共查询到18条相似文献,搜索用时 156 毫秒
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先进的相变储能材料是推动储能技术发展的核心和关键,在促进新能源开发和提高能源利用率中起着至关重要的作用。因在相变过程中具有高储能密度和小体积变化等优势,相变材料中应用最多的是固?液相变材料。然而在其相变过程中会发生固态向液态的转变,为了避免其在液相状态下的泄露,需要加以定形才能使用。多孔基复合相变材料在有效防止固液相变发生泄露的同时,还需兼顾定形复合相变材料传热性能的提升。本文针对这个问题进行了大量的调研,对近年来国内外在提高多孔基定形复合相变材料传热性能方面的研究进行了综合分析,介绍了三种强化传热的方法,分别是使用高导热多孔材料做载体材料、掺杂高导热纳米材料做添加剂以及构筑高导热多级结构多孔材料,并对提升复合相变材料传热性能研究方法的前景作了展望。 相似文献
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考虑污垢时强化传热性能的评价 总被引:1,自引:1,他引:0
以强化传热性能评价准则(Nu/Nus)/(f/fs)^1/3为基础,在考虑污垢的条件下,对纵向翅片管的强化传热性能进行了评价。结果表明,与不考虑污垢的情况相比,两者的评价结果有明显差异。本文的有关结果为工程上强化传热性能的评价提供参考。 相似文献
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超声波在线防垢、除垢与强化传热的实验研究 总被引:3,自引:0,他引:3
超声波防垢除垢与强化传热的机理是超声波的空化效应与机械效应.根据这一机理并由水力学计算,首次设计出了较完善的超声波防垢除垢及强化传热实验台,并确定防垢除垢与强化传热实验中所要控制的主要物理参数为:超声波频率、功率、反应体系温度.实验表明:适当提高超声波频率、功率和反应体系温度有利于提高清洗效率. 相似文献
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双辊倾斜式薄带连铸传热过程数学模型和计算机模拟 总被引:3,自引:0,他引:3
本文建立了双辊倾斜式薄带连铸传热过程的数学模型,妥善处理了影响传热过程的主要因素,采用有限差分法及三对角矩阵算法进行数值计算。初步验证了数学模型的可靠性。计算模拟揭示了各主要工艺、设备参数对薄带连铸过程的影响规律。 相似文献
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本文以套筒式金属辐射换热器为研究对象,建立了换热器空气侧及烟气侧强化传热的数学模型,并对不同的强化方案进行了数值计算,讨论了不同方案的强化传热机理及强化效果。 相似文献
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有机相变材料具有热存储密度高、自身温度和体积变化小、腐蚀性小和化学性质稳定等优点,能有效提升不可再生能源的利用率,是一种绿色节能环保材料,在新能源开发和热能储存领域起着至关重要的作用。然而,有机相变储能材料普遍存在相变过程中熔融泄漏和热导率低的问题,严重制约了相变材料的实际应用。因此,相变材料的封装定形和导热强化成为近年来的研究热点。本文针对有机相变材料普遍存在的泄漏和热导率低问题,综述了有机相变材料的封装技术和导热强化技术的基本方法及最新研究成果,并总结了复合相变储能材料的能量转换机理,浅谈了复合定形相变储能材料在建筑节能、太阳能和电子设备等领域的应用情况。最后,对未来复合定形相变储能材料发展的研究重点和方向进行了展望。 相似文献
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William A. Marra 《Canadian Metallurgical Quarterly》2006,19(1):55-58
The solar radiation absorbed in massive building components is stored and later emitted as long-wave thermal radiation into the interior space. Heat storage capacity is directly related to the mass of the building envelope surrounding this space and particularly that of high-mass, homogeneous earthen or cementitious material. A thermal storage cycle is created by the time-lag effect if sufficient mass is available. A similar strategy applied to the lunar and/or Martian regolith would provide a surface structure with micrometeorite and radiation protection, thermal insulation, and natural supplemental heat energy that would significantly reduce the energy requirements met by mechanical equipment. HEAT2 is an energy simulation program that solves heat transfer problems using the partial differential heat conduction equation in two dimensions with the method of explicit finite differences. HEAT2 simulation data suggests that, although thermal mass is most suitable for climates where desired indoor temperatures fall within a large daily external temperature gradient, the heat storage cycle is least effective at the annual extremes occurring in midwinter and in midsummer. A more moderate climate will allow the heat storage cycle to modulate between positive and negative heat flows which are then shifted to align with peak load conditions, reducing energy demand. Also, diurnal and seasonal temperature gradients can initiate a sequence of phase transitions in the soil’s moisture content affecting the overall conductivity. This study will present a more accurate explanation of the heat transfer processes occurring in soils of varying compositions when thermal properties are altered by transient climatic conditions. 相似文献
