Izinguquko ze-Enthalpy Ezinhlelweni Zokushisa Kobunjiniyela Bemishini
Ezweni lobunjiniyela bemishini, izingxoxo ngamandla zixhunyaniswe ngokungenakuhlukaniswa nezinhlelo zokushisa ezifana nama-boiler, ama-turbine omusi, ama-compressor, ama-condenser, ama-heat exchanger, kanye nezinjini zokushisa zangaphakathi. Enye yezinhlobo ze-thermodynamic ezisetshenziswa kakhulu ukuhlaziya ukudluliselwa kwamandla kula madivayisi yi-enthalpy. I-enthalpy iwusizo kakhulu ngoba izinqubo kumadivayisi okushisa zivame ukwenzeka ngaphakathi kokugeleza koketshezi (ivolumu yokulawula), kunokuba zivele ngaphakathi kohlelo oluvaliwe (isisindo sokulawula). Ngakho-ke, ukuqonda izinguquko ze-enthalpy kubalulekile ekuqondeni ukuthi amandla aya kuphi enkambisweni.
1. Ukuqonda i-Enthalpy kanye nencazelo yayo yomzimba
Ngokwencazelo, i-enthalpy (H) iyinani le-thermodynamic elakhiwe kanje:
H = U + pV
no:
– U = amandla angaphakathi
– p = ingcindezi
– V = ivolumu
Ekuhlaziyweni kwezinhlelo zokugeleza, ifomu elithile livame ukusetshenziswa:
h = u + pv
lapho i-h iyi-enthalpy ethile (kJ/kg). Igama le-pv elengeziwe livame ukuhunyushwa njengamandla ahlotshaniswa "nomsebenzi wokugeleza," okungukuthi, umsebenzi odingekayo ukuhambisa uketshezi lungene noma luphume kuvolumu yokulawula. Yingakho i-enthalpy ilula kakhulu ekuhlaziyeni amadivayisi afana nama-turbine, ama-nozzle, ama-diffuser, amaphampu, nama-compressor.
2. Ushintsho lwe-Enthalpy (Δh) Ezinqubweni Zokushisa
Ekwenzeni ubunjiniyela bemishini, into ebaluleke kakhulu akuyona nje inani le-enthalpy, kodwa noshintsho ku-enthalpy:
Δh = h₂ − h₁
Lolu shintsho luchaza ushintsho kokuqukethwe kwamandla koketshezi ngenxa yokushisa, ukupholisa, ukwanda, ukucindezela, noma ushintsho lwesigaba (isb., amanzi abe umusi). Ezingxenyeni eziningi zokushisa, ushintsho lwe-enthalpy luhlobene ngqo nokushisa nomsebenzi ohilelekile.
Isibonelo:
– Kubhoyila, i-enthalpy iyanda ngoba uketshezi luthola ukushisa.
– Kuma-turbine, i-enthalpy iyancipha ngoba amandla oketshezi aguqulwa abe umsebenzi womgodi.
– Ku-condenser, i-enthalpy iyancipha ngoba umusi ukhipha ukushisa endaweni ezungezile noma endaweni yokupholisa.
3. I-Enthalpy ku-Steady Flow Energy Equation
Ukuhlaziywa okuvame kakhulu kwezinhlelo zokushisa zobunjiniyela bemishini ukugeleza okuzinzile. Isibalo samandla sevolumu yokulawula ukugeleza okuzinzile (i-Steady Flow Energy Equation/SFEE) sivame ukubhalwa kanje:
q − w = (h₂ − h₁) + (V₂² − V₁²)/2 + g(z₂ − z₁)
no:
– q = ukushisa ngesisindo seyunithi (kJ/kg)
– w = umsebenzi ngeyunithi ngayinye yesisindo (kJ/kg)
– V = ijubane lokugeleza (m/s)
– z = ukuphakama (m)
– g = ukusheshisa ngenxa yamandla adonsela phansi (m/s²)
Ezinhlelweni eziningi zobunjiniyela bemishini, izinguquko ku-kinetic kanye namandla angase abe khona zincane kakhulu uma kuqhathaniswa noshintsho ku-enthalpy, ngakho-ke zivame ukwenziwa lula ukuze:
q − w ≈ h₂ − h₁
Lobu budlelwano obulula bunamandla kakhulu: uma sazi ukuthi ukushisa nomsebenzi kwenzeka kanjani, singalinganisa ushintsho lwe-enthalpy; noma ngokuphambene nalokho, uma idatha ye-enthalpy yaziwa (isb. kusukela ematafuleni omusi), singabala umsebenzi we-turbine noma izidingo zamandla e-compressor.
4. Izinguquko ze-Enthalpy Ezingxenyeni Eziyinhloko Zesistimu Yokushisa
a) Ibhoyila kanye neHetha
Kubhoyila, amanzi ayafudunyezwa aze aphenduke umusi. Inqubo ingabandakanya:
1) ukufudumeza amanzi acwebezelayo (ukushisa okunengqondo),
2) ukuhwamuka (ukushisa okucashile),
3) ukushisa kakhulu (ukushisa okwengeziwe ngomusi).
