Kuti awane nzira yekuwedzera kushanda kweinjini yekupisa , musayendisiti wekuFrance ainzi Sadi Carnot (1796-1832) akaongorora muchina wemacalorie chaiwo muna 1824. Panguva iyoyo, mutemo wekutanga wethermodynamics wakanga usati wagadzirwa, kana mutemo wechipiri wethermodynamics. Mutemo wekutanga hausati wagadzirwa nekuti masayendisiti haasati aziva kuti kupisa isimba. Mushure mekunge Joule nevamwe vake vaedza muma1830, masayendisiti akawana kuti kupisa isimba rinofamba nekuda kwekusiyana kwekupisa. Saka, mutemo wekutanga wethermodynamics wakagadzirwa mushure ma1830. Sadi Carnot akanga achitsvakurudza injini yemacalorie chaiyo yedzidziso muna 1824. Tsvagiridzo yake yaive yekuwedzera kushanda kweinjini yekupisa. Mazhinji emainjini emhepo epanguva iyoyo akanga asina kushanda zvakanaka.
Kutenderera kweinjini yekupisa yakakodzera yepfungwa dzaSadi Carnot kunonzi kutenderera kweCarnot. Tisati tadzidza kutenderera kweCarnot, takanzwisisa maitiro asingadzoreki zvakare. Maitiro ese ekuchinja kwesimba uye kutamiswa kwesimba kunoitika zvisingadzoreki. Semuenzaniso, tinokwesha maoko kuitira kuti maoko adziye. Kupisa kunogadzirwa nebasa ratinoita. Maitiro acho haadzoreki. Kupisa hakugone kukwesha maoko.
Chinangwa cheinjini yekupisa ndechekudzosera shure mamwe maitiro aya, uko kupisa kunogona kushandiswa kuita basa nekushanda kwakasimba. Kuti injini yekupisa ishande zvakanaka, tinofanira kudzivirira maitiro ese asingadzoreki. Kutamiswa kwekupisa hakudzoreki zvekuti kufamba kwekupisa hakufanirwe kuitika.
Kana injini ichitora kupisa (Q H ) patembiricha yepamusoro (T H ), mvura inoshanda mumuchina inofanirawo kunge iri patembiricha yeT H. Saizvozvowo, kana injini ikapedza kupisa kweQ L patembiricha yakaderera (T L ), mvura inoshanda mumuchina inofanirawo kunge iri patembiricha yeT L. Saka, chero maitiro anosanganisira kutamiswa kwekupisa anofanira kunge ari isothermal (tembiricha yakafanana). Kusiyana neizvi, kana tembiricha yechinhu chebasa mumuchina iri pakati peT H neT L , hapana kutamiswa kwekupisa kunoitika pakati pemuchina nenzvimbo ine tembiricha yeT H (mupi wekupisa) nenzvimbo ine tembiricha yeT L (discharge). Nekuti kupisa hakufambi, saka maitiro acho anofanira kuitwa nekukurumidza.
Kutenderera kweCarnot kune maitiro maviri e isothermal anodzoserwa uye maitiro maviri e adiabatic anodzoserwa.
Mufananidzo uri padivi ndewekuti The piston Carnot cycle yegesi rakakodzera. Chekutanga, kupisa kunonyudzwa panguva yekuwedzera kwemafuta (ab). Munguva yekuwedzera kwemafuta (isothermal expansion), tembiricha yegesi mu cylinder inochengetwa yakafanana.
Tevere, gasi rinokura nekukurumidza zvekuti tembiricha inodzikira kubva paT H kuenda kuT L (bc). T H = tembiricha yakakwira, T L = tembiricha yakaderera. Munguva yekuwedzera kweadiabatic, hapana kupisa kunopinda kana kubuda mu cylinder. Mushure mezvo, gasi rinodzvanywa ne isothermally (cd). Munguva yekudzvanywa ne isothermal, tembiricha yegasi inochengetwa yakafanana. Gasi rinodzvanywa nekukurumidza (da). Nekuti rinodzvanywa nekukurumidza, tembiricha yegasi inowedzera. Tembiricha yegasi inowedzera zvekuti kudzvanywa kwegasi kunowedzerawo. Maitiro ese muCarnot cycle anodzoserwa.
