Low-temperature Condensation Research Articles

ТЕХНОЛОГИИ ПОЛУЧЕНИЯ СЖИЖЕННОГО МЕТАНА КАК КОМПОНЕНТА РАКЕТНОГО ТОПЛИВА

Further development of rocket-and-space, aviation and other special equipment can be based on the use of liquefied natural gas (LNG), including pure liquefied methane (LM). This cryogenic fuel is characterized by relative safety; on its basis it is possible to provide such technical and tactical indicators of aircraft that are unattainable when using traditional fuels. Cryogenic systems for liquefying natural gas developed by PJSC Cryogenmash with extraction of liquid methane by condensation and stage separation methods, as well as rectification, are considered in the paper. The calculations show that the choice of the technology for extracting liquid methane from LNG is implemented depending on the requirements for LM as a fuel component of liquid rocket engines. The method of low-temperature condensation with stage separation provides a reduction in the concentration of low-boiling impurities (nitrogen, oxygen, hydrogen, helium). The method based on rectification allows reducing the content in LM not only of low-boiling impurities, but also of high-boiling impurities.

Investigation of the Special Features of Low-Temperature Carbon Coating Deposition on the Permalloy Film Surface Under Normal Conditions During Interaction with Aromatic Solvents

Permalloy Fe19Ni81 films are prepared by the method of ion plasma deposition on a single crystal silicon substrate in the presence of a technological magnetic field (100 Oe). The surface of the samples so obtained is modified under various conditions either with preliminary exposure in the presence of atmospheric oxygen or without it. Processes of low-temperature carbon condensation and defective graphene-like coating formation are observed for the sputtered and toluene exposed films, correspondingly. The method of energy dispersive analysis demonstrates that after fortnight modification in toluene the carbon content on the surface exceeds 30%, which is much higher than the natural ambient carbon background. An increase in the surface modification time in the aromatic toluene solvent to 11 weeks leads to a linear growth of the carbon content on the surface up to 97%. Time of preliminary holding in air before immersion into the aromatic solvent does not influence significantly the kinetics of the carbon coating formation. As a whole, this coating does not influence significantly on the static magnetic properties of the film samples.

Dual Stage Sodium Thermo-Electro-Chemical Converter (Na-TECC)

The need for reliable and distributable energy is evident, but one prominent obstacle is the lack of an efficient direct heat-to-electricity converter. The sodium thermo-electro-chemical converter (Na-TECC) is a highly efficient thermally regenerative electrochemical system (TRES) that can fill this void. This device uses an ion-selective solid-electrolyte called beta”-alumina that is highly conductive to sodium cations. The Na-TECC generates electric power by allowing high pressure sodium cations to expand isothermally through the solid-electrolyte. Theoretically, a device interacting with thermal reservoirs at 1150 K and 550 K should operate above 45% efficiency, but actual devices have not surpassed efficiencies of 20%. The maximum potential voltage in these previous devices was substantially reduced by the kinetic limitations of the charge transfer in the cathode, by pressure losses through the porous electrodes, and by Joule heating losses caused by the solid-electrolyte, electrode, and current collector resistances. To overcome these low efficiencies, a dual stage conversion process is being proposed. Rather than using one isothermal expansion step, the dual cycle will employ a second electrolyte to allow two separate expansion steps: one at the high temperature, and another at an intermediate temperature. This new cycle is thermodynamically favorable as it allows for regeneration from the isobaric cooling of the first expansion step, and reheat to complete the expansion in the second step. This allows the engine to reach a lower condenser temperature than its single stage counterpart for a given heat input, resulting in an increased overall efficiency. The temperature drop across each electrolyte in the dual stage device (e.g., ~ 400 K) is smaller than the temperature drop across a comparable single stage device (e.g., ~ 600 K). This makes the device amenable to better thermal management and allows for less heat loss. Also, the intermediate stage will mitigate the thermal shock across the very thin (< 1 mm) solid electrolyte, reduce crack propagation, limit the percolation of the molten dendrites, and ultimately increase the lifetime of the device. A dual stage concept for the Na-TECC has never been demonstrated in literature, so it is necessary to properly re-define the thermodynamic parameters such as heat loss, maximum power, and optimal current density. Certain drawbacks from a dual stage concept will also be addressed, such as the need for larger electrochemical area and the increased pressure losses. It will be demonstrated that the dual stage device must have lower thermal losses than a single stage device if it is to have a higher efficiency. The improved operation of the Na-TECC can have a transformational effect on small combined heat and power (CHP) systems at the 1-5 kW range.

