The Thermal Conductivity of Ordinary Water Substance_26407044

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thermal conductivity单位

热导率（Thermal Conductivity）概述热导率（Thermal Conductivity）是一个用于描述材料导热性能的物理量，指的是材料单位长度内传导热量的能力。

在物理学和工程学中，热传导是热量从高温区域向低温区域传递的过程。

热导率是一个重要的物理参数，可以帮助我们理解材料在热传导方面的性能。

定义与单位热导率可用下述公式来定义：热导率 = 传热速率 / 温度梯度其中，传热速率是单位时间内经过单位面积的热量，温度梯度是温度的空间变化率。

热导率的单位在SI国际单位制中为瓦特/（米·开尔文）（W/(m·K)），也可使用国际单位制词头来表示更大或更小的热导率。

例如，千瓦特/（米·开尔文）（kW/(m·K)）表示较高的热导率，毫瓦特/（米·开尔文）（mW/(m·K)）表示较低的热导率。

决定热导率的因素热导率受多种因素的影响，包括材料的物理性质和结构、温度以及湿度等。

材料的物理性质和结构材料的物理性质和结构对其热导率起着决定性作用。

具有高导热性能的材料通常具有较低的电阻率，因为热传导与电子在材料中的自由移动密切相关。

晶体结构的存在也会对热导率产生影响，因为传热是由声子传导完成的，而晶格中的缺陷、界面、晶格畸变等因素会影响声子的传输。

温度温度是影响热导率的一个重要因素。

通常情况下，随着温度的升高，热导率会增加，因为热激励使得材料中的粒子更具活性，能量更容易传递。

湿度湿度对于某些材料来说也是一个影响热导率的重要因素。

对于含水材料来说，湿度的增加会增加材料中的热传导。

这是因为水分子可以通过氢键与其他分子相互作用，从而增加整体传热效果。

应用热导率的理解对于许多工程和科学领域都是至关重要的。

以下是一些典型的应用示例：材料选择和设计对于需要具有良好热传导性能的应用，例如散热器、导热界面材料等，热导率是材料选择和设计的重要考虑因素。

较高的热导率可以提高热传递效率，从而降低材料的温度和热应力。

《消防燃烧学》常用缩写符号表

β Cooling modulus 冷却模数
γ Energy modulus 能量模数
γA,γBB Activity coefficients 活度系数
δcr Critical value of Frank-kamanetsikii's δ F-K临界δ值
δh Thickness of hydrodynamic boundary layer (m) 水力边界层厚度
R Burning rate 燃烧速率 Re Reynolds number (ux/ν) 雷诺数 (ux/ν)
S Surface area 表面面积
t Time (seconds) 时间（秒） te Escape time 逃离时间 tu Time to achieve untenable conditions 从火灾开始到人体不能承受的时间 T Temperature (C or k) 温度
∆U Change in internal energy (kJ/mol) 内能变化
ε Emissivity 发射率
θ
Temperature difference (e.g. T-T∞ ) 温差(例如 T-T∞ )
θ Dimensionless temperature 无量纲温度
θ Angle 角度
q& Rate of heat transfer (W or kW) 传热速率 qf Fire load (MJ or kg) 火灾荷载 Q& Rate of heat transfer (W or kW) 传热速率 Q&c Rate of heat release (W or kW) 热释放速率 Q&conv Rate of convective heat release from a frame 火焰对流热释放速率 Q&c′′′ Rate of heat production per unit volume (W/m3) 单位体积生热速率 Q* Dimensionless heat release rate 无量纲热释放速率

