Search

Proton-exchange membrane (PEM) electrolysis is one of the mostly used principles for H2 generation. To increase its efficiency, an enhanced O2 separation in the anodic cycle is necessary to reduce overvoltage and improve cooling. In this work, we investigate the surface functionalization with direct laser interference pattering (DLIP) and plasma coating (PECVD) of Ti64 and polypropylene to tune the affinity of the nonpolar gas to the materials by varying the hydrophilicity/hydrophobicity. The water contact angle is used to characterize the wettability. It gradually increases after the DLIP due to the adsorption of carbon compounds from the environment [1]. We observed that the effect is highly dependent on the surrounding media and also is reversible. Our experimental findings are supported by XPS and confocal microscopy measurements. Since DLIP requires heat resistant materials, we further investigated low-pressure plasma coating. Via optical recording we analyse the influence of the wettability on the O2 nucleation and provide first insights on how the oxygen separation of the anodic cycle of PEM electrolysers can be tuned by surface functionalization.

We study the role of surface topology, surface chemistry, and wall superheat temperature on the onset of boiling, bubble nucleation and growth, and the possible formation of an insulating vapour film by means of a novel setup for large-scale MD simulations. To minimise the effects of the system size on the bubble growth and the formation of the vapour film, we perform simulations in a box larger than those previously considered. The effect of the system pressure on bubble nucleation and growth is isolated by imposing a constant force on a moving piston and mechanically controlling the pressure. The simulations reveal that the presence of a nanostructure determines the nucleation site and facilitates the energy transfer from the hot substrate to the water. The surface chemistry, on the other hand, governs the shape of the formed bubble. A hydrophilic surface accelerates the bubble nucleation, however, decelerates the bubble expansion, thus postponing the formation of the film of vapour. Hence, a hydrophilic surface provides better energy transfer from the hot wall to the water. By analysing the system energy, we show that irrespective of wall topology and chemistry, there is a wall temperature for which the amount of transferred energy from the wall is maximum., QC 20210804

In the framework of the search for dark matter in the form of WIMPs using superheated liquids, a study is conducted to establish a computational procedure aimed at determining how the thermodynamic conditions kept inside a particle detector affect the acoustic signal produced by bubble nucleation. It is found that the acoustic energy injected into the liquid by the growing vapour bubble increases as the liquid pressure is decreased and the superheat degree is increased, the former effect being crucial for the generation of a well-intelligible signal. A good agreement is met between the results of the present study and some experimental data available in the literature for the amplitude of the acoustic signal. Additionally, the higher loudness of the alpha-decay events compared with those arising from neutron-induced nuclear recoils is described in terms of multiple nucleations.

Flash evaporation of superheated liquid to vapour by depressurization is frequently encountered in the nature and technology, but computational fluid dynamics modelling and simulation of such scenarios is still at the embryo stage. Attempts having been made before are all based on the assumption of mono-disperse bubbles by prescribing either the size or number density, which deviates largely from the physical picture. In the present work the poly-disperse multiple-size-group approach is used for the first time to simulate the water evaporation process under pressure release transients. Complex bubble dynamics and non-equilibrium processes such as bubble nucleation, growth, coalescence and breakup as well as interfacial heat transfer are accounted for. The comparison with experimental data demonstrates that the model is effective in capturing the temporal course of vapour bubbles’ generation and growth as well as their spatial distribution. The agreement between measured and simulated cross-section averaged flow parameters such as void fraction, liquid temperature and bubble size distribution is satisfying.

Flash evaporation of superheated liquid to vapour by depressurization is frequently encountered in the nature and technology, but computational fluid dynamics modelling and simulation of such scenarios is still at the embryo stage. Attempts having been made before are all based on the assumption of mono-disperse bubbles by prescribing either the size or number density, which deviates largely from the physical picture. In the present work the poly-disperse multiple-size-group approach is used for the first time to simulate the water evaporation process under pressure release transients. Complex bubble dynamics and non-equilibrium processes such as bubble nucleation, growth, coalescence and breakup as well as interfacial heat transfer are accounted for. The comparison with experimental data demonstrates that the model is effective in capturing the temporal course of vapour bubbles’ generation and growth as well as their spatial distribution. The agreement between measured and simulated cross-section averaged flow parameters such as void fraction, liquid temperature and bubble size distribution is satisfying.

