过程进行了数值模拟，得出了炉内燃烧器区域以及出口处烟气温度场和燃烧产物的组分浓度分布。分析了一次风率和煤粉细度对煤粉着火燃烧和飞灰含碳量的影响规律，并确定了优化的运行参数。结果表明：一次风率对煤粉气流的着火影响较大，而对出口处烟气温度、氧量以及飞灰含碳量影响较小。煤粉细度对煤粉气流的着火、燃烧以及燃尽均有较大影响。图8表2参9     

HG-35-3.82/450-HM5型煤粉炉的技术改造及经济效益分析

通过对燃用褐煤的３５ｔ／ｈ煤粉锅炉运行中存在的热效率低、粉尘大的原因分析,提出了把煤粉锅炉改造成流化床锅炉的改造方案。运行结果表明,锅炉达到了预期效果。     

锅炉煤粉混合器的节能改造设计

在煤粉锅炉运行中，煤粉混合器的堵塞及气流不畅，一直困扰着锅炉的安全经济运行。本文叙述了利用管路低压、炉膛高负压的方法对煤粉混顺进行节能改造设计 。     

中压锅炉煤粉经济细度的确定

通过对中国长城铝业公司热力厂８台中压煤粉锅炉燃煤特性的分析，煤粉经济细度的计算以及球磨机运行实践的阐述，确定了本厂锅炉的煤粉经济细度，对企业煤粉锅炉安全经济运行，节能降耗具有一定的指导意义。     

《煤粉燃烧器设计及运行》

机械工业出版社即将出版由哈尔滨工业大学秦裕琨、机械委哈尔滨电站设备成套设计研究所何佩鏊及水电部西安热工研究所赵仲琥编写的《煤粉燃烧器设计及运行》一书。本书详细介绍了我国多年来在煤粉燃烧器设计、运行及试验研究方面的大量经验,同时也收集了一些国外有关资料,其中简略地介绍了煤及煤粉的燃烧特性以及燃烧器的设计和运行调整方法。重点介绍了燃烧器的设计和结构以及在生产实践中的运行情况。同时对国内外     

煤粉浓缩器在超细煤粉再燃系统中的应用

超细煤粉再燃降低氮氧化物排放技术具有较强的经济性和实用性,而超细煤粉的制备是这项技术实施的关键。采用离心式旋转煤粉浓缩器对三次风中的超细煤粉进行浓缩,弱化了三次风对机组运行的不良影响,同时解决了超细煤粉的来源问题,为再燃技术的实施奠定了基础。     

Numerical simulation of fluid flow and heat transfer in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall

The paper is focused on the investigation of fluid flow and heat transfer characteristics in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall. In contrast to the new microchannel heat sink, the corresponding conventional rectangular microchannel heat sink is chosen. The computational fluid dynamics is used to simulate the flow and heat transfer in the heat sinks. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. The SIMPLEX method is used for the computations. The effects of flow rate and heat flux on pressure drop and heat transfer are presented. The results indicate that the microchannel heat sink with offset fan-shaped reentrant cavities in sidewall improved heat transfer performance with an acceptable pressure drop. The fluid flow and heat transfer mechanism of the new microchannel heat sink can attribute to the interaction of the increased heat transfer surface area, the redeveloping of the hydraulic and thermal boundary layers, the jet and throttling effects and the slipping over the reentrant cavities. The increased heat transfer surface area and the periodic thermal developing flow are responsible for the significant heat transfer enhancement. The jet and throttling effects enhance heat transfer, simultaneously increasing pressure drop. The slipping over the reentrant cavities reduces pressure drop, but drastically decreases heat transfer.     

Heat prices for public buildings in Tianjin

Energy-saving awareness of heat users and heating enterprises can be stimulated by implementing heat metering for public buildings and by establishing scientific and reasonable policies for heat prices in China. In this paper, a two-part heat price for public buildings in Tianjin is introduced, which divides the heat price into a basic part and a metering part. According to the statistical analysis of information collected from two pilot heating enterprises, the specific heat load for public buildings in Tianjin is calculated, and three candidate schemes of heat price are proposed. A simulation of heat cost is also conducted, and the benefits for both heat users and heating enterprises are balanced. Finally, the two-part heat price for public buildings in Tianjin is determined: the basic heat price is recommended to be 20 CNY/m², and the metering heat price is recommended to be 76.10 CNY/GJ. Such a price could be implemented in the initial stage of heat metering for public buildings in Tianjin.     

