Ho Bala Mosebetsi le Matla a Thermodynamic Systems
Thermodynamics e ithuta kamano pakeng tsa mocheso, mosebetsi le matla ka har'a sistimi. Ha e le hantle—ebang ke lienjineng tsa likoloi, lifemeng tsa motlakase, li-compressor tsa indasteri, kapa esita le lihatsetsing—likhopolo tsa mosebetsi le matla ke tsa bohlokoa tlhahlobong ea katleho ea sistimi, litlhoko tsa matla le bokhoni ba ho hlahisa kapa ho monya matla. Sengoloa sena se tšohla kamoo mosebetsi le matla li baloang kateng litsamaisong tsa thermodynamic, likhopolo tsa bohlokoa tseo li li hlokang, le mehlala ea ts'ebeliso ea tsona lits'ebetsong tsa motheo.
1. Litsamaiso, meeli ea litsamaiso, le mefuta ea matla
Pele re etsa dipalo, re tlameha ho hlalosa sistimi (karolo e ithutwang) le tikoloho (kantle ho sistimi). Meeli ya sistimi e ka ba ya nnete (mabota a setshelo) kapa ya boiqapelo. Ho na le dihlopha tse tharo tse akaretsang:
1. Sistimi e koetsoeng: boima ha bo tšele meeli, empa matla a ka khona.
2. Sistimi e bulehileng (tsamaiso e bulehileng/bophahamo ba taolo): boima le matla li ka tšela meeli.
3. Sistimi e arohaneng: ha ho na phapanyetsano ea boima kapa matla (e loketseng).
Matla a thermodynamics a hlaha ka mefuta e 'maloa e meholo:
– Matla a ka hare (U): matla a microscopic ka lebaka la motsamao le tšebelisano-'moho ea limolek'hule.
– Matla a Kinetic (KE): a amanang le lebelo la macroscopic la mokelikeli/ntho, \( KE = \frac{1}{2} m V^2 \).
– Matla a ka bang teng (PE): a amanang le bophahamo tšimong ea matla a khoheli, \(PE = mgz \).
– Matla a phallo tsamaisong e bulehileng hangata a hlaha ka sebopeho sa (pv) (bophahamo bo itseng ba nako ya kgatello).
Tlhahlobong e sebetsang, re fumana hore na ke eneji efe e bohlokoa. Mohlala, ka tankeng e sa sisinyeheng, liphetoho ho KE le PE hangata lia hlokomolohuoa. Leha ho le joalo, ka har'a turbine kapa nozzle, liphetoho ho KE li ka ba matla.
2. Mosebetsi ho thermodynamics
Mosebetsi ke phetiso ea matla e hlahang ka lebaka la matla a sebetsang ka ho falla moeling oa sistimi. Ho thermodynamics, mokhoa o sebelisoang haholo oa letšoao ke:
– Mosebetsi o tswang tsamaisong o motle (tsamaiso e a sebetsa).
– Kenyelletso ea mosebetsi tsamaisong e mpe (tikoloho e sebetsa tsamaisong).
Mefuta e tloaelehileng ea mosebetsi:
1. Mosebetsi oa moeli: o etsahala ha bophahamo ba sistimi bo fetoha.
2. Mosebetsi wa shaft: mosebetsi wa mechini ka hara shaft, mohlala, diturbine le di-compressor.
3. Mosebetsi oa motlakase: litsamaiso li sebelisana ka motlakase le motlakase.
4. Mosebetsi wa bokahodimo le mefuta e meng (mohlala, mosebetsi wa selemo).
2.1 Fokotsa mosebetsi lits'ebetsong tse sa fetoheng
Bakeng sa lits'ebetso tsa quasi-static (khatello moeling oa sistimi e hlalositsoe hantle), mosebetsi oa moeli o hlalositsoe:
\[
W_b = \int_{V_1}^{V_2} p \, dV
\]
Boleng ba mosebetsi bo itshetlehile hodima tsela eo tshebetso e tsamayang ka yona, e seng feela maemong a pele le a ho qetela. Sena se bohlokwa: le hoja matla a ka hare e le mosebetsi wa mmuso, mosebetsi ha o jwalo.
