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锅炉结渣会降低水冷壁及对流受热面的传热效率,严重影响锅炉的正常运行。为了实现锅炉大比例掺烧易结渣的准东煤,急需一种能够准确检测炉内结渣程度的工业装置及自动化控制系统来保证锅炉的安全运行。本文建立了一维导热模型,研究了不同参数对热流计测量过程中响应时间的影响,研究表明热流计对热流变化敏感,响应时间约为30s,满足结渣监测要求;基于温差法原理设计了超细高温热流计,在此基础上开发了基于微型热流计的水冷壁结渣实时监测系统,并在吉林省某热电厂进行了现场测试。现场测试结果表明,该装置可在不破坏锅炉水冷壁的前提下准确测量热流密度,同时也证明了该系统预报结渣程度的可行性和可靠性。 相似文献
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文章计算辐射传热以区域假想面模型为基础,把炉膛沿烟气流动方向分区,以炉膛内最为复杂的燃烧器区域的燃烧与辐射传热过程为研究对象,建立炉内能量平衡方程,并求解出炉内燃烧的一维温度场,以及水冷壁的吸热量和热流密度.计算结果与三维模型的实测数据非常一致.由于模型采用了一维简化处理,收敛结果较快,可以快速得到电站需要的数值. 相似文献
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以东方锅炉600MW超临界W火焰锅炉为研究对象,从非预混燃烧、气相湍流、颗粒相轨道模型、辐射传热、煤粉挥发分燃烧等模型入手,运用计算流体力学软件FLUENT进行了计算流体力学(CFD)模拟,同时建立了炉膛水冷壁一维分布参数模型,将其得到的水冷壁温度分布作为CFD模拟的边界条件,通过两种模型的混合模拟,得到了更为准确的基础工况和变负荷工况下炉膛内温度场、流场、组分浓度场的分布特性,并分析了炉内煤粉燃烧规律的变化。 相似文献
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600 MW偏转二次风系统锅炉炉内结渣特性的数值模拟 总被引:1,自引:1,他引:1
偏转二次风系统已广泛应用于大型四角切圆燃烧锅炉,用以报制炉内结渣,防止水冷壁高温腐蚀等。为降低炉膛出口扭转残余,通常采和下部二次风大角度正切、上部二次风和OFA风反切的布置方式。本文对某台采用偏转二次风系统的600MW燃煤四角切圆燃烧锅炉的炉内结渣过程进行模拟,对炉内气固相流动、温度场、气固相燃烧、固相向水冷的输运过程和灰粒在水冷壁上的附生长过程进行了数值模拟,结果表明,偏转二次风系统具有较强的防结渣性能,这一点也被锅炉的实际运行所证实。 相似文献
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随着环保和节能要求的不断提高,高参数大容量燃煤机组的发展成为了必然趋势,机组参数的提高对机组安全高效运行提出了更高的要求,特别是炉膛内吹灰器的合理动作缺乏理论指导。基于炉膛出口烟温的炉膛结渣整体判断方法难以指导布置在炉膛内部的大量吹灰器的合理动作,不仅会浪费吹灰蒸汽,同时给水冷壁的运行带来安全隐患。通过在炉膛的膜式水冷壁的向火侧鳍片处布置热电偶测点,实时监测热电偶测点的温度变化,建立了炉膛局部结渣监测模型,同时结合机组的运行数据给出了吹灰优化方案。监测结果表明:根据测点温度值建立的局部结渣监测模型能够反映炉膛不同高度层的结渣状况及其变化规律,高负荷下炉膛结渣严重,但结渣能够达到动态平衡,低负荷下结渣较轻但增长趋势明显。炉膛结渣能够优化各受热面的吸热量分配,特别是低负荷下可以减轻过热器、再热器的欠温问题,结合受热面的热量分配比例合理吹灰可优化电厂定时定量吹灰方式,减轻运行人员的督查力度,实时指导吹灰。 相似文献
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本文为切圆燃烧炉膛的传热建立了一个一维区域模型。在模型中考虑了部分烟气由上而下回流的实际情况.此模型能够反映出沿炉膛高度方向热流和温度分布随炉内工况变化.文中还以1000t/h直流锅炉的双炉膛为例,在IBM-PC/AT机上进行了计算,结果准确,且计算过程极短,可用于锅炉的实时模型中。 相似文献
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研究了自然循环锅炉膜式水冷壁管的传热,采用编制程序对水冷壁进行温度场分布的计算,在研究方法上考虑了欠热沸腾起始点的问题,探讨了入口工质状态、炉内热流密度、质量流量、质量舍汽率等对水冷壁温度的影响。计算结果表明,入口水温的变化会影响欠热沸腾起始点的高度,但对温度的影响较小;炉内热流密度、质量流量和质量舍汽率的波动都会对温度产生影响,这主要是由于它们影响了换热系数的大小。 相似文献
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本文采用有限元分析计算方法对宝丽华300MW循环流化床锅炉水冷壁模型的热传导分布规律进行了系列计算。分析总结出了炉外侧的管壁鳍片间的温差同管内工质与管内壁面、床侧与炉内侧金属壁面间换热系数及床内热流密度间的变化规律,为间接测量床内热流密度的分布提供了基础数据。通过测量炉外侧金属壁温并结合数值计算结果来反推无法直接测量的床内热流密度分布规律的方法具有较高的可性度和工程应用价值。 相似文献
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以太阳能烟囱发电(SCPP)系统为研究对象,比较定热流密度、离散纵坐标(DO)辐射模型、表面对表面(S2S)辐射模型对SCPP温度、速度等性能模拟结果,将3种模型模拟结果与试验数据对比,选择更合适的辐射模型应用于SCPP数值模拟。结果表明,S2S辐射模型集热棚出口流体最大速度比定热流密度和DO辐射模型分别高0.13、0.36 m/s;S2S辐射模型沿烟囱入口流体最大湍流黏度比定热流密度和DO辐射模型分别高16.87%、8.44%;定热流密度、DO辐射模型、S2S辐射模型沿集热棚半径流体温度与试验结果的误差分别为3.09%、0.98%、10.14%。DO辐射模型更适合SCPP系统的数值模拟计算。 相似文献
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In this study, a mathematical analysis is presented on the complete interface problem between solar concentration systems and high temperature thermochemical processes. This includes the thermal process starting from the incoming solar radiation up to the heat transfer to a heat carrier fluid or reactants in a given reactor. The system considered comprises a heliostat, a parabolic concentrator and a receiver. The hourly incoming radiation, the hourly reflection and absorption losses on the heliostat and concentrator systems, the radiation flux density distribution in the receiver space, the solar and IR bands radiation exchange and the useful heat transfer are all considered in the analysis. The parameters such as temperature distribution in the receiver as well as thermal efficiency can be calculated for a given case. The model has been verified using the experimental results obtained in two different systems. In addition, a parametric study has been carried out on the global receiver efficiency with respect to temperature. 相似文献
