Fisica Tecnica Industriale
ING-IND/10
Gian Paolo Beretta, Adriano Maria Lezzi, Mariagrazia Pilotelli
Pietro Poesio
Thermal and fluid Science Group
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
People
Prof. Gian Paolo Beretta
Prof. Adriano Maria Lezzi
Dr. Ing. Mariagrazia Pilotelli
Dr. Ing. Pietro Poesio
Sig. A. Tortelli
Assegnisti
Dr. Ing. Claudia Foletti
Ing. Benedetta Grassi
Dottorandi
Ing. Fabio Di Fede
Ing. Davide Luscietti
Ing. Michele Margarone
Dott. Simone Parmigiani
Ing. Domenico Strazza
Ing. Paolo Borioli
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Two phase flow: Gas-Liquid & Liquid-Liquid
Fluids properties
Air-Oil flow map
Water-Oil flow map
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
Collaboration
Prof. Dr. Ir. G. Ooms (TUD)
Prof. Dr. P.K. Das (IIT)
Prof. Ing. G. Sotgia (PoliMi)
02/04/09 - Brescia
Three phase flow
Pipelines present flow conditions more complex than laboratory
experiments:
- oil-water-gas flows (three phase flows);
- oil-water-gas-sand flows (four phase flows);
- five or more phases.
Influence of gas injection on CAF?
1.6
3.0
Jo=0.51 m/s - Jw=0.32 m/s (1)
Jo=0.51 m/s - Jw=0.52 m/s (1)
Jo=0.62 m/s - Jw=0.20 m/s (1)
Jo=0.31 m/s - Jw=0.52 m/s (1)
Jo=0.31 m/s - Jw=0.39 m/s (1)
1.5
40 mm ID
1.4
2.5
1.3
Dynamical behavior
2.0
f
(1/s)
1.2
1.1
R
L/g 1.0
0.9
Pressure Drops
0.8
1.5
0.7
40 mm ID
0.6
Jo=0.51 m/s - Jw=0.32 m/s (1)
Jo=0.51 m/s - Jw=0.52 m/s (1)
Jo=0.62 m/s - Jw=0.20 m/s (1)
Jo=0.31 m/s - Jw=0.52 m/s (1)
1.0
0.0
0.5
1.0
1.5
R L =g =
2.0
2.5
3.0
3.5
4.0
¢ po i l ¡ w a t er ¡ g a s
¢ po i l ¡ w a t er
4.5
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
ε
g/L
0.5
0.0
ε
g/L
0.5
5.0
Collaboration
Prof. Ing. G. Sotgia (PoliMi)
Jw=0.24 m/s Jo=0.74 m/s Jg=6.33 m/s - ID 40 mm
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
5.0
Experimental facility main components
Collaboration
Prof. V. Ferrari
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Spinodal decomposition
Dynamics of phase
separation
Heat transfer
enhancement
Collaboration
Prof. R. Mauri (Uni Pisa)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Aortic valves tests
Collaboration
Prof. Ing. G. Donzella (DIMI)
Prof. Ing. R. Faglia (DIMI)
Dr. R. Lorusso (Spedali Civili Brescia)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Turbulent suspensions
Influence of particles
on turbulence spectrum
Collaboration
Prof. Dr. Ir. G.Ooms (TUDelft)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Dissolution of micro-droplets
Generation of micro-droplets
by microfluidic devices
Study of their dissolution
Prof. Dr. T. Thorsen (MIT)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Microfluidics & lab-on-a-chip
WATER
25 μm
OIL
50 μm
Prof. Dr. T. Thorsen (MIT)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Foundations of Themodynamics
- rigorous definition of Entropy for nonequilibrium
states
- mathematical modeling of the relaxation of
nonequilibrium states along the path of steepest
entropy ascent (also known as “maximum entropy
production principle”)
- the role of thermodynamics in the foundations of
quantum theory and viceversa
www.quantumthermodynamics.org
Collaborations:
Proff. E.P. Gyftopoulos, G.N. Hatsopoulos, A.F. Ghoniem (MIT)
Prof. E. Zanchini (Uni Bologna)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
BiRS (Biomass-fired Ringbom-Stirling motor)
ENFASI 2009
Student Contest Sponsored by Rotary
Development of a low-cost, biomass-fired,
1kWel Ringbom-Stirling motor for smallscale power plants in remote sites in
underdeveloped countries
Collaboration:
- CeTamb
- Ingegneri senza Frontiere – Sez. Milano
- Politecnico di Milano
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Simulations
Simulations of industrial thermo fluid dynamics problems with the
commercial code Fluent
-Brake cooling
-Ingot mold filling
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Dissolution of a liquid micro-droplet in a
non-ideal liquid-liquid mixture far from
thermodynamic equilibrium
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Outline
•Introduction
•Epstein & Plesset theory
•Experimental set-up
•Results
•Discussion & conclusions
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
The problem
A droplet of liquid 1 placed in a liquid 2, how does it dissolve?
