Difusivitas termal

Dalam analisis perpindahan panas, Difusivitas termal adalah konduktivitas termal dibagi dengan massa jenis dan panas jenis pada tekanan yang konstan. Difusivitas termal mengukur kemampuan material untuk mengonduksi energi panas relatif terhadap kemampuannya untuk menyimpan energi panas. Difusivitas termal memakai lambang α namun a, κ,^[1] K,^[2] dan D juga digunakan. Satuan SI yang digunakan adalah m²/s. Difusivitas termal dirumuskan dengan:

\alpha ={k \over {\rho c_{p}}}

di mana

$k$ adalah konduktivitas termal (W/(m·K))
$\rho$ adalah densitas (kg/m³)
$c_{p}$ adalah panas jenis (J/(kg·K))

$\rho c_{p}\,$ dapat disebut sebagai kapasitas panas volumetrik (J/(m³·K)).

Seperti dilihat pada persamaan panas,^[3]

{\frac {\partial T}{\partial t}}=\alpha \nabla ^{2}T

,

difusivitas termal adalah rasio turunan waktu terhadap temperatur pada turunan keduanya. Difusivitas termal dapat disebut juga sebagai ukuran dari inersia termal.^[4] Dalam zat dengan difusivitas termal yang tinggi, panas bergerak cepat karena zat tersebut menghantarkan panas relatif terhadap kapasitas panas volumetriknya.

Difusivitas termal beberapa bahan^[5]^[6]
Bahan	Difusivitas termal (m²/s)	Difusivitas termal (mm²/s)
Karbon pirolitik, sejajar dengan lapisan	1.22 × 10⁻³	1220
Perak (99.9%)	1.6563 × 10⁻⁴	165.63
Emas	1.27 × 10⁻⁴^[7]	127
Tembaga at 25 °C	1.11 × 10⁻⁴^[8]	111
Aluminium	8.418 × 10⁻⁵	84.18
Al-10Si-Mn-Mg (Silafont 36) at 20 °C	74.2 × 10⁻⁶^[9]	74.2
Aluminum paduan 6061-T6	6.4 × 10⁻⁵ ^[7]	64
Al-5Mg-2Si-Mn (Magsimal-59) at 20 °C	44.0 × 10⁻⁶^[10]	44.0
Baja, 1% carbon	1.172 × 10⁻⁵	11.72
Baja tahan karat 304A at 27 °C	4.2 × 10⁻⁶^[7]	4.2
Baja tahan karat 310 at 25 °C	3.352 × 10⁻⁶ ^[11]	3.352
Inconel 600 at 25 °C	3.428 × 10⁻⁶^[12]	3.428
Molybdenum (99.95%) at 25 °C	54.3 × 10⁻⁶^[13]	54.3
Besi	2.3 × 10⁻⁵^[7]	23
Silikon	8.8 × 10⁻⁵^[7]	88
Quartz	1.4 × 10⁻⁶^[7]	1.4
Komposit karbon pada 25 °C	216.5 × 10⁻⁶^[8]	216.5
Aluminium oksida (polikristalin)	1.20 × 10⁻⁵	12.0
Silikon dioksida (polikristalin)	8.3 × 10⁻⁷^[7]	0.83
Si₃ N₄ dengan CNTs 26 °C	9.142 × 10⁻⁶^[14]	9.142
Si₃ N₄ tanpa CNTs 26 °C	8.605 × 10⁻⁶^[14]	8.605
Polikarbonat pada 25 °C	0.144 × 10⁻⁶^[15]	0.144
Polipropilena pada 25 °C	0.096 × 10⁻⁶^[15]	0.096
Parafin pada 25 °C	0.081 × 10⁻⁶^[15]	0.081
PVC	8 × 10⁻⁸^[7]	0.08
PTFE pada 25 °C	0.124 × 10⁻⁶^[16]	0.124
Air at 25 °C	0.143 × 10⁻⁶^[15]	0.143
Alkohol	7 × 10⁻⁸^[7]	0.07
Uap air (1 atm, 400 K)	2.338 × 10⁻⁵	23.38
Udara (300 K)	1.9 × 10⁻⁵^[7]	19
Argon (300 K, 1 atm)	2,2×10⁻⁵^[17]	22
Helium (300 K, 1 atm)	1,9×10⁻⁴^[17]	190
Hidrogen (300 K, 1 atm)	1,6×10⁻⁴^[17]	160
Nitrogen (300 K, 1 atm)	2,2×10⁻⁵^[17]	22
Timah	4.0 × 10⁻⁵ ^[7]	40
Kaca jendela	3.4 × 10⁻⁷	0.34
Karet	1.3 × 10⁻⁷^{[butuh rujukan]} \|\| 0.13
Nilon	9 × 10⁻⁸	0.09
Kayu (Pinus Kuning)	8.2 × 10⁻⁸	0.082
Pelumas mesin (jenuh 100 °C)	7.38 × 10⁻⁸	0.0738