英文原文

Liang Guo Stephen L.Hodson Timothy S.FisherXianfan Xu1e-mail:xxu@ School of Mechanical Engineering and Birck Nanotechnology Center,Purdue University,West Lafayette,IN47907Heat Transfer AcrossMetal-Dielectric Interfaces During Ultrafast-Laser Heating Heat transfer across metal-dielectric interfaces involves transport of electrons and pho-nons accomplished either by coupling between phonons in metal and dielectric or by cou-pling between electrons in metal and phonons in dielectric.In this work,we investigate heat transfer across metal-dielectric interfaces during ultrafast-laser heating of thin metalﬁlms coated on dielectric substrates.By employing ultrafast-laser heating that cre-ates strong thermal nonequilibrium between electrons and phonons in metal,it is possible to isolate the effect of the direct electron–phonon coupling across the interface and thus facilitate its study.Transient thermo-reﬂectance measurements using femtosecond laser pulses are performed on Au–Si samples while the simulation results based on a two-temperature model are compared with the measured data.A contact resistance between electrons in Au and phonons in Si represents the coupling strength of the direct electron–phonon interactions at the interface.Our results reveal that this contact resist-ance can be sufﬁciently small to indicate strong direct coupling between electrons in metal and phonons in dielectric.[DOI:10.1115/1.4005255]Keywords:interface thermal resistance,ultrafast laser,thermo-reﬂectance,two-temper-ature model,electron–phonon coupling1IntroductionInterface heat transfer is one of the major concerns in the design of microscale and nanoscale devices.In metal,electrons,and pho-nons are both energy carriers while in dielectric phonons are the main energy carrier.Therefore,for metal-dielectric composite structures,heat can transfer across the interface by coupling between phonons in metal and dielectric or by coupling between electrons in metal and phonons in dielectric through electron-interface scattering.Phonon–phonon coupling has been simulated mainly by the acoustic mismatch model and the diffuse mismatch model[1].As for electron–phonon coupling,there are different viewpoints.Some studies have assumed that electron–phonon coupling across a metal-dielectric interface is negligible and heat transfer occurs as electron–phonon coupling within metal and then phonon–phonon coupling across the interface[2].Electron–phonon coupling between metal(Cr,Ti,Al,Ni,and Pt)and SiO2 has exhibited negligible apparent thermal resistance using a parallel-strip technique[3].On the other hand,comparison between simulations and transient thermal reﬂectance(TTR) measurements for Au-dielectric interfaces reveals that energy could be lost to the substrate by electron-interface scattering dur-ing ultrafast-laser heating,and this effect depends on electron temperature and substrate thermal properties[4–6].In this study,we employ TTR techniques to investigate inter-face heat transfer for thin goldﬁlms of varying thicknesses on sili-con substrates.(Here,we consider silicon as a dielectric since heat is carried by phonons in silicon.)Similar work has been reported [5].In our model,we consider two temperatures in metal and also the temperature in the dielectric substrate.This allows us to inves-tigate the effect of both the coupling between electrons in metal and phonons in the dielectric substrate,and the coupling between phonons in metal and phonons in the dielectric substrate,and allows us to isolate the effect of the electron–phonon coupling across the interface that can be determined from the TTR mea-surement.Experimentally,we employ pulse stretching to mini-mize the effect of nonequilibrium among the electrons.As a result,the experimental data can be well-explained using the com-putational model.The thermal resistance between electrons in Au and phonons in Si,which quantiﬁes the direct electron–phonon coupling strength,is calculated from the measured data.The results reveal that in the thermal nonequilibrium state,this electron–phonon coupling at the interface is strong enough to dominate the overall interface heat transfer.2TTR MeasurementAu–Si samples of varying Au thicknesses were prepared by thermal evaporation at a pressure of the order of10À7Torr.The thicknesses of the goldﬁlms are39,46,60,77,and250nm,meas-ured using an atomic force microscope.The pump-and-probe technique is used in a collinear scheme to measure the thermo-reﬂectance signal.The laser pulses are generated by a Spectra Physics Ti:Sapphire ampliﬁed femtosecond system with a central wavelength of800nm and a repetition rate of5kHz.The wave-length of the pump beam is then converted to400nm with a sec-ond harmonic crystal.The pump pulse has a pulse width(full width at half maximum-FWHM)of390fs measured by the sum-frequency cross-correlation method and is focused onto the sam-ple with a spot radius of20.3l m.The probe beam has a central wavelength of800nm and a pulse width of205fs measured by autocorrelation and is focused with a spot radius of16.9l m.This pump pulse width is intentionally stretched from the original pulse width of50fs to minimize the inﬂuence of thermal nonequili-brium among electrons since the electron thermalization time in Au can be of the order of100fs[7].This thermalization time is pump wavelength and pumpﬂuence dependent,and can be of the order of10fs if higher laserﬂuence is used[8,9].Our experiments did show the importance of pulse stretching.Figure1shows the TTR measurement results for the sample of thickness77nm with different pumpﬂuences before and after stretching the pulse.The plots show the normalized relative reﬂectance change(ÀD R/R)1Corresponding author.Contributed by the Heat Transfer Division of ASME for publication in the J OURNAL OF H EAT T RANSFER.Manuscript received May18,2011;ﬁnal manuscript received September30,2011;published online February13,2012.Assoc.Editor: Robert D.Tzou.with the delay time between the pump and the probe pulses to show the contrast in cooling rates.With a shorter pulse (Fig.1(a )),a steep initial drop is seen in the signal,which is attributed to the behavior of nonequilibrium among electrons.Since the TTM to be used for simulation assumes a well-deﬁned tempera-ture for electrons,i.e.,the electrons in gold have reached thermal equilibrium (not necessarily a uniform temperature),the model cannot predict the fast initial drop in the signals in Fig.1(a ).As will be shown later,the signals obtained by stretching the pulse can be predicted well using the TTM.3Two-Temperature Model for Thermal Reflectance MeasurementsUltrafast-laser heating induces thermal nonequilibrium between electrons and phonons in metal,which can be described by the TTM [10–13].We note that the heterogeneous interface consid-ered here involves three primary temperature variables (two in the metal and one in the dielectric).The “two-temperature”model is applied to the metal side.For investigating electron–phonon and phonon–phonon coupling at the interface,two thermal resistances are deﬁned:R es (its reciprocal)indicates the coupling strength between electrons in metal and phonons in dielectric,while R ps indicates the coupling strength between phonons in metal and phonons in dielectric.(Large thermal resistance corresponds to weak coupling.)The resulting governing equations,initial,and interface conditions areC e @T e @t ¼k e @2T e@x2ÀG ðT e ÀT p ÞþS (1a )C p @T p @t ¼k p @2T p @x 2þG ðT e ÀT p Þ(1b )C s @T s @t ¼k s @2T s@x(1c )T e ðt ¼0Þ¼T p ðt ¼0Þ¼T s ðt ¼0Þ¼T 0(2)Àk e@T e @xx ¼L ¼T e ÀT s R es x ¼L(3a )Àk p @T px ¼L ¼T p ÀT s ps x ¼L(3b )Àk s@T sx ¼L ¼T e ÀT s es x ¼L þT p ÀT s ps x ¼L(3c )The subscripts e ,p ,and s denote electrons in metal,phonons in metal,and phonons in the dielectric substrate,respectively.C is the volumetric heat capacity,k is the thermal conductivity,G is the electron–phonon coupling factor governing the rate of energy transfer from electrons to phonons in metal,and L is the thickness of the metal layer.At the front surface of the metal layer insula-tion boundary condition is used due to the much larger heat ﬂux caused by laser heating relative to the heat loss to air.At the rear surface of the substrate,since the thickness of the substrate used is large enough (1l m)so that there is no temperature rise during the time period of consideration,the insulation boundary condition is also applied.Thermal properties of phonons in both metal and dielectric are taken as temperature-independent due to the weak temperature dependence.The thermal conductivity of phonons in metal is much smaller than that of the electrons and is taken in this work as 0.001times the bulk thermal conductivity of gold (311W/(mK)).The volumetric heat capacity of the metal phonon is taken as that of the bulk gold.C e is taken as proportional to T e [14]with the proportion coefﬁcient being 70J/(m 3K 2)[15],and k e is calculated by the model and the data used in Ref.[13]which is valid from the room temperature to the Fermi temperature (6.39Â104K in Au,[14]).G can be obtained using the model derived in Ref.[16].In this work,the value of G at the room tem-perature is taken as 4.6Â1016W/(m 3K)[17],and its dependence on electron and phonon temperatures follows [16].The laser heat-ing source term S is represented by the model used in [13]asS ¼0:94ð1ÀR ÞJ t p ðd þd b Þ1Àexp ÀL d þd bexp Àx d þd b À2:77t t p2"#(4)which assumes all the absorbed laser energy is deposited in the metal layer.J is the ﬂuence of the pump laser,R is the surface re-ﬂectance to the pump,t p is the pulse width (FWHM),d is the opti-cal penetration depth,and d b is the electron ballistic length (around 100nm in Au,[18]).R es and R ps are treated as free pa-rameters for ﬁtting the experimental data.The wavelength of the probe laser in the experiment is centered at 800nm.For this wavelength,the incident photon energy is below the interband transition threshold in Au,which is around 2.47eV [18],and the Drude model can be used to relate the tem-peratures of electrons and phonons to the dielectric function and then the index of refraction,which is expressed as [19]e ¼e 1Àx 2px ðx þi x s Þ(5)x is the frequency of the probe laser and x p is the plasma fre-quency (1.37Â1016rad/s in Au evaluated using the data in Ref.[14]).x s is the electron collisional frequency,the inverse of the electron relaxation time.The temperature dependence ofelectricalFig.1TTR measurement results for the Au–Si sample of Authickness 77nm with different ﬂuences.(a )Results before pulse stretching;(b )results after pulse stretching.resistivity indicates that x s is approximately proportional to pho-non temperature at high temperature [14]and from the Fermi liq-uid theory,its variation with electron temperature is quadratic (T e 2)[20].Therefore,x s is related to T e and T p approximately asx s ¼A ee T 2e þB ep T p(6)A ee is estimated from the low-temperature measurement [21]andB ep is usually estimated from the thermal or electrical resistivity near the room temperature [14].In this work,A ee is taken as the lit-erature value 1.2Â107s À1K À2[6]while e 1and B ep are evaluated by ﬁtting the room-temperature value of the complex dielectric con-stant at 800nm wavelength provided in Ref.[22],which are found to be 9.7and 3.6Â1011s À1K À1,respectively.The complex index of refraction n 0þin 00is the square root of the dielectric ing Eqs.(5)and (6),n 0and n 00are evaluated as 0.16and 4.90,respectively,which agree with the empirical values [23].The re-ﬂectance is then calculated from n 0and n 00by the method of transfer matrix [24],which considers multiple reﬂections in thin ﬁlms.4Results and DiscussionThe results of TTR measurements with a pump ﬂuence of 147J/m 2are plotted in Fig.2.The fast decrease of the reﬂectance indicates that energy transfer between electrons and phonons in metal,followed by a relatively slow decrease after several ps which indicates electrons and phonons have reached thermal equi-librium.The initial cooling rates are smaller for samples with thicknesses less than the electron ballistic length since the electron temperature is almost uniform across the thin ﬁlm,and coupling with phonons within the metal ﬁlm and the dielectric substrate is the only cooling mechanism.For a thicker sample of thickness 250nm,the initial decrease is much faster due to thermal diffu-sion in the gold ﬁlm caused by a gradient of the electron tempera-ture in the ﬁlm.We investigate the effect of R es and R ps using the thermo-reﬂectance signal.Two values of R ps ,1Â10À10m 2K/W and 1Â10À7m 2K/W,are used,each with a parameterized range of values for R es .Figure 3shows the calculated results for the sample with a 39nm-thick gold ﬁlm.Little difference can be seen between Figs.3(a )and 3(b )while different cooling rates are obtained with varying R es in either plot,indicating that the cooling rate is not sensitive to the coupling strength between phonons in metal and dielectric.Note that an interface resistance of 1Â10À10m 2K/W is lower than any reported value,indicating a very high coupling strength between the phonons in metal and dielectric.Conversely,the results vary greatly with the coupling strength between electrons in metal and phonons in dielectric at the interface.This is because the lattice (phonon)temperature rise in metal is much smaller than the elec-tron temperature that the interface coupling between phonons in metal and dielectric does not inﬂuence the surface temperature,which directly determines the measured reﬂectance.On the other hand,the temperature rise of electrons is much higher,and conse-quently,the cooling rate is sensitive to R es .The relatively high sensitivity of R es to that of R ps demonstrates that the former can be isolated for the study of the coupling between electrons in metal and phonons in dielectric.We now use the measured TTR data to estimate R es ,the thermal resistance between electrons in metal and phonons in dielectric.R es is adjusted by the least square method to ﬁt the simulation results with the measured data,and the results are shown in Fig.4.We note that it is impossible to ﬁt the measured results using insu-lation interface condition (i.e.,no coupling or extremely large thermal resistance between electrons in metal and phonons in the dielectric substrate),which will signiﬁcantly underestimate the cooling rate.For thin samples,we ﬁnd that the value of R es is of the order of 10À10to 10À9m 2K/W.This value is below the ther-mal resistances of representative solid–solid interfaces measured in thermal equilibrium [25].This indicates that the direct coupling between electrons in metal and phonons in dielectric is strong.It is also noted that the resistance values increases with the thickness of the gold ﬁlm,indicating a decrease in the coupling strength between electrons in metal and the dielectric substrate.This could be due to the lower electron temperature obtained in thicker ﬁlms,and a decrease of the coupling strength with a decrease in the electron temperature [5].For the sample of thickness 250nm,R es has little effect on the simulation result since the interface is too far from the absorbing surface to inﬂuence the surface tempera-ture,and therefore it is not presented here.The agreement between the ﬁtted results and the measured data is generally good.The small discrepancy between the measured and the ﬁtted results can result from inaccuracy in computingtheFig.2TTR measurement results on Au–Si samples of varying AuthicknessesFig.3Simulation results with varying R es for the Au–Si sample of Au thickness 39nm.(a )R ps 51310210m 2K/W;(b )R ps 5131027m 2K/W.absorption or the temperature.Figure 1(b)shows the normalized TTR measurement results on the sample of thickness 77nm with three laser ﬂuences.It is seen that small variations in the shape of the TTR signals can be caused by different laser ﬂuences and thus the maximum temperature reached in the ﬁlm.Absorption in metal,multiple reﬂections between the metal surface and the Au–Si inter-face,and possible deviations of the properties of thin ﬁlms from those of bulk can all contribute to uncertainties in the temperature simulation;therefore affecting the calculated reﬂectance.With the values of R es shown in Fig.4,the calculation shows that the highest electron temperature,which is at the surface of 39nm–thick gold ﬁlm,is about 6700K.The highest temperature of electrons is roughly inversely proportional to the thickness of the ﬁlms for the four thinner ﬁlms.The highest temperature of elec-trons is much less than the Fermi temperature and thus ensures the validity of the linear dependence of C e on T e [14].The highest temperature for the lattice in metal is about 780K,also in the 39nm-thick gold ﬁlm.This large temperature difference between electrons and lattice indicates that the interface heat transfer is dominated by the coupling between electrons in metal and the phonons in the dielectric substrate.As shown in Fig.4,the meas-ured R es is very low,of the order of 10À10to 10À9m 2K/W.Even if R ps ,which is not determined in this study,is also that low (note that 10À10to 10À9m 2K/W is lower than any reported values),because of the large difference in temperatures between electrons and the phonons in metal,the interface heat transfer rate (Eqs.(3a )–(3c ))due to the coupling between electrons in metal and the substrate is much larger than that due to the coupling between phonons in metal and the substrate.5ConclusionsIn conclusion,TTR measurements using femtosecond laser pulses are performed on Au–Si samples and the results are analyzed using the TTM model.It is shown that due to the strong nonequilibrium between electrons and phonons during ultrafast-laser heating,it is possible to isolate the effect of the direct electron–phonon coupling across the interface,allowing investiga-tion of its ing stretched femtosecond pulses is shown to be able to minimize the nonequilibrium effect among electrons,and is thus more suitable for this study.The TTR measurement data can be well-represented using the TTM parison between the TTR data and the TTM results indicates that the direct coupling due to electron-interface scattering dominates the interface heat transfer during ultrafast-laser heating of thin ﬁlms.AcknowledgmentThis paper is based upon work supported by the Defense Advanced Research Projects Agency and SPAWAR Systems Cen-ter,Paciﬁc under Contract No.N66001-09-C-2013.The authors also thank C.Liebig,Y.Wang,and W.Wu for helpful discussions.NomenclatureA ee ¼coefﬁcient in Eq.(6),s À1K À2B ep ¼coefﬁcient in Eq.(6),s À1K À1C ¼volumetric heat capacity,J/(m 3K)G ¼electron–phonon coupling factor,W/(m 3K)i ¼unit of the imaginary number J ¼ﬂuence of the pump,J/m 2k ¼thermal conductivity,W/(mK)L ¼metal ﬁlm thickness,mn 0¼real part of the complex index of refractionn 00¼imaginary part of the complex index of refraction R ¼interface thermal resistance,m 2K/W;reﬂectance S ¼laser source term,W/m3Fig.4Comparison between the measurement and the simulation results for Au–Si samples of different Au thicknesses.The open circle represents the meas-ured data and the solid line represents the simulation results.(a )39nm ﬁtted by R es 55310210m 2K/W;(b )46nm ﬁtted by R es 56310210m 2K/W;(c )60nm ﬁtted by R es 51.231029m 2K/W;and (d )77nm ﬁtted by R es 51.831029m 2K/W.T¼temperature,Kt¼time,st p¼pulse width of the pump(FWHM),sx¼spatial coordinate,me¼complex dielectric constante1¼constant in the Drude modeld¼radiation penetration depth,md b¼electron ballistic depth,mx¼angular frequency of the probe,rad/sx p¼plasma frequency,rad/sx s¼electron collisional frequency,rad/sSubscripts0¼initial statee¼electron in metales¼electron in metal and phonon in dielectricp¼phonon in metalps¼phonon in metal and phonon in dielectrics¼phonon in dielectricReferences[1]Cahill,D.G.,Ford,W.K.,Goodson,K.E.,Mahan,G.D.,Majumdar,A.,Maris,H.J.,Merlin,R.,and 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[14]Kittel,C.,1976,Introduction to Solid State Physics,John Wiley&Sons,Inc.,New York.[15]Smith,A.N.,and Norris,P.M.,2001,“Inﬂuence of Intraband Transitions onthe Electron Thermoreﬂectance Response of Metals,”Appl.Phys.Lett.,78(9), pp.1240–1242.[16]Chen,J.K.,Latham,W.P.,and Beraun,J.E.,2005,“The Role of Electron–Phonon Coupling in Ultrafast Laser Heating,”ser Appl.,17(1),pp.63–68.[17]Hostetler,J.L.,Smith,A.N.,Czajkowsky,D.M.,and Norris,P.M.,1999,“Measurement of the Electron-Phonon Coupling Factor Dependence on Film Thickness and Grain Size in Au,Cr,and Al,”Applied Optics,38(16),pp.3614–3620.[18]Hohlfeld,J.,Wellershoff,S.-S.,Gudde,J.,Conrad,U.,Jahnke,V.,and Mat-thias,E.,2000,“Electron and Lattice Dynamics Following Optical Excitation of Metals,”Chem.Phys.,251(1–3),pp.237–258.[19]Maier,S.A.,2007,Plasmonics:Fundamentals and Applications,SpringerScienceþBusiness Media,New York.[20]Ashcroft,N.W.,and Mermin,N.D.,(1976),Solid State Physics,W.B.Saun-ders,Philadelphia.[21]MacDonald,A.H.,1980,“Electron-Phonon Enhancement of Electron-ElectronScattering in Al,”Phys.Rev.Lett.,44(7),pp.489–493.[22]Johnson,P.B.,and Christy,R.W.,1972,“Optical Constants of the Noble Met-als,”Phys.Rev.B,6(12),pp.4370–4379.[23]Palik,E.D.,(1998),Handbook of Optical Constants of Solids,Academic,SanDiego.[24]Pedrotti,F.L.,Pedrotti,L.S.,and Pedrotti,L.M.,(2007),Introduction toOptics,Pearson Prentice Hall,Upper Saddle River,NJ.[25]Incropera,F.P.,Dewitt,D.P.,Bergman,T.L.,and Lavine,A.S.,2007,Funda-mentals of Heat and Mass Transfer,John Wiley&Sons,Inc.,Hoboken,NJ.。

