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词条 Thermal diffusivity
释义

  1. See also

  2. References

In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure.[1] It measures the rate of transfer of heat of a material from the hot end to the cold end. It has the SI derived unit of m²/s. Thermal diffusivity is usually denoted α but a,h,κ,[2] K,[3] and D are also used. The formula

is:

[4]

where

  • is thermal conductivity (W/(m·K))
  • is specific heat capacity (J/(kg·K))
  • is density (kg/m³)

Together, can be considered the volumetric heat capacity (J/(m³·K)).

As seen in the heat equation,[5]

,

one way to view thermal diffusivity is as the ratio of the time derivative of temperature to its curvature, quantifying the rate at which temperature concavity is "smoothed out". In a sense, thermal diffusivity is the measure of thermal inertia.[6] In a substance with high thermal diffusivity, heat moves rapidly through it because the substance conducts heat quickly relative to its volumetric heat capacity or 'thermal bulk'.

Thermal diffusivity is often measured with the flash method.[7][8] It involves heating a strip or cylindrical sample with a short energy pulse at one end and analyzing the temperature change (reduction in amplitude and phase shift of the pulse) a short distance away.[9][10]

Thermal diffusivity of selected materials and substances[11]
Material Thermal diffusivity
(m²/s) 		Thermal diffusivity
(mm²/s)
Pyrolytic graphite, parallel to layers 1.22 × 10−3 1220
Silver, pure (99.9%) 1.6563 × 10−4 165.63
Gold 1.27 × 10−4 [12] 127
Copper at 25 °C 1.11 × 10−4 [13] 111
Aluminium 9.7 × 10−5 [12] 97
Al-10Si-Mn-Mg (Silafont 36) at 20 °C 74.2 × 10−6 [14] 74.2
Aluminium 6061-T6 Alloy 6.4 × 10−5 [12] 64
Al-5Mg-2Si-Mn (Magsimal-59) at 20 °C 4.4 × 10−5 [15] 44.0
Steel, AISI 1010 (0.1% carbon) 1.88 x 10−5 [16] 18.8
Steel, 1% carbon 1.172 × 10−5 11.72
Steel, stainless 304A at 27 °C 4.2 × 10−6 [12] 4.2
Steel, stainless 310 at 25 °C 3.352 × 10−6 [17] 3.352
Inconel 600 at 25 °C 3.428 × 10−6 [18] 3.428
Molybdenum (99.95%) at 25 °C 54.3 × 10−6 [19] 54.3
Iron 2.3 × 10−5 [12] 23
Silicon 8.8 × 10−5 [12] 88
Quartz 1.4 × 10−6 [12] 1.4
Carbon/carbon composite at 25 °C 2.165 × 10−4 216.5
Aluminium oxide (polycrystalline) 1.20 × 10−5 12.0
Silicon Dioxide (Polycrystalline) 8.3 × 10−7 [12] 0.83
Si3 N4 with CNTs 26 °C 9.142 × 10−6 [20] 9.142
Si3 N4 without CNTs 26 °C 8.605 × 10−6 8.605
PC (Polycarbonate) at 25 °C 1.44 × 10−7 [21] 0.144
PP (Polypropylene) at 25 °C 9.6 × 10−8 [21] 0.096
Paraffin at 25 °C 8.1 × 10−8 [21] 0.081
PVC (Polyvinyl Chloride) 8 × 10−8 [12] 0.08
PTFE (Polytetrafluorethylene) at 25 °C 0.124 × 10−6 [22] 0.124
Water at 25 °C 1.43 × 10−7 [21] 0.143
Alcohol 7 × 10−8 [12] 0.07
Water vapour (1 atm, 400 K) 2.338 × 10−5 23.38
Air (300 K) 1.9 × 10−5 [12] 19
Argon (300 K, 1 atm) 2.2|e=-5}}[23] 22
Helium (300 K, 1 atm) 1.9|e=-4}}[23] 190
Hydrogen (300 K, 1 atm) 1.6|e=-4}}[23] 160
Nitrogen (300 K, 1 atm) 2.2|e=-5}}[23] 22
Pyrolytic graphite, normal to layers 3.6 × 10−6 3.6
Sandstone 1.12–1.19 × 10−6 1.15
Tin 4.0 × 10−5 [12] 40
Brick, common 5.2 × 10−7 0.52
Brick, adobe 2.7 × 10−7 0.27
Glass, window 3.4 × 10−7 0.34
Rubber [3] - 1.3{{Citation needed>date=December 2011}} × 10−7 0.089 - 0.13
Nylon 9 × 10−8 0.09
Wood (Yellow Pine) 8.2 × 10−8 0.082
Oil, engine (saturated liquid, 100 °C) 7.38 × 10−8 0.0738