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Epstein-Plesset theory
Mass conservation
∂c
= −∇ ⋅ j
∂t
j = −D∇c
Fick’s law
∂c
= D∇ 2c
∂t
Epstein and Plesset (1950) showed that the droplet radius shrinks as t1/2
Hypothesis: the liquids form a IDEAL MIXTURE
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Duncam and Needham Experiments
Air bubble in water
Duncam & Needham, Langmuir 2004
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Our conditions
Acetone-Hexadecane mixture
re
gi
on
H A
Tw
oph
as
e
T (°C)
Non ideal mixture
%vol, acetone
B
•A droplet of pure hexadecane H is
injected into phase B
•Phase B can not take hexadecane H
anymore
•The system separates into
phase B + phase A
•To do that, it passes through
non equilibrium states
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Non-linear diffusion equation
Fick’s law + Cahn-Hillard + Margules
Mass conservation
∂c
= −∇ ⋅ j
∂t
Fick’s law
j = −D∇c + c ⋅ (1− c) ⋅ D ⋅ (a 2∇∇ 2c + 2Ψ∇c )
Finite width
interface
(Cahn-Hillard)
∂c
= D∇ 2c − ∇ ⋅ [c ⋅ (1− c) ⋅ D ⋅ (a 2∇∇ 2c + 2Ψ∇c)]
∂t
Partial mixing
(Margules)
Numerical solution showed that the droplet radius shrinks as t1/2
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Experimental set-up
25
25 μm
m
μ
Inverted microscope
Ziess Axiovert 200M
PDMS microchip
50 μm
High-speed camera
(60 fps)
25
m
μ
Droplet generator - Flow focusing
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Experimental set-up
Droplet generator
by flow focusing
B
Hexadecane
B
H A
re
gi
on
T (°C)
se
a
Ph
Acetone-Hexadecane mixture
Tw
oph
as
e
Ph
as
e
B
%vol, acetone
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Discussion & Interpretation
Example of hexadecane droplet
dissolution in phase B
Initial center of the droplet
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Results #1
R (μm)
The hexadecane droplet radius
scales as
≈ α.t1
t (s)
This observation holds for
all 32 repetitions of the same
experiment
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Results #2
time
tim
e
|V| (μm/s)
y (μm)
The hexadecane droplet
self-propels around
x (μm)
t (s)
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Discussion
eq
ui
lib
ri u
m
st
at
es
T (°C)
Acetone-Hexadecane mixture
No
n
H A
%vol, acetone
B
•A droplet of pure hexadecane H is
injected into phase B
•Phase B can not take hexadecane H
anymore
•The system separates into
phase B + phase A
•To do that, it passes through
non equilibrium states
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Interpretation & discussion
We believe that the self-generated motion is
driven by non-equilibrium (non-dissipative)
Korteweg forces F =−µ
˜ ∇φ
The observed motion produces instead
higher local concentration gradients
speeding up the diffusive mixing
The difference in the scaling from t1/2 to t1 between Duncam & Needham (2004,2006)
occurs because the system passes through non-equilibrium states
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Interpretation & discussion
This behaviour was predicted
by Vladimirova et al. (1999)
but never measured
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia
Conclusions
•Experiments on dissolving micro-droplets
•If the system passes through non-equilibrium states the dynamics is
completely different
•The scaling exponent changes from t1/2 to t1
•Droplet self-propels around as a consequence of Korteweg forces
DIMI – Dipartimento di Ingegneria Meccanica e Industriale
02/04/09 - Brescia