An experimental study on desalination at vacuum environment under low pressure and low condensation temperatures

Earth's current lack of clean water has necessitated a search for new water sources; desalination of the sea water has been regarded as the best solution. Many techniques have been developed to make sea water into drinking and utility water. Recently, clean water production by the condensation of evaporated salt water at low pressure is one of the commonly applied techniques. Low pressure is obtained by a natural vacuum and renewable energy using a vacuum pump. In the study, system efficiency was examined for desalination at low pressure formed by vacuum pump at 0, −15 or −25°C condensation temperatures. The volume of desalinated water was measured for each evaporation temperature at 45, 50, 55 and 60°C, and the efficiency for a given volume of desalinated water at decreased temperatures at condensation temperatures below 0°C. In each experimental group, salt water could be purified by an average of 99.6%. However, according to the data obtained at 0, −15 or −25°C condensation temperatures, it was determined that decreasing the condensation temperature to −25°C was redundant: a similar efficiency could be obtained using less condensation energy at 0°C.

Controllable synthesis of iron oxide nanoparticles in porous NaCl matrix

The paper gives the results of studying the structure of porous condensates of Fe + NaCl composition, chemical and phase compositions and dimensions of nanoparticles produced from the vapor phase by EB-PVD. Iron nanoparticles at fast removal from the vacuum oxidize in air and possess significant sorption capacity relative to oxygen and moisture. At heating in air, reduction of porous condensate weight occurs right to the temperature of 650 °C, primarily, due to desorption of physically sorbed moisture. Final oxidation of Fe3O4 to Fe2O3 proceeds in the range of 380 °C–650 °C, due to the remaining fraction of physically adsorbed oxygen. At iron concentrations of up to 10–15 at%, condensate sorption capacity is markedly increased with increase of iron concentration, i.e. of the quantity of fine particles. Increase of condensation temperature is accompanied by increase of nanoparticle size, resulting in a considerable reduction of the total area of nanoparticle surface, and, hence of their sorption capacity. In addition to condensation temperature, the size and phase composition of nanoparticles can also be controlled by heat treatment of initial condensate, produced at low condensation temperatures. Magnetite nanoparticles can be transferred into stable colloid systems.

Dust formation at cryogenic temperatures

AbstractThe efficiency of dust formation in a variety of environments is an ongoing topic for discussions, especially if it comes to dust formation in the interstellar medium. Although this possibility is discussed in a wide range of numerical studies, experiments on the formation of dust at low densities and temperatures are mostly lacking. This contribution summarizes the main findings of our low-temperature condensation experiments including the formation of silica, complex silicates with pyroxene and olivine stoichiometry, and of carbonaceous refractory materials. Atomic and molecular species to be expected as products of supernovae shock fronts were produced by laser ablation of silicates and graphite. These species were deposited together with a rare gas on cold substrates representing the surfaces of surviving dust grains in the interstellar medium. After characterizing the precursor species, the rare gas matrix was annealed to induce diffusion and reactions between the initial components. We found the production of amorphous and homogeneous silica and magnesium iron silicates at temperatures of about 12 K in a barrierless reaction as monitored by infrared spectroscopy. The 10 μm band of the low-temperature siliceous condensates shows a striking similarity to the 10 μm band of interstellar silicates. Carbonaceous atoms and molecules can also react without a barrier and form an amorphous or hydrogenated amorphous carbon material. The refractory condensate has properties comparable to fullerene-like carbon grains formed at high temperatures.

Fabrication of Mechanically Stable Superhydrophobic Aluminium Surface with Excellent Self-Cleaning and Anti-Fogging Properties.

