Diskontinualni granični sloj i analogije prenosa u pakovanim, fluidizovanim i transportnim sistemima tečnost-čestice
Discontinued boundary layer and transport phenomena analogies in liquid-particles packed and fluidiyed beds and transport systems
Doktorand
Jaćimovski, Darko R.Mentor
Bošković-Vragolović, NevenkaČlanovi komisije
Garić-Grulović, RadmilaPjanović, Rada
Metapodaci
Prikaz svih podataka o disertacijiSažetak
U ovom radu eksperimentalno je ispitivan diskontinualni granični sloj i
analogije prenosa količine kretanja, toplote i mase u fluidizovanim i pakovanim
slojevima i pri hidrauličkom transportu sistema tečnost-čestice. Cilj ovog rada je upravo
povezivanje karakteristika graničnog sloja sa prenosom količine kretanja, toplote i
mase, sa akcentom na analogije između ovih prenosa. Fenomenološkim pristupom ovoj
problematici, daje se doprinos koji bi olakšao teorijsko razmatranje višefaznih sistema
tečnost-čestice (pakovani sloj, fluidizovani sloj, vertikalni transport), koji su izuzetno
složeni.
Za izvođenje eksperimentalnog dela istraživanja u ovoj doktorskoj disertaciji
korišćeni su različiti sistemi: standardne kolone različitih prečnika sa omotačem ili bez
omotača, sa pakovanim, fluidizovanim i transportnim sistemima u cilju dobijanja
parametara za koeficijente prenosa količine kretanja, mase i toplote i segmentirane
kolone sa fluidizovanim česticama u cilju dobijanja parametara na koje u...tiče debljina
graničnog sloja. Sva eksperimentalna merenja su izvršena u širokom opsegu
hidrodinamičkih uslova: brzina strujanja fluida, veličina čestica čvrste faze i poroznosti
slojeva.
Kao rezultat istraživanja razvijen je novi teorijski model za prenos mase i toplote
zasnovan na analizi graničnog sloja koji se u disperznom sistemu formira od sudara do
sudara čestica. Na osnovu modela dobijena je debljina difuzionog i termičkog graničnog
sloja, izvedene su jednačine za korelisanje koeficijenata prelaza, Sherwood-ovog i
Nusselt-ovog broja i faktora prenosa mase i toplote. Na osnovu uspostavljenog modela
izvedena je jednačina za određivanje maksimalne vrednosti koeficijenata prelaza toplote
i poroznosti sloja pri kojoj do nje dolazi.
U ovom radu je uspostavljena analogija prenosa količine kretanja, mase i toplote
u partikulativno fluidizovanim slojevima zasnovana na modelu graničnog sloja.
Postojeća analogija u fluidizovanom sloju, data na osnovu normalizovanih vrednosti
koeficijenta trenja čestice-fluid i faktora prenosa mase proširena je na analogiju sva tri
prenosa. Dobijeni model je upotrebljen za definisanje faktora prenosa mase i toplote pri
minimalnoj fluidizaciji i transportu čestica...
In this thesis the discontinued boundary layer and the analogues among
momentum, heat and mass transfer were examined experimentally for fluidized and
packed beds and for hydraulic transport in liquid-particles systems. The aim of this
paper is to connect the characteristics of the boundary layer with the momentum, heat
and mass transfer, with an emphasis on analogies between these phenomena. Transport
phenomena approach to this problem provides a contribution that facilitates theoretical
description of multiphase liquid-particles systems (packed beds, fluidized beds, vertical
transport), which are extremely complex.
Different experimental systems have been used to perform the research in this
dissertation: standard columns of different diameters with or without heating jacket,
with packed and fluidized beds and transport systems in order to obtain parameters for
the momentum, heat and mass transfer coefficients, and segmented fluidized beds
columns in order to obtain parameters influe...nced by the thickness of the boundary layer.
All experimental measurements were performed in a wide range of hydrodynamic
conditions: fluid velocities, solid particles sizes and bed voidages.
As a result of this research, a new theoretical model for mass and heat transfer s
developed. Model is based on the analysis of the boundary layer, which in disperse
systems forms between the two adjacent particles collisions. Based on the model, the
thickness of the concentration and thermal boundary layer was obtained and the
equations for correlating the transfer coefficients with Sherwood and Nusselt numbers
and the mass and heat transfer factors were derived. On the basis of the established
model, the equation for determining the maximum value of the heat transfer coefficient
and the bed voidage for this value is derived. In this thesis, the analogue based on the boundary layer model for the
momentum, mass and heat transfer in particulate fluidized beds is established. The
existing analogy for the fluidized beds, based on the normalized values of the friction
coefficient fluid-particles and the mass transfer factor, has been extended to analogy for
all three phenomena. The obtained model was used to define the mass and heat transfer
factors at the minimum fluidization and transport of particles...