Role of heat pipes in improving the hydrogen charging rate in a metal hydride storage tank

Metal hydrides can store hydrogen at high volumetric efficiencies. As the process of charging hydrogen into a metal powder to form its hydride is exothermic, the heat released must be removed quickly to maintain a rapid charging rate. An effective heat removal method is to incorporate a heat exchanger such as a heat pipe within the metal hydride bed. In this paper, we describe a two-dimensional numerical study to predict the transient heat and mass transfer in a cylindrical metal hydride tank embedded with one or more heat pipes. Results from a parametric study of hydrogen storage efficiency are presented as a function of storage tank size, water jacket temperature and its convective heat transfer coefficient, and heat pipe radius and its convective heat transfer coefficient. The effect of enhancing the thermal conductivity of the metal hydride by adding aluminum foam is also investigated. The study reveals that the cooling water jacket temperature and the heat pipe's heat transfer coefficient are most influential in determining the heat removal rate. The addition of aluminum foam reduces the filling time as expected. For larger tanks, more than one heat pipe is necessary for rapid charging. It was found that using more heat pipes of smaller radii is better than using fewer heat pipes with larger radii. The optimal distribution of multiple heat pipes was also determined and it is shown that their relative position within the tank scales with the tank size.     

Numerical study of heat pipe application in heat recovery systems

Heat pipes are two-phase heat transfer devices with extremely high effective thermal conductivity. They can be cylindrical or planar in structure. Heat pipes can be embedded in a metal cooling plate, which is attached to the heat source, and can also be assembled with a fin stack for fluid heat transfer. Due to the high heat transport capacity, heat exchangers with heat pipes have become much smaller than traditional heat exchangers in handling high heat fluxes. With the working fluid in a heat pipe, heat can be absorbed on the evaporator region and transported to the condenser region where the vapour condenses releasing the heat to the cooling media. Heat pipe technology has found increasing applications in enhancing the thermal performance of heat exchangers in microelectronics, energy and other industrial sectors.Utilisation of a heat pipe fin stack in the drying cycle of domestic appliances for heat recovery may lead to a significant energy saving in the domestic sector. However, the design of the heat pipe heat exchanger will meet a number of challenges. This paper presents a design method by using CFD simulation of the dehumidification process with heat pipe heat exchangers. The strategies of simulating the process with heat pipes are presented. The calculated results show that the method can be further used to optimise the design of the heat pipe fin stack. The study suggests that CFD modelling is able to predict thermal performance of the dehumidification solution with heat pipe heat exchangers.     

Heat extraction characteristic of embedded heat exchanger in honeycomb ceramic packed bed

On the basis of experimental verification of mathematical model, the influence of honeycomb ceramic on heat extraction is numerically studied under the steady state condition. The calculation results show the packed honeycomb ceramic influences the extracted heat of heat exchanger by changing the flow field while not radiation heat transfer of heat exchanger outer wall, and the difference between the extracted heat of heat exchanger embedded in packed bed and that of heat exchanger in empty bad is gradually obvious with gas temperature increasing under the condition of the same gas mass flow rate. In addition, under the same operating condition, when the two characteristic sizes of heat extraction zone honeycomb ceramic in the vertical gas flow direction increase, the extracted heat of embedded heat exchanger shows a trend of first increase while extracted heat of embedded heat exchanger shows a trend of decrease because the decreasing of the windward and leeward side gas flow velocity of heat exchanger results into weakening of convective heat transfer of embedded heat exchanger outer wall.     

A review on the application of horizontal heat pipe heat exchangers in air conditioning systems in the tropics

A literature review on the application of horizontal heat pipe heat exchangers for air conditioning in tropical climates was conducted. This paper focused on the energy saving and dehumidification enhancement aspects of horizontal heat pipe heat exchangers. The related papers were grouped into three main categories and a summary of experimental and theoretical studies was made. It was revealed that although there are a number of valuable researches on the impact of heat pipe heat exchangers on the energy consumption and dehumidification enhancement of air conditioning systems in the tropics, but only limited research work on the application of horizontal configuration heat pipe heat exchangers in air conditioning systems has been carried out in these regions. Therefore, it needs more research to deepen the understanding of the benefits of this heat recovery device in the air conditioning systems. On the basis of results obtained from the reviewed research studies, the application of horizontal heat pipe heat exchangers in terms of energy saving, dehumidification enhancement and condensate drainage is recommended for the tropics.     

