Ntau dua li muab cov khoom sib cais, lub raj nws tus kheej tuaj yeem tsim nrog dimples, corrugations, lossis spirals thaum tsim khoom. Cov yam ntxwv tseem ceeb no cuam tshuam qhov ntws thiab txhim kho cov cua sov hloov pauv yam tsis muaj kev pheej hmoo ntawm kev ntxig los yog ua rau txhaws.
Yog vim li cas xav txog Passive Enhancement Los ntawm Tube Geometry
Hauv ntau cov txheej txheem tshuaj thiab tshuaj, kev cia siab ntawm cov khoom siv hluav taws xob yog qhov tseem ceeb raws li kev ua haujlwm thermal. Cov txheej txheem kev txhim kho ib txwm muaj-xws li cov kab xev sib tw lossis cov xaim coil inserts- ntxiv cov khoom siv sab hauv uas tuaj yeem txav mus los, qaug zog, lossis ua qhov chaw fouling. Lwm txoj hauv kev yog hloov lub raj phab ntsa nws tus kheej. Dimpled los yog corrugated PTFE hlab ua tiav nto roughness los yog waviness uas yog ib qho tseem ceeb rau lub raj. Vim tias tsis muaj qhov sib cais, qhov kev pheej hmoo ntawm kev ua haujlwm tsis ua haujlwm, kev nkag mus rau hauv qhov chaw, lossis cov dej txhaws yog qhov tseem ceeb tshem tawm.
Txoj hauv kev no yog qhov tshwj xeeb tshaj yog rau kev tuav cov kua dej uas raug tshem tawm, crystalline slurries, lossis cov khoom siv polymerization-prone media. Rau cov ntawv thov nyuaj no, lub raj sab hauv du nrog dimples lossis corrugations muab turbulence yam tsis muaj crevices qhov twg cov khib nyiab tuaj yeem sau tau.
Yuav ua li cas Dimples thiab Corrugations cuam tshuam qhov ntws
Lub dimpled los yog corrugated PTFE raj muaj ib tug series ntawm periodic indentations (dimples) los yog alternating expansions thiab contractions (corrugations) raws nws ntev. Thaum cov kua dej dhau los ntawm cov kev hloov pauv ntawm geometric, cov ciam teb nyob ze ntawm phab ntsa yog rov ua dua thiab rov tsim dua. Swirling vortices yog los tom qab txhua qhov dimple lossis corrugation ridge, txhawb kev sib xyaw radial ntawm cov dej hauv nruab nrab thiab thaj tsam phab ntsa. Qhov kev sib xyaw no ua tau zoo thins cov txheej txheem thermal ciam teb, ua rau ntau dua convective tshav kub hloov coefficient.
Cov txheej txheem txhim kho yog qhov sib txawv ntawm qhov sib tw ntawm daim kab xev ntxig. Ib daim kab xev sib tw ua kom muaj kev sib tw helical tas mus li, qhov dimples thiab corrugations ua rau thaj tsam, ntu ntu. Qhov tshwm simDimpled corrugated PTFE raj cua sov hloovkev ua tau zoo feem ntau yog nruab nrab ntau dua - ntawm qhov kev txiav txim ntawm 20-60% kev txhim kho ntawm lub raj du -tab sis nrog qhov sib npaug ntawm qhov siab poob qis, feem ntau ntawm 30-100%.
Hauv kev xyaum, qhov ntsuas geometric (dimple qhov tob, corrugation pitch, thiab qhov siab) tuaj yeem hloov kho kom sib npaug ntawm cov cua sov hloov mus rau kev sib txhuam. Shorter pitch corrugations los yog ntxaum ntxaum tsim muaj zog turbulence tab sis kuj muaj zog dua. Ntev, ntiav cov qauv muab smoother ntws nrog ib tug me ntsis txhim khu kev qha.
Advantages Over Separate Inserts
Dimpled los yog corrugated PTFE hlab muaj ntau yam kev pab cuam piv rau twisted daim kab xev los yog lwm yam xoob inserts:
Tsis muaj kev pheej hmoo ntawm kev nkag mus: Qhov kev txhim kho geometry yog tas mus li tsim rau hauv lub raj phab ntsa. Tsis muaj qhov ua tau ntawm qhov ntxig txav mus rau hauv qab, ua rau lub raj puas, lossis tiv tauj cov ntawv raj.
Tsis muaj kev tiv thaiv ntxiv: Nrog rau ib qho kev sib cais, ib qho kev tiv thaiv thermal muaj nyob nruab nrab ntawm qhov ntxig thiab lub raj phab ntsa. Integral dimples lossis corrugations zam qhov kev tiv thaiv ntxiv vim tsis muaj qhov cuam tshuam.
Yooj yim ntxuav thiab tshuaj xyuas: Sab hauv ntawm lub raj corrugated tseem qhib, tsis muaj kev cuam tshuam. Kev tu npua lossis txhuam hniav tuaj yeem dhau los ntawm ib txwm, tsis zoo li hauv lub raj uas muaj cov kab xev sib tw, qhov kev tu yuav tsum tau tshem tawm qhov ntxig.
