Research
Transport Phenomena with Bubbles, Drops, and Particles
Transport Phenomena with Bubbles, Drops, and Particles
My main research area is transport phenomena (fluid mechanics, heat transfer, and mass transfer) with bubbles, drops, and particles. This is a field with many industrial applications and it is also a topic of basic scientific interest.
My main research area is transport phenomena (fluid mechanics, heat transfer, and mass transfer) with bubbles, drops, and particles. This is a field with many industrial applications and it is also a topic of basic scientific interest.
Bubble Nucleation and Growth
Bubble Nucleation and Growth
The problem of bubble growth is of great importance in the polymer processing industry. It can be found in polymer melt devolatilization and also in the production of polymeric foam materials. In the first process, low concentrations of volatile components are removed from the polymer melt in order to improve the properties of the product, to meet environmental and health-related standards and for chemical recovery. The second process, aims to produce materials with unique properties such as light mass, high strength to mass ratio and good insulators. Both processes are common in the fact that they are conducted under superheated conditions for the volatile components resulting in the nucleation and growth of bubbles.
The problem of bubble growth is of great importance in the polymer processing industry. It can be found in polymer melt devolatilization and also in the production of polymeric foam materials. In the first process, low concentrations of volatile components are removed from the polymer melt in order to improve the properties of the product, to meet environmental and health-related standards and for chemical recovery. The second process, aims to produce materials with unique properties such as light mass, high strength to mass ratio and good insulators. Both processes are common in the fact that they are conducted under superheated conditions for the volatile components resulting in the nucleation and growth of bubbles.
Transport Phenomena with Slender Drops
Transport Phenomena with Slender Drops
High viscosity liquids such as polymer melts, foods and biological materials are usually processed in rotary equipment under conditions in which the flow contains shear or extensional components. A drop (or bubble) present in these types of flow will deform and, under some conditions, highly elongated drops can be obtained. Furthermore, if the strength of the flow exceeds some critical value, the drop will break into two or more fragments. This phenomenon of deformation and breakup of drops plays a major role in many physical processes. For example, in the rheology of emulsions, where one fluid is dispersed into another, in the design of efficient mixing devices. Furthermore, since mass transfer is proportional to the surface area, slender drops, having very large surface area, offer extremely large mass transfer rates.
High viscosity liquids such as polymer melts, foods and biological materials are usually processed in rotary equipment under conditions in which the flow contains shear or extensional components. A drop (or bubble) present in these types of flow will deform and, under some conditions, highly elongated drops can be obtained. Furthermore, if the strength of the flow exceeds some critical value, the drop will break into two or more fragments. This phenomenon of deformation and breakup of drops plays a major role in many physical processes. For example, in the rheology of emulsions, where one fluid is dispersed into another, in the design of efficient mixing devices. Furthermore, since mass transfer is proportional to the surface area, slender drops, having very large surface area, offer extremely large mass transfer rates.
Mass Transfer around Deformed Bubbles and Drops
Mass Transfer around Deformed Bubbles and Drops
Mass Transfer between a drop or a bubble and a liquid has been extensively studied in the literature because of its importance to the chemical process industry. Most of the mathematical models presented in the literature were developed for the case of a spherical drop under steady-state conditions. When a drop with constant density deforms, its surface area increases with respect to that of a spherical drop. Since mass transfer is proportional to the surface area, drop deformation should be taken into account. Furthermore, unsteady-state effects can play a very significant role, especially at the initial stages of the process which are usually characterized by high concentration gradients.
Mass Transfer between a drop or a bubble and a liquid has been extensively studied in the literature because of its importance to the chemical process industry. Most of the mathematical models presented in the literature were developed for the case of a spherical drop under steady-state conditions. When a drop with constant density deforms, its surface area increases with respect to that of a spherical drop. Since mass transfer is proportional to the surface area, drop deformation should be taken into account. Furthermore, unsteady-state effects can play a very significant role, especially at the initial stages of the process which are usually characterized by high concentration gradients.
Bubbles, Drops, and Particles in Nonlinear Flows
Bubbles, Drops, and Particles in Nonlinear Flows
Many industrial products take the form of foams, emulsions or suspensions in which a gas bubble, a liquid droplet, or a solid particle is embedded in a liquid. Hence, transport phenomena (fluid mechanics, heat transfer, and mass transfer) with bubbles, drops, and particles, has been the subject of many scientific reports since it affects the properties of such systems. These two phase systems are many times processed in rotary equipment generating shear, extensional but in general much more complicated flows such as nonlinear flows. While most of the studies in the literature simulate these processes with linear flows, such as simple shear flow or simple extensional flow, very little is dedicate to nonlinear flows which certainly can explain better (than the linear flow) the actual flow which is produced in industrial rotary devices. The purpose of my research in this subject is to explore the influence of the nonlinear intensity of the flow on drop deformation, breakup and mass transfer.
Many industrial products take the form of foams, emulsions or suspensions in which a gas bubble, a liquid droplet, or a solid particle is embedded in a liquid. Hence, transport phenomena (fluid mechanics, heat transfer, and mass transfer) with bubbles, drops, and particles, has been the subject of many scientific reports since it affects the properties of such systems. These two phase systems are many times processed in rotary equipment generating shear, extensional but in general much more complicated flows such as nonlinear flows. While most of the studies in the literature simulate these processes with linear flows, such as simple shear flow or simple extensional flow, very little is dedicate to nonlinear flows which certainly can explain better (than the linear flow) the actual flow which is produced in industrial rotary devices. The purpose of my research in this subject is to explore the influence of the nonlinear intensity of the flow on drop deformation, breakup and mass transfer.
Compound Drops
Compound Drops
There are many types of compound drops and one of them consists of an inner spherical drop positioned at the center of a spherical fluid shell. This structure, which sometimes is called a double emulsion, a globule, or an encapsulated droplet, is further embedded in an external fluid. In the pharmaceutical, cosmetic and food industry, compound drops are used to protect and maintain important substances within the inner drop, which can be then released, in a control form, to the external fluid. Contrary to a single drop, a compound drop consist of an additional phase resulting that, sometimes it behaves like a single drop (small inner drop) and sometimes it mimics a single solid particle (large inner drop). Thus, compared to single drops, compound drops offer more possibilities. My work addresses the importance of the type of flow on the deformation, breakup and mass transfer with compound drops.
There are many types of compound drops and one of them consists of an inner spherical drop positioned at the center of a spherical fluid shell. This structure, which sometimes is called a double emulsion, a globule, or an encapsulated droplet, is further embedded in an external fluid. In the pharmaceutical, cosmetic and food industry, compound drops are used to protect and maintain important substances within the inner drop, which can be then released, in a control form, to the external fluid. Contrary to a single drop, a compound drop consist of an additional phase resulting that, sometimes it behaves like a single drop (small inner drop) and sometimes it mimics a single solid particle (large inner drop). Thus, compared to single drops, compound drops offer more possibilities. My work addresses the importance of the type of flow on the deformation, breakup and mass transfer with compound drops.