k = isoenttropic exponent
Qhov tseem ceeb ntawm k rau kev nyab xeeb valve
edited los ntawm Alessandro Ruzza
Qhov luaj li cas ntawm kev nyab xeeb li qub tsim los tawm cov pa roj los yog cov vapors, raws li lspesl Collection "E", yuav tsum muaj kev paub txog isoenttropic exponent k ntawm kev tso tawm.
Daim ntawv thov tsis tu ncua ntawm lspesl Collection "E" tshooj "E.1", hais txog qhov loj ntawm qhov kev nyab xeeb li qub, tuaj yeem ua rau muaj kev kwv yees ntau dhau ntawm lub peev xwm ntawm cov li qub thiab cov discs tawg.
Kab lus no muab qee cov lus qhia los kwv yees tus nqi ntawm k rau cov pa roj tiag tiag thiab
taw qhia qhov yuam kev los ntawm kev txiav txim siab k sib npaug rau qhov piv ntawm cov cua sov tshwj xeeb Cp / Cv
Isoenttropic outflow los ntawm lub nozzle
Cov qauv [1] uas yog siv nyob rau hauv sau "E", raws li zoo raws li nyob rau hauv lwm yam Italian [2] thiab txawv teb chaws [3] standards, rau kev xam cov kev nyab xeeb li qub uas yuav tsum tau tso pa tawm los yog vapors, yog ntawm isoenttropic outflow los ntawm lub nozzle nyob rau hauv ib qho tseem ceeb dhia tej yam kev mob, uas rau ib tug zoo tagnrho roj yog:
qha expansintawm coefficient C yog muab los ntawm:
ua k tus exponent ntawm isoenttropic expansintawm equation: 
| Mob khaub thuas | P1 (bar) | T1 (°C) | q' (kg/h) | q (kg / h) | (q'/q) x 100 |
|---|---|---|---|---|---|
| Methane | 12 | 50 | 1472 | 1466 | 100.4 |
| Methane | 23 | 200 | 2314 | 2267 | 102.1 |
| Dab Neeg | 12 | 100 | 2261 | 2181 | 103.7 |
| Hexane | 12 | 178 | 3099 | 2740 | 113.1 |
| Hexane | 23 | 220 | 6519 | 5111 | 127.5 |
| Heptane | 12 | 215 | 3232 | 2821 | 114.4 |
q' = ntws tus nqi xam nrog k = Cp / Cv (20 ° C, 1 atm)
q = flow rate xam nrog k = (Cp/Cv) • (Z/Zp)
Los ntawm kev qhia qhov kev sim coefficient k ntawm kev ruaj ntseg valve outflow, uas thoob ntiaj teb txiav txim siab qhov tseeb outflow kev ua tau zoo ntawm lub valve, kev nyab xeeb coefficient ntawm 0.9 thiab compressibility yam Z1 Rau cov kua dej tiag tiag, peb tuaj txog ntawm qhov kev sau ntawm "E":
Lub isoenttropic exponent k tuaj yeem qhia tau tias:
![[2]](https://i0.wp.com/www.besa.it/wp-content/uploads/2022/06/Schermata-2022-06-30-alle-15.39.24.png?ssl=1)
Rau ib qho zoo tagnrho gas, rau uas P x V / R x T = 1 , nws yog qhia tias k yog sib npaug rau qhov piv ntawm Cp / Cv ntawm qhov tshwj xeeb cua sov ntawm qhov siab thiab ntim.
rau ib tug gas tiag, k tuaj yeem hais tau (saib Daim Ntawv Ntxiv B) los ntawm:
![[3]](https://i0.wp.com/www.besa.it/wp-content/uploads/2022/07/Schermata-2022-06-30-alle-15.39.46.png?ssl=1)
qhov twg Z yog qhov compressibility yam txhais los ntawm Z =P x V / R x T thiab Zp yog "los ntawm compressibility yam". Thaum thov cov mis [3], raws li kev sau "E", qhov tseem ceeb ntawm Cp / Cv, Z thiab Zp yuav tsum raug ntsuas ntawm qhov kev tso tawm P1 thiab T1.
