He tuhinga mō te Huringa Mīhini Carnot
Untuk mengetahui bagaimana menaikkan efisiensi mesin kalor, seorang ilmuwan Perancis bernama Sadi Carnot (1796‐1832) meneliti suatu mesin kalor ideal secara teoritis pada tahun 1824. Pada waktu itu hukum pertama termodinamika belum dirumuskan, demikian juga hukum kedua termodinamika. Hukum pertama belum dirumuskan karena para ilmuwan belum mengetahui bahwa kalor merupakan energi. Setelah Joule dan teman‐temannya melakukan percobaan pada tahun 1830-an, para ilmuwan baru mengetahui secara pasti bahwa kalor merupakan energi yang berpindah akibat adanya perbedaan suhu. Jadi hukum pertama termodinamika dirumuskan setelah tahun 1830. Sadi Carnot sudah meneliti mesin kalor ideal secara teoritis pada tahun 1824. Penelitian yang beliau lakukan sebenarnya untuk menaikkan efisiensi mesin uap yang pada waktu itu sudah digunakan. Kebanyakan mesin uap waktu itu kurang efisien.
Ko te huringa i roto i te miihini wera tino pai, i whakawhanakehia e Sadi Carnot, e kiia ana ko te huringa Carnot. I mua i te arotake i te huringa Carnot, he mea āwhina kia mārama ki ngā tukanga kore e taea te whakakore. Ko ia tukanga hurihanga me te whakawhiti pūngao e puta noa ana i te ao he mea kore e taea te whakakore. Hei tauira, ki te mirimiri tātou i ō tātou ringa, ka mahana. I tēnei wā, ka puta te wera mā te mahi e mahia ana e tātou. Kāore e taea te whakakore i te tukanga. Kāore e taea e te wera e puta ana te mahi māna ake mā te mirimiri i ō tātou ringa. Ko te whāinga o te miihini wera he huri i tēnei tukanga, ka taea te whakamahi i te wera hei mahi i te mahi me te tino whai hua. Kia eke ai te miihini wera ki te tino whai hua, me karo tātou i ngā tukanga kore e taea te whakakore. Ko te whakawhiti wera e puta noa ana i te ao he mea kore e taea te whakakore, nō reira ka whakapau kaha ki te aukati i te whakawhiti wera.
Ina wera te mīhini, QH i ngā wāhi he teitei te pāmahana (TH), me noho hoki te matū mahi i roto i te mīhini ki te pāmahana THWaihoki, ki te tangohia e te miihini te wera QL i ngā wāhi he iti te pāmahana (TL), me noho hoki te matū mahi i roto i te mīhini ki te pāmahana TLNō reira, me rite te pāmahana o ia tukanga e pā ana ki te whakawhiti wera ki te pāmahana kotahi. I tetahi atu taha, ki te mea kei waenganui i te T te pāmahana o te matū mahi i roto i te mīhiniH me TL, kaua e puta he whakawhiti wera i waenga i te mīhini me te wāhi he pāmahana T tōnaH (kaiwhakarato wera) me tētahi wāhi he pāmahana T tōnaL (te whakakorenga). Kia kore ai te wera e puta, me whakahaere te tukanga mā te kore e nekeneke haere.
Ko te huringa Carnot he mea tito mai i ngā tukanga isothermal e rua ka taea te huri me ngā tukanga adiabatic e rua ka taea te huri.
E whakaatu ana te ahua kei te taha matau i te huringa Carnot mō tētahi hau pai. I te tīmatanga, ka mimitihia te wera i te wā e whakawhanui ana te wera (a-b). I te wā e whakawhanui ana te wera, ka mau tonu te pāmahana o te hau i roto i te rango.
Muri iho, ka horapa te hau i runga i te āhua ā-adiabatic kia heke ai tōna pāmahana mai i te T H ki te T L (b-c). T H = pāmahana teitei (Pāmahana teitei), T L = pāmahana iti (Pāmahana iti). I te wā e horapa ana te hau, kāore he wera e tomo, e puta rānei i te rango. Whai muri i tēnā, ka pēhia te hau i runga i te āhua isothermal (c-d). I te wā e pēhia ana te hau i runga i te āhua isothermal, ka mau tonu te pāmahana o te hau. Muri iho, ka pēhia te hau i runga i te āhua adiabatic (d-a). Nā te mea e pēhia ana i runga i te āhua adiabatic, ka piki ake te pāmahana o te hau. Ka piki ake te pāmahana o te hau, ā, ka piki ake anō hoki te pēhanga o te hau. Ka taea te huri i ngā tukanga katoa o te huringa Carnot.