In the framework of the search for dark matter in the form of WIMPs using superheated liquids, a study is conducted to establish a computational procedure aimed at determining how the thermodynamic conditions kept inside a particle detector affect the acoustic signal produced by bubble nucleation. It is found that the acoustic energy injected into the liquid by the growing vapour bubble increases as the liquid pressure is decreased and the superheat degree is increased, the former effect being crucial for the generation of a well-intelligible signal. A good agreement is met between the results of the present study and some experimental data available in the literature for the amplitude of the acoustic signal. Additionally, the higher loudness of the alpha-decay events compared with those arising from neutron-induced nuclear recoils is described in terms of multiple nucleations.

In this master thesis project, the formation of fouling on heat exchanger surfaces in dairy processing and mainly the influence of air was examined. Based on prior experimental findings regarding the influence of air bubbles in combination with calculations based on solubility properties of air in milk, a hypothesis was stated. Milk can enter the processing system without any undissolved air, with altered equilibrium due to change in temperature and pressure the solubility can decrease. From this phenomenon, air bubbles can be created which are simultaneously filled with steam at the corresponding steam pressure. Assuming the steam is evaporated from the boundary layer of the bubble a local increase in TS would be present, creating a fouling footprint. The influence of dissolved air and processing pressure on the fouling rate was examined in the thesis and the reason behind the creation of fouling is assumed to be drying. A lab scale tubular heat exchanger UHT was used in the experiments and a part of the thesis is focused on the instrumentation of the machine. The results points in two directions. While processing milk entering with a high level of dissolved air, an increased process pressure led to a decreased initial fouling rate and prolonged induction period. The results from processing milk with low level of dissolved oxygen were inconclusive. Either a point of low enough oxygen level and high enough pressure was reached for nil creation of bubbles, or the milk properties were changed from the pre-processing which intended to lower the oxygen level., How come some milk can be stored outside of the refrigerator for several months without going bad? How is this milk processed and does the air content affect the processing? If these questions have stumbled upon your mind this is the article to point your eyes towards. Milk has not always been an as obvious choice for a nutritional beverage as it is considered today. Since it is almost an optimal environment for the growth of microorganisms, without proper processing several dangerous organisms can be found in milk. Raw milk has been known to contain pathogens like Salmonella, E. coli, Listeria and Campylobacter and historically, raw milk was a common source of spreading diseases like tuberculosis, typhus and scarlet fever. To kill the harmful substances milk is heated to a certain temperature for a certain time, called pasteurization. It was from the work performed by Louis Pasteur in the 19th century regarding the lethal effect heat has on microbes the process today commemorates his name. The kind of processing this thesis deals with is called Ultra High Temperature (pasteurization) which is performed in the temperature range of 135-140 °C for a couple of seconds. UHT milk is defined as commercially sterile meaning that the product is free from microbes that can grow in the conditions it is meant to be stored. The product is packed in sterile packages in a sterile environment and can be stored in ambient temperature (25-40 °C depending on location) up to a couple of months. Of course, once the product is opened it spoils in a matter of days just as regular milk. When heating the milk, a build-up is created on the hot pipes, called fouling, similar to the burnt milk seen in your pan when you forget to stir your béchamel sauce continuously. Fouling consists of fat, proteins and minerals, all originating from the milk. Fouling is money down the drain in the dairy industry since the process must be shut down regularly for cleaning, you lose product to the fouling and

