Puas yog Wavy lossis Helical PFA Tube Shape Txhim Kho Thaum tshav kub kub faib hauv qis-Flow, Siab-Viscosity Roj Baths?

Kev tswj cua sov ntawm siab -cov roj viscosity da dej, xws li siv rau cov khoom siv polymer, kev kho cua sov thiab cov tshuaj reactor jacketing yog ib qho kev sib tw: cov roj ntws maj mam (natural convection ib leeg lossis qis dua -flow recirculation) thiab resists mixing. Nyob rau hauv xws li ib qho chaw ib tug ncaj PFA raj cua sov ua ib tug txwv plume ntawm rhuab roj nce vertically tawm qhov tseem ceeb ntim ntawm da dej ntawm qis kub. Qhov sib txawv ntawm qhov kub thiab txias ntawm lub tshuab cua sov thiab cov roj ntau yog qee zaum ntau dua 30-40 degree, uas ua rau kom ceev PFA degradation ntawm cov chaw kub. Nyob rau hauv txoj kev xav, ib tug wavy los yog helical nkhaus PFA raj ua rau kom zoo dua cua sov faib los ntawm theem nrab ntws thiab cuam tshuam ntawm thermal barrier txheej. Cov℃uas qhov kev hloov pauv hauv cov duab no ua rau pom kev txhim kho nyob ntawm qhov viscosity ntawm cov roj ntawm kev ua haujlwm kub, qhov ntsuas ntawm lub tank thiab qhov tso cai poob siab hauv cov txheej txheem quab yuam.

Helical Geometry Flow Pattern Hloov
Cov kua dej ntws hauv thiab ib ncig ntawm lub raj helical PFA (coiled zoo li lub caij nplooj ntoos hlav) los yog lub raj sinusoidal (wavy khoov rau hauv ib lub dav hlau) raug rau centrifugal rog. Txoj kev hloov tshav kub hauv quiescent roj da dej yog ntuj convection. Nyob rau hauv cov ntaub ntawv ntawm ib tug ncaj ntsug raj, lub ntuj convection ntws yog tshwj xeeb tshaj yog axial thiab tsuas muaj ib kem ntawm rhuab roj ascending upward. Ntawm qhov tod tes, ib lub raj helical muaj qhov nkhaus uas khoov cov roj tawm sab nraud thaum nws nce. Particle duab velocimetry ntsuas nyob rau hauv 1000 cP silicone roj ntawm 120℃qhia hais tias ib tug helical PFA raj (coil ntawm 100 mm txoj kab uas hla, qhov siab ntawm 200 mm) tsim ib tug revolving toroidal flow qauv nyob ib ncig ntawm lub rhaub. Cov roj rhuab tau nce hauv cov qauv kauv thiab tom qab ntawd txo qis hauv cov phab ntsa tank, tsim kom muaj cov kab hluav taws xob loj loj uas siv li 70?80% ntawm lub tank ntim. Qhov kev ncig no txo ​​qis qhov kub siab tshaj qhov sib txawv thoob plaws lub tank los ntawm 25-30℃(rau lub raj ncaj) mus rau 10-15℃(rau lub helix) rau tib lub zog tawm tswv yim.

Qhov kev txhim kho nce ntxiv nrog tus lej Dean, qhov tsis muaj qhov loj me uas ntsuas lub zog ntawm theem nrab ntws hauv cov hlab ntsha nkhaus. Rau cov roj viscosities tshaj 10,000 cP ntawm kev khiav hauj lwm kub, tus Dean tus naj npawb tsawg dua 5 thiab qhov thib ob ntws yog tsawg. Nyob rau hauv cov roj viscous heev no daim ntawv helical tsis muab lub tshav kub faib kom zoo dua ib lub raj ncaj raws li cov kua dej ntws tsis tsim cov hlaws ntws. Lub tswv yim sab saum toj viscosity txwv rau cov txiaj ntsig helical yog li 8,000-10,000 cP. Lub viscosity yuav tsum tsawg dua 1,000 cP rau qhov thib ob ndlwg kom muaj zog txaus los cuam tshuam PFA sheath kev ncaj ncees los ntawm qhov chaw yaig ntawm lub vojvoog sab nraud ntawm qhov khoov.

Kev tsis sib xws ntawm qhov kub thiab txias thiab cuam tshuam ntawm cov txheej txheem ciam teb
Cov wavy raj zoo li (sinusoidal nrog 30-50 mm amplitude thiab 100-150 mm wavelength) cuam tshuam nrog thermal ciam txheej nyob rau hauv ib txoj kev sib txawv ntawm ib tug helix. Raws li cov roj ntws los ntawm cov undulating nto (los ntawm ntuj convection los yog tswj ndlwg), lub convex thiab concave qhov chaw tsim siab gradients uas tshwm sim nyob rau hauv kev sib cais thiab reattachment. Txhua nthwv dej tsim ib qho me me recirculation cheeb tsam ntawm downstream sab ntawm lub ncov convex uas yog 3-5 txoj kab uas hla. Cov chaw recirculation no thauj cov roj txias los ntawm cov dej ntws mus rau ntawm lub tshuab cua sov thiab txo cov ciam teb hauv zos txheej tuab los ntawm 30-50% piv rau cov ntaub ntawv ncaj nraim. Kev sim thermocouple ntawm lub tshuab cua sov PFA hauv 5,000 cP roj ntawm 150℃qhia tias qhov kub ntawm qhov chaw txawv ntawm ± 4-6℃raws qhov ntev, piv rau ± 12-18℃rau lub rhaub ncaj nrog tib qhov chaw tag nrho. Qhov ntsuas kub zoo sib xws ncaj qha txhim kho PFA lub neej los ntawm kev txo qis qhov kub siab tshaj plaws. Qhov kub siab tshaj plaws saum npoo yog txo los ntawm 10℃rau qhov txo qis ntawm 40-50% ntawm PFA (raws li Arrhenius kinetics).