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R. G. Alderfer 《Solar Energy》1973,15(1):77-82
The interaction of solar radiation with plant systems is described in terms of a modified form of the Kubelka-Munk model for light transmission through scattering media. This model is used to predict upward and downward radiation flux densities in plant systems as a function of leaf optical properties, depth in the system, and reflectance of the soil surface. The model can be used for monochromatic radiation or wavebands of desired width. The results of the Kubelka-Munk model are incorporated into a set of simultaneous energy budget equations in order to predict the profile of leaf temperature within plant systems. Measurements testing the reliability of the above theoretical treatment are discussed. 相似文献
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Yong Shuai Bachirou Guene Lougou Hao Zhang Jiupeng Zhao Clément Ahouannou Heping Tan 《International Journal of Hydrogen Energy》2021,46(16):10104-10118
Converting solar energy efficiently into hydrogen is a promising way for renewable fuels technology. However, high-temperature heat transfer enhancement of solar thermochemical process is still a pertinent challenge for solar energy conversion into fuels. In this paper, high-temperature heat transfer enhancement accounting for radiation, conduction, and convection heat transfer in porous-medium reactor filled with application in hydrogen generation has been investigated. NiFe-Aluminate porous media is synthesized and used as solar radiant absorber and redox material. Experiments combined with numerical models are performed for analyzing thermal characteristics and chemical changes in solar receiver. The reacting medium is most heated by radiation heat transfer and higher temperature distribution is observed in the region exposed to high radiation heat flux. Heat distribution, O2 and H2 yield in the reacting medium are facilitated by convective reactive gas moving through the medium's pores. The temperature gradient caused by thermal transition at fluid-solid interface could be more decreased as much as the reaction chamber can store the transferred high-temperature heat flux. However, thermal losses due to radiation flux lost at the quartz glass are obviously inevitable. 相似文献
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For solar cavity-receivers operating at high temperatures, the optimum aperture size results from a compromise between maximizing radiation capture and minimizing radiation losses. When the absorbed solar energy is utilized as high temperature process heat, the energy conversion efficiency can be represented as the product of the energy absorption efficiency and the Carnot efficiency. We describe a simple, semiempirical method to determine the optimum aperture size and optimum operating temperature of a solar cavity-receiver for which its energy conversion efficiency is maximum. Such optimization strongly depends on the incident solar flux distribution at the aperture plane of the receiver. We analytically examine the case of a Gaussian distribution of the incident power flux, and we compare theoretical results with the results obtained when using an optically measured flux distribution. Using Monte-Carlo ray tracing, we further investigate the influence of sunshape on the optimal parameters of a cavity-receiver in a paraboloidal concentrator. 相似文献