Tsawg kev pheej hmoo ntawm kev siv tshuab: Swirling inserts tuaj yeem vibrate lossis abrade lub PTFE raj phab ntsa nyob rau lub sij hawm, tshwj xeeb tshaj yog nyob rau hauv siab velocities. Integral geometry ua rau tsis muaj kev sib txheeb ntawm lub raj thiab qhov kev ua kom zoo dua qub.
Nws yog ib qho tsim nyog sau cia tias rau lub hom phiaj kev txhim kho kub kub heev (tshaj li 100%), ib daim kab xev sib txuas tseem ua tau zoo dua cov raj dimpled lossis corrugated. Txawm li cas los xij, rau cov ntawv thov uas qhov kev txhim kho nruab nrab yog qhov txaus thiab kev ntseeg siab yog qhov tseem ceeb, cov raj raj geometry feem ntau yog qhov kev daws teeb meem zoo dua.
Kev txiav txim siab tsim khoom rau PTFE
Corrugated thiab dimpled hlab yog dav siv nyob rau hauv cov hlau kub exchangers (xws li, stainless hlau los yog tooj liab). Lawv adaptation rau PTFE yuav tsum tau tshwj xeeb extrusion los yog thermoforming hom kev kawm. PTFE tsis yaj-ua tau zoo ib yam li cov thermoplastics; nws yog feem ntau ram-extruded los yog paste-extruded. Kev tsim cov dimples los yog corrugations hauv PTFE yog ua tiav los ntawm kev hla lub raj los ntawm cov cua kub tuag los yog los ntawm kev siv cov txheej txheem rotary-punch tom qab sintering. Rau cov kab me me (feem ntau 6-25 hli), PTFE corrugated corrugated raj yog muag los ntawm cov kws tsim khoom tshwj xeeb.
Phab ntsa thickness yuav tsum tau ua tib zoo tswj. Ib phab ntsa nyias dhau tuaj yeem tawg nyob rau hauv lub siab sab hauv ntawm cov corrugation peaks; phab ntsa tuab heev txo cov flexural ua raws li xav tau los tsim kom nruj corrugations. Hom phab ntsa thicknesses rau corrugated PTFE tshav kub exchanger raj muaj li ntawm 0.8 mus rau 2.0 hli, nyob ntawm txoj kab uas hla thiab siab ntsuas.
Siab poob thiab Flow Regime Effects
Hauv laminar ntws (Re < 2000), dimples thiab corrugations muaj qhov cuam tshuam loj heev. Lawv ua rau muaj kev hloov pauv thaum ntxov mus rau qhov tsis muaj zog, sib xyaw ua ke-tswj tswj hwm txawm tias tsawg Reynolds tus lej, nce Nusselt tus lej los ntawm 40-80% piv rau cov raj du. Lub siab poob lub txim kuj tseem ceeb heev, raws li qhov khiav yog yuam kom ceev thiab decelerate dua.
Nyob rau hauv turbulent flow (Re > 4000), tus txheeb ze txhim kho me me -feem ntau 20-40%-vim qhov inherent turbulence twb muab kev sib tov zoo. Txawm li cas los xij, qhov kev poob siab nce kuj tseem qis dua nyob rau hauv feem pua. Lub raj dimpled tsim tau zoo tuaj yeem ua tiav qhov kev ua tau zoo thermal (qhov sib piv ntawm kev hloov pauv hluav taws xob hloov mus rau kev sib txhuam nce mus rau 1/3 lub zog) ntau dua 1.2, qhia txog kev txuag hluav taws xob piv rau lub raj du rau tib lub zog siv.
Cov lus hauv qab no qhia txog cov kev ua tau zoo ib yam rau dimpled lossis corrugated PTFE hlab ntsig txog cov PTFE leeg, raws li cov kua dej zoo li ntawm Re=2000-5000.
| Parameter | Hom Kev Txhim Kho Ntau Yam |
|---|---|
| Nusselt tooj (kub hloov coefficient) txhim kho | +20% rau +60% |
| Friction factor (siab poob) nce | +30% rau +100% |
| Thermal Performance Factor (η) | 1.1 – 1.3 |
Xaus
Dimpled los yog corrugated PTFE hlab muab ib qho yooj yim, passive txoj kev los txhim kho tshav kub hloov nrog kev ntseeg tau zoo. Los ntawm kev tsim ib qho chaw geometry uas cuam tshuam cov ciam teb txheej thiab txhawb kev sib xyaw radial, cov hlab no ua tiav qhov nruab nrab (20-60%) kev hloov hluav taws xob kom tsis txhob muaj kev pheej hmoo ntawm kev nkag mus, kev tiv thaiv kev tiv thaiv, lossis kev tu cov teeb meem. Cov geometry yog tshwj xeeb tshaj yog muaj nqis nyob rau hauv cov kev pab cuam uas muaj particulates, muaju, los yog fouling kua uas cais inserts yuav impractical. Tube geometry tseem yog qhov sib txawv tseem ceeb hauv kev tsim hluav taws xob hloov hluav taws xob- thiab rau PTFE, corrugated los yog dimpled cov ntaub ntawv muab qhov sib npaug ntawm kev ua tau zoo, kev huv, thiab kev ruaj khov mus ntev.