In this master thesis project, the formation of fouling on heat exchanger surfaces in dairy processing and mainly the influence of air was examined. Based on prior experimental findings regarding the influence of air bubbles in combination with calculations based on solubility properties of air in milk, a hypothesis was stated. Milk can enter the processing system without any undissolved air, with altered equilibrium due to change in temperature and pressure the solubility can decrease. From this phenomenon, air bubbles can be created which are simultaneously filled with steam at the corresponding steam pressure. Assuming the steam is evaporated from the boundary layer of the bubble a local increase in TS would be present, creating a fouling footprint. The influence of dissolved air and processing pressure on the fouling rate was examined in the thesis and the reason behind the creation of fouling is assumed to be drying. A lab scale tubular heat exchanger UHT was used in the experiments and a part of the thesis is focused on the instrumentation of the machine. The results points in two directions. While processing milk entering with a high level of dissolved air, an increased process pressure led to a decreased initial fouling rate and prolonged induction period. The results from processing milk with low level of dissolved oxygen were inconclusive. Either a point of low enough oxygen level and high enough pressure was reached for nil creation of bubbles, or the milk properties were changed from the pre-processing which intended to lower the oxygen level., How come some milk can be stored outside of the refrigerator for several months without going bad? How is this milk processed and does the air content affect the processing? If these questions have stumbled upon your mind this is the article to point your eyes towards. Milk has not always been an as obvious choice for a nutritional beverage as it is considered today. Since it is almost an optimal environment for the growth of microorganisms, without proper processing several dangerous organisms can be found in milk. Raw milk has been known to contain pathogens like Salmonella, E. coli, Listeria and Campylobacter and historically, raw milk was a common source of spreading diseases like tuberculosis, typhus and scarlet fever. To kill the harmful substances milk is heated to a certain temperature for a certain time, called pasteurization. It was from the work performed by Louis Pasteur in the 19th century regarding the lethal effect heat has on microbes the process today commemorates his name. The kind of processing this thesis deals with is called Ultra High Temperature (pasteurization) which is performed in the temperature range of 135-140 °C for a couple of seconds. UHT milk is defined as commercially sterile meaning that the product is free from microbes that can grow in the conditions it is meant to be stored. The product is packed in sterile packages in a sterile environment and can be stored in ambient temperature (25-40 °C depending on location) up to a couple of months. Of course, once the product is opened it spoils in a matter of days just as regular milk. When heating the milk, a build-up is created on the hot pipes, called fouling, similar to the burnt milk seen in your pan when you forget to stir your béchamel sauce continuously. Fouling consists of fat, proteins and minerals, all originating from the milk. Fouling is money down the drain in the dairy industry since the process must be shut down regularly for cleaning, you lose product to the fouling and

In this master thesis project, the formation of fouling on heat exchanger surfaces in dairy processing and mainly the influence of air was examined. Based on prior experimental findings regarding the influence of air bubbles in combination with calculations based on solubility properties of air in milk, a hypothesis was stated. Milk can enter the processing system without any undissolved air, with altered equilibrium due to change in temperature and pressure the solubility can decrease. From this phenomenon, air bubbles can be created which are simultaneously filled with steam at the corresponding steam pressure. Assuming the steam is evaporated from the boundary layer of the bubble a local increase in TS would be present, creating a fouling footprint. The influence of dissolved air and processing pressure on the fouling rate was examined in the thesis and the reason behind the creation of fouling is assumed to be drying. A lab scale tubular heat exchanger UHT was used in the experiments and a part of the thesis is focused on the instrumentation of the machine. The results points in two directions. While processing milk entering with a high level of dissolved air, an increased process pressure led to a decreased initial fouling rate and prolonged induction period. The results from processing milk with low level of dissolved oxygen were inconclusive. Either a point of low enough oxygen level and high enough pressure was reached for nil creation of bubbles, or the milk properties were changed from the pre-processing which intended to lower the oxygen level., How come some milk can be stored outside of the refrigerator for several months without going bad? How is this milk processed and does the air content affect the processing? If these questions have stumbled upon your mind this is the article to point your eyes towards. Milk has not always been an as obvious choice for a nutritional beverage as it is considered today. Since it is almost an optimal environment for the growth of microorganisms, without proper processing several dangerous organisms can be found in milk. Raw milk has been known to contain pathogens like Salmonella, E. coli, Listeria and Campylobacter and historically, raw milk was a common source of spreading diseases like tuberculosis, typhus and scarlet fever. To kill the harmful substances milk is heated to a certain temperature for a certain time, called pasteurization. It was from the work performed by Louis Pasteur in the 19th century regarding the lethal effect heat has on microbes the process today commemorates his name. The kind of processing this thesis deals with is called Ultra High Temperature (pasteurization) which is performed in the temperature range of 135-140 °C for a couple of seconds. UHT milk is defined as commercially sterile meaning that the product is free from microbes that can grow in the conditions it is meant to be stored. The product is packed in sterile packages in a sterile environment and can be stored in ambient temperature (25-40 °C depending on location) up to a couple of months. Of course, once the product is opened it spoils in a matter of days just as regular milk. When heating the milk, a build-up is created on the hot pipes, called fouling, similar to the burnt milk seen in your pan when you forget to stir your béchamel sauce continuously. Fouling consists of fat, proteins and minerals, all originating from the milk. Fouling is money down the drain in the dairy industry since the process must be shut down regularly for cleaning, you lose product to the fouling and