材料科学与工程专业英语1-18单元课后翻译答案

材料科学与工程专业英语1-18单元课后翻译答案Unit 1Translation.1.“材料科学”涉及到研究材料的结构与性能的关系。

相反，材料工程是根据材料的结构与性质的关系来涉及或操控材料的结构以求制造出一系列可预定的性质。

2.实际上，所有固体材料的重要性质可以分为六类：机械、电学、热学、磁学、光学、腐蚀性。

3.除了结构与性质，材料科学与工程还有其他两个重要的组成部分，即加工与性能。

4.工程师或科学家越熟悉材料的各种性质、结构、性能之间的关系以及材料的加工技术，根据以上的原则，他或她就会越自信与熟练地对材料进行更明智的选择。

5.只有在少数情况下，材料才具有最优或最理想的综合性质。

因此，有时候有必要为某一性质而牺牲另一性能。

6.Interdisciplinary dielectric constant Solid materials heat capacity Mechanical property electromagnetic radiation Material processing elastic modulus7.It was not until relatively recent times that scientists came to understand therelationships between the structural elements of materials and their properties.8. Materials engineering is to solve the problem during the manufacturing andapplication of materials.9.10.Mechanical properties relate deformation to an applied load or force.Unit 21. 金属是电和热很好的导体，在可见光下不透明；擦亮的金属表面有金属光泽。

玻璃热导率

玻璃热导率
玻璃热导率（Thermal Conductivity of Glass）是指玻璃在受热作用时，热能跨越单位立方英寸温度差的传导率。

玻璃热导率的大小与玻璃中的物理和化学组成有关。

在物理上，玻璃热导率与玻璃中非金属组分（比如硅酸盐和碳酸盐）的含量有关，因为这些物质具有较低的热导率。

同样，玻璃的化学成分也会影响玻璃的热导率，尤其是金属的含量，因为它们具有较高的热导率。

热导率的单位是watts per metre kelvin（W/m*K），通常玻璃的热导率大约为0.9-2.2W/m*K，与玻璃中包含量不同而变化，一些玻璃的热导率可以接近50 W/m*K。

玻璃的热导率较低，因此它们也被称为隔热材料，它们可以保护室内的暖气，阻止外部的热量进入室内；另一方面，它们也可以用来防止室内的温度过高。

如果窗户上做好玻璃的隔热处理，可以有效降低家庭的能源消耗，节省能源。

此外，玻璃的热导率还可以用于热污染控制。

例如，可以使用合适的热导率值来保护室内环境中的温度，以控制冷却系统的热污染。

因此，从目前的情况来看，玻璃热导率是一种非常有用的参数，它在日常生活中有着多种应用，特别是在节能、能源利用和环境控制方面。

在设计窗口时，玻璃热导率也是一个需要考虑的重要参数。

石墨烯复合绝缘结构的轮毂电机定子散热能力研究

立有限公式法温度场数学模型的基础上，分别研究了冷却水温、冷却水流速与电机温升分布的规律。
从上述文献可以看出目前解决电机温升问题的主要方法还是通过在定子与水套之间填充导热材料或增加冷却水道，这些方法都会增大电机的体积。轮毂电机内部空间有限，水道的添加也为轮毂电机的设计增加了难度。因此本文以电机绝缘材料为研究点,在不改变电机结构的前提下，增大电机绝缘的导热性能以提高轮毂电机的散热能力。
第25卷第6期 2021年6月
电机与控制学报 Electric Machines and Control
Vol. 25 No. 6 Jun. 2021
石墨烯复合绝缘结构的轮毂电机定子散热能力研究
陶大军，潘博，戈宝军，王立坤，候鹏，徐骁
(哈尔滨理工大学电气与电子工程学院，哈尔滨150080)
摘要:轮毂电机的效率和稳定性对新能源汽车的品质起着决定性的作用。轮毂电机工作空间紧
DOI：10. 15938/j. emc. 2021.06. 011
中图分类号:TM 341
文献Байду номын сангаас志码:A
文章编号：1007- 449X(2021 )06- 0091-10
Research on heat dissipation capacity of hub motor stator with graphene composite insulation structure
Abstract: The efficiency and stability of hub motor play a decisive role in the quality of new energy vehi cles. The working space of the hub motor is compact, and the temperature rise directly determines the working efficiency and life of the wheel hub motor・ In this paper, taking 75 kW outer rotor hub motor as an example, the three-dimensional physical model of the motor is established, the loss and heat genera・ tion of the hub motor under rated conditions are calculated, and the thermal conductivity and heat transfer coefficient of each part of the hub motor are calculated・ The thermal conductivity and electrical insulation properties of three kinds of epoxy resin composites were compared・ Finally, alumina @ graphene / epoxy resin composite was selected as the insulation structure material of motor. The temperature distribution of the stator with ordinary insulation material and graphene composite insulation material was compared and analyzed・ By extracting the temperature distribution of the characteristic points in the key position of the stator core, the axial temperature distribution of each characteristic point in the two materials was re vealed ・ The research shows that the graphene composite material can significantly enhance the heat dissi-

毕业设计谋画翻译

Earthwork and Reinforcing Steels for ConcreteBecause earthmoving methods and costs change more quicly than those in ang other branch of civil engineering this is a field where are real opprtunities for the enthusiast. In 1935most of the methods now in use for carrying and excavating earth with rubber-tyred equipment did not exist. Most earth was moved by narrow rail track now relatively rare and the main methods of excavation with face shovel backacter or dragline or grab though they are still widely used are only a few of the mang current metods To keep his konwledge of earthmoving equipment up date an engineer must therefore spend time studying modern machines. Generally the only reliable up-to-date information on excavators loaders and transport is obtainable from the makers.Earthwork or earthmoving means cutting into grond where its surface is too high (cuts) and dumping the earth in other places where the surface is too low (fills). To reduce earthwork costs the volome of the fills of equal volume of the cuts and wherever possible the cuts should be placed near to fill of equal volome so as to refuce transport and double handing of the fill .This work of earthwork design falls on the engineer who lays out the road since it is the layout of the earthwork more than anying else which decides its cheapness From the avaible maps and levels the engineer must try to reach as many decides as possilble in the drawing office by drawing cross sections of the earthwork. On the site when further information becimes avaible he can make changes in his sections and layout but the drawing office work will not have been lost. It will have helped him to reach the best solution in the shortest time.The cheapest way of moving earth is to take it directly out of the cut and drop it as fill with the same mathine. This is not always possible but when it can be done it is ideal being both quick and cheap. Draglinesbulldozers and face shoels can do this. The largest radius is obtaind with the dragline and the largest tonnage of earth is moved by the bulldozer though only over short distanse. Thedisadvantages of the dragline are that must dig below itself it connot dig with force into compacted terial it cannot dig on steep slopes and its dumping and digging are not accurate.Face shovels are between bggulldozers and draglines having a larger radius of action than bulldozers but less than draglines. They are able to dig into a vertical cliff face in a way which wouldbe dangerous for a bulldozer operator and impossible for a dragline. Each piece of equipment should be given the work for which it is best suited. Face shovls cannot dig much below the level of their tracks and for deep digs in compact meterial a backacter is most useful but its dumping radius is considerably less than that of the same excavator fitted with a face shovel.Rubber-tyred bowl scraper are indispensable for fairly level digging where the distance of transport is too much for a dragingor face shovel. They can the material deeply (but only below themselves )to a fairly flat surface carry it hundreds of meters if need be then drop it and level it roughly during the dumping . For hard diggging it is often found economical to keep a pusher tractor (wheeled or tracked )on the digging site to push each scraper as it returns to dig . as soon as the scraper is full the pusher tractor returns to the beginning of the di to help the next scraper .Compared with concrete steel is a high strength material. The useful strenth of ordinary reinforcing steels in tension as well as compression the yield strength is about 15 times the compressive strength of common structural concrete and well over 100 times its tensile the other hand steel is a high cost material compared with concrete. It follows that the two materials are best used in combination if the concrete is made to resist the compressive stresses and the steel tensile stresses. Thus in reinforced concrete beams the concrete resists the compressive force longitudinal steel reinforcing bars are located close to the tension force to resist the tension force and usually additional steel bars are so disposed that theny resisit the inclined tension stresses that are caused by the shear force in the beams. Howver reinforcement is also used for resisting compressive forces primarily where it is desisired to redurce the cross-sectinnal dimensionsions of compression members as in the lower floor columns of multistory buildings. Even if no such nessity exists a minimum amount of reinforcement is placed in all compression members to safeguard them against the effects of small accidental bending moments that might crack and even fail an unreinforced member.For most effective reinforcing action it is essential that steel and concrete deform there be a sufficiently strong bond between the two materials to ensure that no relative movemens of the steel bars and the surroundng concrete occur . This bond is provided by the relatively large chemical adhesion which develops at the steel concrete interfaceby the naturral roughness of the mill scale ofhot-roolled reinforing bars and by the closely spaced rib-shaped surface deformations with which reinforcing bars are furnished in order to provide a high degree of interlocking of the two materials.Additional features which make for the satisfactory joint performance of steel and concrete are following:(1) The thermal expansion coefficients of the two materials about *10^-6k for steelvs. An average of *10^-6k for concrete are suffcientiyclose to forestall cracking and other undesirable effects of differential thermal deformations.(2) While the corrosion resistance of bars steel is poor the concrete which surrds the steel reinforcement provides excellent corrosion protectionminnimizing corrosion problems and corresponding maintenance costs.(3) The fire resistance of unprotected steel is impaired by its high thermal conductivity and by the fact that its strengh decreases sizably at high temperratures. Conversely the thermal conductivity of concete is relatively low . Thus damage caused by even prolonged fier exposure if any is generally limited to the uter layer of concrete and amoderate amount of cover prvides suffcient thermal insulation for the embeddedreiforcement.Steel is used in two different ways in concrete structures: as reinforce steel and as prestress steel . Reinforcing steel is placed in the forms prior to casting of the concrete. Stresses in the steel as in the hardened concrete are caused onlyby the loades on the structure except for possible parasitic stresses from shrinkage or similar causes. In contrast in prestresssed concrete structures large tension forces are applied to the reinforcement prior to letting it act jointly with the concrete in resisting external loads .The most common type of reinforcing steel ( as distinct from prestressing steel )is in the from of round bars sometimes called rebars avavilable in a large of diameters from 10 mm to 35 mm for ordinary applications and in two heavy bar sizes of 44 mm and 57 mm .These bars are funisished with surface deformations for these deformations (spcing projection ect .)have been developed inexperimental research. Different bar producers use different patterns all of which satisfy these requirements.Welding of rebars in making splices or for convenience in fabricating reinforcing cages for placemint in the forms may result in metallurgical changes that reduce both strength and ductiliy and special restrictions must be placed both on the type of steel used and the welding provision of ASTM A 706 relate specifically to welding .In reinforced concrete a long –time trend is evident toward the use of higher strengh maerials bothconcrete. Reinforcing bars with 40ksi (276 Mpa ) yield stress almost standard 20 years ago have largely been replaced by bars with 60 ksi (414 Mpa) yield stressboth because they are economical and their use tends to reduce congestion of steel in the forms .The ACI Code permits reinforcing steel up to f=80 ksi (552 Mpa ) . Such high strength steel usually yield gradually but have no yield plateau . In this situation the ACI Code requires that at the specified minimum yield strength the total strain should not is necessary to make current design methods which were developed for shap yielding steels with a yield plateau applicable to such higher strength steels. There is no ASTM specification for deformed bars with yield stress abvoe 60 ksi but such bars may be used according to the ACICode providing they meet the requirements stated. Under special circumstance steel in this higher strength range has its place e g in lower-story columns of high-rise bulidings .In order to minimize corrosion of reinforcement and consequent spalling of concrete under severe exposure conditio such as in bridge decks subjected to deicing chemicals galvanized or epoxy –coated rebars may be specified.土方与用于混凝土中的钢筋由于和土木工程中任何其他工种的施工方式与费用相较，土方挖运的施工方式与费用的转变都要快的多，因此对于有事业心的人来讲，土方工程是一个能够大有作为的领域。