Munguva yekuwedzera kwemafuta anodziya uye kudzvanywa kwemafuta anodziya, tembiricha yegesi inochengetwa yakafanana. Chinangwa ndechekudzivirira chero musiyano wetembiricha. Kuvapo kwemusiyano wetembiricha kunogona kukonzera kutamiswa kwekupisa (maitiro asingadzoreki). Kuti maitiro ekupisa anodziya aitike (tembiricha yegesi inogara yakafanana) gasi rinofanira kuwedzerwa zvishoma nezvishoma kana kudzvanywa. Muchokwadi, kuwedzera, kana kudzvinyirirwa kwegasi, kunoitika nekukurumidza. Izvi zvinokonzerwa nekutenderera (yeuka dynamic fluid material), kukweshana, viscosity, nezvimwewo. Nekuda kweizvozvo, maitiro akakwana ekupisa anodziya haazombovipo. Kusiyana neizvi, kuwedzera nekudzvinyirirwa kwemafuta anodziya kunokurumidza.
Chinangwa ndechekudzivirira kupisa kuti kusapinde mu cylinder kana kubuda mu cylinder. Kuvapo kwekukweshana, viscosity, nezvimwewo hakukonzere kuwedzera kwe adiabatic uye kusimbiswa. Rangarira kuti injini yeCarnot ingori yedzidziso chete. Muchina weCarnot haupo muhupenyu hwedu. Kunyangwe zvichingova zvedzidziso chete, kuvapo kweinjini yeCarnot ndiko kukura kunobatsira kwethermodynamics. Inogona kuzivikanwa nezvechero maitiro asingadzoreki anogona kuitika panguva yekushanda uye kuedza kudzikisa kuitira kuti kushanda kweinjini kuve kwakanyanya.
Mhedzisiro yakakosha yeinjini yeCarnot ndeyekuti injini iite zvakanaka, kupisa kunogamuchirwa (Q H ) kunoenderana nekupisa kwakanyanya (T H ), uye utsi hwakanyungudika (Q L ) hunoenderana nekupisa kwakaderera (T L ). Saka, kushanda zvakanaka kweinjini yekupisa yakakwana ndekwekuti:
Uyu ndiwo muyero wekushanda zvakanaka kweinjini yekupisa.
Mubvunzo wechi1:
Injini yemutsi inoshanda pakati pe500 o C ne300 o C. Sarudza kushanda zvakanaka kweinjini yemutsi.
mhinduro
Tembiricha inofanira kuchinjwa kuita Kelvin scale.
T H (tembiricha yepamusoro) = 500 o C = 500 + 273 = 773 K
T L (tembiricha yakaderera) = 300 o C = 300 + 273 = 573 K
Kushanda zvakanaka kweinjini yekupisa yakakwana inoshanda pakati pe500 °C ne300 °C i26%. Kana michina yatinoshandisa muhupenyu hwedu hwezuva nezuva ichishanda pakati pe500 °C ne300 °C, kushanda zvakanaka kwazvo kunogona kuitwa nemashini kunosvika ka0.7 muzana (18.2%).
Mubvunzo wechi2:
Injini yekupisa inogamuchira 600 J patembiricha ye300 °C, inoita basa (W) 100 Joules uye inoburitsa 500 J pa100 °C. Sarudza kushanda chaiko uye kushanda kwakakodzera (Carnot efficiency) yemuchina uyu.
Tembiricha inofanira kushandurwa kuita Kelvin scale
T H (tembiricha yepamusoro) = 300 o C — 300 + 273 = 573 K
T L (tembiricha yakaderera) = 100 o C — 100 + 273 = 373 K
Q H = 600 J
Q L = 500 J
Kushanda zvakanaka kweinjini:
Kushanda zvakanaka kwemuchina uyu:
Kushanda zvakanaka kweinjini yekupisa yakakwana inoshanda pakati pe300 °C ne100 °C i35%. Kushanda zvakanaka kwazvo kunogona kuitwa nemuchina kunowanzoita ka0.7 pane kushanda zvakanaka kwakakodzera = 0.7 x 35% = 24.5% (24.5% x 600 J = 147 J kupisa kunoshandiswa pabasa).