Zontathu lezi zinto zandisa kakhulu i-enthalpy. Ngomqondo:
q_in ≈ h_out − h_in
Uma ingcindezi kanye nokushisa kwe-boiler outlet kuphakeme, kulapho i-enthalpy yomusi ikhiqizwa khona inkulu, futhi ngokuvamile kulapho umsebenzi ongase ukhishwe ku-turbine uphakama khona.
b) Ama-Turbines Omusi kanye nama-Turbines Egesi
Ku-turbine, uketshezi lusebenza kuma-blades kanye ne-shaft. Ngaphansi kwezimo ze-adiabatic (cishe akukho ukudluliselwa kokushisa):
ukuphuma_kwe-w ≈ h_in − h_out
Lokhu kusho ukuthi ukwehla kwe-enthalpy ku-turbine kuhlobene ngqo nomsebenzi owenziwe. Kuma-turbine omusi, idatha ye-enthalpy ivame ukutholakala kumathebula noma kuma-dayagramu e-Mollier (hs). Kuma-turbine omusi, i-enthalpy ivame ukubalwa kusetshenziswa umthamo wokushisa othize, kusetshenziswa indlela efanele yegesi.
c) Amaphampu namaCompressor
Amaphampu (oketshezi) nama-compressor (amagesi) adinga umsebenzi wokufaka. Kumaphampu, njengoba uketshezi lucishe lungacindezelwa, ushintsho lwe-enthalpy luncane kakhulu futhi luvame ukulinganiselwa ku:
w_in ≈ v (p₂ − p₁)
Kuma-compressor egesi, ukwanda kwe-enthalpy kungaba kukhulu futhi kuhlobene nokwenyuka kwezinga lokushisa ngenxa yokucindezelwa. Ku-compressor ye-adiabatic:
w_in ≈ h_out − h_in
Ukwanda kwe-enthalpy kubonisa amandla angeziwe oketshezini ngokusebenzisa umsebenzi womgodi.
d) I-Condenser
I-condenser isusa ukushisa kumusi kuze kube yilapho kuqina kube uketshezi. Uma kungekho msebenzi we-shaft:
ukuphuma_kwe-q ≈ h_in − h_out
Ukwehla kwe-enthalpy ku-condenser ngokuvamile kukhulu ngoba kuhilela ukukhishwa kokushisa okucashile ngesikhathi sokujiya, okuyinto ebaluleke kakhulu uma kuqhathaniswa nokwehla kwezinga lokushisa okuvamile.
e) Ivalvu Yokukhulisa (Ivalvu Yokugoqa)
Ama-valve okwandisa avame ukutholakala ezinhlelweni zokuqandisa kanye nakwezinye izinhlelo zomusi. Inqubo yokubhoboza inesici esibalulekile: i-enthalpy engaguquki (isenthalpic) ngaphansi kwezimo eziningi zobunjiniyela.
h₁ ≈ h₂
Nakuba i-enthalpy ingashintshi, ingcindezi yehla kakhulu, futhi olunye uketshezi lungashintsha isigaba (isb., lube yingxube yoketshezi nomhwamuko). Lokhu kubalulekile emijikelezweni yokuqandisa ngoba kuphumela ekushiseni okuphansi ngemva kokukhula.
5. Izinguquko ze-Enthalpy kanye neSigaba Soketshezi Olusebenzayo
Izinguquko ze-enthalpy zibonakala kakhulu ezinqubweni ezihilela izinguquko zesigaba, njenge:
– amanzi abilayo aphenduka umusi,
– umusi ujiya ube ngamanzi,
– isiqandisi siyahwamuka ku-evaporator.
Ukushisa okucashile kokuhwamuka noma ukujiya kukhiqiza ukwanda kwe-enthalpy ngaphandle kokunyuka okukhulu kwezinga lokushisa ngaphansi kwengcindezi engaguquki. Ngakho-ke, ukuhlaziywa kwe-enthalpy kubalulekile ekwakhiweni kwama-boiler, ama-condenser, ama-evaporator, kanye nama-heat exchanger ezigaba ezimbili.
6. Ukusetshenziswa Kwedatha Ye-Enthalpy Ekuzijwayezeni Kobunjiniyela Bemishini
Ezimweni eziningi zangempela, onjiniyela ababali i-enthalpy kusukela kufomula eyisisekelo, kodwa basebenzisa:
– amatafula omusi,
– umdwebo we-hs (Mollier),
– isofthiwe yempahla ye-thermodynamic (i-REFPROP, i-EES, i-CoolProp),
– idatha yomkhiqizi.
Amaphutha amancane ekufundweni kwe-enthalpy angenza umehluko omkhulu ekulinganisweni kwamandla e-turbine, izidingo zikaphethiloli, noma amandla okupholisa. Ngakho-ke, ukukhetha izimo zokusebenza ezifanele (ingcindezi/izinga lokushisa) nokuqonda ikhwalithi yomusi kubalulekile.
7. Isiphetho
Ushintsho lwe-enthalpy luwumqondo oyinhloko ekuhlaziyweni kwezinhlelo zokushisa zobunjiniyela bemishini ngoba luxhumanisa ngqo izimo zokushisa, umsebenzi, kanye noshintsho lwesimo soketshezi emishinini yokugeleza. Ngokusebenzisa i-equation yamandla ezinzile, ushintsho lwe-enthalpy lungasetshenziswa ukubala umsebenzi we-turbine, amandla e-compressor, ukushisa okungeziwe kubhoyila, kanye nokwenqatshwa kokushisa ku-condenser. I-enthalpy isebenza "njengolimi" olusebenzayo konjiniyela ukuqonda ukusebenza kanye nokusebenza kahle kwemijikelezo yokushisa efana ne-Rankine, i-Brayton, kanye nezinhlelo zokuqandisa. Ukuqonda kahle ushintsho lwe-enthalpy kusho ukukwazi ukufunda nokuklama izinhlelo zokushisa ngokunembe, ngokuphephile, nangokusebenza kahle.
Uma uthanda, ngingangeza izibonelo ezilula zokubala (isibonelo ama-turbine omusi noma ama-compressor) ukuze ngenze isihloko sisebenze kakhulu futhi sisondele ezidingweni zezinkulumo/umsebenzi osebenzayo.
