Condensation Chamber Research Articles

Corrosion resistance of zinc electrodeposited from acidic and alkaline electrolytes using pulse current

AbstractCorrosion resistance of zinc coatings was investigated in an accelerated corrosion test in a condensation chamber. Zinc was electrodeposited from alkaline and acidic electrolytes using direct current (DC) or pulse current (PC). The zinc coating was subsequently protected against corrosion with a chrome (III) layer. Morphology and structure of the coatings was investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) before and after the corrosion test. Corrosion resistance of alkaline zinc coatings electrodeposited with DC and PC under test conditions was found to be comparable. The corrosion resistance of zinc coatings deposited from acidic electrolytes by PC was lower in comparison with corrosion resistance of zinc coatings deposited using DC.

Hydrogen Sorption in Magnesium Nanoparticles: Size- and Surface-related Phenomena

AbstractThe aim of this work is the investigation of the metal-hydride transformation in magnesium (Mg) nanoparticles both as a function of particle size and in response to surface functionalization by clusters of transition metals (TM): Pd, Ni, Ti.Mg nanoparticles were synthesized by the inert-gas condensation technique, which yields single crystals with six-fold symmetry whose average size can be controlled by tuning the inert gas pressure. After the synthesis the nanoparticles were passivated by slow exposure to oxygen, obtaining a core-shell morphology where a metallic core is coated by a MgO shell of about 5 nm thickness.The material structure was investigated by Transmission Electron Microscopy (TEM), also in High Resolution (HRTEM) mode, and by X-Ray Diffraction (XRD). The sorption kinetics were analysed by a volumetric Sievert apparatus, which also allowed for a determination of the activation energies.Small nanoparticles (≈35 nm) display interesting kinetics with gravimetric capacity of 4.5 wt.% at saturation, limited by the oxide fraction. Hydride formation proceeds by one-dimensional growth controlled by diffusion through the hydride, while the reverse transformation to metal involves interface-controlled three-dimensional growth of nuclei formed at constant rate.On the contrary, large nanoparticles (≈450 nm) exhibit very low reactivity due to reduced probability of hydrogen dissociation/recombination and nucleation at the particle surface. For this reason, large nanoparticles were surface-decorated by TM through in situ evaporation in the inert-gas condensation chamber. This procedure results in clusters of 3-4 nm located over a portion of the MgO shell, as shown by XRD and HRTEM on Pd-decorated sample. This treatment results in dramatically improved hydrogen sorption behavior. In fact, previously inert nanoparticles now exhibit of up to 5.6 wt.%.Real-time diffraction studies using Synchrotron Radiation were carried out during hydrogen desorption on the Pd-decorated nanoparticles. We clearly show that a Mg-Pd intermetallic phase is formed after the first heating treatment and takes active part in the transformation.

Anticorrosion properties of polyaniline-coated pigments in organic coatings

Four pigments of various morphology – specularite, α-Fe 2O 3; goethite, α-FeO(OH); talc, (Mg 3(OH) 2(Si 4O 10); and graphite, C – without and with polyaniline phosphate coating, were tested for the anticorrosion performance in coatings produced by epoxy binders on iron plates. The corrosion tests were carried out in a condenser chamber with continuous water condensation or humidity with sulfur dioxide, and in a salt mist cabinet. Polyaniline coating of pigments in all cases improved the anticorrosion properties. Graphite coated with polyaniline performed the best among eight systems under investigation. The role of graphite and polyaniline conductivity in the electron transfers associated with corrosion of iron has been proposed.

An adsorptive solar ice-maker dynamic simulation for north Mediterranean climate

This paper presents a model for dynamic simulation of an adsorptive ice-maker. The model describes the different phases of the thermodynamic cycle of the ice-maker components: solar collector, adsorbent bed, condenser and cold chamber (evaporator and water to be frozen). The adsorbent/adsorbate working pair is active carbon/methanol. The simulations were performed for a whole year using measured climatic data of Messina (38°12′N). The detailed results of a week of June and December 2005 are shown, as representative of typical summer and winter conditions. These simulations showed that the ice-maker is able to freeze 5 kg of water during all days of June, and, if the weather conditions are not too unfavourable, also during December. Further simulations, carried out for the whole year 2005, demonstrated that during the most part of the year (from April to October) a daily ice production (DIP) of 5 kg can be obtained, and an equivalent daily ice production (DIP eq) near to 5.5 kg can be reached. During the months of February and March the average monthly DIP is about 4 kg. Finally, for the coldest months (January, November and December) the DIP was 2.0–3.5 kg. The average monthly solar coefficient of performance (COPs) varies from a minimum of about 0.045 (July) to a maximum of 0.11 (January), with an annual mean of 0.07.