In this master thesis project, the formation of fouling on heat exchanger surfaces in dairy processing and mainly the influence of air was examined. Based on prior experimental findings regarding the influence of air bubbles in combination with calculations based on solubility properties of air in milk, a hypothesis was stated. Milk can enter the processing system without any undissolved air, with altered equilibrium due to change in temperature and pressure the solubility can decrease. From this phenomenon, air bubbles can be created which are simultaneously filled with steam at the corresponding steam pressure. Assuming the steam is evaporated from the boundary layer of the bubble a local increase in TS would be present, creating a fouling footprint. The influence of dissolved air and processing pressure on the fouling rate was examined in the thesis and the reason behind the creation of fouling is assumed to be drying. A lab scale tubular heat exchanger UHT was used in the experiments and a part of the thesis is focused on the instrumentation of the machine. The results points in two directions. While processing milk entering with a high level of dissolved air, an increased process pressure led to a decreased initial fouling rate and prolonged induction period. The results from processing milk with low level of dissolved oxygen were inconclusive. Either a point of low enough oxygen level and high enough pressure was reached for nil creation of bubbles, or the milk properties were changed from the pre-processing which intended to lower the oxygen level., How come some milk can be stored outside of the refrigerator for several months without going bad? How is this milk processed and does the air content affect the processing? If these questions have stumbled upon your mind this is the article to point your eyes towards. Milk has not always been an as obvious choice for a nutritional beverage as it is considered today. Since it is almost an optimal environment for the growth of microorganisms, without proper processing several dangerous organisms can be found in milk. Raw milk has been known to contain pathogens like Salmonella, E. coli, Listeria and Campylobacter and historically, raw milk was a common source of spreading diseases like tuberculosis, typhus and scarlet fever. To kill the harmful substances milk is heated to a certain temperature for a certain time, called pasteurization. It was from the work performed by Louis Pasteur in the 19th century regarding the lethal effect heat has on microbes the process today commemorates his name. The kind of processing this thesis deals with is called Ultra High Temperature (pasteurization) which is performed in the temperature range of 135-140 °C for a couple of seconds. UHT milk is defined as commercially sterile meaning that the product is free from microbes that can grow in the conditions it is meant to be stored. The product is packed in sterile packages in a sterile environment and can be stored in ambient temperature (25-40 °C depending on location) up to a couple of months. Of course, once the product is opened it spoils in a matter of days just as regular milk. When heating the milk, a build-up is created on the hot pipes, called fouling, similar to the burnt milk seen in your pan when you forget to stir your béchamel sauce continuously. Fouling consists of fat, proteins and minerals, all originating from the milk. Fouling is money down the drain in the dairy industry since the process must be shut down regularly for cleaning, you lose product to the fouling and

Molecular dynamics simulations were carried out for a nanoscale spherical bubble in water at room temperature. The pressure difference between inside and outside of the bubble was investigated and the surface tension was evaluated with assumption of the Young-Laplace (Y-L) equation. The obtained surface tension shows little dependence on the bubble size and agrees with that of flat surface. Thus it is confirmed that the Y-L equation holds for nanobubbles in water. Based on the Y-L equation and the density-dependence of the liquid pressure, mechanical stability of a bubble in a finite system was discussed. The existence of mechanical instability leads to a mechanical definition of critical nucleus size in cavitation nucleation.

This first chapter will give an introduction to what is a BLEVE, Boiling Liquid Expanding Vapor Explosion, and its hazards particularly in relation to tunnel safety. It will be shown that several definitions of a BLEVE can be given, depending on the aspect put in focus. In particular distinction can be made between two groups of references, respectively giving an engineering definition and a physical definition. As a result of our literature survey, our own definition of BLEVE will be presented trying to bridge the gap between these two groups of definitions. In the following chapters, we stick to that definition unless specified otherwise. First of all, we would like to consider some basic concepts, i.e. superheated liquid, explosive boiling and bubble nucleations, by an easy example. It is well known that when we heat the water in a tea kettle up to the temperature of 100 ±C at the atmospheric pressure, the water will start to boil or vaporize. In this case, invisible active nuclei formed on the inner surface of the kettle or at any impurities in the water will grow to be a visible bubble which will detach from the wall and move upwards due to buoyancy. Such a type of bubble nucleation is called heterogeneous nucleation since the bubble nucleation only occurs at the locations where there is a boundary between two different phases. However if we put the water into a very smooth glass and heat it in the microoven, the boiling will not occur even the temperature already exceeds the normal boiling point at the atmospheric pressure. At this moment, the water is said to be superheated and if we keep heating the water, a rapid ’explosive-like’ boiling, termed explosive boiling, will suddenly occur and may cause serious damage to the microoven. In this explosive boiling, the active nuclei are evenly formed throughout the liquid, therefore it is called homogeneous nucleation. Superheating sometimes is referred to as boiling retardation, or boiling delay. It refers to the p