Kushanda zvakanaka kwemuchina uyu i17% (100 J chete ndiyo inoshandiswa pakuita basa). Kuchine 147 J – 100 J = 47 J inogona kushandiswa pakuita basa.
Mubvunzo wechi3:
Muchina unogamuchira macalorie zana eJoule uye unogadzira maJoule mazana mana ebasa padanho rega rega. Muchina uyu unoshanda pakati pe500 o C ne200 o C. Verenga kushanda chaiko uye kushanda kwakakodzera kwemuchina uyu.
mhinduro
T H (tembiricha yepamusoro) = 500 o C — 500 + 273 = 773 K
T L (tembiricha yakaderera) = 200 o C — 200 + 273 = 473 K
Q H = 1000 J
Q L = 400 J
Kushanda zvakanaka kweinjini:
Kushanda zvakanaka kwemuchina uyu:
Kushanda zvakanaka kweCarnot = 40%. Kushanda zvakanaka kweinjini chaiyo = 60%. Muchina uyu haupo. Kushanda zvakanaka kwemuchina hakugone kunge kwakakura kupfuura kushanda zvakanaka kweCarnot.
Mubvunzo wechi4:
Kuti kushanda zvakanaka kweinjini yeCarnot kusvike 100% (1), tembiricha yekubuditsa inodiwa inofanira kunge yakaita sei (T L )?
mhinduro
Kuti injini ishande zvakanaka isvike 100% (kupisa kwese kunogona kushandiswa kuita basa), saka tembiricha yakaderera (T L ) inofanira kuva 0 Kelvin.
Kusvika pa 0 0 temperature yaKelvin hazvigoneke. Chirevo ichi ndicho mutemo wechitatu wethermodynamics.
Sezvo r yega yega 0 Kelvin isingagoneke, saka injini yekupisa yakakwana inogona kunge isina kushanda zvakanaka kwe100%. Sezvo injini yekupisa isingakwanise kushanda zvakanaka kwe100%, zvinogona kugumiswa kuti hazvigoneke kushandisa kupisa kwese (Q H ) kuita basa. Panofanira kunge paine kupisa kwakarasika (Q L ).
Hapana injini yekupisa (inoshanda mudenderedzwa) inogona kushandura kupisa kwese kuita basa (Mutemo wechipiri wethermodynamics, chirevo chaKelvin-Planck).
Girafu iri rinoratidza maitiro e-isothermal (kuwedzera kwe-isothermal) ari kuitika muchikamu chimwe chete. Mukuita uku, kupisa kwese (Q) kunogona kushandurwa kuita basa (W). Huwandu hwebasa rinoitwa = nzvimbo ine mumvuri.
Injini yekupisa inofanira kushanda nguva dzose (maitiro anofanira kuitika kakawanda, haagone kuitika munhanho imwe chete). Semuenzaniso, injini yekupisa yemhando yekuchinjana. Piston iri painjini yekupisa inochinjana inofanira kufamba kurudyi nekuruboshwe nguva dzose, kuitira kuti mavhiri agone kutenderera (anogona kushandiswa kufambisa chimwe chinhu). Mavhiri haagone kutenderera kana piston ichifamba kuti imire ipapo ipapo (maitiro anoitika muchikamu chimwe chete). Kana maitiro acho akaitika kakawanda, hazvigoneke kuti kupisa kwese kugone kushandurwa kuita basa (Kelvin-Planck statement).
Girafu riri kuruboshwe rinoratidza kuwedzera kwemafuta (museve wepasi) uye kudzvanywa kwemafuta (museve wekumusoro). Maitiro acho anoitika nguva dzose ari isothermal (Hapana basa rinogadzirwa). Girafu riri kurudyi inzira yekuwedzera mafuta (museve wepasi), nzira yekudhinda mafuta (museve kuruboshwe) uye nzira yekubvisa mafuta ( museve wekumusoro). Kubva pamagirafu maviri aya, zvinoita sekunge kune nzira inoenderera mberi, pane kupisa kunorasika nguva dzose.
