Low-boiling Liquids Research Articles

Alternative energy-saving technologies based on low-boiling working fluids

World economic development is accompanied by an increase in the consumption of energy resources, whose potential reserves are limited. Assessments given in show that every 25 years, energy consumption in the world doubles and environmental problems increase as well. In industrial processes, a large amount of spent energy is often lost as waste heat, which is generated as a by-product and released into the atmosphere. The Global Energy Review notes that energy consumption in the form of heat released into the environment in both the USA and EU-27 is approximately 60% of all clean primary energy consumed. Currently, to reduce the global demand for primary energy, the use of energy-saving technologies is fast-growing in many countries of the world instead of direct combustion of coal, oil and gas involving low-grade coolants and environmental heat. This paper discusses low-temperature energy-saving technologies in heat and power supply systems. A technical and economic assessment of these areas is given. The results of using low-boiling liquids for power generation on the basis of hot Earth strata are reported.

Relationship Between Properties of Floating Systems and Flammable Liquids in the Stopping Their Burning Technology

The contributions balance of isolation and cooling effects relative to the liquids surface to slow down their evaporation and to achieve safe vapor concentrations is determined. The influence of liquids characteristic temperatures and their water solubility on this process is considered. It is proven that the long-term effect of such means is provided by systems based on closed-pore floating solid materials (for example, foam glass). It is proposed to increase the foam glass low isolation and cooling capacity either by coating it with an inorganic gel or by wetting it with water. Smaller evaporation retardation coefficients by gel were obtained for liquids with the higher water solubility. A 5–6 times greater cooling capacity of the wet foam glass than dry foam glass was obtained for both polar and non-polar liquids. A smaller cooling effect is observed for liquids with a higher vaporization heat and is similar for both the use of the dry and wet foam glass. It was found that for low-boiling non-polar liquids, the evaporation slowing down is more effectively achieved by using isolation effects, and for high-boiling polar and non-polar liquids - by using cooling effects. It is proved that the fire extinguishing effect by applying the foam glass layer on the flammable liquid surface occurs in a similar way for liquids with close equivalent cluster lengths and not flash temperatures.

Experimental Study of the Thermal and Wear Characteristics of a Foil Bearing Lubricated with a Low-Boiling Liquid

Developing high-speed rotating machines, such as microturbines, requires new solutions for bearing systems. Foil bearings are one of the fastest-growing high-speed bearing technologies. This article presents the results of experimental studies on foil bearings conducted on a test rig reflecting the operating conditions of the target machine. The tested bearings were therefore placed in a chamber filled with a low-boiling medium used as a working fluid in vapour microturbines. The experiments were carried out for several test cycles following a repeatable procedure. To carry out the tests under specific environmental conditions, a measurement cycle according to the developed test procedure and a temperature stabilization system for long-term measurements were proposed. The research involved determining the thermal characteristics of four foil bearing variants and assessing the impact of operating conditions on their wear. Additional research has shown that the operating characteristics are highly dependent not only on the materials and geometry of the bearing but also on the surface roughness of the mating parts. This study is part of ongoing work to select appropriate designs and material packages for foil bearings operating under conditions involving lubricating film formation and heat dissipation.

Experimental research of a micropower volumetric expander for domestic applications at constant electrical load

This paper presents the results of experimental research carried out on a scroll expander with a rated power of 1 kWe which operates in an ORC system. The low-boiling liquid HFE7100, which has an Ozone Depletion Potential (ODP) of zero, was used as the working fluid. The research was carried out at a constant load of the expander and constant thermal power of the heat source. Research shows that the maximum power output of the cogeneration system was 976 We, nearly equal to the rated power of the expander. The maximum efficiency of the expander unit was found to be equal to 49.31%, and the thermal and exergetic efficiency of the cycle was 5.97% and 15.82% respectively. The paper also presents the determined functions and characteristics of the selected operating parameters of the cogeneration system which are dependent on the mass flow rate of the HFE7100 fluid. Dimensionless indicators were used to evaluate the operating parameters and performance of the expander and the electric generator.