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K. s. Chapman S. Ramadhyani R. Viskanta 《Metallurgical and Materials Transactions B》1991,22(4):513-521
A mathematical system model of a direct-fired continuous reheating furnace has been developed. The furnace is modeled as several
well-stirred gas zones with one-dimensional (1-D) heat conduction in the refractory walls and two-dimensional heat transfer
in the load. The load travels either parallel or counterflow to the combustion gases which enter the furnace throughout its
length. The convective heat-transfer rate to the load and refractory surfaces is calculated using existing correlations from
the literature. Radiative heat exchange within the furnace is calculated using Hottel’s zone method by considering the radiant
energy exchange between the load, the combustion gases, and the refractories. The nongray characteristics of the combustion
gases are considered by using a four-gray gas model to treat the mixture as a radiatively participating medium. An extensive
parametric investigation has been completed to determine the furnace design and operating characteristics that lead to optimum
furnace efficiency. The parametric investigations included in this paper study the effects of the load and refractory emissivities
and the height of the combustion space on the thermal performance of the furnace. 相似文献
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以茄子为原材料,通过水热处理–后续热解法及直接热解法分别制备出两种不同的茄子衍生多孔碳材料(HBPC和BPC)。以茄子衍生多孔碳材料为载体,采用真空浸渍法负载相变芯材聚乙二醇(PEG2000),制备出聚乙二醇/茄子衍生多孔碳材料复合相变材料。通过扫描电镜、拉曼光谱、压汞法、傅里叶变换红外光谱分析、X射线衍射仪、热重分析仪和差示扫描量热仪对其进行结构表征及性能测试。结果表明,通过直接热解法制得的茄子衍生多孔碳材料为载体的聚乙二醇/茄子衍生多孔碳材料复合相变材料具有更好的相变储热效果,负载聚乙二醇的质量分数高达90.60%,熔融潜热为133.98 J·g?1,达到了较好的定形相变效果及良好的循环稳定性。 相似文献
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阐述了蓄热式燃烧系统/热回收系统的原理,以及通过在赣州铝厂熔铝炉上的设计、使用,证明该系统在熔铝炉上的应用是有效的。 相似文献
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以相变材料为核心的潜热储存技术,对加快新能源开发和提高能源利用率起着关键性作用。以油酸钙为前驱体,通过水热法合成了具有自支撑网络结构的羟基磷灰石(HAP)气凝胶,并采用浸渍法制备出自支撑羟基磷灰石复合相变材料。通过扫描电镜、傅里叶红外光谱、X射线衍射、热重法、差示扫描量热法等手段对所制备复合相变材料的形貌、稳定性、热性能等进行了表征及测试。实验结果表明,负载石蜡或十八醇的羟基磷灰石气凝胶复合相变材料均具有良好的热性能,质量分数60%石蜡@HAP气凝胶复合相变材料的熔融焓和凝固焓测量值分别为85.10和85.30 J·g?1,结晶度为81.50%;质量分数60%十八醇@HAP气凝胶复合相变材料的熔融焓和凝固焓测量值为113.78和112.25 J·g?1,结晶度为86.20%,且具有很好的热稳定性和化学稳定性。此外,羟基磷灰石气凝胶载体材料阻燃性好,无腐蚀且安全环保,有效拓展了相变材料在智能保温纺织物和建筑材料等领域的实际应用。 相似文献
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A parameter perturbation for the unsteady state heat transfer characteristics of honeycomb regenerator is presented. It is limited to the cases where the storage matrix has a small wall thickness so that no temperature variation in the matrix perpendicular to the flow direction is considered. Starting from a two phase transient thermal model for the gas and storage matrix, an approximate solution for regenerator heat transfer process is derived using the multiple scale method for the limiting case where the longitudinal heat conduction of solid matrix is far less than the convective heat transfer between the gas and the solid. The regenerator temperature profiles are expressed as Taylor series of the coefficient of solid heat conduction item in the model. The analytical validity is shown by comparing the perturbation solution with the experiment and the numerical solution. The results show that it is possible for the perturbation to improve the effectiveness and economics of thermal research on regenerators. 相似文献