共查询到20条相似文献，搜索用时 421 毫秒
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研究了MWCNT－H2O纳米流体的光学及光热特性,利用紫外-可见-近红外分光光度计结合积分球原理测试了不同质量分数的纳米流体在太阳能全波段（250 nm＜λ＜2500 nm）的透射率。利用太阳辐射对纳米流体的光热转换特性进行了测试。实验结果表明：纳米流体的透射率明显低于水的,并且纳米流体的透射率随着粒子质量分数的增加而降低。纳米流体（质量分数为0.02%）的最高温度比水提高了31.87%,集热量比水增加了54.14%。MWCNT－H2O纳米流体有望用在直接吸收式太阳能集热系统中。 相似文献
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基于目前制造半导体的技术,LED输入功率中绝大多数的能量转化为热能,大约只有15%的能量转化为光能,因此必须提高LED的散热能力以保证LED的正常使用.研制了一种新型热管式大功率LED路灯散热器,该散热器的方向垂直于基板,且开设了通孔以便于液体工质在金属薄片的相邻缝隙间流通,以利于降低芯片的结温.通过对LED路灯样品温度测试实验表明安装有新型热管式散热器的LED路灯,温度变化平稳,测量到的最高温度为41.2℃. 相似文献
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纳米级半导体微晶掺入玻璃可产生非线性光学性质,其量子尺寸效应非常明显.用溶胶-凝胶法制备半导体纳米微晶玻璃具有工艺简单和所得产品纯度高、均匀性好的特点.本文对溶胶-凝胶法制备纳米级半导体微晶玻璃的方法及其性能测试的新进展进行综合评述. 相似文献
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纳米级半导体微晶掺入玻璃可产生非线性光学性质，其量子尺寸效应非常明显，用溶胶-凝胶法制备半导体纳米微晶玻璃具有工艺简单和所得产品纯度高、均匀性好的特点，本文对溶胶-凝胶法制备纳米级半导体微晶玻璃的方法及其性能测试的新进展进行综合评述。 相似文献
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以多孔氧化铝膜为模板,通过液-液接触沉淀法成功制备出大面积、高度有序的8-羟基喹啉铝的纳米棒阵列,并对其形貌、成份及荧光性能等进行了表征。结果表明,实验所得8-羟基喹啉铝纳米棒为非晶态结构,相对于8-羟基喹啉,其荧光强度显著增强,荧光峰的位置发生蓝移。 相似文献
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为优化直接乙醇燃料电池的阴极催化剂,该文采用化学还原一步法分别制备出以活性炭、纳米碳和多壁碳纳米管为载体的Pt/C催化剂,研究了载体对催化剂性能的影响,并确定纳米碳为最优载体。以纳米碳为载体,采用相同工艺制备出具有核壳结构的Pt-Fe和Pt-Co合金催化剂,将其与Pt/纳米碳催化剂进行对比分析,探究了Fe、Co两种过渡金属对催化剂氧还原性能、稳定性等的影响,最终获得性能优于商业Pt/C催化剂的Pt-Fe/纳米碳合金催化剂。改进了电极制备及单电池装配工艺,提高了电池性能和实验成功率。 相似文献
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采用表面修饰法制备了聚合物包覆的纳米SiC颗粒,采用M-200环块试验机进行摩擦学试验,研究了表面修饰的纳米SiC颗粒添加剂在钢-铝摩擦副中对发动机润滑油(15W/40)减摩性能的影响,并利用扫描电子显微镜对磨块的磨损表面形貌进行观察,分析了润滑剂的减摩机理。结果表明:当载荷为700N、1000N时,以纳米油作润滑剂的磨块磨痕宽度低于以基础油作润滑剂的磨块磨痕宽度;以纳米润滑油作润滑剂的磨块磨损表面出现了大量的表面膜,减少了磨损。 相似文献
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说起“纳米”，大家可能都不陌生。这是一个近些年来被炒得沸沸扬扬的词汇，什么“纳米冰箱”、“纳米眼镜”、“纳米化妆品”……仿佛我们已经进入了一个“纳米时代”。但说到纳米艺术，可能绝大多数人还比较陌生。 相似文献
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Performance of a single-stage Linde-Hampson refrigerator operating with binary refrigerants at the temperature level of-60 ℃＊ 总被引：1，自引：1，他引：0
The optimization of the performance of a single-stage Linde-Hampson refrigerator （LHR） operating with six different binary refrigerants （R23/R134a, R23/R227ea, R23/R236ea, R170/R290, R170/R600a and R170/R600） with ozone depletion potentials （ODPs） of zero was conducted using a new approach at the temperature level of-60℃. Among these binary refrig- erants, the 0.55 and the 0.6 mole fractions of R23 for R23/R236ea are the most prospective nonflammable ones for the medium and low suction pressure compressors, respectively. For these two kinds of compressors, the 0.6 and the 0.65 mole fractions of R170 for R 170/R600, respectively, are the most prospective binary refrigerants with low global warming potentials （GWPs）. The results of optimization of pressure levels indicate that the optimum low pressure value for coefficients of performance （COP） is achieved when the minimum temperature differences occur at both the hot and the cold ends of the recuperator at a specified composition and pressure ratio. Two useful new parameters, the entropy production per unit heat recuperated and the ratio of heat recuperating capacity to the power consumption of the compression, were introduced to analyze the exergy loss ratio in the recuperator. The new approach employed in this paper also suggests a promising application even to the optimization of the performance with multi-component refrigerants. 相似文献
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The optimization of the performance of a single-stage Linde-Hampson refrigerator (LHR) operating with six different binary refrigerants (R23/RI34a, R23/R227ea, R23/R236ea, R170/R290, RI70/R600a and R170/R600) with ozone depletion potentials (ODPs) of zero was conducted using a new approach at the temperature level of-60 ℃. Among these binary refrig-erants, the 0.55 and the 0.6 mole fractions of R23 for R23/R236ea are the most prospective nonflammable ones for the medium and low suction pressure compressors, respectively. For these two kinds of compressors, the 0.6 and the 0.65 mole fractions of R170 for R170/R600, respectively, are the most prospective binary refrigerants with low global wanning potentials (GWPs). The results of optimization of pressure levels indicate that the optimum low pressure value for coefficients of performance (COP) is achieved when the minimum temperature differences occur at both the hot and the cold ends of the recuperator at a specified composition and pressure ratio. Two useful new parameters, the entropy production per unit heat recuperated and the ratio of heat recuperating capacity to the power consumption of the compression, were introduced to analyze the exergy loss ratio in the recuperator. The new approach employed in this paper also suggests a promising application even to the optimization of the performance with multi-component refrigerants. 相似文献