Maemong a mang a tloaelehileng:
– Ts'ebetso ea khatello e sa khaotseng (isobaric)
\[
W_b = p(V_2 – V_1)
\]
– Ts'ebetso ea molumo o sa khaotseng (isochoric)
Kaha \( dV = 0 \), joale \( W_b = 0 \).
– Ts'ebetso ea Polytropic \( pV^n = \text{constant} \)
Bakeng sa \( n \neq 1 \):
\[
W_b = \frac{p_2 V_2 – p_1 V_1}{1-n}
\]
Bakeng sa \( n = 1 \) (isotherm e loketseng ea khase):
\[
W_b = mRT \ln\left(\frac{V_2}{V_1}\right)
\]
Khetho ea mohlala oa ts'ebetso (isobaric, isothermal, adiabatic, polytropic) e bohlokoa haholo bakeng sa ho fumana liphetho tsa lipalo, kahoo data kapa likhakanyo li hloka ho boleloa ka ho hlaka.
3. Mocheso le kamano ea oona le mosebetsi
Mocheso (Q) ke phetiso ea matla ka lebaka la phapang ea mocheso. Kopanong e tšoanang:
– \( Q > 0 \): mocheso o kena tsamaisong.
– \( Q < 0 \): mocheso o tloha tsamaisong. Ho thermodynamics, mocheso le mosebetsi ke mefuta ea phetisetso ea matla, eseng "matla a bolokiloeng". Matla a bolokiloeng a hlahisoa ka \( U \), \( KE \), \( PE \), kapa enthalpy \( H \). 4. Molao oa Pele oa Thermodynamics: motheo oa lipalo tsa matla 4.1 Sistimi e koetsoeng Molao oa Pele o bolela paballo ea matla: \[ \Delta E = Q - W \] ka \( E = U + KE + PE \). Kahoo: \[ \Delta U + \Delta KE + \Delta PE = Q - W \]
Mathata a mangata, diphetoho ho \( KE \) le \( PE \) di nyane hoo: \[ \Delta U = Q - W \] Sena se fana ka motheo wa ho bala mocheso kapa mosebetsi haeba phetoho ya matla a ka hare e tsejwa (mohlala, ho tswa tafoleng ya thepa kapa equation e loketseng ya kgase). 4.2 Sistimi e bulehileng (bophahamo ba taolo) le diekabone tsa matla a phallo e tsitsitseng Bakeng sa phallo e tsitsitseng, foromo e tsebahalang ke: \[ \dot{Q} - \dot{W}_s = \dot{m}\left( h_2 - h_1 + \frac{V_2^2 - V_1^2}{2} + g(z_2 - z_1) \right) \] Mona: - \( \dot{W}_s \) ke mosebetsi wa shaft ka nako ya yuniti. - \( h \) ke enthalpy \( h = u + pv \), e bohlokwa haholo ditsamaisong tse bulehileng hobane e kenyeletsa matla a ka hare le a phallo. Likarolo \( \frac{V^2}{2} \) le \( gz \) ka linako tse ling li ka hlokomolohuoa, empa bakeng sa li-nozzle/diffuser kapa litsamaiso tse nang le phapang e kholo ea bophahamo, likarolo tsena li lokela ho nahanoa. 5. Mekhoa e akaretsang ea ho bala mosebetsi le matla Ha ho rarolloa mathata a thermodynamic, mehato e hlophisitsoeng e thusa ho qoba liphoso: 1. Hlalosa sistimi (e koetsoeng kapa e butsoeng) 'me u thale setšoantšo se bonolo. 2. Fumana ts'ebetso (isobaric, adiabatic, isothermal, polytropic, jj.). 3. Ngola tekanyo ea matla (Molao oa Pele) ho latela mofuta oa sistimi. 4. Hlalosa bongata bo hlokomolohuoang (mohlala, \( \Delta KE \approx 0 \)). 5. Sebelisa likamano tsa thepa: litafole tsa mouoane, likhase tse loketseng, kapa li-equation tsa boemo. 6. Bala mosebetsi ho tsoa ho integral \( \int p\,dV \) kapa ho tsoa ho equation ea matla a phallo. 7. Hlahloba li-unit le matšoao (a matle/a mabe ho latela moetlo). Phoso e tloaelehileng ke ho ferekanya tlhaloso ea mosebetsi oa moeli tsamaisong e koetsoeng le mosebetsi oa shaft tsamaisong e bulehileng, le ho lebala hore mosebetsi o itšetlehile ka tsela. 6. Mehlala ea likhopolo tse sebelisoang lisebelisoa tsa thermodynamic 6.1 Li-turbine Li-turbine li fetola matla a mokelikeli hore e be mosebetsi oa shaft. Bakeng sa phallo e tsitsitseng, hangata ho nahanoa hore ke adiabatic (\( \dot{Q} \approx 0 \)) 'me phetoho ea bophahamo e nyane: \[ \dot{W}_s \approx \dot{m}(h_1 - h_2) \]