I te wā e whakawhanui ana, e pēhi ana hoki i te pāmahana o te hau, ka mau tonu te pāmahana o te hau. Ko te whāinga kia kaua e rerekē te pāmahana. Ka taea e ngā rerekētanga pāmahana te whakaputa i te whakawhiti wera (he tukanga kore e taea te hoki). Kia puta ai he tukanga whakawhanui (kia mau tonu te pāmahana o te hau), me whakawhanui, me pēhi āta rānei te hau. Ko te mea pono, ka tere ake te whakawhanui, te pēhi rānei o te hau. Nā te pōrearea tēnei (kia mahara ki te kaupapa o te nekehanga wai), te waku, te matotoru, me ētahi atu. Nō reira, kāore rawa he tukanga whakawhanui tino pai. Engari, ka tere te whakawhanui me te pēhi adiabatic.
Ko te whāinga he ārai i te wera kei rere ki roto, ki waho rānei i te rango. Ka ārai te waku, te matotoru, me ētahi atu āhuatanga i te whānui me te pēhanga adiabatic tino pai. He mea nui kia mōhio ko te miihini Carnot he ariā noa iho; kāore i roto i ō tātou oranga o ia rā. Ahakoa he ariā, he nui te takoha a te miihini Carnot ki te whanaketanga o te thermodynamics. I te iti rawa, ka taea e tātou te tautuhi i ngā tukanga kore e taea te huri ka puta i te wā o te tukanga me te ngana ki te whakaiti i aua tukanga, kia nui ake ai te whai huatanga o tā tātou miihini wera i hangaia.
Ko tētahi hua tino nui o te miihini Carnot ko te mea mō tētahi miihini wera tino tika, ko te wera e whiwhihia ana (Q₂H₃ ) he rite ki te pāmahana T₂H₃ , ā, ko te wera i peia (Q₂L₃ ) he rite ki te pāmahana T₂H₃ . Nō reira, ko te whai huatanga o tētahi miihini wera tino tika ko:
Tauira pātai 1:
Ka mahi te mīhini mamaoa i waenga i te 500 ° C me te 300 ° C. Tātaihia te whai huatanga pai rawa atu (te whai huatanga Carnot) o te mīhini mamaoa.
Kōrero
Me huri te pāmahana ki te tauine Kelvin.
T H (mahana teitei) = 500 o C = 500 + 273 = 773 K
T L (pāmahana iti) = 300 o C = 300 + 273 = 573 K
Ko te pai o te mahi, te whaihua rānei o tētahi mīhini wera tino pai e mahi ana i waenga i te 500 ° C me te 300 ° C he 26%. Mena ka mahi te mīhini e whakamahia ana e tātou i ia rā i waenga i te 500 ° C me te 300 ° C, ko te pai mōrahi ka taea e te mīhini te whakatutuki he tata ki te 0,7 ngā wā o te pai o te mahi (18,2%).
Tauira pātai 2:
Ka whiwhi tētahi mīhini wera i te 600 Joule o te wera (Q) i te pāmahana o te 300 ° C, ka mahi i te 100 Joule o te mahi (W) ā, ka whakakore i te 500 J i te pāmahana o te 100 ° C. Whakatauhia te whai huatanga tuturu me te whai huatanga pai (te whai huatanga Carnot) o tēnei mīhini...
Kōrero
Me huri te pāmahana ki te tauine Kelvin.
T H (mahana teitei) = 300 o C ‐‐‐ 300 + 273 = 573 K
T L (pāmahana iti) = 100 o C ‐‐‐ 100 + 273 = 373 K
Q H = 600 J
Q L = 500 J
Te whai huatanga o te miihini:
Ko te pai o te mahi, te whaihua rānei o tētahi mīhini wera tino pai e mahi ana i waenga i te 300 ° C me te 100 ° C he 35%. Ko te pai mōrahi ka taea e te mīhini te whakatutuki he tata ki te 0,7 ngā wā o te pai o te mahi = 0,7 x 35% = 24,5% (24,5% x 600 J = 147 J o te wera ka taea te whakamahi hei mahi).
Ko te tino whai huatanga o tēnei mīhini he 17% (100 J anake te wera e whakamahia ana hei mahi). Kei te toe tonu te 147 J – 100 J = 47 J o te wera ka taea te whakamahi hei mahi. He pai mēnā ka taea te whakanui ake i te whai huatanga o tēnei mīhini hei whakaiti i ngā mate e pā ana ki a tātou.
Tauira pātai 3:
E whiwhi ana tētahi mīhini i te 1000 Joule o te wera, ā, e whakaputa ana i te 400 Joule o te mahi i ia huringa. Ka mahi tēnei mīhini i waenga i te 500 ° C me te 200 ° C. He aha te whai huatanga tuturu me te whai huatanga pai o tēnei mīhini?