Highly size-controlled synthesis of Au/Pd nanoparticles by inert-gas condensation

Gold/Palladium nanoparticles were fabricated by inert-gas condensation on a sputtering reactor. With this method, by controlling both the atmosphere on the condensation chamber and the magnetron power, it was possible to produce nanoparticles with a high degree of monodispersity in size. The structure and size of the Au/Pd nanoparticles were determined by mass spectroscopy, and confirmed by atomic force microscopy and electron transmission microscopy measurements. The chemical composition was analyzed by X-ray microanalysis. From these measurements we confirmed that with the sputtering technique we are able to produce particles of 1, 3, and 5 nm on size, depending on the choice of the synthesis conditions. From TEM measurements made both in the regular HREM, as well as in STEM-HAADF mode, we found that the particles are icosahedral in shape, and the micrographs show no evidence of a core-shell structure, in contrast to what is observed in the case of nanoparticles prepared by chemical synthesis.

Anisotropic growth of indium antimonide nanostructures

InSb nanostructures have been synthesized by the use of gas aggregation process. Nanoparticles with different shapes are obtained by controlling the growth and deposition temperature of the InSb nanoclusters. Triangular nanocrystals are commonly observed when the clusters are extracted from the condensation chamber of the source and deposited on the room temperature substrate at high vacuum. When the deposition is performed inside the condensation chamber at high temperature near the melting point of bulk InSb, nanoparticles formed on the substrate surface show several kinds of 3-dimensional morphologies, such as triangular or rectangular prisms, as well as hexagonal tablets. Keeping the same conditions for the cluster source operation and deposition, after long time growth, nanorods with hexagonal and quadrangular cross sections are formed through vapor-liquid-solid (VLS) process. The origin of the difference on the morphologies and shapes of the nanostructures is attributed to the anisotropic growth of InSb, which is temperature dependent.

Growth Dynamics of Water Drops on a Square-Pattern Rough Hydrophobic Surface

Condensation on rough or superhydrophobic substrates can induce wetting behavior that is quite different from that of deposited or impinging drops. We investigate the growth dynamics of water drops in a well-controlled condensation chamber on a model rough hydrophobic surface made of square pillars. After having followed growth laws similar to those observed on flat surfaces, a transition to an air-pocket-like state occurred because of the bridging of the drops between the pillars. Another transition to the more stable Wenzel state is later ensured by a noticeable pillar self-drying process. Condensation ends up in a few large drops in a mixed Wenzel penetration regime. The drops are fed by neighboring channels and the adjacent pillars stay almost dry, a remarkable and seemingly general property of rough hydrophobic substrates.

Experimental studies on desalination system for ocean thermal energy utilisation

A desalination system has been designed for converting brackish water into potable water utilizing ocean thermal gradient. The desalination plant evaporates the water by flash and surface evaporation and subsequently the vapour is condensed to get potable water. An experimental plant with a capacity of 20 lph was designed for a typical ocean thermal gradient. The designed operating conditions of the plant are evaporator temperature, 30°C and condenser temperature, 10°C. Experimental performance of the system was evaluated by varying the condenser and evaporator temperatures and chamber vacuum pressure.

Design parameters and preliminary experimental investigation of an indirect vertical solar still

Obtaining water is one of the major occupations of rural peoples in the desert of Algeria. In some zones of desert, the available water is too salty for humans to consume without serious consequences. The only reliable source is groundwater accessible through foggara or the well. The introduction of solar distillation in arid areas of Algeria promises to enhance the quality of life and to improve health standards. An indirect vertical solar still consisting of a flat plate collector, an evaporation chamber and condensation chamber, forms a compact unit. The principle of operation of such a still, the main design parameters and the results of solar still preliminary performance tests are presented in this paper. The present discussion is restricted to the design parameters and preliminary performance testing of the solar still with a nominal flat plate collecting area of 0.942 m 2 and an evaporation area of 0.869 m 2, utilizing solar energy as source of heat. The daily productivity of the solar still during winter period, December 2005 to January 2006, varied from 0.863 to 1.323 l/m 2.d, when the solar radiation intensity was in the range 19.15–26.08 MJ/m 2, under daily ambient temperature that varied from 10.68 to 15.19°C, maximum hourly efficiency ranged from 47.69 to 57.85%.