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This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator (ACR) operating with a
rectifying column and six types of binary refrigerants (R23/R134a, R23/R227ea, R23/R236fa, R170/R290, R170/R600a, and R170/R600)
at a temperature level of −60 °C. Half of the six binary refrigerants are nonflammable, of which the 0.5 and the 0.6 mole
fractions of R23 for the R23/R236fa possess the most prospective composition for the medium and low suction pressure compressors,
respectively. The remaining three binary refrigerants are flammable but with low global warming potentials, of which the 0.6
mole fraction of R170 for the R170/R600 is the most prospective one. The results show that the overall matching as well as
local matching of heat capacity rates of hot and cold refrigerants in the recuperators are important for the improvement of
coefficient of performance of the cycle, which can be adjusted through the simultaneous optimization of the pressure level
and composition. The new approach proposed also offers a wider range of applications to the optimization in performance of
the cycle using multi-component refrigerants. 相似文献
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杨惠山 《泉州师范学院学报》2002,20(4):22-25
建立一类不可逆斯特林制冷机模型，研究一般传热规律下斯特林制冷机的基本优化关系，并讨论热阻，回热损失对斯特林制冷机性能的影响，所得结论可为二热源机的研制和优化设计提供新的理论指导。 相似文献
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王生软 《黄冈职业技术学院学报》2012,14(5):100-102
压缩机是电冰箱核心部件,它为整个制冷系统提供动力,其选择是否合理,关系到整个系统的经济性和可靠性。针对分凝式双温冰箱在230K温区及混合工质R32/R 600a(30/70)的最佳配比下,进行压缩机的选型计算。 相似文献
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Seyed Sahand SEBTI Mohammad MASTIANI Hooshyar MIRZAEI Abdolrahman DADVAND Sina KASHANI Seyed Amir HOSSEINI 《浙江大学学报(A卷英文版)》2013,14(5):307-316
A comprehensive numerical study was conducted to investigate heat transfer enhancement during the melting process in a 2D square cavity through dispersion of nanoparticles. A paraffin-based nanofluid containing various volume fractions of Cu was applied. The governing equations were solved on a non-uniform mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid-liquid interface. The effects of nanoparticle dispersion in a pure fluid and of some significant parameters, namely nanoparticle volume fraction, cavity size and hot wall temperature, on the fluid flow, heat transfer features and melting time were studied. The results are presented in terms of temperature and velocity profiles, streamlines, isotherms, moving interface position, solid fraction and dimensionless heat flux. The suspended nanoparticles caused an increase in thermal conductivity of nano-enhanced phase change material (NEPCM) compared to conventional PCM, resulting in heat transfer enhancement and a higher melting rate. In addition, the nanofluid heat transfer rate increased and the melting time decreased as the volume fraction of nanoparticles increased. The higher temperature difference between the melting temperature and the hot wall temperature expedited the melting process of NEPCM. 相似文献
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杨惠山 《泉州师范学院学报》2004,22(4):12-16
应用有限时间热力学理论,建立铁磁斯特林制冷循环模型,考虑有限速率热传导、回热损失等因素,基于铁磁材料的热力学性质,导出铁磁斯特林制冷循环的优化性能,进而以利润率为目标,导得最大利润率情况时的制冷系数及其他性能参数,所得结论可为铁磁斯特林制冷机的研制和设计提供理论指导.① 相似文献
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根据工程热力学、传热学、热工测试技术等关于换热器性能的基本测试原理和方法,结合现行的国家标准与规范要求,研发了水源热泵用换热器综合实验台.该实验台利用控制与测量技术,采用被测换热器与辅助换热器水侧部分的冷热负荷,通过水-水板式热交换器相互抵消方法,以及换热器两侧热平衡工作原理,即换热器水侧吸收或放出的热量与制冷剂侧放出或吸收的热量基本相等,可以实现在不同工况下对不同结构形式的R22蒸发器及冷凝器的换热性能和流体阻力性能进行全面的测试.为换热器的选型、优化设计和新产品开发提供依据和验证手段. 相似文献
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CHERALATHAN M VELRAJ R. RENGANARAYANAN S. 《浙江大学学报(A卷英文版)》2006,7(11):1886-1895
INTRODUCTION Cool thermal energy storage (CTES) using the latent heat concept as an alternative to sensible heat storage offers a good option because of its high storage density and the nearly constant temperature heat removal characteristics during the discharging cycle. Since the principle of latent cool storage nec- essarily involves a change of state, heat transfer must occur in different modes depending on the state of charging and discharging. During the periods of low cooling dema… 相似文献
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溴化锂吸收式制冷机的性能，通常指运行时所产生的冷量及与之相关的热力系数，蒸汽单耗等技术经济指标而言，分析影响溴冷机性能的各种因素，研究提高溴冷机性能，延长使用寿命的方案。 相似文献