Nanofluid in the multiphase flow field and heat transfer: A review

Two-phase heat transfer is widely used in the heat transfer field, for example, condenser and evaporator in the refrigeration system, riser, and condenser in thermal power plants, and so on. The advantage of two-phase heat transfer is that it gives a very-high convective heat transfer coefficient compared to other modes of heat transfer. Nanofluid is a comparatively new heat transfer fluid and very popular because of its improved thermophysical properties. If nanofluid is used in a two-phase heat transfer field, then the convective heat transfer coefficient may improve further. Nanofluids are possibly useful in many studies in two-phase heat transfer like pool boiling heat transfer, flow boiling heat transfer, nanofluids in a microchannel, forced convective heat transfer, condensation, spray cooling, enhanced oil recovery, and so on. The effect of nanoparticles on wettability, contact angle, and nucleation sites are also reviewed in this paper. Numerical studies in two-phase heat transfer are also reviewed and summarized in this paper. In this review, the chronological development of heat transfer in the two-phase field is provided in a tabular form. This table covers a wide period starting Before Common Era ages until the recent addition of nanoparticles in the two-phase heat transfer fluid.     

强化太阳能相变蓄热技术的研究进展

为解决太阳能的间歇性问题,常将其与相变蓄热技术进行结合。与传统显热蓄热相比,相变蓄热可将蓄热能量提高数倍以上,具有巨大的研究和应用价值。本文总结分析了相变蓄热的传热机制及在强化太阳能相变蓄热技术上的研究手段,如变换蓄热结构、添加肋片、使用相变胶囊、充注多相变材料、蓄热材料中添加高导热物质等。分析结果显示,相变传热机制中,融化过程主要考虑对流换热,凝固过程热传导占主导;使用肋片、相变胶囊等,主要增大相变材料接触面与蓄热体的比值,进而改善传热;蓄热材料添加高导热物质,可以改善相变材料的团聚、结核及使用寿命,从而提高导热性能,其中添加泡沫金属效果最为显著。     

Research,development and industrial application of heat pipe technology in China

This paper introduces some typical cases of industrial applications, which include the equipment for the waste heat recovery and the industrial process equipment. Carbon steel–water heat pipe technology, applied to air preheater and waste heat boiler, has been successfully used in many fields, such as waste heat recovery, energy conservation and environmental protection. Liquid metal high-temperature heat pipe technology has been extensively employed in the process equipment, for example, high-temperature hot air generators and heat extractors. Heat pipe technology also finds its use in chemical reactors including ammonia converters. The success of applications is founded on the basis of fundamental research of heat pipe technology, which includes the theoretical and experimental researches on the vapor–liquid two-phase flow and heat transfer inside the heat pipe, the heat transfer limits of heat pipes, the heat transfer enhancement with heat pipes, and researches on the material compatibility and life tests of heat pipes. Hi-efficient heat pipe heat and mass transfer equipment is going to play a more and more important role in the various industrial fields.     

The cost-effectiveness of heat pumps in specific buildings in South Africa

Water heating heat pumps are extremely energy efficient and large savings can be realized when they are compared to direct electrical resistance heaters. In spite of the energy efficiency of heat pumps, a large number of residential buildings in South Africa still use electrical heaters to heat water. The reason for this is that heat pumps are considerably more expensive than electrical heaters. Building owners tend to choose the system with the smallest initial cost and do not compare the two systems on the basis of life-cycle cost. It is also difficult to calculate the life-cycle cost of a heat pump because it depends on many factors like climatological conditions and water temperature. In this paper a methodology is developed to calculate the life-cycle cost of a heat pump hot water installation. The model is used to investigate the effect of daily runtime, electricity tariff, hot water consumption and geographical location on the cost-effectiveness of heat pumps. The cost-effectiveness of heat pumps increases with daily run time, water consumption and electricity tariff. Heat pumps are more cost-effective near the coast than in the interior. If sized correctly, heat pumps are more cost-effective than electrical heaters for all major cities in South Africa. The cost-effectiveness of heat pumps for two specific buildings, one a university student hostel in Potchefstroom and the other a hotel in Durban, is also investigated. For both cases it was found that heat pumps are more cost-effective than direct electrical resistance heaters.