F232 複数の平行細管からなる二相熱輸送デバイスの特性(ヒートパイプ)

The present paper introduces some characteristics of two phase flow in a newly developed heat transport device (HTD). The device consists of five parallel copper tubes of same diameter which connect an electrically heated evaporator and a water cooled condenser. Experiments were conducted under different conditions and the correlation between the heat transport performance and the inner flow behavior was investigated. Pure water was used as working fluid. Time-dependent temperatures and pressures inside evaporator and condenser chambers were continuously measured and recorded as well as wall temperatures of evaporator, condenser and tubes. The flow situation deduced from the tube-wall temperature measurements was in good agreement with the flow visualization results.

Comparison of the efficiency of inorganic nonmetal pigments with zinc powder in anticorrosion paints

This paper deals with the study of properties of anticorrosion pigments of varying chemical composition in epoxyester paints. Two type lines of paints were prepared. The first line comprised an anticorrosion pigment with a PVC concentration of 10% while the other line comprised an anticorrosion pigment with a PVC concentration = CPVC. The following nontoxic anticorrosion pigments were observed: zinc phosphate, zinc phosphomolybdate, calcium hydrogen phosphate, zinc phosphate modified with an organic corrosion inhibitor, strontium–aluminum polyphosphosilicate, zinc–aluminum polyphosphate, calcium metaborate, calcium ferrite, calcium borosolicate, and strontium chromate. The epoxyester primers were observed for the effect of the type of pigment on the anticorrosion properties. Anticorrosion efficiency was derived from tests in a condenser chamber and in a salt spray cabinet as well as from a test of chemical resistance of pigmented coatings. The evaluation of anticorrosion efficiency of inorganic nonmetal pigments was carried out by means of comparison with anticorrosion efficiency of metal dust.

Durability of pultruded glass-fiber-reinforced polyester profiles for structural applications

Results of an experimental research into the physical, chemical, mechanical, and aesthetical changes suffered by pultruded glass-fiber-reinforced polyester profiles during their testing for accelerated aging under the action of moisture, temperature, and ultraviolet (UV) radiation are presented. The profiles were submitted to the influence of four different exposure environments: (i) in an immersion chamber, (ii) in a condensation chamber, (iii) in a QUV accelerated weathering apparatus, and (iv) in a xenon-arc accelerated weathering apparatus. The results obtained were analyzed regarding the changes in their weight, sorption ability, tensile and flexural strength characteristics, color, and gloss; the chemical changes were investigated by means of Fourier-transform infrared spectroscopy. Considerable chromatic changes were observed, especially owing to the UV radiation. Although some reduction in the mechanical properties was observed, particularly in the immersion and condensation chambers, the durability tests proved a generally good behavior of this material under the aggressive conditions considered.

Modeling and Characterization of a Particle-into-Liquid Sampler (PILS)

A modified particle-into-liquid sampler (PILS), based on the original design of CitationWeber et al. (2001), is presented. The principal modification in this design is that collected liquid sample is delivered to vials held on a rotating carousel as opposed to an on-line analytical detector. A model is developed to predict aerosol mass concentrations measured by a PILS based on operating parameters and characteristics of the sampled aerosol. A backward model predicts the concentrations of the sampled aerosol based on operating parameters and concentrations measured by the PILS. Both models, which consider plumbing transmission efficiencies, droplet growth, mixing effects, and volatilization losses, predict mass concentrations that are consistent with laboratory tests for step changes in concentration. The average collection efficiency for species (Na + , K + , SO 4 2− , Cl − , NO 3 − ) from a variety of aerosols compared to simultaneous measurements with a differential mobility analyzer (DMA) exceeded 96% except for NH 4 + (88%); NH4 + is theoretically shown to be the most vulnerable to volatilization, followed by Cl − and then NO 3 − , with greater losses caused by increasing droplet pH and temperature. The characterization tests highlight the importance of reducing NH 4 + volatilization by keeping a stable tip temperature of 100°C at the point where steam and ambient air mix in the condensation chamber. Maintaining a stable tip temperature also avoids fluctuations in supersaturations that lead to increased deposition losses of larger droplets. Sample data from the 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) field campaign are presented.