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A dimension-reducing method for calculating the radiant heat transfer with two-dimensional characteristics is introduced in this article. Using this dimension-reducing method, the two-dimensional discrete transfer method (DTM) was applied to a cylindrical enclosure where the medium was absorptive and emissive. The two-dimensional DTM was proved to produce equivalent prediction results as the three-dimensional radiation computation. Then the two-dimensional DTM was incorporated into a general pulverized coal combustion model to estimate radiant heat transfer. The temperature distribution and the net heat flux distribution of an axisymmetric pilot furnace, in which three kinds of lignite were burned, respectively, were calculated using the comprehensive model. The prediction using this model has been found to have a high agreement with the measured data, that the temperature errors was at ± 5% and the net heat flux error was at about ± 15%. The results have demonstrated the feasibility and potential of using the two-dimensional DTM for radiation modeling in pulverized coal flame, and confirmed that the dimension-reducing method and the overall model will be simple and convenient for engineers to use. 相似文献
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Clayton A. Pullins Tom E. Diller 《International Journal of Heat and Mass Transfer》2010,53(17-18):3429-3438
Recent advances in heat flux measurement have resulted in the development of a robust thermopile heat flux sensor intended for use in extreme thermal environments. The High Temperature Heat Flux Sensor (HTHFS) is capable of simultaneously measuring thermopile surface temperature and heat flux at sensor temperatures up to 1000 °C. The need for high temperature heat flux calibration of the HTHFS has resulted in the development of a new wide angle radiation calibration system, which operates with the sensor at elevated temperatures. The temperature dependence of the sensor output over the range of 100–900 °C has been successfully characterized with acceptable uncertainty limits. The calibrated HTHFS sensitivity agrees well with a theoretical sensitivity model, suggesting that the primary cause for the sensor’s output temperature dependence is due to the change in thermal conductivity of the sensor elements with temperature. 相似文献
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V. P. Sethi 《国际可持续能源杂志》2019,38(1):24-36
Global solar radiation availability model and thermal model for newly designed asymmetric overlap roof shape (AORS) greenhouse are presented and experimentally validated. Instantaneous solar radiation flux is utilised in a dynamic thermal model to ascertain the hourly plant and inside air temperature. The AORS is also compared with the previously developed two best greenhouse shapes. An experimental validation of both the models is carried out for the measured instantaneous solar radiation, plant and inside air temperature for a typical day in summer at Ludhiana (31°N and 77°E), Punjab, India. During the experimentation, a tomato crop was grown inside the greenhouse. From the results, it can be inferred that an east–west orientation AORS greenhouse should be preferred due to a lesser solar radiation capture in summer months. The predicted plant and air temperatures are in good agreement with the measured data having a root mean square error of 4.69 and 3.7, respectively. 相似文献