This first chapter will give an introduction to what is a BLEVE, Boiling Liquid Expanding Vapor Explosion, and its hazards particularly in relation to tunnel safety. It will be shown that several definitions of a BLEVE can be given, depending on the aspect put in focus. In particular distinction can be made between two groups of references, respectively giving an engineering definition and a physical definition. As a result of our literature survey, our own definition of BLEVE will be presented trying to bridge the gap between these two groups of definitions. In the following chapters, we stick to that definition unless specified otherwise. First of all, we would like to consider some basic concepts, i.e. superheated liquid, explosive boiling and bubble nucleations, by an easy example. It is well known that when we heat the water in a tea kettle up to the temperature of 100 ±C at the atmospheric pressure, the water will start to boil or vaporize. In this case, invisible active nuclei formed on the inner surface of the kettle or at any impurities in the water will grow to be a visible bubble which will detach from the wall and move upwards due to buoyancy. Such a type of bubble nucleation is called heterogeneous nucleation since the bubble nucleation only occurs at the locations where there is a boundary between two different phases. However if we put the water into a very smooth glass and heat it in the microoven, the boiling will not occur even the temperature already exceeds the normal boiling point at the atmospheric pressure. At this moment, the water is said to be superheated and if we keep heating the water, a rapid ’explosive-like’ boiling, termed explosive boiling, will suddenly occur and may cause serious damage to the microoven. In this explosive boiling, the active nuclei are evenly formed throughout the liquid, therefore it is called homogeneous nucleation. Superheating sometimes is referred to as boiling retardation, or boiling delay. It refers to the p

This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated. In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents. In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment. Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures. The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV, QC 20101118

This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated. In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents. In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment. Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures. The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV, QC 20101118

This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated. In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents. In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment. Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures. The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV, QC 20101118

This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated. In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents. In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment. Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures. The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV, QC 20101118

This thesis deals with the engineering of novel nanomaterials, particularly nanocomposites and nanostructured surfaces with enhanced functionalities. The study includes two parts; in the first part, an in situ sol-gel polymerization approach is used for the synthesis of polymer-inorganic hybrid material and its exceptional transparent UV-shielding effect has been investigated. In the second part, electrodeposition process has been adapted to engineer surfaces and the boiling performance of the fabricated nanostructured surfaces is evaluated. In the first part of the work, polymer-inorganic hybrid materials composed of poly(methylmethacrylate) (PMMA) and zinc compounds were prepared by in situ sol-gel transition polymerization of zinc complex in PMMA matrix. The immiscibility of heterophase of solid organic and inorganic constituents was significantly resolved by an in situ sol-gel transition polymerization of ZnO nanofillers within PMMA in the presence of dual functional agent, monoethanolamine, which provided strong secondary interfacial interactions for both complexing and crosslinking of constituents. In the second part of the work, nanoengineering on the surface of copper plates has been performed in order to enhance the boiling heat transfer coefficient. Micro-porous surfaces with dendritic network of copper nanoparticles have been obtained by electrodeposition with dynamic templates. To further alter the grain size of the dendritic branches, the nanostructured surfaces underwent a high temperature annealing treatment. Comprehensive characterization methods of the polymer-inorganic hybrid materials and nanoengineered surfaces have been undertaken. XRD, 1H NMR, FT-IR, TGA, DSC, UV-Vis, ED, SEM, TEM and HRTEM have been used for basic physical properties. Pool boiling tests were performed to evaluate the boiling performance of the electrodeposited nanostructured micro-porous structures. The homogeneous PZHM exhibited enhanced UV-shielding effects in the entire UV, QC 20101118

Measurements of micro bubble nucleation temperature in single-stranded DNA (ssDNA) solution with four different concentrations (0.4, 1, 6.4 and 10 μ g μ l(-1)) and under different heat fluxes are presented in this paper. A micro thermal bubble was generated periodically by a micro bubble actuator under pulse-heating conditions. The bubble nucleation temperature was measured by employing a micro Pt heater as a self-sensing resistive temperature sensor, and the voltage signal was recorded by a 100 MHz high-speed digitizer. By examining the temporal temperature variation of the micro heater during the pulse-heating period, one can observe a `V' shape temperature change for the cases when bubble nucleation occur-red, which was speculated to be the beginning of bubble nucleation. It is found that (1) the onset bubble nucleation temperature increases with the DNA concentration and (2) at a fixed concentration, the bubble nucleation temperature increases with the heat flux from the micro heater. Based on a transient 3D heat conduction model, it is found that the size of the superheated region in the fluid just before bubble nucleation is comparable to the feature size of the micro heater, and. relatively independent of the ssDNA concentration and heat flux.

[no abstract]

The objective of this project was to investigate the feasibility of using the bubble dosimeter as an alternative to the present methods used to verify nuclear arms treaties. Because of the draw-downs of nuclear forces associated with the end of the cold-war, demand has increased for an unobtrusive technology that could be used in the field by inspectors to measure whether the nuclear weapons inspected meet the guidelines of the treaties. The Defense Nuclear Agency (DNA) sponsored the project, believing that the bubble dosimeter could fulfill this need. Although the bubble dosimeter is a rugged device, ideally suited for field work, three problems must be tackled and overcome before use of the dosimeter can be considered feasible. This project focussed upon evaluating and solving the problems of temperature dependence, bubble growth rate and accurate statistical analysis of the data. Extensive theoretical and experimental work was undertaken to design new detectors which would have a response which remained consistent with temperature. Furthermore, extensive experimentation was conducted at USNA's Neutron Generator Facility, with the purpose of evaluating the neutron detection characteristics of the bubble dosimeter.

peer-reviewed, Foam and bubbles are ubiquitous in industry and nature. They have a wide range of applications but are also an undesirable product of certain processes. This thesis considers two individual industrial problems with the common phenomenon of bubble and foam formation. Bubble nucleation is a phenomenon observed in many different physical situations from decompression sickness to champagne effervescence. It is of vital importance to the formation of a creamy head that is distinctive to stout beers. I present experimental work that demonstrates that cellulose fibres can be used to initiate stout beers and could serve as an alternative to widget technology. I derive mathematical models for the various gas pocket geometries I observed in cellulose fibres that produce bubbles when submerged in stout beer. These models are solved and compared to experimental results where possible to give the first quantitative evaluation of the current models of bubble nucleation. I present the work done to model a novel design for accurate volume measurement of milk. The new design proposes a modification of the air elimination vessel used in current milk pumping systems to increase accuracy by preventing air bubbles being pumped with milk. We consider the operation of the entire system to pump milk, the flow of milk inside the air elimination vessel, the entrainment of air bubbles into a pool of milk and the drainage of foam.

peer-reviewed, Foam and bubbles are ubiquitous in industry and nature. They have a wide range of applications but are also an undesirable product of certain processes. This thesis considers two individual industrial problems with the common phenomenon of bubble and foam formation. Bubble nucleation is a phenomenon observed in many different physical situations from decompression sickness to champagne effervescence. It is of vital importance to the formation of a creamy head that is distinctive to stout beers. I present experimental work that demonstrates that cellulose fibres can be used to initiate stout beers and could serve as an alternative to widget technology. I derive mathematical models for the various gas pocket geometries I observed in cellulose fibres that produce bubbles when submerged in stout beer. These models are solved and compared to experimental results where possible to give the first quantitative evaluation of the current models of bubble nucleation. I present the work done to model a novel design for accurate volume measurement of milk. The new design proposes a modification of the air elimination vessel used in current milk pumping systems to increase accuracy by preventing air bubbles being pumped with milk. We consider the operation of the entire system to pump milk, the flow of milk inside the air elimination vessel, the entrainment of air bubbles into a pool of milk and the drainage of foam.

High speed motion pictures of bubble nucleation from glass capillaries were obtained. The fluids used were: distilled water, water with wetting agent, water with sucrose, and ethanol. Capillaries of cylindrical, conical, and reentrant geometries were used with inner diameters ranging from .0182 to .0381 inches. The penetration of the liquid-vapor interface into a cavity after bubble departure appeared to be inertia controlled. Cavity interior geometry and cleanliness had a direct effect upon the liquid-vapor interface penetration distance. The depth of penetration of the interface increased as cavity size increased. Viscosity reduced the interface penetration. Bubble growth curves were obtained for a typical bubble i n each fluid. Bubble departure diameter appeared to be independent of cavity geometrybut increased as cavity size increased. Viscosity retarded bubble growth during the initial stages of growth., http://archive.org/details/aphotographicinv1094529601, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.