Properties of anticorrosion pigments depending on their chemical composition and PVC value

PurposeTo identify the dependence of the anticorrosion efficiency of chemically varying pigments on their concentration in steel protecting paints.Design/methodology/approachAnticorrosion pigments from a group of nontoxic substances were chosen and compared with a chromate pigment. With all pigments, the following parameters were observed namely, oil absorption, critical pigment volume concentration value, density, extract pH, specific surface, particle size, water‐borne substances content, and the specific electrical conductivity of pigment extracts. The aqueous extracts of pigments were used to determine the corrosion loss of steel. The morphology of pigment particles was observed by means of an electron‐scanning microscope. Paints containing these pigments were formulated on the binder basis of an epoxy resin. The paints prepared were subjected to measurement of physical‐mechanical properties such as hardness and resistance in deep drawing. Paints containing anticorrosion pigments were subjected to corrosion tests in a SO2 condenser chamber, salt spray cabinet and to a test according to Machu and Schiffman.FindingsThe experimental investigations revealed the absolute values of the anticorrosion effects of individual pigments as well as dependence of efficiency on the concentration of the pigments in the paints. It was found that environment‐friendly pigments achieved comparable or even better anticorrosion efficiency than toxic strontium chromate.Research limitations/implicationsThe anticorrosion properties of the paints concerned can be tested in paints by means of atmospheric exposure such as the Florida test.Practical implicationsThe results find their application in the formulation of anticorrosion paints for industrial applications with environment‐friendly effects.Originality/valueThis research paper presents the results of the anticorrosion effects of a great number of industrially used pigments. Based on this paper, the formulation of highly effective steel‐protecting paints can be optimised.

A study of the effects of pigments and fillers on the properties of anticorrosive paints

PurposeTo investigate the properties of coatings containing various types of fillers from the point of view of their physical‐mechanical properties and anticorrosive properties.Design/methodology/approachResearch used fillers of different types varying in morphology and/or chemical composition; these were then compared with selected pigments and zinc phosphate, an anticorrosive pigment. The following parameters were observed for all of the fillers and pigments: oil absorption, CPVC value, density, extract pH, specific surface, particle size, and water‐soluble substances. The morphology of particles was observed by means of an electron‐scanning microscope. The coatings of these fillers and pigments were formulated on an epoxy resin binder basis cured with a polyamine hardener. The coatings prepared were subjected to the measurement of physical‐mechanical properties such as hardness and deepening resistance, flex resistance, adhesion to steel, and the gloss of the coatings. The coatings containing the fillers and pigments studied underwent corrosion tests in a condenser chamber and in a salt‐spray cabinet.FindingsThe results obtained through the tests allowed the selection of the optimum filler for an epoxy coating with barrier anticorrosive properties. As per respective findings, some fillers in these coatings of significant thickness can be comparable to their zinc phosphate counterparts.Research limitations/implicationsThe anticorrosive properties of the coatings studied can also be tested in paints by means of atmospheric exposure, for instance, with the aid of a Florida test.Practical implicationsThe findings are helpful towards applications in the formulations of anticorrosive coatings of significant thickness that offer an effective barrier mechanism.Originality/valueThe research presents the results of the properties of a whole range of industrially employed fillers and pigments contained in paints. Based on this study, the formulation of steel protecting coatings can be optimised.

Aqua Solaris – an optimized small scale desalination system with 40 litres output per square meter based upon solar-thermal distillation

Classical small scale solar distillers (flat collector solar stills) have been in use especially in remote tropical locations for more than a century, but they only utilize a fraction of the available solar energy flux per area. Our aim was to develop a system that optimizes the energy efficiency and approaches the physical limit of freshwater output as close as possible. The construction takes into consideration the general principles of thermodynamics. The evaporation and (cooled) condensation chambers were separated, the evaporation chamber and surface increasing material were expanded into the third dimension (a collector cubicle instead of flat collector), additional mirrors are applied to increase the solar energy input and for wind protection, and the necessary electronic microcontroller that controls the airflow rhythm was empirically optimized by a long series of test runs and measurements. A prototype on the Island of Bonaire currently produces 40 l of freshwater per square meter surface area at an ambient temperature of 30°C for an estimated life cycle of 20 years. The applications are broad. Each unit can supply a large family with freshwater at low costs, and the water source can be anything from sea water to water polluted with heavy metals and mineral poisons (e.g. arsenic polluted wells in Bangladesh). The concept builds upon readily available low-cost standard materials and parts and can help to alleviate numerous social and environmental problems, including local dependence on bottled water import, the related garbage build-up on islands and adjacent coral reefs, water borne diseases as well as desertification, deforestation and even unemployment. In addition to scientific and technical details various project proposals, participatory approaches with local end-users and business models are presented.