Lub waviness imposes ib tug tswv yim txwv: qhov tsawg kawg nkaus khoov vojvoog ntawm lub raj yuav tsum ntau tshaj 8-10 lub sij hawm lub raj txoj kab uas hla, kom tsis txhob muaj kev ntxhov siab ntau dhau ntawm PFA. Rau PFA tubing nrog txoj kab uas hla 12 mm ib wavy zoo nrog khoov vojvoog 60 mm yog ua tau. Ib lub vojvoog nruj dua (30 hli) ua rau hauv ib cheeb tsam thinning ntawm PFA phab ntsa ntawm qhov khoov sab nraud, uas txo cov neeg kho tshuab lub zog los ntawm 20-30% thiab ua rau muaj kev phom sij ntawm permeation. Cov neeg tsim khoom ntawm wavy lossis helical PFA cov cua sov yuav tsum siv mandrel dabtsi yog khoov nrog cov cua sov tswj kom cov phab ntsa tsis tawg. Kev ua tsis tiav ntawm qhov khoov PFA cov cua sov feem ntau tshwm sim hauv qhov tsis muaj kev khoov nrog lub vojvoog tsawg dua 6x txoj kab uas hla.

Shape Selection Guide for Applications
Viscosity Operating Temp & Oil TypeFlow ConditionPreferred Tube ShapeKev txhim kho nyob rau hauv Uniformity ntawm TemperaturePrincipal limitation
Lub teeb roj (100-500 cP), 80-120℃Ntuj convection nkaus xwb Helical (coil txoj kab uas hla 8-10 zaug raj OD) Txo tank ΔT los ntawm 25℃mus rau 10-12℃Secondary flow erodes PFA saum 200 degree
Ntuj convection 120-150℃Cov roj nruab nrab (500-2,000 cP) Wavy (amplitude 4-6 × raj OD) txo qhov kub qhov chaw 8-12 degree; Wave spacing tseem ceeb; nruj dhau diminishes txiaj ntsig
Cov roj nruab nrab (500-2,000 cp) Tsawg quab yuam qis (Re 100-500) Helical nrog dav coil pitchIncrease tshav kub hloov coefficient los ntawm 30 mus rau 50 feem pua ​​​​siab txo 2-3x ncaj yeeb nkab
Cov roj hnyav (2000-8000 cP), 150-180℃Natural convectionFinned ncaj raj lossis txuas ntxiv ntoHelical / wavy kom zoo dua yog me (Dean<5)Change of shape not justified
Cov roj hnyav (10,000+ cP) Ncaj raj; Cov cua sov luv luv yuav tsum tau txiav txim siab.Tsis muaj kev txhim kho tseem ceeb los ntawm moldingViscosity damps theem nrab ntws tag
Txhua yam viscosity, tank nrog cov khoom sib tovHigh turbulence inducedStraight raj (tseem ceeb agitation) Shaping tus nqi nyiaj thiab muab tsis muaj nuj nqis Uniform kub twb muab agitation,
Tank nrog me me ntoo khaub lig-section (qhov chaw txwv) Ntuj convection Helical (me me ntsug profile) Kev txhim kho cov duab yog qhov tseem ceeb tshaj qhov chaw txuag Kev ntsuas ncaj nraim ntau lub tshuab cua sov ua kom zoo dua qub
Xaus: Cov Duab Teebmeem Tsuas yog hauv Cov Txheej Txheem Nruab Nrab Viscosity
A waved or helical The PFA tube design increases the heat dispersion only in a certain viscosity window of 500–8,000 cP at working temperature in low-flow, high-viscosity oil baths. Below 500 cP natural convection is strong enough that a straight tube already gives a good homogeneity. At $>8000 \\text{cP}$ lub siab viscosity ntawm cov kua inhibits theem nrab ntws thiab nkhaus hlab tsis zoo dua li cov hlab ncaj. Helical hlab txo qhov kub ntawm lub tank gradients los ntawm 40 mus rau 60 feem pua ​​thiab wavy hlab txo qhov kub ntawm qhov chaw los ntawm 30 mus rau 50 feem pua ​​ntawm 1,000 mus rau 5,000 cP ntau yam rau kev ua tau zoo tshaj plaws. Qhov kev ua kom zoo sib xws ncaj qha ua rau PFA rhaub lub neej los ntawm kev txo qis qhov kub siab tshaj plaws. Rau cov engineers xav txog cov kev qhia tshwj xeeb ntawm cov cua sov rau nruab nrab viscosity roj da dej nws raug pom zoo kom lawv thov kev suav cov kua hluav taws xob (CFD) ua qauv ntawm cov raj zoo li hauv lawv lub tank geometry ua ntej cog lus rau kev tsim khoom. Cov txiaj ntsig zoo yog nyob ntawm qhov sib piv ntawm lub tank thiab qhov chaw tso ntawm lub tshuab rhaub rau cov phab ntsa. Tshaj li 8,000 cP, saib ob peb lub tshuab cua sov ncaj thiab yuam kom rov ua dua tshiab dua li cov duab nyuaj, raws li tus nqi ntawm lub helical PFA raj, uas feem ntau yog 30-50% ntau tshaj qhov ncaj, tsis rov qab los ntawm qhov sib npaug ntawm qhov sib npaug.