共查询到20条相似文献,搜索用时 203 毫秒
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针对空间相机内部隔热板起到隔离入射太阳光影响相机内部光学结构的作用,其厚度较小,一般不采用额外的散热措施,入射太阳光能量作用其上会引起较大的温升,温度增加的不均匀会增加相机内部的红外杂散辐射,提出一套完整的隔热板厚度优化方法。在保证隔热板体积不变的前提下,利用仿生优化原理,根据隔热板各处的温度梯度差异调整隔热板的厚度。对优化出的隔热板厚度函数进行高斯滤波处理,使隔热板的厚度变化均匀,便于加工。通过对比优化前后的温度场与红外场,发现优化后最高温度降低了3.8℃,其3 m ~5 m,8 m~12 m波段的红外辐出度降低了15%,该优化方法可以作为内部杂散辐射的抑制手段与其他方法一起实施。 相似文献
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袁培康浩杰李丹吕彦力 《低温与超导》2017,(3):62-66
数值模拟了汽车车室内的温度场和速度场,忽略太阳辐射,采用RNG模型,近壁面用壁面函数法进行处理,分析了不同的送风速度,送风温度,出口压力对汽车室内温度场和速度场分布的影响,对车室内的温度场和速度场的均匀性做出评价并对其优化。结果表明在车室后排空间添加一个送风口,可以有效地改善车室内温度场和速度场分布的均匀性,温度场均匀性提高了36.5%,速度场均匀性提高了45.2%。 相似文献
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煤粉炉内弥散介质辐射传热的综合模拟 总被引:3,自引:0,他引:3
本文基于辐射传热计算的DT法和颗粒运动计算的随机轨道法,并结合单颗粒的辐射特性模型,构造了能够详细考虑颗粒燃尽、湍流弥散诸因素对炉内空间局部辐射特性及总体辐射传热影响的弥散介质辐射传热计算模型,并将其耦合到炉内过程的总体数值模型中。采用该程序,比较计算了几种颗粒辐射特性模型对某300MW锅炉炉内温度场的预报结果,结果表明:通常采用的均匀颗粒辐射特性模型会导致温度场的极大误差;由于炉内颗粒浓度的不均匀分布,炉内的温度分布呈现高度非均匀状态,在炉膛轴线上有大面积的高温烟气区存在;考虑残炭存在时,温度分布的不均匀性更显著. 相似文献
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《工程热物理学报》2020,(8)
为明确冷压缩机整机温度场分布,寻求最优冷却设计参数,本文以理化所自主研制的冷压缩机为背景,对冷压缩机进行传热与温度场分布分析。基于流体力学与传热学基本理论建立了涵盖整个冷压缩机的物理模型进行仿真计算。在此基础上,通过CCD(中心组合设计)采样,结合最小二乘法构建系统温度场等各变量的二阶响应面近似模型。随后以向叶轮传热最小与转子焊缝处平均温度最高为优化目标,采用多目标遗传算法对整机冷却参数进行优化,探求最优Pareto解组合方案。研究结果表明:冷压缩机内部负压氦气流场复杂,转子散热能力较差,冷却参数对冷压机温度场分布影响较大。优化得到冷压缩机最优冷却参数,并发现铜热锚结构有较大优化空间,为以后冷压缩机设计加工提供必要依据。 相似文献
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A comparison of different entransy flow definitions and entropy generation in thermal radiation optimization
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In thermal radiation, taking heat flow as an extensive quantity and defining the potential as temperature T or the black body emissive power U will lead to two different definitions of radiation entransy flow and the corresponding principles for thermal radiation optimization. The two definitions of radiation entransy flow and the corresponding optimization prin ciples are compared in this paper. When the total heat flow is given, the optimization objectives of the extremum entransy dissipation principles (EEDPs) developed based on potentials T and U correspond to the minimum equivalent temperature difference and the minimum equivalent blackbody emissive power difference respectively. The physical meaning of the definition based on potential U is clearer than that based on potential T, but the latter one can be used for the coupled heat transfer optimization problem while the former one cannot. The extremum entropy generation principle (EEGP) for thermal radiation is also derived, which includes the minimum entropy generation principle for thermal radiation. When the radiation heat flow is prescribed, the EEGP reveals that the minimum entropy generation leads to the minimum equivalent thermodynamic potential difference, which is not the expected objective in heat transfer. Therefore, the minimum entropy generation is not always appropriate for thermal radiation optimization. Finally, three thermal radiation optimization examples are discussed, and the results show that the difference in optimization objective between the EEDPs and the EEGP leads to the difference between the optimization results. The EEDP based on potential T is more useful in practical application since its optimization objective is usually consistent with the expected one. 相似文献