See also

  • Heat equation
  • Laser flash analysis
  • Thermodiffusion
  • Thermal effusivity
  • Thermal time constant

References

1. ^{{CRC90|page=2-65}}
2. ^{{cite book|last=Gladwell|first=Richard B. Hetnarski, M. Reza Eslami ; edited by G.M.L.|title=Thermal Stresses - Advanced Theory and Applications|year=2009|publisher=Springer Netherlands|location=Dordrecht|isbn=978-1-4020-9247-3|pages=170|edition=Online-Ausg.}}
3. ^1 {{citation|last=Unsworth|first=J.|last2=Duarte|first2=F. J.|author2-link=F. J. Duarte|title=Heat diffusion in a solid sphere and Fourier Theory|journal=Am. J. Phys.|pages=891–893|doi=10.1119/1.11601|volume=47|bibcode = 1979AmJPh..47..981U|issue=11| year=1979}}
4. ^{{cite book|last=Lightfoot|first=R. Byron Bird, Warren E. Stewart, Edwin N.|title=Transport Phenomena|publisher=John Wiley and Sons, Inc.|year=1960|isbn=978-0-471-07392-5|at=Eq. 8.1-7}}
5. ^{{citation|last=Carslaw|first=H. S.|author1-link=Horatio Scott Carslaw|last2=Jaeger|first2=J. C.|author2-link=John Conrad Jaeger|year=1959|title=Conduction of Heat in Solids|edition=2nd|publisher=Oxford University Press|isbn=978-0-19-853368-9}}
6. ^{{cite book|last=Venkanna|first=B.K.|title=Fundamentals of Heat and Mass Transfer|url=https://books.google.com/books?id=IIIVHRirRgEC&pg=PA38|accessdate=1 December 2011|year=2010|publisher=PHI Learning|location=New Delhi|isbn=978-81-203-4031-2|page=38}}
7. ^NETZSCH-Gerätebau, Germany
8. ^{{cite journal |author1=W.J. Parker |author2=R.J. Jenkins |author3=C.P. Butler |author4=G.L. Abbott |title=Method of Determining Thermal Diffusivity, Heat Capacity and Thermal Conductivity |journal=Journal of Applied Physics |volume=32 |issue=9|page=1679 |year=1961 |doi= 10.1063/1.1728417|bibcode = 1961JAP....32.1679P }}
9. ^{{cite journal |author1=J. Blumm |author2=J. Opfermann |title= Improvement of the mathematical modeling of flash measurements |journal=High Temperatures – High Pressures |volume=34 |issue=5 |page=515 |year=2002 |doi= 10.1068/htjr061 }}
10. ^{{cite conference|last=Thermitus|first=M.-A.|editor= Gaal, Daniela S. |editor2=Gaal, Peter S. |title=New Beam Size Correction for Thermal Diffusivity Measurement with the Flash Method|conference=30th International Thermal Conductivity Conference/18th International Thermal Expansion Symposium|conferenceurl=https://web.archive.org/web/20100128105338/http://www.thermalconductivity.org/|booktitle=Thermal Conductivity 30/Thermal Expansion 18|url=https://books.google.com/books?id=F9row3bxLuYC&pg=PA217|accessdate=1 December 2011|date=October 2010|publisher=DEStech Publications|location=Lancaster, PA|isbn=978-1-60595-015-0|page=217}}
11. ^{{cite book| title=Introduction to Heat Transfer|edition= 3rd|publisher=McGraw-Hill| year=1958| last1=Brown |last2= Marco}} and {{cite book| last1=Eckert |last2=Drake| title=Heat and Mass Transfer| publisher=McGraw-Hill| year=1959| isbn=978-0-89116-553-8}} cited in {{cite book| first=J.P. |last=Holman| title=Heat Transfer| edition=9th| publisher=McGraw-Hill|year= 2002| isbn=978-0-07-029639-8}}
12. ^1 2 3 4 5 6 7 8 9 10 11 {{cite journal|url=http://www.electronics-cooling.com/2007/08/thermal-diffusivity/ |title=Materials Data| author= Jim Wilson | date= August 2007 }}
13. ^{{cite journal|url= http://www.sciencedirect.com/science/article/pii/S0022311510005337 |title= Measurement of thermal properties of a ceramic/metal joint by laser flash method |journal= Journal of Nuclear Materials |volume=407 |issue=2|page=83 |author1=V. Casalegno |author2=P. Vavassori |author3=M. Valle |author4=M. Ferraris |author5=M. Salvo |author6=G. Pintsuk | year= 2010 |doi=10.1016/j.jnucmat.2010.09.032|bibcode = 2010JNuM..407...83C }}