Lub derived compressibility factor Zp yog txhais nyob rau hauv formula [4] raws li:
![[3.1]](https://i0.wp.com/www.besa.it/wp-content/uploads/2022/07/Schermata-2022-06-30-alle-15.40.20.png?ssl=1)
Lub compressibility factor Z tuaj yeem qhia tau tias:
![[4]](https://i0.wp.com/www.besa.it/wp-content/uploads/2022/07/Schermata-2022-06-30-alle-15.40.29.png?ssl=1){kind=small}
thiab zoo sib xws, tuaj yeem qhia tau tias:
![[5]](https://i0.wp.com/www.besa.it/wp-content/uploads/2022/07/Schermata-2022-06-30-alle-15.40.36.png?ssl=1){kind=small}
qhov twg qhov txiaj ntsig ntawm Z^0, Z^1, Zp^0, Zp^1 yog tabulated hauv Appendix A raws li kev ua haujlwm ntawm Pr thiab Tr.
In [4] thiab [5], Ω yog Pitzer's acentric factor txhais los ntawm:
![[10]](https://i0.wp.com/www.besa.it/wp-content/uploads/2022/07/Schermata-2022-06-30-alle-15.40.44.png?ssl=1){kind=small}
Qhov twg Pr^SAT yog qhov txo vapor siab sib xws rau qhov txo qis tus nqi Tr = T / Tc = 0,7. Cov ntawv ntxiv A qhia txog Ω qhov tseem ceeb ntawm qee cov kua dej. Z e Zp kuj tuaj yeem muab ncaj qha los ntawm kev sib npaug ntawm lub xeev.
Ib qho piv txwv ntawm tus lej
Tig mus rau tus lej piv txwv, piv txwv li peb yuav tsum suav cov peev txheej tawm ntawm lub valve kev nyab xeeb raws li hauv qab no:
| Mob khaub thuas | n-Butano | |
| Lub cev lub cev | superheated vapors | |
| Molecular loj | M | 58,119 |
| Teeb lub siab | P | 19,78 bar |
| Tshaj siab | 10% | |
| Dej kub | T | 400 K |
| Efflux coefficient | 0,9 | |
| Orifice txoj kab uas hla | Do | 100 hli |
qhov tso tawm siab yog muab los ntawm:
rau n-Butane: Tc=425,18 K thiab Pc=37,96 bar, peb muaj:
thiab siv cov ntxhuav hauv Cov Ntawv Ntxiv A, peb muaj:
Paub qhov ntim tshwj xeeb ntawm cov vapor ntawm qhov paug tawm (P1, T1) sib npaug rau 0,01634 m^3 / kg (0,0009498 m^3 / g-mole), peb kuj tuaj yeem suav Z los ntawm:
Muab qhov sib piv ntawm cov cua kub tshwj xeeb ntawm qhov siab thiab ntim tas li, ntawm kev tso tawm (P1, T1), sib npaug rau 1,36, los ntawm formula [3] peb muaj:
147060
Siv cov mis [1], uas tau daws rau qhov kev suav ntawm tus nqi ntws, peb muaj tus nqi ntws tawm tus nqi ntawm 147.060 kg / h.
174848
Yog tias peb tau siv tus nqi ntawm Cp / Cv ntawm 1 atm thiab 20 ° C, peb yuav muaj k = 1,19 hli thiab los ntawm formula [1] ib qho paug ntws tus nqi ntawm 174.848 kg / h.
Qhov no yuav tau coj peb mus overestimate qhov tso tawm muaj peev xwm ntawm kev ruaj ntseg valve los ntawm ib ncig 19%
CEEB TOOM:
Qhov yuam kev uas tuaj yeem ua los ntawm kev muab tus nqi Cp / Cv rau k tuaj yeem siab dua li qhov piv txwv no.
Tshaj 20%
Txhawm rau muab ib lub tswv yim, cov lus hauv qab no qhia cov nqi ntws ntawm 18-mm orifice rau lwm cov hydrocarbons saturated, suav hauv ob kis. Cov kev suav tau ua nrog tshwj xeeb developed Software.
| Mob khaub thuas | P1 (bar) | T1 (°C) | q' (kg/h) | q (kg / h) | (q'/q) x 100 |
|---|---|---|---|---|---|
| Methane | 12 | 50 | 1472 | 1466 | 100.4 |
| Methane | 23 | 200 | 2314 | 2267 | 102.1 |
| Dab Neeg | 12 | 100 | 2261 | 2181 | 103.7 |
| Hexane | 12 | 178 | 3099 | 2740 | 113.1 |
| Hexane | 23 | 220 | 6519 | 5111 | 127.5 |
| Heptane | 12 | 215 | 3232 | 2821 | 114.4 |
Lub software tsis siv cov qauv [4] [5] tab sis, pib los ntawm kev hloov kho Redlich thiab Kwong equation of state, suav tus nqi ntawm isoenttropic exponent siv cov thermodynamic correlations.