十种园林植物叶片导热系数及对流换热系数测定

接收日期：2022-01-17接受日期：2022-02-07 基金项目：国家自然科学基金资助项目(41371445) *通信作者。

E-mail:***********.cn十种园林植物叶片导热系数及对流换热系数测定孙逸，张言进，付海明*(东华大学环境科学与工程学院，上海 201600)摘要：为研究植物层传热特性，选取校园内十种常见园林植物测定其叶片导热系数、叶片与周边空气对流换热系数，拟合导热系数与叶片含水量的近似关系式，对比实验测定对流换热系数与通过经验公式理论计算所得对流换热系数，比较与叶片接触前后空气的相对湿度。

结果表明，叶片存在降温增湿作用，在5～25 ℃下叶片导热系数随温度变化较小；叶温20 ℃时，叶片导热系数随叶片含水量降低而减小；实验测试对流换热系数与理论计算结果吻合度较高。

关键词：叶片导热系数；对流换热系数；植被层热阻；叶片含水量；降温增湿Doi: 10.3969/j.issn.1009-7791.2022.01.006中图分类号：TK6 文献标识码：A 文章编号：1009-7791(2022)01-0042-06Determination of Thermal Conductivity and Convective Heat TransferCoefficient of Leaves of 10 Species of Landscape PlantsSUN Yi, ZHANG Yan-jin, FU Hai-ming *(College of Environmental Science and Engineering, Donghua University, Shanghai 201600, China)Abstract: In order to study the heat transfer characteristics of plant layer, this paper selected ten species of common landscape plants on the campus, and determined the thermal conductivity of their leaves, convective heat transfer coefficient between leaves and surrounding air, conducts several experimental measurements and analyses, fit the approximate relationship between thermal conductivity and leaf water content, compare the experimentally determined convective heat transfer coefficient with the convective heat transfer coefficient obtained through theoretical calculation of empirical formula, and compare the relative humidity of air before and after contact with leaves. The results showed that there was a cooling and humidifying effect of the leaves; the thermal conductivity of the blade changed less with temperature at 5 to 25 ; ℃When the leaf temperature was 20 , the thermal ℃conductivity of the blade decreased with the reduction of leaf water content; the convective heat transfer coefficient of the experimental test was in high agreement with the theoretical calculation.Key words: leaf thermal conductivity convective; heat transfer coefficient; vegetation layer thermal resistance; leafwater content; cooling and humidification随着国家低碳战略的提出，越来越多的研究尝试通过降低建筑能耗来保护环境[1]，随之出现各种创新的建筑解决方案。

Thermal_conductivity

Thermal conductivityIn physics, thermal conductivity, , is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction. Thermal conductivity is measured in watts per kelvin-meter (W·K−1·m−1, i.e. W/(K·m) or in IP units (Btu·hr−1·ft−1·F−1, i.e. Btu/(hr·ft⋅F). Multiplied by a temperature difference (in kelvins, K) and an area (in square meters, m2), and divided by a thickness (in meters, m), the thermal conductivity predicts the rate of energy loss (in watts, W) through a piece of material. In the window building industry "thermal conductivity" is expressed as the U-Factor [1], which measures the rate of heat transfer and tells you how well the window insulates. U-factor values are generally recorded in IP units (Btu/(hr·ft⋅F)) and usually range from 0.15 to 1.25. The lower the U-factor, the better the window insulates.The reciprocal of thermal conductivity is thermal resistivity.MeasurementThere are a number of ways to measure thermal conductivity. Each of these is suitable for a limited range of materials, depending on the thermal properties and the medium temperature. There is a distinction between steady-state and transient techniques.In general, steady-state techniques are useful when the temperature of the material does not change with time. This makes the signal analysis straightforward (steady state implies constant signals). The disadvantage is that a well-engineered experimental setup is usually needed. The Divided Bar (various types) is the most common device used for consolidated rock samples.The transient techniques perform a measurement during the process of heating up. Their advantage is quicker measurements. Transient methods are usually carried out by needle probes.Standards•IEEE Standard 442-1981, "IEEE guide for soil thermal resistivity measurements", ISBN 0-7381-0794-8. See also soil thermal properties. [2] [3]•IEEE Standard 98-2002, "Standard for the Preparation of Test Procedures for the Thermal Evaluation of Solid Electrical Insulating Materials", ISBN 0-7381-3277-2 [4] [5]•ASTM Standard D5334-08, "Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal Needle Probe Procedure" [6]•ASTM Standard D5470-06, "Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials" [7]•ASTM Standard E1225-04, "Standard Test Method for Thermal Conductivity of Solids by Means of the Guarded-Comparative-Longitudinal Heat Flow Technique" [8]•ASTM Standard D5930-01, "Standard Test Method for Thermal Conductivity of Plastics by Means of a Transient Line-Source Technique" [9]•ASTM Standard D2717-95, "Standard Test Method for Thermal Conductivity of Liquids" [10]•ISO 22007-2:2008 "Plastics -- Determination of thermal conductivity and thermal diffusivity -- Part 2: Transient plane heat source (hot disc) method" [11]•Note: What is called the k-value of construction materials (e.g. window glass) in the U.S., is called λ-value in Europe. What is called U-value (= the inverse of R-value) in the U.S., used to be called k-value in Europe, but is now also called U-value in Europe.DefinitionsThe reciprocal of thermal conductivity is thermal resistivity, usually measured in kelvin-meters per watt (K·m·W−1). When dealing with a known amount of material, its thermal conductance and the reciprocal property, thermal resistance, can be described. Unfortunately, there are differing definitions for these terms.ConductanceFor general scientific use, thermal conductance is the quantity of heat that passes in unit time through a plate of particular area and thickness when its opposite faces differ in temperature by one kelvin. For a plate of thermal conductivity k, area A and thickness L this is kA/L, measured in W·K−1 (equivalent to: W/°C). Thermal conductivity and conductance are analogous to electrical conductivity (A·m−1·V−1) and electrical conductance (A·V−1).There is also a measure known as heat transfer coefficient: the quantity of heat that passes in unit time through unit area of a plate of particular thickness when its opposite faces differ in temperature by one kelvin. The reciprocal is thermal insulance. In summary:•thermal conductance = kA/L, measured in W·K−1•thermal resistance = L/(kA), measured in K·W−1 (equivalent to: °C/W)•heat transfer coefficient = k/L, measured in W·K−1·m−2•thermal insulance = L/k, measured in K·m²·W−1.The heat transfer coefficient is also known as thermal admittanceResistanceWhen thermal resistances occur in series, they are additive. So when heat flows through two components each with a resistance of 1 °C/W, the total resistance is 2 °C/W.A common engineering design problem involves the selection of an appropriate sized heat sink for a given heat source. Working in units of thermal resistance greatly simplifies the design calculation. The following formula can be used to estimate the performance:where:•Ris the maximum thermal resistance of the heat sink to ambient, in °C/Whs•is the temperature difference (temperature drop), in °Cis the thermal power (heat flow), in watts•Pthis the thermal resistance of the heat source, in °C/W•RsFor example, if a component produces 100 W of heat, and has a thermal resistance of 0.5 °C/W, what is the maximum thermal resistance of the heat sink? Suppose the maximum temperature is 125 °C, and the ambient temperature is 25 °C; then the is 100 °C. The heat sink's thermal resistance to ambient must then be 0.5 °C/W or less.TransmittanceA third term, thermal transmittance , incorporates the thermal conductance of a structure along with heat transfer due to convection and radiation. It is measured in the same units as thermal conductance and is sometimes known as the composite thermal conductance . The term U-value is another synonym.SummaryIn summary, for a plate of thermal conductivity k (the k value [12] ), area A and thickness t :•thermal conductance = k /t , measured in W·K −1·m −2;•thermal resistance (R-value ) = t /k , measured in K·m²·W −1;•thermal transmittance (U-value ) = 1/(Σ(t /k )) + convection + radiation, measured in W·K −1·m −2.•K-value refers in Europe to the total insulation value of a building. K-value is obtained by multiplying the form factor of the building (= the total inward surface of the outward walls of the building divided by the total volume of the building) with the average U-value of the outward walls of the building. K value is therefore expressed as (m 2·m −3)·(W·K −1·m −2) = W·K −1·m −3. A house with a volume of 400 m³ and a K-value of 0.45 (the new European norm. It is commonly referred to as K45) will therefore theoretically require 180 W to maintain its interiortemperature 1 K above exterior temperature. So, to maintain the house at 20 °C when it is freezing outside (0 °C),3600 W of continuous heating is required.ExamplesIn metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann-Franz law,as freely moving valence electrons transfer not only electric current but also heat energy. However, the general correlation between electrical and thermal conductance does not hold for other materials, due to the increased importance of phonon carriers for heat in non-metals. As shown in the table below, highly electrically conductive silver is less thermally conductive than diamond, which is an electrical insulator.Thermal conductivity depends on many properties of a material, notably its structure and temperature. For instance,pure crystalline substances exhibit very different thermal conductivities along different crystal axes, due to differences in phonon coupling along a given crystal axis. Sapphire is a notable example of variable thermal conductivity based on orientation and temperature, with 35 W/(m·K) along the c-axis and 32 W/(m·K) along the a-axis.[13]Air and other gases are generally good insulators, in the absence of convection. Therefore, many insulating materials function simply by having a large number of gas-filled pockets which prevent large-scale convection. Examples of these include expanded and extruded polystyrene (popularly referred to as "styrofoam") and silica aerogel. Natural,biological insulators such as fur and feathers achieve similar effects by dramatically inhibiting convection of air or water near an animal's skin.Ceramic is used for its low thermal conductivity on exhaust systems to prevent heat from reachingsensitive componentsLight gases, such as hydrogen and helium typically have high thermalconductivity. Dense gases such as xenon and dichlorodifluoromethanehave low thermal conductivity. An exception, sulfur hexafluoride, adense gas, has a relatively high thermal conductivity due to its highheat capacity. Argon, a gas denser than air, is often used in insulatedglazing (double paned windows) to improve their insulationcharacteristics.Thermal conductivity is important in building insulation and relatedfields. However, materials used in such trades are rarely subjected tochemical purity standards. Several construction materials' k values are listed below. These should be considered approximate due to the uncertainties related to material definitions.The following table is meant as a small sample of data to illustrate the thermal conductivity of various types of substances. For more complete listings of measured k -values, see the references.Experimental valuesExperimental values of thermal conductivity.This is a list of approximate values ofthermal conductivity, k , for somecommon materials. Please consult thelist of thermal conductivities for moreaccurate values, references anddetailed information.Material Thermal conductivityW/(m·K)Silica Aerogel 0.004 - 0.04Air 0.025Wood0.04 - 0.4Hollow Fill Fibre Insulation 0.042Alcohols and oils0.1 - 0.21Polypropylene0.25 [14]Mineral oil0.138Rubber0.16LPG0.23 - 0.26Cement, Portland0.29Epoxy (silica-filled)0.30Epoxy (unfilled)0.59Water (liquid)0.6Thermal grease0.7 - 3Thermal epoxy1 - 7Glass1.1Soil1.5Concrete, stone1.7Ice2Sandstone2.4Stainless steel 12.11 ~ 45.0Lead35.3Aluminium237 (pure)120—180 (alloys)Gold318Copper401Silver429Diamond900 - 2320Graphene(4840±440) - (5300±480)Physical originsHeat flux is exceedingly difficult to control and isolate in a laboratory setting. Thus at the atomic level, there are no simple, correct expressions for thermal conductivity. Atomically, the thermal conductivity of a system is determined by how atoms composing the system interact. There are two different approaches for calculating the thermal conductivity of a system.•The first approach employs the Green-Kubo relations. Although this employs analytic expressions which in principle can be solved, in order to calculate the thermal conductivity of a dense fluid or solid using this relation requires the use of molecular dynamics computer simulation [15].•The second approach is based upon the relaxation time approach. Due to the anharmonicity within the crystal potential, the phonons in the system are known to scatter. There are three main mechanisms for scattering:•Boundary scattering, a phonon hitting the boundary of a system;•Mass defect scattering, a phonon hitting an impurity within the system and scattering;•Phonon-phonon scattering, a phonon breaking into two lower energy phonons or a phonon colliding with another phonon and merging into one higher energy phonon.Lattice wavesHeat transport in both glassy and crystalline dielectric solids occurs through elastic vibrations of the lattice (phonons). This transport is limited by elastic scattering of acoustic phonons by lattice defects. These predictions were confirmed by the experiments of Chang and Jones on commercial glasses and glass ceramics, where mean free paths were limited by "internal boundary scattering" to length scales of 10−2 cm to 10−3 cm. [16][17]The phonon mean free path has been associated directly with the effective relaxation length for processes without directional correlation. Thus, if Vgis the group velocity of a phonon wave packet, then the relaxation length is defined as:where t is the characteristic relaxation time. Since longitudinal waves have a much greater phase velocity thantransverse waves, Vlong is much greater than Vtrans, and the relaxation length or mean free path of longitudinalphonons will be much greater. Thus, thermal conductivity will be largely determined by the speed of longitudinal phonons. [16][18]Regarding the dependence of wave velocity on wavelength or frequency (dispersion), low-frequency phonons of long wavelength will be limited in relaxation length by elastic Rayleigh scattering. This type of light scattering form small particles is proportional to the fourth power of the frequency. For higher frequencies, the power of the frequency will decrease until at highest frequencies scattering is almost frequency independent. Similar arguments were subsequently generalized to many glass forming substances using Brillouin scattering. [19][20][21][22]EquationsFirst, we define heat conduction, H:where is the rate of heat flow, k is the thermal conductivity, A is the total cross sectional area of conductingsurface, ΔT is temperature difference, and x is the thickness of conducting surface separating the 2 temperatures. Dimension of thermal conductivity = M1L1T−3K−1Rearranging the equation gives thermal conductivity:(Note: is the temperature gradient)I.E. It is defined as the quantity of heat, ΔQ, transmitted during time Δt through a thickness x, in a direction normal to a surface of area A, per unit area of A, due to a temperature difference ΔT, under steady state conditions and when the heat transfer is dependent only on the temperature gradient.Alternatively, it can be thought of as a flux of heat (energy per unit area per unit time) divided by a temperature gradient (temperature difference per unit length)Typical units are SI: W/(m·K) and English units: Btu/(h·ft·°F). To convert between the two, use the relation 1 Btu/(h·ft·°F) = 1.730735 W/(m·K). [Perry's Chemical Engineers' Handbook, 7th Edition, Table 1-4]In the textile industry, a tog value may be quoted as a measure of thermal resistance in place of a measure in SI units.References[1]/index.cfm?c=windows_doors.pr_ind_tested[2]/servlet/opac?punumber=2543[3]IEEE Standard 442-1981- IEEE guide for soil thermal resistivity measurements, doi:10.1109/IEEESTD.1981.81018[4]/servlet/opac?punumber=7893[5]IEEE Standard 98-2002 - Standard for the Preparation of Test Procedures for the Thermal Evaluation of Solid Electrical InsulatingMaterials, doi:10.1109/IEEESTD.2002.93617[6]ASTM Standard D5334-08 - Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal NeedleProbe Procedure, doi:10.1520/D5334-08[7]/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/D5470.htm?E+mystore[8]/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/E1225.htm?L+mystore+wnox2486+1189558298[9]/cgi-bin/SoftCart.exe/STORE/filtrexx40.cgi?U+mystore+wnox2486+-L+THERMAL:CONDUCTIVITY+/usr6/htdocs//DATABASE.CART/REDLINE_PAGES/D5930.htm[10]/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/D2717.htm?L+mystore+wnox2486+1189564966[11]/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=40683[12]Definition of k value from Plastics New Zealand (/page.asp?id=468)[13]/sapphire.htm[14]Walter Michaeli, Extrusion Dies for Plastics and Rubber, 2nd Ed., Hanser Publishers, New York, 1992.[15].au/~evans/evansmorrissbook.htm[16]P.G. Klemens (1951). "The Thermal Conductivity of Dielectric Solids at Low Temperatures". Proc. Roy. Soc. Lond. A208: 108.doi:10.1098/rspa.1951.0147.[17]G.K. Chan, R.E Jones (1962). "Low-Temperature Thermal Conductivity of Amorphous Solids". Phys. Rev.126: 2055.doi:10.1103/PhysRev.126.2055.[18]I. Pomeranchuk (1941). "Thermal conductivity of the paramagnetic dielectrics at low temperatures". J. Phys.(USSR)4: 357.ISSN 0368-3400.[19]R.C. Zeller, R.O. Pohl (1971). "Thermal Conductivity and Specific Heat of Non-crystalline Solids". Phys. Rev. B4: 2029.doi:10.1103/PhysRevB.4.2029.[20]W.F. Love (1973). "Low-Temperature Thermal Brillouin Scattering in Fused Silica and Borosilicate Glass". Phys. Rev. Lett.31: 822.doi:10.1103/PhysRevLett.31.822.[21]M.P. Zaitlin, M.C. Anderson (1975). "Phonon thermal transport in noncrystalline materials". Phys. Rev. B12: 4475.doi:10.1103/PhysRevB.12.4475.[22]M.P. Zaitlin, L.M. Scherr, M.C. Anderson (1975). "Boundary scattering of phonons in noncrystalline materials". Phys. Rev. B12: 4487.doi:10.1103/PhysRevB.12.4487.Further reading•Callister, William (2003). "Appendix B". Materials Science and Engineering - An Introduction. John Wiley & Sons, INC. pp. 757. ISBN 0-471-22471-5.•Halliday, David; Resnick, Robert; & Walker, Jearl(1997). Fundamentals of Physics (5th ed.). John Wiley and Sons, INC., NY ISBN 0-471-10558-9.•Srivastava G. P (1990), "The Physics of Phonons." Adam Hilger, IOP Publishing Ltd, Bristol.•TM 5-852-6 AFR 88-19, Volume 6 (Army Corp of Engineers publication)External links•Table with the Thermal Conductivity of the Elements (/yogi/periodic/ thermal.html)•Calculation of the Thermal Conductivity of Glass (/thermal-conductivity/) Calculation of the Thermal Conductivity of Glass at Room Temperature from the Chemical Composition •Viscosity and Thermal Conductivity Equations for Nitrogen, Oxygen, Argon, and Air (http://www.boulder.nist.gov/div838/theory/refprop/NAO.PDF)•Conversion of thermal conductivity values for many unit systems (/units/ convert_units.cfm?From=245)Article Sources and Contributors8Article Sources and ContributorsThermal conductivity Source: /w/index.php?oldid=421624822 Contributors: -xfi-, Aanidaani, Aazn, AdamW, Adams13, Akilaa, Alex Crikey, Alex43223, Alfio, Andy Dingley, Andy G, AquaDTRS, Aulis Eskola, AxelBoldt, Az7997, Baderimre, Barak Sh, Bendzh, Blazotron, Bo-Kaj-R, Bobblewik, Brockert, Brossow, Bryan Derksen, Buster2058, C-Therm,CMD Beaker, CSTAR, Cadmium, Carandbike, Ccrrccrr, Cfsenel, Charles Matthews, Chronodm, Ciphers, Clarince63, Cperabo, Craklyn, Cxz111, CyrilB, Dan Pangburn, David Biddulph, DavidH. Flint, David Haslam, Dfeuer, Dhollm, Discospinster, DocWatson42, Doubleplusjeff, Dougthebug, Draxtreme, Druiids, Durplub, EagleFan, El C, Electron9, Elvire, Ericl234, Ezzt, FF2010,Falk Lieder, Femto, Fizicist, Fiziker, Frap, Fyyer, Gene Nygaard, Geniescience, Gentgeen, Ghostwo, Giftlite, Gknor, Glacier Wolf, Glane23, Glenn, Glloq, Gonzonoir, Gouryella24, Gralo,Gscshoyru, HamburgerRadio, Hankwang, Hbent, Headbomb, Heron, Hukseflux, Icairns, Ido50, Illinoisavonlady, Inc ru, Isaac Dupree, Itub, IvanLanin, Jaganath, Jdpipe, JesperDoffe, Jim1138, Joanjoc, John254, Jswaim, Jth299, Kdn1982, Kittell, Kjkolb, Kmarinas86, Kungfuadam, Kuru, KyraVixen, L33tminion, Leon7, Lightdarkness, Lights, LilHelpa, Logger9, LokiClock, Loodog, Looxix, MER-C, MONGO, Magioladitis, Maniadis, Marie Poise, Mark Foskey, Mat-C, Matt H, Mav, Mdf, Mdkoch84, Melchoir, Metaphase2, Micah Fitch, Michael Hardy, Mike92591,Mikiemike, Mjager, Montgomery '39, Mr Gronk, Mrdarrett, Munden, Mxn, N3362, NPKResults, Nelienke, Nemontemi, Nickersonl, Nirmos, Nirvelli, OliRG2, Omegatron, On5deu, Orionus,Patrick, Peterlin, Pharaoh of the Wizards, Polonium, Proepro, Pyrotec, R'n'B, RSRScrooge, Radon210, RazorICE, RexNL, Riana, Rich 988, Rl, Rlsmalling, Ronhjones, Rtdrury, Rxjensen,SCEhardt, Salih, Salsa Shark, Sbmehta, Scanrod, Sebastian, SebastianHelm, Shepplestone, SimonP, Smjg, Somerandom, Srleffler, Stan J Klimas, StanBrinkerhoff, Stevenmitchell, Stevertigo,Strait, , Tantalate, Tardis, Tavernsenses, Temporaluser, That Guy, From That Show!, The Anome, The Anonymous One, The Thing That Should Not Be, Thegeneralguy, TomR,ToobMug, Trevor MacInnis, Tunheim, UberCryxic, Uiteoi, Vadim Makarov, Wahoofive, Why Not A Duck, WilfriedC, William Avery, Wizard191, Woohookitty, Wraith69, Yamamoto Ichiro, Yurik, Zavod219, Zolot, Þjóðólfr, Јованвб, 452 anonymous editsImage Sources, Licenses and ContributorsFile:Coloured ceramic thermal barrier coating on exhaust component.jpg Source:/w/index.php?title=File:Coloured_ceramic_thermal_barrier_coating_on_exhaust_component.jpg License: Attribution Contributors: File:Thermal conductivity.svg Source: /w/index.php?title=File:Thermal_conductivity.svg License: Public Domain Contributors: User:GknorLicenseCreative Commons Attribution-Share Alike 3.0 Unported/licenses/by-sa/3.0/。

传热学定理的英文表达

传热学定理的英文表达English:The principles of heat transfer are fundamental concepts that govern the transfer of thermal energy from one place to another. These principles are based on the laws of thermodynamics and include conduction, convection, and radiation.Conduction is the transfer of heat through a solid or stationary fluid by direct molecular contact. It occurs when there is a temperature difference across a medium and the energy is transferred through molecular collisions. The rate of heat conduction is determined by the thermal conductivity of the material, the temperature difference, and the surface area.Convection, on the other hand, involves the transfer of heat through the movement of a fluid, either a liquid or a gas. It occurs due to the combined effects of conduction and fluid motion. Convection can be natural, occurring due to density differences in the fluid, or forced, produced by external factors such as fans or pumps. The rate of heat transfer through convection depends on the fluid properties, such asdensity and viscosity, as well as the velocity of the fluid and the temperature difference.Radiation is the transfer of heat through electromagnetic waves. Unlike conduction and convection, radiation does not require a medium for energy transfer. It can occur through a vacuum and is the primary mode of heat transfer in space. The rate of heat transfer through radiation depends on the surface area and temperature difference between two objects, as well as the emissivity and absorptivity of the materials involved.In summary, the principles of heat transfer encompass conduction, convection, and radiation. These mechanisms govern how thermal energy is transferred from one location to another. Understanding these principles is crucial in various fields, including engineering, physics, and environmental science.中文翻译:传热学定理是关于热能从一个地方传递到另一个地方的基本概念。

热扩散系数

热扩散系数1. 引言热扩散系数是热传导过程中的一个重要参数，它描述了物质内部热量传导的能力。

在热传导中，根据傅里叶定律，热量传导的速率与物质的热扩散系数成正比。

热扩散系数的研究对于材料工程、物理学、化学等领域都具有重要意义。

本文将介绍热扩散系数的定义、计算方法和应用领域。

2. 定义热扩散系数（thermal diffusivity）是描述材料热传导性能的物理量。

它定义为材料的热导率（thermal conductivity）与材料的热容（specific heat capacity）之比。

数学表达式为：热扩散系数 = 热导率 / 热容热扩散系数的单位通常为m²/s。

3. 计算方法3.1 导热板法（Laser Flash Method）导热板法是一种常用的测量热扩散系数的方法。

该方法利用热脉冲在材料中的传播过程来测量热扩散系数。

具体步骤如下：1.制备一个热传导性能良好的材料样品，将其放置在一个加热器上。

2.使用一个光脉冲，将热量传递到样品的一端。

光脉冲可以通过激光器产生。

3.使用一个接收器，测量在样品的另一端产生的温度变化。

4.根据测得的温度曲线，计算热扩散系数。

3.2 热脉冲法（Transient Hot Wire Method）热脉冲法是测量液体或薄膜材料热扩散系数的一种方法。

该方法通过观察热脉冲在液体或薄膜中的传播过程来测量热扩散系数。

具体步骤如下：1.制备一个导热性能良好的导线样品，将其置于待测液体或薄膜中。

2.在导线上施加一个电流脉冲，加热导线。

3.使用温度传感器测量导线上的温度变化。

4.根据测得的温度变化，计算热扩散系数。

3.3 其他方法除了导热板法和热脉冲法外，还有其他一些方法可以测量热扩散系数，如雷诺法（Reynolds Method）、球法（Sphere Method）等。

具体选择哪种方法取决于材料的性质和实验条件。

4. 应用领域热扩散系数在许多领域中都有广泛的应用。

以下是几个常见的应用领域：4.1 材料工程热扩散系数是研究材料热传导性能的重要参数。

碳纳米管材料导热性能的实验研究

华南理工大学硕ｆ：学位论文或（０，ｍ）时，手性角０＝００，管壁柱面上碳六元环的两个Ｃ．Ｃ键垂直于管中心轴，此类ＣＮＴ被称为“锯齿形ＣＮＴ”，因为此时碳原子在管子圆周上的分布呈锯齿状；当月≠ｍ≠０，００＜口＜３００时，ＣＮＴ的构型为螺旋型碳纳米管，螺旋型碳纳米管具有手性特征，所以被称为“手性ＣＮＴ”，如图１．１所示。

以（１１７ｍ）＝（５，５）的扶手椅管为例，其结构如图１．１ａ）所示，其周长Ｌ＝４７５ａ，直径ｄ，＝ｏ．６７８ｎｍ。

该管的直径，与Ｃ６０分子的直径（０．７１ｎｍ）很接近，所以在该管两端均可置一ｃ６０半球，此Ｃ６０半球的周长也呈扶手椅状，它是垂直于Ｃ６０分子的五次对称轴一部分得到的。

（１１，ｍ）＝（９，０）之字形纳米管的结构如图１－ｌｂ）所示，其周长Ｌ＝９ａ。

直径ｄｒ＝０．７０５ｎｍ。

在此管两端也可以罩上Ｃ６０半球。

此半球的边沿也呈之字形，它是垂直于Ｃ６０分子的三次对称轴平分得到。

图１—１ｃ）所示的是（１０，５）手性纳米管，其周长上＝√１７５Ⅱ，直径ｄｒ＝１．０３６ｎｍ，其两端可罩Ｃ…半球。

１．３．２双壁与多壁碳纳米管的结构模型由两层或两层以上的石墨片卷曲而成的管被称为ＤＷＣＮＴｓ或ＭＷＣＮＴｓ，如图１—３所示。

他们的层结构可能是同一ｆｉ，圆柱或是蛋卷状，还有可能是两者的混合性的结构。

ＤＷＣＮＴｓ与ＭＷＣＮＴｓ的结构比较复杂，不易确定。

图卜３双肇ＣＮＴＦｉｇ．１－３Ｄｏｕｂｌｅ—ｗａｌｌｃａｒｂｏｎｎａｎｏｔｕｂｅ１．４碳纳米管的制备方法自１９９１年Ｉｉｊｉｍａ发现ＣＮＴｓ以来，已有数十种合成ＣＮＴｓ的方法问世，也发现一些新的转化途径…。

这些方法方法丰要包括以下几种：１．电弧法１９９３年，Ｔｉｊｉｍａ教授与ＩＢＭ实验室的Ｂｅｔｈｕｎｅ教授改进了电弧法，他们在阳极置入催化荆金属，在放电室器壁中发现了单层碳纳米管１１０１。

４华南理工大学硕Ｅ学位论文系在小的温度区域呈线性，这就导致电阻也有频率为２。

SPACESHIP HEAT-DISSIPATING SYSTEM

专利名称：SPACESHIP HEAT-DISSIPATING SYSTEM 发明人：ROBAATO EE HASURETSUTO,ROBAATO ERU KOTSUSON,MAATEIN SORON申请号：JP41308890申请日：19901221公开号：JPH04208393A公开日：19920730专利内容由知识产权出版社提供摘要：PURPOSE: To strengthen the resistance of a heat pipe radiator system against laser attack, achieve weight saving, and enhance temperature performance, by incorporating therein film material of carbon-carbon which is resistant to laser destruction and metal foil heat-insulating material. CONSTITUTION: A fin 58 of a radiator 50 is fabricated from a carbon-carbon material. This material exhibits a quite high resistance against laser destruction as well as twice the thermal conductivity of ordinary metals, such as aluminum. An integral clamp secures the fin 58 to each heat pipe 53, thereby thermally decoupling the fin from the heat pipe when laser heating occurs. A mesh heat pipe wick creates a vapor barrier in the interior of the heat pipe so that continuous operation of the heat pipe is ensured, even when the pipe is subjected to localized laser heating. The heat pipe is wrapped in multilayer metal foil insulation to greatly reduce direct laser heating of the heat pipe.申请人：GRUMMAN AEROSPACE CORP更多信息请下载全文后查看。

导热灌封胶英语

导热灌封胶英语一、单词1. encapsulant [ɪnˈkæpsjələnt]- 释义：n. 密封剂；包封剂，在导热灌封胶语境下可表示灌封胶这种密封材料。

- 用法：This encapsulant is widely used in electronic device packaging.（这种灌封胶广泛用于电子设备封装。

）2. thermal [ˈθɜːml]- 释义：adj. 热的；热量的；由热造成的。

- 用法：Thermal conductivity is an important property of the encapsulant.（导热性是灌封胶的一个重要特性。

）3. conductive [kənˈdʌktɪv]- 释义：adj. 传导（性）的；能传导（热、电等）的。

- 用法：The conductive encapsulant can effectively dissipate heat.（这种导电灌封胶能有效地散热。

）4. adhesive [ədˈhiːsɪv]- 释义：n. 黏合剂；adj. 黏合的；有黏性的。

在导热灌封胶中也涉及到黏合的性能。

- 用法：The adhesive property of the encapsulant helps it to bond firmly.（灌封胶的黏合性有助于它牢固粘结。

）5. curing [ˈkjʊərɪŋ]- 释义：n. （使）固化；（使）变干；（使）硬化；v. cure的现在分词。

导热灌封胶需要经过固化过程。

- 用法：The curing time of the encapsulant is about 24 hours.（灌封胶的固化时间大约是24小时。

）二、短语1. thermal conductive encapsulant- 释义：导热灌封胶。

- 用法：We need to choose a suitable thermal conductive encapsulant for this project.（我们需要为这个项目选择一种合适的导热灌封胶。

稳态法测量热导率实验分析

稳态法测量热导率实验分析董光兴;孙桂华;王新星;林秀娟【摘要】The thermal conductivity of a poor conductor of heat (rubber) and a good conductor of heat (copper) were measured on the application of the steady -state method in this paper. It is found that the accuracy of experiment is higher when the temperature difference is equal to 20℃. And there is significant difference in the experiment of two masteries with different heat transfer mechanism in the same steady-state method, the precision of rubber's experiment is better than the copper's.%应用稳态法分别测量热的不良导体（橡胶）和热的良导体（铜棒）的热导率，发现用稳态法测量热导率，在稳定传热条件下，增大被测量材料两端温差到20℃左右，热的良导体和热的不良导体材料的热导率的测量精度都会提高；在同样的实验环境中，稳态法测定热的不良导体的热导率比其测定热的良导体热导率实验精度高。