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《中国物理 B》2019,(6)
The uniformity principle of temperature difference field is very useful in heat exchanger analyses and optimizations.In this paper, we analyze some other heat transfer optimization problems in the thermal management system of spacecrafts,including the cooling of thermal components, the one-stream series-wound heat exchanger network, the volume-to-point heat conduction problem, and the radiative heat transfer optimization problem, and have found that the uniformity principle of temperature difference field also holds. When the design objectives under the given constraints are achieved, the distributions of the temperature difference fields are uniform. The principle reflects the characteristic of the distribution of potential in the heat transfer optimization problems. It is also shown that the principle is consistent with the entransy theory. Therefore, although the principle is intuitive and phenomenological, the entransy theory can be the physical basis of the principle. 相似文献
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基于绝热过程(火积)耗散极值原理, 分别在对流传热和复合传热(对流和辐射传热)边界条件下, 对轧钢加热炉壁变截面绝热层进行构形优化, 得到(火积)耗散率最小的绝热层最优构形. 结果表明: 与等截面绝热层相比, (火积)耗散率最小的变截面绝热层整体绝热性能更优. 热损失率最小和(火积)耗散率最小的绝热层最优构形是不同的. 热损失率最小的绝热层最优构形使得其能量损失减小, 而(火积)耗散率最小的绝热层最优构形使得其整体绝热性能提高. (火积)耗散率最小和最大温度梯度最小的变截面绝热层最优构形差别较小, 此时(火积)耗散率最小的绝热层最优构形在提高绝热层整体绝热性能的同时也提高了其热安全性. 基于(火积)理论的绝热层构形优化为绝热系统的优化设计提供了新的指导. 相似文献
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The entransy theory developed in recent years is used to optimize the aspect ratio of a plate fin in heat convection.Based on a two-dimensional model,the theoretical analysis shows that the minimum thermal resistance defined with the concept of entransy dissipation corresponds to the maximum heat transfer rate when the temperature of the heating surface is fixed.On the other hand,when the heat flux of the heating surface is fixed,the minimum thermal resistance corresponds to the minimum average temperature of the heating surface.The entropy optimization is also given for the heat transfer processes.It is observed that the minimum entropy generation,the minimum entropy generation number,and the minimum revised entropy generation number do not always correspond to the best heat transfer performance.In addition,the influence factors on the optimized aspect ratio of the plate fin are also discussed.The optimized ratio decreases with the enhancement of heat convection,while it increases with fin thermal conductivity increasing. 相似文献
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基于构形理论, 以(火积)耗散率最小为优化目标, 在微、纳米尺度下对圆盘导热问题进行构形优化, 得到尺寸效应影响下的无量纲当量热阻最小的圆盘构造体最优构形. 结果表明: 在微、纳米尺度下, 尺寸效应影响下的圆盘构造体最优构形与无尺寸效应影响时的圆盘构造体最优构形有明显区别. 存在最佳无量纲高导热材料通道长度使无量纲当量热阻取得最小值; 随着扇形单元体数目的增大, 最小无量纲当量热阻先减小后增大, 存在最佳的扇形单元体数目使得无量纲当量热阻取得双重最小值, 这与常规尺度下圆盘构造体相应的性能特性明显不同. (火积)耗散率最小的圆盘构造体(火积)耗散率比最大温差最小的构造体(火积)耗散率降低了7.31%, 也即圆盘构造体的平均传热温差降低了7.31%. 微、纳米尺度下基于(火积)耗散率最小的圆盘构造体最优构形能够降低圆盘构造体的平均传热温差, 同时有助于提高其整体传热性能. 本文工作有助于进一步拓展(火积)耗散极值原理的应用范围.
关键词:
构形理论
(火积)耗散率最小
微、纳米尺度
广义热力学优化 相似文献
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提高传热过程的性能是解决能源问题的重要途径之一. 本文通过与力学中相关概念进行对比,分析了传热过程性能优化的新物理量——(火积)的宏观物理意义. 通过(火积)与物体对外传热能力、(火积)定义的传热过程效率以及(火积)与热量传递驱动力的关系三方面分析,发现(火积)具有的宏观物理意义是物体包含的热量在温度场中所具有的势能. 并且,通过对流换热的(火积)理论优化介绍了(火积)理论在工程实际中的应用.