The development of a self-cleaning and anti-fogging superhydrophobic coating for aluminium surfaces that is durable in aggressive conditions has raised tremendous interest in materials science. In this work, a superhydrophobic Al surface was synthesized by employing chemical etching technique with a mixture of hydrochloric and nitric acids, followed by passivation with lauric acid. The surface morphology analysis revealed the presence of rough microstructures on the coated Al surface. Superhydrophobicity with water contact angle of 170 ± 3.9° and sliding angle of 4 ± 0.5° was achieved. The surface bounced off the high-speed water jet, indicating the excellent water-repellent nature of the coating. It also continuously floated on a water surface for four weeks, showing its excellent buoyancy. Additionally, the coating maintained its superhydrophobicity after undergoing 100 cycles of adhesive tape peeling test. Its superhydrophobic nature withstood 90° and 180° bending and repeated folding and de-folding. The coating exhibits an excellent self-cleaning property. In a low temperature condensation test, almost no accumulation of water drops on the surface showed the excellent anti-fogging property of the coating. This approach can be applied to any size and shape of Al surface, and hence has great industrial applications.

Nonstationary nucleation (explosive crystallization) in layers of amorphous ice prepared by low-temperature condensation of supersonic molecular beams

Layers of amorphous ice were prepared by deposition of supersonic molecular beams of rarefied vapor on a substrate cooled by liquid nitrogen. Molecular beam entered a vacuum chamber through Laval nozzle, which accelerated it to a supersonic speed. An adiabatic expansion of molecular beam leads to a decrease in the temperature at the nozzle outlet and formation of crystalline nanoclusters of water. Under heating of nonequilibrium condensates one could observe a glass transition (softening) and subsequent spontaneous crystallization. The presence of water clusters introduced into nonequilibrium condensates artificially ensured conditions for the initiation of “hot” centers and a transition to an explosive regime of crystallization in an amorphous medium. A theoretical analysis has been made of the role of the thermal conditions in which the crystallization of an amorphous substance proceeds, with allowance for the nonstationary nucleation.

Adsorptive Exhaust Gas Cleaning for Recycling of Li-Ion-Batteries

Increasing the usage of lithium-ion batteries requires sufficient recycling strategies in order to save resources. In the collaborative research project LithoRecII a recycling process was investigated, that combines the process steps of discharging, dismantling, shredding, extraction, drying and separation. The grinding and drying stages are flushed with an inert drying gas producing an off-gas loaded with different organic solvent components. High boiling components can be easily removed with condensation, while low boiling components require very low condensation temperatures to achieve sufficient cleaning. Hence the final cleaning can be achieved by adsorption. This paper addresses the identification of the main influences on the exhaust gas flow and composition based on drying and condensation parameters as well as the results of adsorptive off-gas cleaning experiments carried out in a fixed-bed adsorber.

Superhydrophobic coatings for aluminium surfaces synthesized by chemical etching process

ABSTRACTIn this paper, the superhydrophobic coatings on aluminium surfaces were prepared by two-step (chemical etching followed by coating) and one-step (chemical etching and coating in a single step) processes using potassium hydroxide and lauric acid. Besides, surface immersion time in solutions was varied in both processes. Wettability and surface morphologies of treated aluminium surfaces were characterized using contact angle measurement technique and scanning electron microscopy, respectively. Microstructures are formed on the treated aluminium surfaces which lead to increase in contact angle of the surface (>150°). Also on increasing immersion time, contact angle further increases due to increase in size and depth of microstructures. Additionally, these superhydrophobic coatings show excellent self-cleaning and corrosion-resistant behavior. Water jet impact, floatation on water surface, and low temperature condensation tests assert the excellent water-repellent nature of coatings. Further, coatings are to be found mechanically, thermally, and ultraviolet stable. Along with, these coatings are found to be excellent regeneration ability as verified experimentally. Although aforesaid both processes generate durable and regenerable superhydrophobic aluminium surfaces with excellent self-cleaning, corrosion-resistant, and water-repellent characteristics, but one-step process is proved more efficient and less time consuming than two-step process and promises to produce superhydrophobic coatings for industrial applications.

Thermodynamic analysis and performance of an adsorption refrigeration system driven by solar collector

This paper presents the operating and performance of an adsorption refrigeration system driven by a solar collector. The thermodynamic cycle and the working principle of the system are based on the adsorption phenomena at a steady temperature. The system operates with activated carbon (AC)-methanol as a working pair, and Dubinin-Astakhov (D-A) equation was used to describe this phenomena. Comparative study between different types of AC reveals that the one based on stone coal had an optimal performance coefficient (COP) equal to 0.73 whereas a total energy input to the system is 18740.05kJ and a total daily ice production of 13.65kg at −3°C. The studied case indicates that the optimal performance of the system can be obtained for low ambient and condensation temperature with high evaporation temperature. Ice produced can also be improved when the initial water temperature is low.

Cryochemical modification of drugs: Nanosized form III piroxicam and its physical and chemical properties

Dynamic sublimation in a stream of heated carrier gas and low-temperature condensation are used to perform structural and dimensional modification of nonsteroidal anti-inflammatory preparation of 4-hydroxy-2-methyl-N-(2-pyridinyl)-2Н-1,2-benzothiazin-3-carboxamide 1,1-dioxide (piroxicam) and to obtain its nanoscale form. Thus obtained samples correspond to the known thermodynamically metastable Form III of the compound. The average particle size of the preparation is dav = 300 ± 30 nm. The resulting nanosized form of piroxicam is relatively stable with respect to structural and dimensional transformations for at least four years.

Pervaporation membrane bioreactor with permeate fractional condensation and mechanical vapor compression for energy efficient ethanol production

Improved process separation factor and heat integration are two key issues to increase the energy efficiency of ethanol production in a pervaporation membrane bioreactor (PVMBR). A PVMBR with permeate fractional condensation and mechanical vapor compression was developed for energy efficient ethanol production. A condensation model based on the mass balance and thermodynamic equilibrium in the partial vacuum condenser was developed for predicting the purification performance of the permeate vapor. Three runs of ethanol fermentation-pervaporation experiment were carried out and ethanol concentration of higher than 50wt% could be achieved in the final condensate, with the separation factor of the process for ethanol increased to 20. Ethanol production could be enhanced in the bioreactor and 17.1MJ of the energy could be produced in per liter of fermentation broth, owing to 27.0MJ/kg heating value of the recovered ethanol. Compared with the traditional pervaporation process with low temperature condensation for ethanol production, 50% of the energy would be saved in the process. The energy consumption would be further reduced, if the available energy of the permeate vapor was utilized by integrating the mechanical vapor compression heat pump.

Feasibility of using vapor compression refrigeration system for cooling steam plant condenser

This study presents a proposal of a combined scheme for applying a vapor compression refrigeration system to cool the condenser of a steam plant. In this scheme the refrigerant (mostly liquid) leaving the throttle valve of the refrigeration system is circulated through the pipes of the shell and tube condenser, while the steam exhausting the plant turbine flows in the shell around the outer surfaces of the tubes. Thus, the refrigerant is vaporized and the steam is condensed. As a result, the maximum coefficient of heat transfer between the steam and refrigerant is achieved, and the condenser becomes compact. In addition, this combined scheme allows controlling the condenser temperature irrespective of the ambient conditions. Thermodynamic analysis of the steam plant, vapor compression refrigeration system and the proposed combined scheme has been developed. The results obtained using this analysis showed that an improvement in thermal efficiency of the combined scheme varying between 1.2 and 12% is achieved over that of the steam plant when the condenser is cooled, using ambient air, for the range of the ambient temperature of 30–50°C and condenser temperature of 15–50°C. The high value of the improvement is valid for higher ambient temperature and lower condenser temperature. Also, the results indicated that the specific refrigerant mass (mass of the refrigerant needed for condensing 1kg of the steam) varies between 1.42 and 1.62kg/kg at condenser temperature of 15 and 50°C, respectively. This specific mass does not depend on the ambient temperature and runs linearly with steam condenser temperature.

