Dab tsi yog qhov txawv ntawm Biot tooj thiab Nusselt tooj?
Dab tsi yog qhov txawv ntawm Biot tooj thiab Nusselt tooj?

Video: Dab tsi yog qhov txawv ntawm Biot tooj thiab Nusselt tooj?

Video: Dab tsi yog qhov txawv ntawm Biot tooj thiab Nusselt tooj?
Video: Tswv Yexus lub neej thaum pib txug thaum xaus 2024, Kaum ib hlis
Anonim

Cov lus teb tsis ntev los no. Biot naj npawb siv thermal conductivity ntawm lub cev (tsis yog kua), whereas Nusselt tus lej siv thermal conductivity ntawm cov kua. Cov qhov sib txawv ntawm Biot thiab Nusselt tus lej yog nyob rau hauv lub ntsiab lus ntawm tshav kub hloov coefficient, uas yog txhais raws li: h = -k (dT / dn) w / (Tw-T0).

Ib yam li ntawd, tib neeg nug, tus lej Biot txhais li cas?

Cov Biot naj npawb (Bi) yog ib tug dimensionless kom muaj nuj nqis siv nyob rau hauv lub tshav kub hloov xam. Nws yog lub npe hu ua tom qab lub kaum yim xyoo pua Fabkis physicist Jean-Baptiste Biot (1774–1862), thiab muab ib qho yooj yim Performance index ntawm qhov piv ntawm cov tshav kub hloov mus rau hauv lub cev thiab nyob rau saum npoo ntawm lub cev.

Ib yam li ntawd, tus lej Biot thiab Fourier yog dab tsi? Fourier tus lej yog ib qho kev ntsuas ntawm cov cua sov ua los ntawm lub cev txheeb ze rau cov cua sov khaws cia. Cov Biot naj npawb yog qhov sib piv ntawm kev ua haujlwm sab hauv ntawm lub cev rau cov khoom siv hluav taws xob rau nws sab nraud tsis kam rau cov cua sov convection.

Ua li no, thaum twg koj yuav siv tus lej Biot?

Cov Biot naj npawb yog ib qho kev ntsuas ntawm qhov tseem ceeb ntawm cov thermal kuj nyob rau hauv lub cev khoom rau convective thermal kuj. Feem ntau cov Biot naj npawb yog siv nyob rau hauv ib ntus conduction tshav kub hloov cov teeb meem cuam tshuam nrog convective ciam teb tej yam kev mob.

Nusselt tus lej puas tuaj yeem tsawg dua 1?

Nws yog tseeb los ntawm cov lus ua ntej hais tias Nusselt tus lej tuaj yeem yeej tsis yog tsawg dua 1 vim lub convective flux ua tau yuav xoom tab sis lub sij hawm molecular flux yuav yuav zoo ib yam nyob rau hauv tus zauv thiab tus denominator. Yog li ntawd, qhov tsawg kawg nkaus tus nqi ntawm Nusselt tus lej yog 1 thaum lub convective flux yog xoom.

Pom zoo: