Qhov sib txawv tseem ceeb ntawm thermal conductivity thiab diffusivity yog qhov thermal conductivity yog hais txog lub peev xwm ntawm cov khoom siv los ua cua sov thaum thermal diffusivity yog hais txog kev ntsuas tus nqi ntawm kev hloov ntawm cov khoom cua sov ntawm nws qhov kub kawg mus rau txias kawg.
Thermal conductivity thiab thermal diffusivity yog ob nqe lus uas piav qhia txog kev hloov hluav taws xob los ntawm ib qho khoom siv.
Tus nqi hluav taws xob yog dab tsi?
Thermal conductivity yog ib lo lus uas piav txog lub peev xwm ntawm cov khoom siv los ua cua sov los ntawm nws tus kheej. Muaj peb txoj hauv kev uas peb tuaj yeem txhais lo lus no: k, λ lossis κ. Feem ntau, cov khoom uas muaj cov thermal conductivity siab qhia tau hais tias tus nqi siab ntawm kev hloov hluav taws xob. Piv txwv li, cov hlau feem ntau muaj cov thermal conductivity siab thiab muaj txiaj ntsig zoo hauv kev ua cua sov. Ib yam li ntawd, cov ntaub ntawv insulating xws li Styrofoam muaj cov thermal conductivity tsawg thiab qhia tau hais tias tus nqi qis ntawm cov cua sov hloov. Yog li ntawd, peb tuaj yeem siv cov ntaub ntawv nrog cov thermal conductivity siab hauv kev siv lub dab dej thaum peb tuaj yeem siv cov ntaub ntawv uas tsis tshua muaj thermal conductivity hauv thermal rwb thaiv tsev daim ntaub ntawv. Ntxiv mus, "thermal resistivity" yog reciprocal ntawm thermal conductivity.
lej, peb tuaj yeem qhia cov thermal conductivity li q=-k∇T, qhov twg q yog cov cua sov flux, k yog thermal conductivity thiab ∇T yog qhov kub thiab txias. Peb hu qhov no "Fourier txoj cai ntawm kev ua cua sov".
Peb tuaj yeem txhais cov thermal conduction raws li kev thauj mus los ntawm lub zog vim yog qhov kev txav ntawm cov molecular random hla qhov ntsuas kub. Yog li ntawd, peb tuaj yeem paub qhov txawv ntawm lo lus no los ntawm kev thauj mus los ntawm lub zog los ntawm kev ua haujlwm ntawm convection thiab molecular vim tias nws tsis cuam tshuam nrog kev siv cov microscopic ntws los yog kev ntxhov siab sab hauv uas ua haujlwm tau zoo.
Thaum xav txog cov ntsuas ntsuas rau thermal conductivity, SI units yog "Watts ib meter-Kelvin" lossis W / mK. Txawm li cas los xij, nyob rau hauv imperial units, peb tuaj yeem ntsuas thermal conductivity hauv BTU / (h.ft.° F) qhov twg BTU yog British thermal unit, h yog lub sij hawm hauv teev, ft yog qhov deb ntawm ko taw, thiab F yog qhov kub hauv Fahrenheit. Tsis tas li ntawd, muaj ob txoj hauv kev loj los ntsuas qhov thermal conductivity ntawm cov khoom: khov kho-lub xeev thiab cov txheej txheem hloov pauv.
Diffusivity Thermal yog dab tsi?
Thermal diffusivity yog qhov ntsuas ntawm tus nqi ntawm kev hloov pauv ntawm cov khoom kub ntawm qhov kub mus rau qhov txias kawg. Yog li ntawd, nws yog qhov thermal conductivity ntawm cov khoom faib los ntawm qhov ntom ntom thiab qhov tshwj xeeb kub muaj peev xwm ntawm lub siab tsis tu ncua. Chav ntsuas ntawm qhov ntsuas no yog m2/s. Nws yog SI derived unit. Feem ntau, peb tuaj yeem txhais lo lus no ua α. Tab sis muaj lwm yam cim thiab. Kev qhia lej ntawm thermal diffusivity yog raws li nram no:
α=k/ρcp
Ntawm no, k yog cov thermal conductivity, c p yog qhov muaj peev xwm kub, thiab ρ si qhov ntom. Txawm li cas los xij, ρcp ua ke yog lub npe hu ua volumetric heat peev.
Feem ntau, thermal diffusivity yog ntsuas los ntawm kev siv lub teeb nyem, uas suav nrog cua sov ntawm ib lub strip lossis cylindrical ib feem ntawm cov khoom siv nrog luv zog mem tes ntawm ib qho kawg thiab ntsuas qhov kub hloov qhov deb deb.
Qhov txawv ntawm Thermal Conductivity thiab Diffusivity yog dab tsi?
Thermal conductivity thiab thermal diffusivity yog ob nqe lus uas piav qhia txog kev hloov hluav taws xob los ntawm cov khoom siv tshwj xeeb. Qhov sib txawv tseem ceeb ntawm thermal conductivity thiab diffusivity yog qhov thermal conductivity yog hais txog lub peev xwm ntawm cov khoom siv los ua cua sov thaum thermal diffusivity yog hais txog kev ntsuas tus nqi ntawm kev hloov cov cua sov ntawm cov khoom los ntawm nws qhov kub kawg mus rau qhov txias kawg.
Hauv qab infographic tabulates qhov sib txawv ntawm thermal conductivity thiab diffusivity rau ib sab ntawm kev sib piv.
Summary – Thermal Conductivity vs Diffusivity
Thermal conductivity thiab thermal diffusivity yog ob nqe lus uas piav qhia txog kev hloov hluav taws xob los ntawm cov khoom siv tshwj xeeb. Qhov sib txawv tseem ceeb ntawm thermal conductivity thiab diffusivity yog qhov thermal conductivity yog hais txog lub peev xwm ntawm cov khoom siv los ua cua sov thaum thermal diffusivity yog hais txog kev ntsuas tus nqi ntawm kev hloov hluav taws xob ntawm cov khoom los ntawm nws qhov kub kawg mus rau qhov txias kawg.