Energy efficiency of a hybrid membrane/condensation process for VOC (Volatile Organic Compounds) recovery from air: A generic approach

The recovery of VOC (Volatile Organic Compounds) from air is a major issue in terms of minimizing the environmental impact of numerous industrial processes (chemistry, food, pharmaceutical, metallurgy, refrigeration…). Non destructive VOC capture technologies are preferentially used in order to enable the recycling of a large ratio of the emitted compounds. To that respect, condensation is attractive because it offers the possibility to recover the VOC from the air stream under liquid state thanks to a physical, non destructive, separation process. Nevertheless, a very low (cryogenic) condensation temperature is often required in order to achieve that target. In that case, a membrane VOC pre-concentration step can be of major interest in order to increase the VOC content of the condensation unit and possibly improve the energy efficiency of the overall operation. In this study, a systematic analysis of the energy efficiency (overall electrical energy needed per kg of recovered VOC) of a standalone condensation process is compared to a hybrid process based on membrane concentration + condensation. It is shown that the standalone condensation remains more energy efficient for high boiling VOC (e.g. toluene, octane, acetone), while a significant improvement of the energy efficiency is obtained with the hybrid process for intermediate to low boiling temperature VOC (e.g. propane, ethane, ethylene…). A generic map of the most energy efficient VOC recovery process as a function of the VOC boiling temperature is finally proposed and potential improvement of the hybrid approach, based on a retentate recycling strategy is discussed.

Using the C-O stretch to unravel the nature of hydrogen bonding in low-temperature solid methanol-water condensates.

Transmission infrared spectroscopy has been used in a systematic laboratory study to investigate hydrogen bonding in binary mixtures of CH3OH and H2O, vapour deposited at 30 K, as a function of CH3OH/H2O mixing ratio, R. Strong intermolecular interactions are evident between CH3OH and H2O with infrared band profiles of the binary ices differing from that of the pure components and changing significantly with R. Consistent evidence from the O-H and C-H band profiles and detailed analysis of the C-O stretch band reveal two different hydrogen bonding structural regimes below and above R = 0.6-0.7. The vapour deposited solid mixtures were found to exhibit behaviour similar to that of liquids with evidence of inhomogeneity and higher coordination number of hydrogen bonds that are concentration dependent. The C-O stretch band is found to consist of three components around 1039 cm(-1) ('blue'), 1027 cm(-1) ('middle') and 1011 cm(-1) ('red'). The 'blue' and 'middle' components corresponding to environments with CH3OH dominating as a proton donor (PD) and proton acceptor (PA) respectively reveal preferential bonding of CH3OH as a PA and H2O as a PD in the mixtures. The 'red' component is only present in the presence of H2O and has been assigned to the involvement of both lone pairs of electrons on the oxygen atom of CH3OH as a PA to two PD H2O atoms. Cooperative effects are evident with concurrent blue-shifts in the C-H stretching modes of CH3OH below R = 0.6 indicating CH3 group participation in hydrogen bonding.

Analysis of a novel combined power and ejector-refrigeration cycle

A novel combined power and ejector-refrigeration cycle using zeotropic mixture is proposed. In the combined cycle, the turbine exhaust from the organic Rankine cycle entrains the vapor from the ejector-refrigeration cycle. And the zeotropic mixture is divided into the power cycle and the ejector-refrigeration cycle through a vapor–liquid separator. And these two flows have different composition. The cycle performance with different fluid composition is evaluated and it is compared with a conventional combined cycle. It is found that the cycle exergy achieves a maximum value of 10.29% with mixture isobutane/pentane (40%/60%), and the thermal efficiency gets a maximum value of 10.77% with mixture isobutane/pentane (70%/30%). The temperature glide in the evaporator achieves a maximum value of 15.09K with mixture isobutane/pentane (80%/20%). The parametric analysis shows that the cycle performs better in lower condenser temperature. Though the refrigeration cycle achieves lower evaporating temperature in higher generating temperature, the power output is reduced.

