Thermodynamics yog ib ceg tseem ceeb ntawm physics uas kawm thiab piav qhia txog cov txheej txheem thermodynamic hauv qhov sib npaug lossis sib npaug rau nws. Yuav kom piav qhia txog kev hloov pauv ntawm qee lub xeev pib mus rau lub xeev kawg uas siv qhov sib npaug ntawm cov thermodynamics, nws yog ib qho tsim nyog yuav tsum ua kom muaj kev kwv yees ntawm cov txheej txheem quasi-static. Qhov kev kwv yees no yog dab tsi, thiab hom txheej txheem no yog dab tsi, peb yuav xav txog hauv kab lus no.
txhais tau li cas los ntawm txheej txheem quasi-static?
Raws li koj paub, thermodynamics los piav txog lub xeev ntawm lub cev siv cov txheej txheem macroscopic uas tuaj yeem ntsuas kev sim. Cov no suav nrog siab P, ntim V, thiab qhov kub thiab txias T. Yog tias tag nrho peb qhov ntau tau paub txog cov txheej txheem hauv kev kawm ntawm lub sijhawm, lawv hais tias nws lub xeev tau txiav txim siab.
Lub tswv yim ntawm cov txheej txheem quasi-static txhais tau tias muaj kev hloov pauv ntawm ob lub xeev. Thaum lub sijhawm hloov pauv no,Lawm, cov yam ntxwv thermodynamic ntawm qhov system hloov. Yog tias txhua lub sijhawm thaum lub sijhawm hloov pauv mus txuas ntxiv, T, P thiab V paub txog qhov system, thiab nws tsis deb ntawm nws lub xeev sib npaug, ces peb hais tias txheej txheem quasi-static tshwm sim. Hauv lwm lo lus, cov txheej txheem no yog ib qho kev hloov pauv ntawm cov txheej txheem sib npaug. Nws xav tias kev cuam tshuam sab nraud ntawm lub kaw lus tsis tseem ceeb kom nws muaj sij hawm los sai sai rau qhov sib npaug.
Cov txheej txheem tiag tiag tsis yog quasi-zoo li qub, yog li lub tswv yim hauv qab kev txiav txim siab yuav ua kom zoo. Piv txwv li, thaum nthuav lossis compressing cov pa roj, muaj kev hloov pauv thiab cov txheej txheem nthwv dej hauv nws, uas yuav tsum muaj qee lub sijhawm rau lawv qhov attenuation. Txawm li cas los xij, nyob rau hauv ib tug xov tooj ntawm cov tswv yim, rau gases nyob rau hauv uas hais tias txav ntawm high speeds, equilibrium teev nyob rau hauv sai sai, yog li muaj ntau yam kev hloov ntawm lub xeev nyob rau hauv lawv yuav xam tau tias yog quasi-static nrog high precision.
Sib npaug ntawm lub xeev thiab hom txheej txheem hauv cov pa roj
Gas yog ib qho yooj yim aggregate xeev ntawm teeb meem rau nws txoj kev kawm nyob rau hauv thermodynamics. Qhov no yog vim lub fact tias rau nws cov lus piav qhia muaj ib tug yooj yim kab zauv uas muaj feem xyuam rau tag nrho peb ntawm cov saum toj no thermodynamic quantities. Qhov kev sib npaug no hu ua Clapeyron-Mendeleev txoj cai. Nws zoo li no:
PV=nRT
Siv qhov sib npaug no, txhua yam ntawm isoprocesses thiab adiabatic hloov pauv thiabgraphs ntawm isobar, isotherm, isochore thiab adiabat yog tsim. Nyob rau hauv kev sib npaug, n yog tus nqi ntawm cov khoom nyob rau hauv lub system, R yog ib tug tas mus li rau tag nrho cov gases. Hauv qab no peb xav txog txhua yam sau tseg ntawm cov txheej txheem quasi-static.
Isothermal hloov pauv
Nws tau kawm thawj zaug thaum kawg ntawm lub xyoo pua 17th uas siv ntau yam roj los ua piv txwv. Cov kev sim sib thooj tau ua los ntawm Robert Boyle thiab Edm Mariotte. Cov kws tshawb fawb tuaj nrog cov txiaj ntsig hauv qab no:
PV=const thaum T=const
Yog tias koj nce siab hauv lub cev, ces nws qhov ntim yuav txo qis rau qhov kev nce no, yog tias lub kaw lus tswj qhov kub thiab txias. Nws yog ib qho yooj yim los muab txoj cai no los ntawm kev sib npaug ntawm lub xeev koj tus kheej.
Lub isotherm ntawm daim duab yog ib qho hyperbola uas ze rau P thiab V axes.
Isobaric thiab isochoric hloov pauv
Isobaric (ntawm qhov siab tsis tu ncua) thiab isochoric (ntawm qhov ntim tas li) hloov pauv hauv cov pa roj tau kawm thaum pib ntawm lub xyoo pua 19th. Muaj txiaj ntsig zoo hauv lawv txoj kev kawm thiab kev tshawb pom ntawm cov kev cai lij choj muaj feem xyuam rau Fabkis Jacques Charles thiab Gay-Lussac. Ob qhov txheej txheem yog lej sawv cev raws li hauv qab no:
V/T=const thaum P=const;
P/T=const thaum V=const
Ob qho kev qhia ua raws li qhov sib npaug ntawm lub xeev yog tias peb teeb tsa qhov sib thooj tsis tu ncua.
Peb tau muab cov kev hloov pauv no nyob rau hauv ib kab lus ntawm kab lus vim lawv muaj cov duab sawv cev tib yam. Tsis zoo li isotherm, isobar thiab isochore yog cov kab ncaj nraimqhia ncaj qha proportionality ntawm ntim thiab kub thiab siab thiab kub raws li.
Adiabatic txheej txheem
Nws txawv ntawm cov isoprocesses tau piav qhia nyob rau hauv uas nws tau ua tiav hauv kev sib cais ntawm ib puag ncig. Raws li qhov tshwm sim ntawm kev hloov pauv ntawm adiabatic, cov pa roj nthuav tawm lossis cog lus tsis muaj kev sib pauv cua sov nrog ib puag ncig. Hauv qhov no, kev hloov pauv hauv nws lub zog sab hauv tshwm sim, uas yog:
dU=- PdV
Hais piav qhia txog cov txheej txheem adiabatic quasi-static, nws yog ib qho tseem ceeb kom paub ob qho: isobaric CP thiab isochoric CVtshav kub muaj peev xwm. Tus nqi CP qhia ntau npaum li cas cov cua sov yuav tsum tau muab tso rau hauv lub kaw lus kom nws nce nws qhov kub ntawm 1 K thaum lub sij hawm isobaric expansion. Tus nqi CV txhais tau tias tib yam, tsuas yog rau qhov ntsuas kub tas li xwb.
Qhov sib npaug rau cov txheej txheem no rau cov roj zoo tagnrho hu ua Poisson equation. Nws yog sau nyob rau hauv parameters P thiab V raws li nram no:
PVγ=const
Ntawm no yog qhov parameter γ hu ua adiabatic exponent. Nws yog sib npaug rau qhov piv ntawm CP thiab CV. Rau cov pa roj monatomic γ=1.67, rau cov roj diatomic - 1.4, yog tias cov roj tau tsim los ntawm cov molecules complex, ces γ=1.33.
Vim tias cov txheej txheem adiabatic tshwm sim nkaus xwb vim nws cov khoom siv hluav taws xob sab hauv, adiabatic daim duab hauv P-V axes coj tau zoo dua li cov duab isotherm.(hyperbole).