14. ^{{cite journal |author1=P. Hofer |author2=E. Kaschnitz | title= Thermal diffusivity of the aluminium alloy Al-10Si-Mn-Mg (Silafont 36) in the solid and liquid states |journal= High Temperatures-High Pressures | volume=40 |issue=3–4 |page=311 | year= 2011|url= http://www.oldcitypublishing.com/HTHP/HTHPcontents/HTHP40.3-4contents.html }}
15. ^{{cite journal |author1=E. Kaschnitz |author2=M. Küblböck |title=Thermal diffusivity of the aluminium alloy Al-5Mg-2Si-Mn (Magsimal-59) in the solid and liquid states|journal=High Temperatures-High Pressures |volume= 37 |issue=3 |page= 221 | year= 2008 |url= http://www.oldcitypublishing.com/HTHP/HTHPcontents/HTHP37.3contents.html }}
16. ^{{cite book|last=Lienhard|first=John H. Lienhard, John H. |title=A Heat Transfer Textbook|year=2006|publisher=Phlogiston Press|pages=698|edition=Third}}
17. ^{{cite journal |author1=J. Blumm |author2=A. Lindemann |author3=B. Niedrig |author4=R. Campbell |title=Measurement of Selected Thermophysical Properties of the NPL Certified Reference Material Stainless Steel 310 |journal=International Journal of Thermophysics |volume=28 |page=674 |year=2007 |doi= 10.1007/s10765-007-0177-z |url= http://www.springerlink.com/content/4kl8p6717705h766/ |issue=2 |bibcode = 2007IJT....28..674B }}
18. ^{{cite journal |author1=J. Blumm |author2=A. Lindemann |author3=B. Niedrig |title= Measurement of the thermophysical properties of an NPL thermal conductivity standard Inconel 600|journal= High Temperatures-High Pressures |volume=35/36 |issue=6 |page=621 | year= 2003-2007 |url=http://www.perceptionweb.com/abstract.cgi?id=htjr145 |doi=10.1068/htjr145}}
19. ^{{cite conference|conference=17th Plansee Seminar |title= Measurement of the Thermophysical Properties of Pure Molybdenum |author1=A. Lindemann |author2=J. Blumm | year= 2009 |volume=3 }}
20. ^{{cite journal |journal=Key Engineering Materials|url= http://www.scientific.net/KEM.409.354 |title= Observation of thermophysical and tribological properties of CNT reinforced Si3 N4 |volume=409 |page=354 |author1=O. Koszor |author2=A. Lindemann |author3=F. Davin |author4=C. Balázsi | year= 2009 |doi= 10.4028/www.scientific.net/KEM.409.354 }}
21. ^1 2 3 {{cite journal |author1=J. Blumm |author2=A. Lindemann |title= Characterization of the thermophysical properties of molten polymers and liquids using the flash technique |journal=High Temperatures-High Pressures |volume= 35/36 |issue=6 |page= 627 | year= 2003-2007 |doi= 10.1068/htjr144 }}
22. ^{{cite journal |author1=J. Blumm |author2=A. Lindemann |author3=M. Meyer |author4=C. Strasser | title= Characterization of PTFE Using Advanced Thermal Analysis Technique |journal= International Journal of Thermophysics| volume=40 |issue=3–4 |page=311 | year= 2011|doi= 10.1007/s10765-008-0512-z |bibcode = 2010IJT....31.1919B }}
23. ^1 2 3 {{cite book|editor-last=Lide|editor-first=David R.|title=CDC Handbook of Chemistry and Physics|edition=71st|year=1992|publisher=Chemical Rubber Publishing Company|location=Boston}} cited in {{cite book|last=Baierlein|first=Ralph|title=Thermal Physics|url=https://books.google.com/books?id=fqUU71spbZYC&pg=PA372|accessdate=1 December 2011|year=1999|publisher=Cambridge University Press|location=Cambridge, UK|isbn=978-0-521-59082-2|page=372}}
{{DEFAULTSORT:Thermal Diffusivity}}

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