Experimental studies of the vapor phase nucleation of refractory compounds. VI. The condensation of sodium

In this paper we discuss the condensation of sodium vapor and the formation of a sodium aerosol as it occurs in a gas evaporation condensation chamber. A one-dimensional model describing the vapor transport to the vapor/aerosol interface was employed to determine the onset supersaturation, in which we assume the observed location of the interface is coincident with a nucleation rate maximum. We then present and discuss the resulting nucleation onset supersaturation data within the context of nucleation theory based on the liquid droplet model. Nucleation results appear to be consistent with a cesium vapor-to-liquid nucleation study performed in a thermal diffusion cloud chamber.

Analysis of a jet-pump-assisted vacuum desalination system using power plant waste heat

With ever-increasing population and rapid growth of industrialization, there is a great demand for fresh water, especially for drinking, as natural resources are becoming limited. In view of the above, different desalination technologies are evolving with a thrust for utilization of renewable energy sources like solar energy, ocean thermal energy, geothermal energy and waste heat. Vacuum desalination is one such technology in which fresh water is produced from brackish water by evaporation and subsequent condensation. This desalination technique involves different processes like pressurization of brackish water by a pump, creation and maintenance of a vacuum using jet pumps, and evaporation of brackish water at reduced pressure using waste heat from a power plant such as water from condenser. In this paper an analysis of a vacuum desalination system is presented. By applying the mass, momentum and energy balances across the various components, the governing equations are obtained for the analysis. These equations are solved using simulation. Validation of the simulated performance is made with the experimental data available in the literature. The study was carried out by varying operational parameters such as evaporator temperature, condenser temperature, evaporator flow rate, condenser flow rate and chamber pressure. Yield of fresh water obtained from the system increased as condenser temperature decreased and the evaporator temperature increased. Further, the yield increased as chamber pressure decreased.

Optimization of the Freeze-Drying Cycle: A New Model for Pressure Rise Analysis

The principal aim of this study was to evaluate the Pressure Rise Analysis (PRA) method as a nonintrusive method for monitoring the product temperature during primary drying of the freeze-drying process of model pharmaceutical formulations. The principle of this method, based on the MTM method initially published by Milton et al.1 consisted in interrupting rapidly the water vapor flow from the sublimation chamber to the condenser chamber and by analyzing the resulting dynamics of the chamber total pressure increase. A new physical model, named PRA model, based on elementary heat and mass balance equations and on constitutive equations expressing the elementary fluxes, was proposed and validated in this study for interpreting the experimental pressure rise data. It was possible to identify very precisely the values of some key parameters of the freeze-drying process such as the ice sublimation interface temperature, the mass transfer resistance of the dried layer and the overall heat transfer coefficient of the vial. The identified ice front temperatures were compared with experimental data obtained from vial bottom temperatures measured by thin thermocouples during freeze-drying runs of 5% w/v mannitol solutions. These two sets of data were found consistent with a maximum difference of no more than 2°C. The dried layer mass transfer resistance increased linearly as a function of its thickness, and the values were coherent with the few literature data published for this system. The method also led to reliable values of the vial overall heat transfer coefficient of approximately 20 Wm−2 K−1 in accordance with the published data for this type of vials and these experimental freeze-drying conditions.

Contact Line Dynamics in Drop Coalescence and Spreading

The dynamics of coalescence of two water sessile drops is investigated and compared with the spreading dynamics of a single drop in partially wetting regime. The composite drop formed due to coalescence relaxes exponentially toward equilibrium with a typical relaxation time that decreases with contact angle. The relaxation time can reach a few tenths of seconds and depends also on the drop size, initial conditions, and surface properties (contact angle, roughness). The relaxation dynamics is larger by 5 to 6 orders of magnitude than the bulk hydrodynamics predicts, due to the high dissipation in the contact line vicinity. The coalescence is initiated at a contact of the drops growing in a condensation chamber or by depositing a small drop at the top of neighboring drops with a syringe, a method also used for the studies of the spreading. The dynamics is systematically faster by an order of magnitude when comparing the syringe deposition with condensation. We explain this faster dynamics by the influence of the unavoidable drop oscillations observed with fast camera filming. Right after the syringe deposition, the drop is vigorously excited by deformation modes, favoring the contact line motion. This excitation is also observed in spreading experiments while it is absent during the condensation-induced coalescence.