Lapho sikhuluma ku-physics nakuma-thermodynamics we Umjikelezo weCarnot Sibhekisela ekulandeleni kwezinqubo ezenzeka enjinini ye-Carnot. Kuyidivayisi ekahle ehlanganisa kuphela izinqubo ezimbalwa zohlobo oluhlehliswayo. Lokhu kusho ukuthi uma lezi zinqubo sezenzekile, isimo sokuqala singabuyiselwa kuso. Lolu hlobo lwenjini luthathwa ku-physics njengenjini ekahle futhi lusetshenziselwa ukuhlela ezinye izinjini, maqondana imigomo ye-thermodynamics.
Kulesi sihloko sizokutshela konke odinga ukukwazi mayelana nomjikelezo weCarnot nezimpawu zawo eziyinhloko.
Izici eziyinhloko
Sikhuluma ukuthi lolu hlobo lwenjini lubhekwa njengenjini ekahle. Lokhu kunjalo ngoba ayinakho ukuchithwa kwamandla, ngenxa yokushayisana nomhlabathi noma umoya futhi alukho uhlobo lwe-viscosity. Zonke lezi zici noma ukungahambi kahle kuvela kunoma iyiphi injini yangempela, ngoba akunakwenzeka ukuguqula amandla ashisayo abe umsebenzi ongasetshenziswa nge-100%. Kodwa-ke, inqwaba yeCarnot ingalingisa zonke lezi zimo ukuze ikwazi ukusebenza kangcono nokwenza izibalo ngendlela elula.
Uma sithenga injini siqala entweni ekwazi ukwenza umsebenzi. Isibonelo, izinto eziyinhloko ezisetshenziswayo yigesi, uphethiloli noma umusi. Lapho lezi zinto ezikwazi ukwenza umsebenzi zingaphansi kwezinguquko ezihlukahlukene kokubili izinga lokushisa nengcindezi, khiqiza ukuhlukahluka kwevolumu yabo. Ngale ndlela, ipiston ingahanjiswa ngaphakathi kwesilinda ukuze injini ibe nayo. Izimiso ze i-thermodynamics dlala indima ebalulekile kulezi zinqubo.
Uyini umjikelezo weCarnot?
Lo mjikelezo wenzeka ngaphakathi kohlelo olubizwa nge-Carnot engine. Kule njini kukhona igesi ekahle evalelwe kusilinda futhi enikezwe ipiston. I-piston ixhumana nemithombo ehlukahlukene esemazingeni okushisa ahlukene. Kulesi simiso kunezinqubo ezithile esingazifingqa ngezinyathelo ezilandelayo:
- Inani elithile lokushisa linikezwa kudivayisi. Leli nani lokushisa livela echibini eliphakeme lokushisa elishisayo.
- Imoto yenza umsebenzi ngenxa yalokhu kushisa okuzonikezwa
- Okunye ukushisa kuyasetshenziswa kanti okunye kuyachithwa. Imfucuza idluliselwa endaweni yokugcina ukushisa okushisayo, esezingeni eliphansi lokushisa.
Lapho sesizibonile zonke izinqubo, sizobona ukuthi yiziphi izigaba zomjikelezo weCarnot. Ukuhlaziywa kwalezi zinqubo kwenziwa kusetshenziswa umdwebo lapho kukalwa khona ingcindezi nevolumu. Inhloso yenjini kungaba ukugcina ithangi lesibili lipholile ngokukhipha ukushisa kulo. Kulokhu sizobe sikhuluma ngomshini wokupholisa. Uma, ngokuphambene nalokho, inhloso ukudlulisa ukushisa echibini elishisayo njengenombolo eyodwa, khona-ke sikhuluma ngempompo yokushisa.
Uma sihlaziya ingcindezi nomdwebo wevolumu siyabona ukuthi izinguquko kwingcindezi nasekushiseni kwenjini zikhonjiswa ngaphansi kwezimo ezithile ezilandelayo:
- Inqobo nje uma izinga lokushisa lihlala lingashintshile. Lapha sikhuluma ngenqubo ye-isothermal.
- Akukho ukudluliswa kokushisa. Yilapho esinokufakwa okushisayo khona.
Izinqubo ze-Isothermal zidinga ukuxhunywa komunye nomunye futhi lokhu kufinyelelwa ngenxa yokufakelwa kwe-thermal, umqondo ohlobene entropy.