【期刊名称】《河西学院学报》【年(卷),期】2014(000)005【总页数】7页(P59-65)【关键词】橡胶;铜棒;稳态法;傅立叶定律【作者】董光兴;孙桂华;王新星;林秀娟【作者单位】河西学院物理与机电工程学院，甘肃张掖 734000;河西学院物理与机电工程学院，甘肃张掖 734000;河西学院物理与机电工程学院，甘肃张掖734000;新疆博尔塔拉蒙古自治州农五师中学，新疆博乐 833400【正文语种】中文【中图分类】O551.3材料的热导率是其热物性的重要参数，直接衡量材料绝热性能的好坏，热导率越小，材料的保温、绝热性能就越好.对材料热导率进行测量的原理和方法主要有稳态法和瞬态法［1］.教学实验中常用的稳态法是一种简易形象的方法，它是基于傅立叶导定律描述的稳态条件进行热导率的测量，只有在系统达到稳定后才能得出正确的结果，主要适用于中低温条件下的测量.根据热力学理论，温度梯度是热传导的动力，傅立叶在大量实验的基础上提出了导热的基本定律：热传导速率与温度梯度和垂直于热流方向的截面积成正比，即dQ/dt µ−A(dT/dn)或dQ/dt =−λA(dT/dn)，这个定律被称为傅立叶定律［2］.当热量传递达到稳定导热时，单位时间内通过单位面积的导热量为定值，可将其表达为φ=Q/t =−λA(dT/dn)，φ也称热流量，单位为W，A是导热面积，λ是比例系数，称为热导率或者导热系数，单位为W/(m·∗K).通过测量温度梯度、传热截面积和热流量，就可以用稳态法测量材料的热导率.根据热导率的大小，把材料分为两类，热的良导体和热的不良导体［2］.在一般的物理教学实验中，热的良导体和热的不良导体材料的热导率都是基于稳态法来测量的，用DH-2型智能导热系数测定仪测橡胶的热导率，用图1所示的装置测定铜棒的热导率.用稳态法测量材料样品的热导率在实验中存在一些误差来源，关于它的研究有不少报道.金忆凡等对稳态法测量热的不良导体热导率实验进行改进以降低误差［3］，黄平等对这个实验提出了用作图软件拟合数据提高实验准确度的方法［4］.孙庆龙和冉凯华等分别研究了稳态法测热的不良导体的热导率实验精度的改进［5，6］.高峰对稳态法测定金属热导率的实验提出了改进方案，降低测量误差［7］.长期实验实践中，人们发现了样品厚度对于稳态法测量热导率的误差影响［8］，贾斐霖等建立简化模型并通过数值计算对稳态法测量热的不良导体的热导率的实验样品厚度给出了限定［9］.但是，稳态法测量热的良导体和热的不良导体材料的热导率的实验比较，仍未见报道.作为热的良导体的铜棒和热的不良导体的橡胶其导热机制是不相同的.橡胶这种固体材料主要依赖微观粒子的热振动来传导热量，而铜棒主要依赖于金属中的自由电子来传导热量，其晶格阳离子的热振动对热量传导的贡献不占主导.本文选用基础物理实验设备，用稳态法分别测量热的良导体和热的不良导体材料的热导率，进行实验效果的对比分析，发现稳态法测量热的不良导体的热导率实验精度较高.实验中用DH-2型智能导热系数测定仪测橡胶的热导率.考虑到热的不良导体热导率较小，材料一般做成盘状或管状，它们有大的截面积，而且在热流方向的长度较短.一块厚度为h，直径为D的热的不良导体(橡胶)样品，当上下表面温度θ1〉θ2时，为保证样品中温度场的分布具有良好的对称性，加热盘、样品、散热盘为截面积等大的圆形.当传热达到稳定时，θ1与θ2的温度值不变，样品盘传热速率与散热盘的散热速率相等，通过散热盘在稳定温度θ2时的散热速率求出样品盘的传热速率∆Q/∆t .若散热盘的质量为m，热容为C，半径为Rc，厚度为 hC可得样品的热导率为［10-11］：同样，由于测量的需要对于热的良导体铜棒，所用的样品要有小的截面积及在热流方向上有相当的长度.如图1所示，被测量的铜金属棒AB，截面积S，长为L.两端分别固定于蒸汽箱C和低温水箱(内有螺旋水管)D中，AB、C、D全部装在有绝热材料(棉花)的铁皮箱中，以避免热量由AB的侧面散失.由C箱上部通入蒸汽向A端供热，B端则由从D箱E口流入、F口流出的冷水来吸热.为了保持水流的稳定，水源经稳压水槽G流入E口，由于稳压水槽设置有溢流管子H，当水流入G时由水源来的多余的水可经过溢流管子排出，从而使水槽中水面维持在管口的高度，达到稳压的目的.温度计T4、T3分别测量流出和流入D的水流温度.水流量的大小可由夹子I来控制，温度计测量A和B处的温度.当认为金属棒的侧面热传递可以忽略时，热流则从左向右流过金属棒.当金属棒内各点的温度沿传热方向均匀减小，且温度不随时间改变时，即达到稳定流动状态，称为“稳态”热流.t秒内，由D流出的水的质量m及流入和流出的水温T4、T3后，则可求出在t秒内流水带走的热量Q,等于测量铜棒传递的热量，可得铜棒的热导率为：其中d为圆柱直径，测量上式中各个量即可求出导热系数K.3.1 热的不良导体热导率测定准确度的分析利用DH-2型智能导热系数测定仪测量热的不良导体——橡胶的热导率，其测量结果有两种方法获得.第一种方法是利用固化在仪器中的程序直接从仪器上读出被测量橡胶在给定热学条件下的热导率.但是，这种方法测量的结果散度很大，准确率小.另一种方法是通过测量绘制冷却曲线的方法获得散热板的散热速率后计算热导率，这个方法会提高测量精度［4，12］.本实验测量了仪器给出的直接测量值，同时在同等条件下测量散热板的散热速率，通过计算机软件绘图得出散热盘的自然冷却曲线图，并求出所需那一点的斜率，再代入相应的公式(1)求出橡胶的热导率λ.两种方法测量的结果在表1中列出.本实验室橡胶的热导率理论值范围为0.15-0.22W/(m·K)［10，13］，若取橡胶热导率真实值λ=0.155 W/(m·K)，则两种方法得到的测量值的相对误差也在表1中列出.分析对比表1中的数据可以看出，从智能导热系数测定仪上读出的热导率偏离理论值太大，而通过拟合散热盘的散热曲线计算散热速率得出的结果要更准确一些.计算直接读取值的标准偏差σ直接读取值=0.110，计算值的标准偏差σ计算值=0.078.因此可以认为用DH-2型智能导热系数测定仪测橡胶的热导率直接读取误差太大，需要进行测量和拟合散热盘散热曲线并进行计算的附加工作.3.2 热的不良导体和热的良导体热导率测定的对比分析由于铜棒和橡胶盘的热导率都用稳态法测量，而它们在微观上的导热机制是不同的.本文设计实验把橡胶和铜棒的热导率随实验中加热端和降温端在稳定传热的情况下温差的变化情况作了对比分析，铜棒在不同温差条件下热导率的测量值和其绝对误差在表2中列出.其中铜棒热导率的理论真值选取为20℃(即常温下)温度条件下401W/mK.在3.1分析的基础上可知，用DH-2型智能导热系数测定仪测量热的不良导体——橡胶的热导率实验中，需要通过拟合散热盘散热曲线的方法获得较为精确的实验数据.本文利用这种方法测量计算了不同温度条件下橡胶盘的热导率和同等条件下该热导率的绝对误差，计算结果在表3中列出.其中橡胶热导率的理论真值选取为0.155W/mK.分析表2数据，可以看出，不同实验条件下测量到的铜棒热导率的数值相差很大，这说明热学实验中，由于散热量与实验室环境温度有很大关系，散热常常是不可能人为精确控制的，导致实验的精密度不好.绘制铜棒在不同温差条件下测量的热导率的数值分布图，如图2所示，则可以发现实验数值有明显的规律走势.图形显示，在稳定传热的情况下，导热物体两端温差增大时，测量和计算的热导率也呈现变大的趋势.这说明材料的热导率是随温度条件变化的，在我们的实验中则常常将这一要素忽略掉.绘制铜棒热导率测量误差与其两端温差的对比图，如图3所示，发现在温差增大时误差也在减小.这是因为理论真值的提供温度正是20℃.在图3中可以看出，光滑曲线在16.5℃处有一个极小值.分析其原因可以得出：在一定的外界环境条件下，当铜棒两端温差增大时铜棒内部自由电子的定向运动趋势增大，自由电子运动速度变大即传热性能越好热导率越大，反之热导率就越小.根据图2和图3的分析可以认为，实验中施加在稳定传热材料两端的温差越大，在经典物理近似条件下的实验精度越高.与铜棒测量结果不同的是，分析表3数据，可以看出，不同实验条件下测量并拟合计算的橡胶热导率的数值相差不是很大，这说明橡胶的导热机制在不可控制的散热过程中丢失而不可计算的热量要少，实验中，相对于铜棒而言，引进的误差要小.绘制橡胶在不同温差条件下测量的热导率的数值分布图，如图4所示，则可以发现实验数值有明显的规律走势.图形显示，在稳定传热的情况下，导热物体两端温差增大时，测量和计算的热导率减小.这个结果也说明材料的热导率是随温度条件变化的.绘制橡胶热导率测量误差与其两端温差的对比图，如图5所示，发现在温差增大时误差也在减小.这同样是因为理论真值的提供温度是常温下.在图5中可以看出，光滑曲线在11℃开始到20℃，其极限值基本维持在一个水平线上，显示实验的精确度较高.同样，根据图4和图5的分析可以认为，实验中施加在稳定传热材料两端的温差越大，在经典物理近似条件下的实验精度越高.本文通过用稳态法测量热的不良导体橡胶盘和热的良导体铜棒的热导率实验数据的对比分析，研究热的不良导体和热的良导体的导热机制对实验精度的影响.经过不同温度条件下的多次实验发现：(1)实验室环境温度下，热的良导体和热的不良导体材料的热导率都与温度有一定的函数关系.(2)用DH-2型智能导热系数测定仪测橡胶的热导率直接读取误差太大，需要进行测量和拟合散热盘散热曲线并进行计算的附加工作.(3)用稳态法测量热导率，在稳定传热条件下，增大被测量材料两端温差到20℃左右，热的良导体和热的不良导体材料的热导率的测量精度都会提高.(4)同样的实验环境中，稳态法测定热的不良导体的热导率实验比其测定热的良导体热导率实验精度高.【相关文献】［1］郝丽宏,林凌,李刚,等.改进的绝热材料导热系数防护热板法测控系统的设计［J］.仪器仪表学报,2003,24(4)：360-361.［2］秦允豪,热学［M］.北京：高等教育出版社,2004.［3］金忆凡,吉唯峰,乔卫平,等.稳态对比法测量不良导体的导热系数［J］.物理实验,2012,32(1)：44-45.［4］黄平,何天德.不良导体导热系数实验误差分析与改进［J］.玉林师范学院学报,2011,32(2)：50-52.［5］孙庆龙.不良导体导热系数与温度关系研究［J］.大学物理实验,2011,24(5)：4-6.［6］冉凯华,冷雪松,王艳东,等.导热系数实验中平衡温度的测量技巧［J］.大学物理实验,2012,25(1)：4-6.［7］高峰.良导体导热率测量装置与实验方法改进［J］.物理实验,2010,30(5)：32-35.［8］王雪珍,马春光,谭伟石.样品厚度对稳态法测定不良导体导热系数实验的影响［J］.物理实验,2011,31(4)：24-27.［9］贾斐霖,李林,史庆藩.稳态法测算导热系数的原理［J］.材料科学与工程学报,2011,29(4)：609-613.［10］丁益民,徐扬子.大学物理实验基础与综合部分［M］.北京：科学出版社,2008.［11］杨述武,赵立竹,沈国土.普通物理实验［M］.北京：高等教育出版社,2007.［12］刘燕,张本刚,张翠萍.非良导体热导率的测定［J］.工业加热,2000(6)：37-39.［13］田志伟.普通物理实验技术［M］.北京：高等教育出版社,1957.。

高导热环氧复合材料干式电抗器热点温升的仿真研究

高导热环氧复合材料干式电抗器热点温升的仿真研究曲展玉1，钟昱尧1，宋岩泽1，2，谢子豪1，孟雨琦1，谢庆1，2（1.华北电力大学电力工程系，河北保定071003；2.华北电力大学新能源电力系统国家重点实验室，北京102206）摘要：干式电抗器的稳定运行影响新型电力系统的输电可靠性。

干式空心电抗器包封材料整体由浸有环氧树脂的玻璃纤维丝经高温固化而成。

本文采用多物理场耦合有限元方法，考虑干式空心电抗器的包封材料热导率对其热点温升的影响，建立了环氧复合材料的COMSOL微观仿真模型和外电路约束下的干式空心电抗器电-磁、流-热耦合计算模型。

将电磁场下的损耗作为热源计算温度场与流场分布，研究在25℃环境温度下常规/高导热环氧复合材料对干式空心电抗器热点温升的影响规律。

结果表明：高导热环氧树脂对复合材料热导率的提升效果显著；包封材料本体及周围空气温度场区域中热点温升最大值为103.75℃，出现在内部第4层包封材料的上端处；不同热导率的复合材料对降低干式电抗器的热点温升有明显差异，其中干式电抗器在高导热环氧树脂复合材料下的热点温度降低了7.55℃。

关键词：干式空心电抗器；热导率；热点温升；多物理场耦合中图分类号：TM215；TM472 DOI:10.16790/ki.1009-9239.im.2024.04.015Simulation study on hot spot temperature rise of dry reactor with high thermal conductive epoxy composite as encapsulating materialQU Zhanyu1, ZHONG Yuyao1, SONG Yanze1,2, XIE Zihao1, MENG Yuqi1, XIE Qing1,2(1. Department of Electrical Engineering, North China Electric Power University, Baoding 071003, China;2. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,North China Electric Power University, Beijing 102206, China)Abstract: The stable operation of dry-type reactors affects the transmission reliability of new power system. The encapsulating material of dry-type reactor is made of glass fiber filament impregnated epoxy resin cured at high temperature. In this paper, a multiphysics coupled finite element method was used to consider the influence of thermal conductivity of the encapsulating material for dry-type reactor on its hot spot temperature rise, and a COMSOL microscopic simulation model of epoxy composites and an electro-magnetic and flow-thermal coupling calculation model of dry-type reactor under the constraints of external circuits were established. The temperature field and flow field distribution were calculated by using the loss under electromagnetic field as the heat source, and the influence of conventional/high thermal conductive epoxy composites on the hot spot temperature rise of the dry-type reactor at 25℃ of ambient temperature was studied. The results show that the high thermal conductive epoxy resin has a significant improving effect on the thermal conductivity of composites. The maximum hot spot temperature rise in the temperature field area of the encapsulating material body and the surrounding air is 103.75℃, which appears at the upper end of the fourth layer of encapsulating material. The epoxy resin composite with different thermal conductivity has obvious difference on decreasing the hot spot temperature of dry-type reactor, and the hot spot temperature of the dry-type reactor with high thermal conductive epoxy resin composite is reduced by 7.55℃.Key words: dry hollow reactor; thermal conductivity; hot spot temperature rise; multiphysical field coupling0　引言干式电抗器凭借线性度好、饱和性高、损耗小、运行维护方便等优点已成为在“双碳”战略下构建新型电力系统的重要发展方向[1]。

基于相变材料的动力电池热管理研究进展

第8卷第6期新能源进展Vol. 8 No. 62020年12月ADVANCES IN NEW AND RENEWABLE ENERGYDec. 2020* 收稿日期：2020-05-08 修订日期：2020-06-30基金项目：广东省重点领域研发计划项目（2019B090909001） † 通信作者：李恺翔，E-mail ：*********************文章编号：2095-560X （2020）06-0493-09基于相变材料的动力电池热管理研究进展*吕少茵，曾维权，杨洋，李恺翔†（广州汽车集团股份有限公司汽车工程研究院，广州 511434）摘要：相变材料（PCM ）由于具有相变潜热大、相变时体积变化小的优点，成为电池热管理研究的主要方向之一。

本文介绍了相变材料的蓄热原理，综述了主要相变材料石蜡以及针对其导热系数不高而进行的强化换热研究成果，介绍了相变材料耦合其他多种冷却方式在动力电池热管理上的应用，并展望了未来PCM 的研究方向。

关键词：相变材料；热管理；动力电池中图分类号：TK02 文献标志码：A DOI ：10.3969/j.issn.2095-560X.2020.06.007Research Progress on Power Battery Thermal Management SystemBased on Phase Change MaterialLÜ Shao-yin, ZENG Wei-quan, YANG Yang, LI Kai-xiang(GAC Automotive Research & Development Center, Guangzhou 511434, China)Abstract: Phase change material (PCM) has become one of the main research areas of battery thermal management because of its large latent heat and small volume change during its phase change. In this paper, the heat storage principle of PCM was introduced. The main phase change material paraffin and researches about enhancing the thermal conductivity of paraffin were reviewed. The applications of other cooling methods coupled with phase change materials in thermal management of power battery were summarized. Finally, the future application of the PCM in thermal management of battery was prospected.Key words: phase change material; thermal management; power battery0 引言随着全球人口和经济的发展，能源短缺和环境污染问题引起了人类广泛关注。

高温溴化锂溶液导热系数和比热容的实验测定与模型计算-化学工程专业论文

优秀毕业论文硕士学位论文高温溴化锂溶液导热系数和比热容的实验测定与模型计算Expe rim ent an d mo del for the therma l c ond uct ivi ty and spe cif ic heat capacity of l ithiu m br omi de solution at high—t emp era tur e学 2 1207036完成日期：2Q!墨二Q鱼大连理工大学Dalian University of Technology优秀毕业论文万方数据优秀毕业论文大连理工大学学位论文独创性声明作者郑重声明：所呈交的学位论文，是本人在导师的指导下进行研究工作所取得的成果。

尽我所知，除文中已经注明引用内容和致谢的地方外，本论文不包含其他个人或集体已经发表的研究成果，也不包含其他已申请学位或其他用途使用过的成果。

与我一同工作的同志对本研究所做的贡献均已在论文中做了明确的说明并表示了谢意。

若有不实之处，本人愿意承担相关法律责任。

学位论文题目：直渔送垡堡渣速昱垫丕数塑出垫窒数塞坠测塞量送型盐篡＆正年—[月业曰作者签名：建立日期：优秀毕业论文万方数据优秀毕业论文大连理工大学硕士学位论文摘要能源是人类最基本的生产要素之一，随着经济发展，能源消费也在不断增长，整个社会对于能源的依赖程度也越来越大；另一方面，由于大量使用化石燃料而产生的环境污染问题日益突出。

采用第二类吸收式热泵将中低温的废热提高到较高品位，在工业余热回收与提高能源利用率方面发挥着重要的作用，受到国内外学者的广泛关注。

目前，已经工业化的热泵工质主要为LiBr．H20工质对，但对高温下LiBr溶液的基础热物性如导热系数、比热容等的研究较少，直接影响了高温热泵的理论研究和应用范围。

因此研究LiBr水溶液的高温热物性具有重要学术意义和实用价值。

瞬态热线法是目前公认的测量导热系数最准确的方法之一，本文在分析传统瞬态热线法的基础上，对其无法测量导电性溶液的缺点进行改进，以充满汞的石英玻璃毛细管作为热线，新建了瞬态热线法测量液体导热系数的装置，并测量了溴化锂溶液在2MPa压力、150．250℃、质量分数45％．65％下的导热系数，实验结果与文献的最大相对偏差为2．97％。

材料科学与工程专业英语第10章翻译

The word "ceramic" is derived from the Greek keramos, which means "potter's clay" or "pottery." Its origin is a Sanskrit term meaning "to burn." So the early Greeks used "keramous" when describing products obtained by heating clay-containing materials. The term has long included all products made from fired clay, for example, bricks, fireclay refractories, sanitaryware, and tableware.“陶瓷”这个词是来自希腊keramos，这意味着“陶土”或“陶”。

它的起源是梵文术语，意思是“燃烧”。

因此，早期的希腊人用“keramous”描述加热含粘土的物料获得的产品。

这个词早已包括所有陶土制成的产品，例如，砖，粘土质耐火材料，卫生洁具，餐具。

In 1822, refractory silica were first made. Although they contained no clay, the traditional ceramic process of shaping, drying, and firing was used to make them. So the term" ceramic," while retaining its original sense of a product made from clay, began to include other products made by the same manufacturing process. The field of ceramics (broader than the materials themselves) can be defined as the art and science of making and using solid articles that contain as their essential component a ceramic. This definition covers the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components, and the study of structure, composition, and properties.1822年，耐火材料二氧化硅被首次提出。

3 omega 和拉曼热导率

3 omega 和拉曼热导率英文回答：The thermal conductivity of materials is an important property that determines their ability to conduct heat. In the field of materials science, there are two commonly used terms to describe thermal conductivity: omega (Ω) and Raman.Omega (Ω) is a measure of the thermal conductivity of a material. It represents the rate at which heat is conducted through a unit area of the material per unit temperature difference. A higher omega value indicates a higher thermal conductivity, meaning the material can efficiently transfer heat.Raman, on the other hand, refers to Raman spectroscopy, a technique used to study the vibrational and rotational modes of molecules. In the context of thermal conductivity, Raman spectroscopy can be used to measure the thermalconductivity of thin films or nanostructures. By analyzing the Raman spectra, researchers can extract information about the phonon transport properties of the material, which is closely related to its thermal conductivity.To better understand the concept, let's take an example of two materials: copper and rubber. Copper has a high thermal conductivity, with an omega value of around 400W/mK, while rubber has a much lower thermal conductivity, with an omega value of around 0.2 W/mK. This means that copper can conduct heat much more efficiently than rubber. If you touch a copper rod and a rubber rod at the same temperature, the copper rod will feel much hotter becauseit quickly transfers heat to your hand, while the rubber rod will feel relatively cooler because it is a poor conductor of heat.Similarly, Raman spectroscopy can also provide insights into the thermal conductivity of different materials. For example, researchers can use Raman spectroscopy to study the thermal conductivity of graphene, a two-dimensional material with exceptional thermal properties. By measuringthe Raman spectra of graphene samples, they can determine the phonon mean free path, which is a key parameter in understanding the thermal conductivity of graphene.中文回答：热导率是材料的一个重要性质，它决定了材料传导热量的能力。

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