关键词:
(火积)
宏观物理意义
势能
对流换热 相似文献
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基于构形理论, 以基于(火积)耗散率定义的当量热阻最小为优化目标对复杂肋片进行构形优化, 得到同时考虑肋片导热和对流换热(火积)耗散性能的肋片最优构形, 并比较不同形状和不同优化目标下的肋片最优构形. 结果表明: 存在最佳单元级直肋、中部空腔以及肋片末梢高度和长度比使得复杂肋片当量热阻取得三重最小值. 当量热阻最小的复杂肋片最优构形与T-Y形肋片最优构形相比, 复杂肋片结构使得肋片整体传热性能大大提高. 当肋片传热为二维传热且根部较宽时, 肋片根部温度越不均匀, 当量热阻最小和最大热阻最小的复杂肋片最优构形差别越大. 在保证热安全性的前提下, 工程上对肋片进行优化设计时可选择当量热阻最小的肋片构形设计方案以降低其平均传热温差、提高整体传热性能. 本文从传热优化角度为复杂肋片的优化设计提供了参考. 相似文献
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对流换热过程的热力学优化与传热优化 总被引:1,自引:0,他引:1
为了进一步明确对流换热过程中热力学优化与传热优化之间的差异,本文分别利用熵产最小原理、(火积)耗散极值原理针对两种边界条件下的对流换热问题进行分析,讨论熵产,(火积)耗散与有用能损失以及对流换热能力之间的关系.结果表明:熵产最小意味着系统的有用能损失最小,但并不反映系统的对流换热能力的强弱;而(火积)耗散取极值意味着系统的对流换热能力最强,但与系统的有用能损失不存在对应关系.因此,对于将降低有用能损失作为优化目标的换热问题应采用熵产最小原理进行分析;而对于需要将提高换热能力作为优化目标的对流换热问题应采用(火积)耗散极值原理进行分析. 相似文献
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基于构形理论, 以(火积)耗散率最小为优化目标, 对冷却流道的“盘点”传热问题进行构形优化, 得到冷却流道的圆盘构造体最优构形. 结果表明: 对于扇形单元体, 在其泵功率给定的条件下, 存在最佳展弦比使得扇形单元体无量纲当量热阻取得最小值; 对于一级树状圆盘, 在其总泵功率给定的条件下, 存在一级与单元级最佳流道宽度比和扇形单元体最佳无量纲半径使 得一级树状圆盘无量纲当量热阻取得最小值, 且一级与单元级最佳流道宽度比仅与单元体分支数有关. 当中心圆盘半径等于0时, 一级树状圆盘最终退化成辐射状圆盘, 此时一级树状圆盘半径为临界半径. 当一级树状圆盘半径大于临界半径时, 需对圆盘冷却流道采用树状布置, 反之则采用辐射状布置. 存在最佳单元体分支数使得无量纲当量热阻取得最小值, 这与高导热材料通道的“盘点”导热构形优化结果有明显区别. (火积)耗散率最小和最大温差最小的一级树状冷却流 道圆盘构造体最优构形是不同的. 与最大温差最小的冷却流道圆盘构造体相比, (火积)耗散率最小的冷却流道圆盘构造体当量热阻得到极大降低, 其整体传热性能得到明显提高. 因此, (火积)耗散极值原理与对流构形优化相结合, 有助于进一步揭示(火积)耗散极值原理在传热优化方面的优越性.
关键词:
构形理论
(火积)耗散率
冷却流道
广义热力学优化 相似文献
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With the aid of constructal theory and entransy theory, a Tau-shaped fin (TAUSF) is investigated in this paper, and the widths of the bend end and elemental fins are assumed to be different. The construct of the TAUSF is optimized by the minimum equivalent thermal resistance (ETR) obtained by entransy dissipation rate. The constraints of total enveloping volume and fin material volume are considered. The results show that in the specified range of width ratio, the twice minimum ETR of the TAUSF can be yielded by an optimal width ratio and an optimal length ratio. In addition, comparing the optimal performance of the TAUSF with the counterpart of a T-shaped fin, the former sacrifices a small amount of heat transfer performance and its stiffness increases due to its structure with the bend end. The optimal structure of the TAUSF yielded from ETR minimization is conspicuously different with the counterpart yielded from maximum thermal resistance minimization. Comparing the thermal performances of the two optimal constructs, the ETR of the former optimal construct is declined by 10.58%, whereas the maximum thermal resistance is augmented by 5.22%. The former optimal construct can lead to the uniformity of temperature gradient and the reduction in thermal stress, and can guide the engineering designs of practical fins. 相似文献