Izigaba zomjikelezo weCarnot
Esikhathini sokuqala singaqala nganoma iyiphi ingxenye yomjikelezo lapho igesi inezimo ezithile zokucindezela, umthamo kanye nezinga lokushisa. Le gesi izokwenza uchungechunge lwezinqubo ezizoyivumela ukuthi ibuyele esimweni sayo sokuqala. Lapho igesi isibuyele ezimeni zayo zakuqala, yayisesimweni esikahle ukuqala omunye umjikelezo. Lezi zimo zifinyelelwa inqobo nje uma amandla angaphakathi ekugcineni afana namandla angaphakathi ekuqaleni. Lokhu kusho ukuthi amandla ayongiwa. Sesiyazi ukuthi amandla awadalwanga futhi awabhujiswa, kodwa ayaguqulwa kuphela.
Isigaba sokuqala somjikelezo weCarnot sisekelwe ekukhulisweni kwe-isothermal. Kulesi sigaba uhlelo ludonsa ukushisa okuvela echibini elishisayo 1 bese luyanda. Ngakho-ke, ivolumu yegesi iyanda futhi ingcindezi iyancipha. Kodwa-ke, izinga lokushisa lihlala lizinzile kusukela lapho igesi inweba iyaphola. Ngakho-ke, siyazi ukuthi amandla alo angaphakathi ahlala njalo ngokuhamba kwesikhathi.
Esigabeni sesibili sine- ukunwetshwa kwe-adiabatic. I-Adiabatic isho ukuthi uhlelo alutholi noma lilahlekelwe ukushisa. Lokhu kutholakala ngokubeka igesi ekufakweni kokushisa njengoba kukhonjisiwe ngenhla. Ngakho-ke, ekunwetshisweni kwe-adiabatic ivolumu iyakhula futhi ingcindezi iyancipha ize ifike kunani layo eliphansi.
Ku isigaba sesithathu sinokucindezelwa kwe-isothermal. Lapha sisusa ukwahlukanisa futhi uhlelo luhlangana nethangi lokushisa elingu-2, elizoba sezingeni lokushisa eliphansi. Ngalesi sizathu, uhlelo lubhekene nokudlulisa ukushisa kwemfucuza okungasetshenziswanga kuleli thangi elishisayo. Njengoba ukushisa kukhipha, ingcindezi iqala ukukhuphuka nevolumu yehle.
Ekugcineni, esigabeni sokugcina somjikelezo weCarnot sine-kokucindezelwa adiabatic. Lapha sibuyela esigabeni sokufakwa okushisayo ngohlelo. Ingcindezi inyusa ivolumu iyancipha ize ifinyelele ezimweni zokuqala futhi. Ngakho-ke, umjikelezo ulungele ukuqala futhi.
Ukulinganiselwa
Njengoba sishilo ngaphambili, injini ye-Carnot yenziwe kahle. Lokhu kusho ukuthi inemikhawulo yayo kusukela ngaleso sikhathi ama-motors wangempela awasebenzi ngendlela eyi-100%. Siyazi ukuthi izinjini ezimbili ze-Carnot zisebenza ngendlela efanayo uma zombili zisebenza ngama-thermal reservoirs afanayo. Lesi sitatimende sisho ukuthi into esiyisebenzisayo ibalulekile, njengoba ukusebenza kuzozimele ngokuphelele futhi ngeke kukhuliswe.
Isiphetho esisithola ekuhlaziyweni kwangaphambilini ukuthi umjikelezo weCarnot ungaphezulu kwenqubo ye-thermodynamic engafinyelelwa kahle. Lokho wukuthi, ngaphezu kwalokho, ngeke kube khona injini esebenza kahle kakhulu. Siyazi ukuthi iqiniso lokufakwa okushisayo alikaze liphelele futhi izigaba ze-adiabatic azikho, ngoba kukhona ukushintshana ngokushisa nengaphandle.
Emotweni, ibhulokhi yenjini iyashisa futhi ingxube kaphethiloli nomoya ayiziphathi ncamashi njengegesi ekahle. Ingasaphathwa ezinye izici ukuthi kubangele ukuncipha okukhulu ekusebenzeni.
Ngiyethemba ukuthi ngalolu lwazi ungafunda kabanzi ngomjikelezo weCarnot nezici zawo.