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