Metal nanoparticles in DBS card materials modification

In the recent years the method of collecting and storing Dried Blood Spots (DBS) on special cellulose membrane (paper) has gained wide popularity. But possible damage of biosamples caused by microorganisms in case of their incomplete drying is a disadvantage of the method. It can be overcome by treating sample-collection membranes with colloidal solutions of metal nanoparticles, having antibacterial effect. The team studied antibacterial properties of nonwoven material samples with various coatings (alcohol sols of copper, aluminium, iron, titanium, silver and vanadium nanoparticles). Colloidal solutions of nanoparticles were obtained by means of electroerosion method with further low-temperature plasma condensation. Antibacterial activity of fiberglass and cellulose membrane samples with nanoparticle coatings was studied using B. cereus and plaque bacteria cultures. It was revealed that nanostructured coatings can suppress bacterial activity; in addition they can diffuse from the membrane surface into medium which leads to widening the areas of inhibiting testing cultures’ growth. Thus, membrane materials treatment with alcohol-sols of metal nanoparticles can be seen as promising for conferring antibacterial properties to DBS carriers.

The Origin of Superflares on G-Type Dwarf Stars of Various Ages

We analyze new observations of superflares on G-stars discovered in the optical and near-IR ranges with the Kepler mission. An evolution of solar-type activity is discussed. We give an estimate of the maximal total energy, $E_{\mathrm{tot}} = 10^{34}~\mbox{erg}$ , of a flare that could have occurred on the young Sun at its age of 1 Gyr when the cycle was formed. We believe that the main source of the flare optical continuum is a low-temperature condensation forming in the course of the response of the chromosphere to an impulsive heating. For a superflare on the young Sun, we adopt an accelerated electron flux, $F_{e}\ (E> 20~\mbox{keV}) = 3 \times 10^{11}~\mbox{erg}\,\mbox{cm}^{-2}\,\mbox{s}^{-1}$ , that is limited by the return current and obtain that the area of the optical continuum source on a G-star is $S \approx 10^{19}~\mbox{cm}^{2}$ . This value is close to the area of the $\mathrm{H}\alpha$ ribbons in the largest solar flares, while the area of bright patches of a white-light flare on the contemporary Sun is lower by about two orders of magnitude. At the same electron flux and hard electron spectrum, a stellar flare of similar energy should be accompanied by a microwave source of about 2 mJy at frequencies 10 – 100 GHz at a distance of 100 pc. We discuss the possible detection of the flare-produced lithium in the course of spallation reactions. The detection of the flare microwave source and the emission in the Li resonant line could demonstrate how effective particle acceleration can be on stars in the lower part of the main sequence.

ОПТИМАЛЬНИЙ СИНТЕЗ ПРОЦЕСІВ ДЛЯ ХОЛОДИЛЬНОЇ СИСТЕМИ КОМПЛЕКСУ НИЗЬКОТЕМПЕРАТУРНОЇ КОНДЕНСАЦІЇ ПОПУТНОГО НАФТОВОГО ГАЗУ

Design of modern high-efficient systems is a key priority for the Energy Sector of Ukraine. The cooling technological streams of gas and oil refineries, including air coolers, water cooling and refrigeration systems for specific refrigerants are the objectives of the present study. Improvement of the refrigeration unit with refrigerant separation into fractions is mandatory in order to increase cooling capacity, lowering the boiling point of coolant and increasing the coefficient of target hydrocarbons extraction from the associated gas flow. In this paper it is shown that cooling temperature plays significant role in low-temperature condensation process. Two operation modes for refrigeration unit were proposed: permanent, in which the concentration of the refrigerant mixture does not change and dynamic, in which the concentration of refrigerant mixtures depends on the ambient temperature. Based on the analysis of exergy losses the optimal concentration of refrigerant mixtures propane/ethane for both modes of operation of the refrigeration unit has been determined. On the basis of the conducted pinch-analysis the modification of refrigeration unit with refrigerant separation into fractions was developed. Additional recuperative heat exchangers for utilization heat were added to the scheme. Several important measures to increase the mass flow rate of refrigerant through the second section of the refrigeration centrifugal compressor from 22.5 to 25 kg/s without violating the agreed operational mode of the compressor sections were implemented.