Kōrero
T H (mahana teitei) = 500 o C ‐‐‐ 500 + 273 = 773 K
T L (pāmahana iti) = 200 o C ‐‐‐ 200 + 273 = 473 K
Q H = 1000 J
Q L = 400 J
Te whai huatanga o te miihini:
Ko te whai huatanga tino pai o tēnei mīhini ko:
Ko te pai o te mahi, e mōhiotia ana ko te pai o Carnot, he 40%. Ko te pai o te mahi tūturu o te miihini he 60%. Kāore he miihini pēnei. Kāore e taea e te pai o te mahi o te miihini te hipa ake i te pai o Carnot.
Tauira pātai 4:
Kia eke te whai huatanga o te miihini Carnot ki te 100% (1), he aha te pāmahana putanga hau (TL ) e hiahiatia ana?
Kōrero
Kia eke te whai huatanga o te miihini wera tino tika ki te 100% (ka taea te whakamahi i te wera katoa e whakauru ana ki te mahi), me rite te pāmahana putanga (TL ) ki te 0 Kelvin.
Kāore e taea te tae ki te pāmahana o te 0 Kelvin. Koinei te ture tuatoru o te thermodynamics.
Nā te mea kāore e taea te whakatutuki i te 0 Kelvin, kāore e taea e te miihini wera tino tika te whai hua 100%. Ahakoa te miihini wera tino tika, kāore e taea te whai hua 100%, me ngā miihini wera e whakamahia ana e tātou i ia rā.
I te mea kāore e taea e te miihini wera te whakatutuki i te whai huatanga 100%, ka taea e tātou te whakatau kāore e taea te whakamahi i te wera whakauru katoa (Q₂H₃ ) hei mahi. Me ngaro te wera (Q₂L₃ ).
Kāore e taea e te miihini wera (e mahi ana i roto i te huringa) te huri i te wera katoa hei mahi (Te ture tuarua o te thermodynamics – te kōrero a Kelvin-Planck).
Ko te tuhinga matotoru kua whakatītahahia i runga ake nei he kōrero motuhake mō te ture tuarua o te thermodynamics. Ka kiia he kōrero motuhake nā te mea e pā ana ki ngā miihini wera anake. Nā Kelvin rāua ko Planck i whakatakoto, ka kiia hoki ko te kōrero Kelvin-Planck. Mātakitaki te aroaro o te kupu "huringa" i roto i te kōrero i runga ake nei. Ko te huringa he tukanga e puta pinepine ana. Nō reira, ka mahi tonu te miihini wera. Ka tāpirihia te kupu "huringa" nā te mea, i roto i te ao tūturu, ka taea te huri i te wera katoa hei mahi mena kotahi noa te puta o te tukanga.
I roto i te ture tuatahi o te thermodynamics, i whakamāramahia ētahi tukanga thermodynamic, tae atu ki ngā tukanga isothermal, isobaric, isochoric, me te adiabatic. I roto i te tukanga isothermal, ka taea te huri i te wera katoa hei mahi (Q = W). Ka taea tēnei mena ka puta te tukanga i te kotahi noa te wāhanga. Tirohia te ahua i raro nei:
E whakaatu ana tēnei kauwhata i tētahi tukanga isothermal (whanui isothermal) e puta ana i te taahiraa kotahi. I tēnei tukanga, ka hurihia te wera katoa (Q) hei mahi (W). Ko te nui o te mahi i mahia = te wāhi kua whakamarumaruhia.
Kia whai hua ai, me mahi tonu te miihini wera (me mahi tonu te tukanga, kaua i te kotahi wāhanga anake). Hei tauira, he miihini mamaoa tauutuutu. Me neke tonu te piston i roto i te miihini mamaoa tauutuutu ki te taha matau me te taha maui kia taea ai e te wira te huri (ka taea te whakamahi hei neke i tetahi mea). Kāore e taea e te wira te huri mena ka neke noa te piston ki te taha matau, ā, muri iho ka mutu (ka puta noa te tukanga i te kotahi wāhanga). Mena ka puta tonu te tukanga (ka neke tonu te piston ki te taha matau me te taha maui), kāore e taea te huri i te wera katoa hei mahi (te kōrero a Kelvin-Planck). Hei tauira, me whakaaro tātou ki te tukanga isothermal e whakaaturia ana i te kauwhata i runga ake nei.
E whakaatu ana te kauwhata i te taha maui i te whānuitanga isothermal (pere whakararo) me te kōpeketanga isothermal (pere whakarunga). Ka puta tonu te tukanga i te isothermal (kāore he mahi e puta). E whakaatu ana te kauwhata i te taha matau i te whānuitanga isothermal (pere whakararo), te kōpeketanga isobaric (pere whakarunga), me te tukanga isochoric (pere whakarunga). Mai i ēnei kauwhata e rua, e mārama ana mō ngā tukanga e puta tonu ana (huringa), ka ngaro tonu te wera. E rite ana tēnei ki te kōrero Kelvin-Planck o mua.