Lihat pula

Referensi

^ Gladwell, Richard B. Hetnarski, M. Reza Eslami ; edited by G.M.L. (2009). Thermal Stresses - Advanced Theory and Applications (edisi ke-Online-Ausg.). Dordrecht: Springer Netherlands. hlm. 170. ISBN 978-1-4020-9247-3.
^ Unsworth, J.; Duarte, F. J. (1979), "Heat diffusion in a solid sphere and Fourier Theory", Am. J. Phys., 47 (11): 891–893, Bibcode:1979AmJPh..47..981U, doi:10.1119/1.11601
^ Carslaw, H. S.; Jaeger, J. C. (1959), Conduction of Heat in Solids (edisi ke-2nd), Oxford University Press, ISBN 978-0-19-853368-9
^ Venkanna, B.K. (2010). Fundamentals of Heat and Mass Transfer. New Delhi: PHI Learning. hlm. 38. ISBN 978-81-203-4031-2. Diakses tanggal 1 December 2011.
^ Brown; Marco (1958). Introduction to Heat Transfer (edisi ke-3rd). McGraw-Hill.
^ Eckert; Drake (1959). Heat and Mass Transfer. McGraw-Hill. ISBN 0-89116-553-3. cited in Holman, J.P. (2002). Heat Transfer (edisi ke-9th). McGraw-Hill. ISBN 0-07-029639-1.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Jim Wilson (August 2007). "Materials Data".
^ ^a ^b V. Casalegno, P. Vavassori, M. Valle, M. Ferraris, M. Salvo, G. Pintsuk (2010). "Measurement of thermal properties of a ceramic/metal joint by laser flash method". 407 (2): 83. Bibcode:2010JNuM..407...83C. doi:10.1016/j.jnucmat.2010.09.032.
^ P. Hofer, E. Kaschnitz (2011). "Thermal diffusivity of the aluminium alloy Al-10Si-Mn-Mg (Silafont 36) in the solid and liquid states". High Temperatures-High Pressures. 40 (3-4): 311. ^{[pranala nonaktif permanen]}
^ E. Kaschnitz, M. Küblböck (2008). "Thermal diffusivity of the aluminium alloy Al-5Mg-2Si-Mn (Magsimal-59) in the solid and liquid states". High Temperatures-High Pressures. 37 (3): 221. ^{[pranala nonaktif permanen]}
^ J. Blumm, A. Lindemann, B. Niedrig, R. Campbell (2007). "Measurement of Selected Thermophysical Properties of the NPL Certified Reference Material Stainless Steel 310". International Journal of Thermophysics. 28 (2): 674. Bibcode:2007IJT....28..674B. doi:10.1007/s10765-007-0177-z. ^{[pranala nonaktif permanen]}
^ J. Blumm , A. Lindemann, B. Niedrig (2003/2007). "Measurement of the thermophysical properties of an NPL thermal conductivity standard Inconel 600". High Temperatures-High Pressures. 35/36 (6): 621. ^{[pranala nonaktif permanen]}
^ A. Lindemann, J. Blumm (2009). Measurement of the Thermophysical Properties of Pure Molybdenum. 17th Plansee Seminar. 3.
^ ^a ^b O. Koszor, A. Lindemann, F. Davin, C. Balázsi (2009). "Observation of thermophysical and tribological properties of CNT reinforced Si₃ N₄". Key Engineering Materials. 409: 354. doi:10.4028/www.scientific.net/KEM.409.354.
^ ^a ^b ^c ^d J. Blumm, A. Lindemann (2003/2007). "Characterization of the thermophysical properties of molten polymers and liquids using the flash technique". High Temperatures-High Pressures. 35/36 (6): 627. doi:10.1068/htjr144.
^ J. Blumm, A. Lindemann, M. Meyer, C. Strasser (2011). "Characterization of PTFE Using Advanced Thermal Analysis Technique". International Journal of Thermophysics. 40 (3-4): 311. Bibcode:2010IJT....31.1919B. doi:10.1007/s10765-008-0512-z.
^ ^a ^b ^c ^d Lide, David R., ed. (1992). CDC Handbook of Chemistry and Physics (edisi ke-71st). Boston: Chemical Rubber Publishing Company. cited in Baierlein, Ralph (1999). Thermal Physics. Cambridge, UK: Cambridge University Press. hlm. 372. ISBN 0-521-59082-5. Diakses tanggal 1 December 2011.