A Novel Approach to Modeling Biomass Pyrolysis in a Fluidized Bed Reactor

A novel approach to simulating biomass pyrolysis in a fluidized bed of mostly inert material is presented. The bed is assumed to be externally heated, although simulation of autothermal operation with partial oxidation of the products is a future objective. Combining pyrolysis reaction kinetics developed by the CRECK Modeling Group and a previously published component properties model, material and energy balances are closed by tracking the residence time of biomass particles without regard for their exact spatial distribution. The model is used to simulate a pilot-scale fluidized bed pyrolysis process being developed at Iowa State University, and model predictions are compared with experimental results for red oak and corn stover feedstocks. The results are in general agreement, with the model typically predicting more noncondensable gas and less low-boiling liquid products. The differences are ascribed to the limitations of the kinetics model. This model provides a rigorous energy balance for fluidized bed pyrolysis processes that can be incorporated into commercial flowsheet models with the capacity for future addition of partial oxidation reactions and implementation of improved kinetics models.

Design and Fabrication of a Low-Cost Silicone and Water-Based Soft Actuator with a High Load-to-Weight Ratio.

Traditional actuators, such as motors as well as hydraulic or pneumatic artificial muscles, demonstrate excessive noise, a heavy weight, and a large size, which limit their practical application in many areas. Therefore, for many decades, scientists have worked to develop new types of silent, small, and light actuators. In this article, a novel soft actuator (actuator3) with a high load-to-weight ratio from silicone and a low-boiling liquid (ethanol: actuator3E or water: actuator3W) is presented and is compared with two actuators (actuator1 and actuator2) fabricated according to a method described in the literature. Compared with actuator1 and actuator2, actuator3 shows a larger volume expansion, output force, and load-to-weight ratio when heated. Owing to the weaker stability and repeatability of actuator3E, many different kinds of applications based on actuator3W are proposed, such as robotic hands and underwater rolling robots with color variations. The experimental results demonstrate that the method proposed in this article may be a viable alternative for fabricating low-cost soft actuators with high load-to-weight ratios that can be useful for future applications of soft robots.

НОВЫЙ ПОДХОД К МОДЕЛИРОВАНИЮ ПРОЦЕССА ФОРМИРОВАНИЯ ТЕПЛОВОГО РЕЖИМА ТЕРМОСИФОНОВ БОЛЬШИХ РАЗМЕРОВ ДЛЯ ИСПОЛЬЗОВАНИЯ ГЕОТЕРМАЛЬНОЙ ТЕПЛОТЫ

Актуальность исследования обоснована необходимостью разработки математических моделей теплофизических процессов, протекающих в термосифонах, существенно менее сложных, по сравнению с известными (в которых решаются сложные задачи гидродинамики для парового канала), но в то же время обеспечивающих возможность адекватного прогностического моделирования процессов теплопереноса в термосифонах и определения их основных характеристик (температур, тепловых потоков, скоростей испарения), необходимых для создания систем теплоснабжения с использованием геотермальной и петротермальной энергии глубинных слоев земли при передаче теплоты системой термосифонов большой высоты. Цель: апробация нового подхода к описанию процессов теплопереноса в термосифонах, являющихся основными элементами системы извлечения теплоты глубинных слоев земли (геотермальной и петротермальной энергии) путем сравнения результатов математического моделирования температур в рамках новой модели в характерных точках слоя теплоносителя и результатов экспериментальных исследований. Объект: замкнутый двухфазный термосифон. Метод. Краевая задача математической физики решалась методом конечных разностей. Результаты. На основании анализа и обобщения результатов экспериментальных исследований разработан новый подход к математическому моделированию процесса формирования теплового режима термосифонов большой высоты для использования геотермальной теплоты. Сформулирована математическая модель, описывающая теплоперенос в слое теплоносителя на нижней крышке термосифона и обеспечивающая возможность достоверного прогноза скоростей испарения (или кипения) теплоносителя. Модель отличается от известных описанием не только теплопроводности, но и процесса естественной конвекции в слое теплоносителя. Численные исследования выполнены на пространственной сетке 36×101, шаг по времени изменялся в диапазоне от 10–3 до 10–6 с. Рассматривался диапазон тепловых потоков q, соответствующих условиям интенсивного испарения на свободной поверхности слоя теплоносителя. Проведено сравнение температур в точке, расположенной на оси симметрии термосифона на расстоянии 6 мм от поверхности его нижней крышки, полученных при проведении численного анализа и установленных в экспериментах. В качестве теплоносителя рассматривался Н-пентан – низкокипящая жидкость, которая может использоваться в термосифонах при относительно низкой (до 40 °С) температуре скальных пород или воды. Установлено хорошее соответствие результатов численного моделирования температурных полей в области анализа и экспериментов. Установлено, что свободная конвекция в слое теплоносителя при достаточно высоких тепловых потоках к нижней поверхности термосифона играет важную роль в формировании температурного поля жидкости и скорости ее испарения со свободной поверхности. Разработанный подход может быть использован при анализе систем геотермального и петротермального теплоснабжения при извлечении теплоты из глубинных слоев земли с использованием группы термосифонов большой высоты.

Recycling and Disposal Methods for Polyurethane Wastes: A Review

Polyurethanes (PU) are a general class of polymers prepared by the polyaddition of isocyanates and hydroxyl group containing compounds. PU foams are formed via the reaction of poly-isocyanate and multi-functional hydroxyl compounds resulting in urethane linkages. The foams are formed in wide range of densities and maybe flexible, semi-flexible or rigid in structure. To control the foam structure, blowing agents are employed. These agents are introduced during foam formation through volatilization of low-boiling liquids or through the formation of gas due to chemical reaction. Additionally, surfactants, catalysts, etc. are used during the manufacturing of foams. PU, including PU foams, is one of the most important groups of materials today and hence, their recycling has been of great interest. Many methods of recycling PU are available and many more are being studied further. However, no method has seen large scale commercialization or is brought into regular practice. The objective of this review is to bring to light the various technologies available and their current status of development as well as newer upcoming methods that may be available in the future.

A novel combustion system for liquid fuel evaporating and burning

To utilize sustainable biofuel, the current study proposes a novel combustion technique that directly burns liquid ethanol without a spray system. Two swirling air flows are induced by tangentially injected the gas from two concentric tubes at different stages. The liquid ethanol is fed by a liquid tank at the center. At the beginning methane flame assists in preheating the system to vaporize liquid ethanol and ignite the vapor. Thereafter methane is switched off, and liquid ethanol can be continuously vaporized through self-burning released heat. The heat and mass transfer processes are examined to illustrate such self-sustained burning–heating–evaporating system. The ethanol flow rate is gradually increased to provide different heat output. The flame structures, temperature distributions and pollutant emissions are carefully examined. The results show that the ethanol can be steadily burned to provide heat output between 0.7 and 2.5 kW. Generally a blue flame is obtained, and the NOx and CO concentrations are ultralow. By increasing ethanol flow rate to exceed 8 mL/min, an unsteady, sooting flame is observed owing to incomplete evaporation and poor mixing. A parametric study is conducted to evaluate the influences of liquid tank position, flow rate and tip structure on the combustion characteristics. Additionally, an optimal operation condition is proposed. The current study provides a promising method to burn low-boiling liquid fuel in a clean, efficient and compact way.

An experimental study of rivulet flow in low-boiling liquid driven by gas flow in a minichannel

Flow regimes in a low-boiling dielectric liquid driven by gas flow in a minichannel have been experimentally studied, and a map of regimes involving 11 varieties has been constructed. It is established that a rectilinear rivulet flow is observed in a restricted range of liquid and gas flow rates.

Lignin conversion in supercritical ethanol in the presence of solid acid catalysts

The effects of sulfated ZrO2 and ZrO2-Al2O3 catalysts and acidic zeolite catalysts with various Si/Al ratios on the thermal conversion of alkali lignin in supercritical ethanol at 300–400°C and on the composition of the resulting products have been investigated. All of the catalysts enhance lignin conversion into liquid products. The strongest effect with the catalysts based on sulfated ZrO2 is attained at 400°C; with the zeolites, at 350°C. The catalysts diminish the concentration of phenol and its derivatives and increase the concentration of ethers (mainly the 1,1-diethoxyethane concentration) in the liquid products. The zeolite catalysts are preferable, since the reaction over the ZrO2-containing catalysts produces gaseous compounds in higher yields. The maximum lignin conversion and a high yield of low-boiling liquid products are achieved at 350°C with the zeolite catalyst with Si/Al = 30, which contains a high concentration of acid sites that are stable at elevated temperatures. The most abundant phenolic liquid products of lignin conversion over the zeolite catalysts at 350°C are methoxyphenols and their methylated and ethylated derivatives.

ФОРМИРОВАНИЕ ПАРОВОЗДУШНОГО ОБЛАКА ПРИ ПРОЛИВЕ НИЗКОКИПЯЩИХ ЖИДКОСТЕЙ

ФОРМИРОВАНИЕ ПАРОВОЗДУШНОГО ОБЛАКА ПРИ ПРОЛИВЕ НИЗКОКИПЯЩИХ ЖИДКОСТЕЙ

Study of Polymer Composites Containing Low-boiling Liquids and Gases by Differential Thermal Analysis

Study of Polymer Composites Containing Low-boiling Liquids and Gases by Differential Thermal Analysis

Boiling up of jets of superheated ethanol-water solutions

The stability and evolution of the shapes of jets of strongly superheated aqueous solutions of ethanol flowing out of a high-pressure chamber are experimentally investigated at various initial parameters. It has been found that a low-boiling liquid causes shifting to lower temperatures of the boundaries between various kinds of boiling-up jets, such as cylindrical, conical, and open. Large-scale pulsations of the jet shapes are observed in the temperature range from 454 to 484 K, where the jet completely breaks down. The conditions for the formation of large-scale low-frequency pulsations with a power spectrum diverging inversely proportional to the frequency f (1/f spectra) have been revealed. Such fluctuations prove that the flow is unstable and large-scale low-frequency ejections are possible.

High-pressure catalytic and thermal cracking of polyethylene

The thermal cracking and catalytic cracking processes of low-density polyethylene were studied in a closed autoclave. The compositions of gaseous and liquid products were analysed by means of GC/FID and GS/MS chromatographic methods. The fractional composition of liquid products was found by distillation. Increased temperature of PE depolymerisation process increases the production of gaseous products and low-boiling liquid compounds; more aromatic hydrocarbons are formed instead of alkenes. When a lower temperature and longer time are adopted for the process to reach the assumed conversion, more straight chained hydrocarbons are produced. The acidic aluminosilicate catalyst yields more low-boiling liquid fractions, more isoalkanes and more aromatics. The neutral alumina is favourable for the production of alkenes and vacuum gas oil fraction in comparison to a non-catalytic process. The Ni–Mo/Al 2O 3 catalyst is efficient in hydrogenation of depolymerisation products. The reaction products contain only saturated compounds then and no aromatics are formed.

Dependence of Surface Tension of Near-boiling Non-associated Liquids on Their Molar Volume and Some Critical Constants

The equation proposed for near-boiling non-associated liquids describes a new functional dependence of their surface tension on such physico-chemical characteristics as: critical volume, critical temperature and molar volume at the temperatures which are near their normal boiling points. It is shown that, in the case of some low-boiling liquids, possessing small molecules, this equation can be used for the adequate calculation of surface tension at different temperatures in the liquid phase.

Heat Transfer from a Local Heat Source to Subcooled Liquid Film

An experimental investigation is performed of heat transfer from a local heat source to films of water and low-boiling dielectric liquid that flow down a vertical plate by gravity. The liquids are substantially subcooled. In the case of perfluorotriethylamine flow, regular structures are formed in the film at the threshold value of the heat flux density. After the heated layer of liquid comes to the film surface, three characteristic modes of heat transfer are observed, which are associated with the variation of the modes of liquid flow caused by thermocapillary convection. At low values of the Reynolds number of the film, a specific form of critical heat transfer is observed, which is characterized by disintegration of the jet into droplets and their separation from the heater.

Thermal Conductivity Reduction of Polyurethane Insulating Foam by In Situ Carbon Dioxide Removal

Polyurethane foam of the type used for most refrigerator insulation is currently blown in the United States with a mixture of diclorofluoroethane (R-141b), and CO2. The object of this work has been to reduce the thermal conductivity of this foam by passively removing CO2 from the cell gas of the foam. This work is applicable to foams blown with R-141b, R-356, cyclopentane, and other low-boiling liquids plus CO2. In work with hand-mixed foams we demonstrated that NaOH in the form of beads or powder is an effective material for in situ CO2 removal from foam. After removal of CO2, originally present at 14%, foam thermal conductivity at refrigerator operating conditions was reduced 9%.

Thermodynamics of coal-derived fluids: 2. Vapour-liquid equilibria of coal liquid fractions

A thermodynamic model for prediction of vapour-liquid equilibria (VLE) in coal-derived fluids has been developed. The model uses group contribution methods for property evaluations and a continuous thermodynamics approach for VLE computations. A coal fluid is defined by multiple molecular weight distributions, and each distribution is represented by an average molecule with fixed relative proportions of different functional groups. Besides the hydrocarbon group, phenolic, pyridinic and thiophenic groups are used to represent O, N and S heteroatoms. From the results it is concluded that for low-boiling coal liquid fractions the phenolic compounds need to be treated separately, as opposed to the use of a single average molecule to define the coal liquid. Comparison with published data shows that the model is successful in predicting boiling ranges for low-boiling fractions. Failure of the model at higher temperatures is attributed to the binary interaction parameters in the UNIFAC model which are regressed from low-temperature binary VLE data.

High-efficiency condenser for low-boiling liquids and gases

Constructing a high-efficiency condenser for low-boiling liquids and gases using a 2 L plastic bottle.