Haeba lebelo la ho tsoa le phahame haholo, joale phetoho ea matla a kinetic e tlameha ho kenyelletsoa ho netefatsa likhakanyo tse nepahetseng tsa matla. 6.2 Li-compressor Li-compressor li hloka mosebetsi oa shaft ho eketsa khatello. Tlas'a maemo a loketseng a adiabatic, mosebetsi o itseng o amana le keketseho ea enthalpy: \[ w_s \approx h_2 - h_1 \] Ha e le hantle, tahlehelo e etsahala, kahoo katleho ea isentropic hangata e sebelisoa ho amahanya maemo a loketseng le a sebele. 6.3 Silindara-piston (tsamaiso e koetsoeng) Katolosong ea khase ka piston, mosebetsi oa moeli o baloa ho tloha sebakeng se ka tlas'a kotopo \( p \)-\( V \). Haeba ts'ebetso e potlakile ebile e se ea quasi-static, khatello ea moeli e kanna ea se be e ts'oanang, e hlokang tlhokomelo ka mokhoa o bonolo oa ho kopanya kapa ho sebelisa khatello ea kantle. 7. Bohlokoa ba 'mele: mosebetsi, matla le katleho Lipalo tsa mosebetsi le matla ha li hlahise lipalo feela, empa li boetse li fana ka kutloisiso ea hore na matla a fetisetsoa joang le hore na tahlehelo e etsahala hokae. Moelelong oa katleho: - Lienjineri tsa mocheso li ikemiselitse mosebetsi o moholo oa tlhahiso ho tsoa mochesong o kenang. - Mekhoa ea sehatsetsing e ikemiselitse ho fetisetsa mocheso o itseng ka mosebetsi o fokolang. - Mekhoa ea indasteri, ntlafatso hangata e shebana le ho fokotsa mosebetsi oa khatello, ho khutlisa mocheso o litšila, kapa ho fokotsa ho se fetohe. Leha Molao oa Pele o netefatsa hore matla "ha a lahlehe," boleng ba matla bo ka fokotsoa ke ho se fetohe - boo ka nako eo bo hlahlojoang ka botebo ka Molao oa Bobeli le mohopolo oa entropy. Leha ho le joalo, e le motheo, ho tseba Molao oa Pele le ho bala mosebetsi le matla ke mohato oa pele oa bohlokoa. Qetello Lipalo tsa mosebetsi le matla litsamaisong tsa thermodynamic li qala ka tlhaloso ea sistimi, ho khetholla mefuta e nepahetseng ea matla, le ho sebelisa Molao oa Pele oa Thermodynamics. Bakeng sa litsamaiso tse koetsoeng, sepheo sa mantlha hangata ke phetoho ea matla a ka hare le mosebetsi oa moeli \( \int p\,dV \). Bakeng sa litsamaiso tse bulehileng, enthalpy ke ea bohlokoa, 'me tlhahlobo e etsoa ho sebelisoa equation ea matla a phallang ka mokhoa o tsitsitseng, e kenyeletsang mosebetsi oa shaft le liphetoho tse ka bang teng matla a kinetic le a ka bang teng. Ka mokhoa o hlophisitsoeng le kutloisiso ea tsela ea ts'ebetso, lipalo tsena li ka sebelisoa ho lekola le ho rala ka nepo lisebelisoa tse fapaneng tsa matla. Haeba ho hlokahala, nka eketsa mehlala e felletseng ea lipalo (mohlala, katoloso ea khase ea polytropic kapa matla a turbine ka data ea enthalpy) ho etsa hore sengoloa se sebetse haholoanyane.