[1] Gladwell, Richard B. Hetnarski, M. Reza Eslami ; edited by G.M.L. (2009). Thermal Stresses - Advanced Theory and Applications (edisi ke-Online-Ausg.). Dordrecht: Springer Netherlands. hlm. 170. ISBN 978-1-4020-9247-3.

[AJP-2] Unsworth, J.; Duarte, F. J. (1979), "Heat diffusion in a solid sphere and Fourier Theory", Am. J. Phys., 47 (11): 891–893, Bibcode:1979AmJPh..47..981U, doi:10.1119/1.11601

[3] Carslaw, H. S.; Jaeger, J. C. (1959), Conduction of Heat in Solids (edisi ke-2nd), Oxford University Press, ISBN 978-0-19-853368-9

[4] Venkanna, B.K. (2010). Fundamentals of Heat and Mass Transfer. New Delhi: PHI Learning. hlm. 38. ISBN 978-81-203-4031-2. Diakses tanggal 1 December 2011.

[5] Brown; Marco (1958). Introduction to Heat Transfer (edisi ke-3rd). McGraw-Hill.

[6] Eckert; Drake (1959). Heat and Mass Transfer. McGraw-Hill. ISBN 0-89116-553-3. cited in Holman, J.P. (2002). Heat Transfer (edisi ke-9th). McGraw-Hill. ISBN 0-07-029639-1.

[eleccool-7] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Jim Wilson (August 2007). "Materials Data".

[Casalegno2010-8] V. Casalegno, P. Vavassori, M. Valle, M. Ferraris, M. Salvo, G. Pintsuk (2010). "Measurement of thermal properties of a ceramic/metal joint by laser flash method". 407 (2): 83. Bibcode:2010JNuM..407...83C. doi:10.1016/j.jnucmat.2010.09.032.

[9] P. Hofer, E. Kaschnitz (2011). "Thermal diffusivity of the aluminium alloy Al-10Si-Mn-Mg (Silafont 36) in the solid and liquid states". High Temperatures-High Pressures. 40 (3-4): 311. ^{[pranala nonaktif permanen]}

[10] E. Kaschnitz, M. Küblböck (2008). "Thermal diffusivity of the aluminium alloy Al-5Mg-2Si-Mn (Magsimal-59) in the solid and liquid states". High Temperatures-High Pressures. 37 (3): 221. ^{[pranala nonaktif permanen]}

[11] J. Blumm, A. Lindemann, B. Niedrig, R. Campbell (2007). "Measurement of Selected Thermophysical Properties of the NPL Certified Reference Material Stainless Steel 310". International Journal of Thermophysics. 28 (2): 674. Bibcode:2007IJT....28..674B. doi:10.1007/s10765-007-0177-z. ^{[pranala nonaktif permanen]}

[12] J. Blumm , A. Lindemann, B. Niedrig (2003/2007). "Measurement of the thermophysical properties of an NPL thermal conductivity standard Inconel 600". High Temperatures-High Pressures. 35/36 (6): 621. ^{[pranala nonaktif permanen]}

[13] A. Lindemann, J. Blumm (2009). Measurement of the Thermophysical Properties of Pure Molybdenum. 17th Plansee Seminar. 3.

[Koszor2009-14] O. Koszor, A. Lindemann, F. Davin, C. Balázsi (2009). "Observation of thermophysical and tribological properties of CNT reinforced Si₃ N₄". Key Engineering Materials. 409: 354. doi:10.4028/www.scientific.net/KEM.409.354.

[HTHP3536pp627-15] J. Blumm, A. Lindemann (2003/2007). "Characterization of the thermophysical properties of molten polymers and liquids using the flash technique". High Temperatures-High Pressures. 35/36 (6): 627. doi:10.1068/htjr144.

[16] J. Blumm, A. Lindemann, M. Meyer, C. Strasser (2011). "Characterization of PTFE Using Advanced Thermal Analysis Technique". International Journal of Thermophysics. 40 (3-4): 311. Bibcode:2010IJT....31.1919B. doi:10.1007/s10765-008-0512-z.

[baierlein-17] Lide, David R., ed. (1992). CDC Handbook of Chemistry and Physics (edisi ke-71st). Boston: Chemical Rubber Publishing Company. cited in Baierlein, Ralph (1999). Thermal Physics. Cambridge, UK: Cambridge University Press. hlm. 372. ISBN 0-521-59082-5. Diakses tanggal 1 December 2011.

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