Generation and Propagation of Thermally Induced Acoustic Waves in Supercritical Fluids: Numerical and Experimental Results

2010 ◽  
Author(s):  
Bakhtier Farouk ◽  
Zhieheng Lei
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluid ◽  
Supercritical Fluids ◽  
Acoustic Waves ◽  
Rapid Heating ◽  
Time Dependent ◽  
Cylindrical Chamber ◽  
Thermally Induced ◽  
Supercritical Carbon

The behavior of thermally induced acoustic waves generated by the rapid heating of a bounding solid wall in a closed cylindrical chamber filled with supercritical carbon dioxide is investigated numerically and experimentally. A time-dependent one-dimensional problem is considered for the numerical simulations where the supercritical fluid is contained between two parallel plates. The NIST Reference Database 12 is used to obtain the property relations for supercritical carbon dioxide. The thermally induced pressure (acoustic) waves undergo repeated reflections at the two confining walls and gradually dissipate. The numerically predicted temperature of the bulk supercritical fluid is found to increase homogeneously (the so called piston effect) within the domain. The details of generation, propagation and dissipation of thermally induced acoustic waves in supercritical fluids are presented under different heating rates. In the experiments, a resistance-capacitance circuit is used to generate a rapid temperature increase in a thin metal foil located at one end of a closed cylindrical chamber. The time-dependent pressure variation in the chamber and the temperature history at the foil are recorded by a fast response measurement system. Both the experimental and numerical studies predict similar pressure wave shapes and profiles due to rapid heating of a wall.

Convection and Transport in a Differentially Heated Enclosure Filled With Supercritical Carbon Dioxide: Short- and Long-Time Solutions

2008 ◽  
Author(s):  
Zhiheng Lei ◽  
Bakhtier Farouk
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
Acoustic Waves ◽  
Stokes Equations ◽  
Rapid Heating ◽  
Navier Stokes ◽  
Convective Flows ◽  
Long Time ◽  
Supercritical Carbon

Supercritical fluids are characterized by high densities, high thermal conductivities (compared to gases) and low viscosities, but low thermal diffusivities (compared to liquids). Due to the high compressibility, thermally induced acoustic waves are generated when supercritical fluids are heated/cooled along any bounding surface. In this study, we obtain both short- and long-time solutions for convective flows in a supercritical carbon dioxide filled enclosure. The NIST database 12 [1] is used to obtain the property relations for supercritical carbon dioxide. The generation and propagation of themoacoustic waves produced immediately after rapid heating of a wall are investigated by solving the fully compressible Navier-Stokes equations with an accurate equation of state, via a high-order explicit numerical scheme. For longer time solutions, when the acoustic waves damp out, an implicit solution algorithm is used to simulate the heat transfer in the above enclosure filled with supercritical carbon dioxide for longer periods time. This novel scheme allows us to investigate convective flows in an enclosure filled with supercritical fluid in a comprehensive manner.

Generation and Propagation of Thermally Induced Acoustic Waves in Supercritical Carbon Dioxide

2007 ◽  
Author(s):  
Zhiheng Lei ◽  
Bakhtier Farouk
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
Acoustic Waves ◽  
Stokes Equations ◽  
Ideal Gas ◽  
Acoustic Energy ◽  
Heat Diffusion ◽  
Thermally Induced ◽  
Supercritical Carbon

The generation and propagation of thermally induced acoustic waves in a confined layer of supercritical carbon dioxide are investigated by solving the fully compressible unsteady Navier-Stokes equations. These waves are generated by rapidly heating/cooling a sidewall. Due to the high compressibility, thermally induced acoustic waves are generated along any heated/cooled surface. The acoustic wave reflects from the opposing sidewall and continues to reverberate between the opposing walls. Even though supercritical fluids have high thermal conductivity, heat diffusion is slow. However, the temperature of the layer of the supercritical carbon dioxide is found to increase due to the dissipation of the acoustic energy. Ideal-gas law does not apply to supercritical fluids. Furthermore the internal energy is also not a function of temperature only. The above property variation effects are considered in the present paper.

Fast Heating Induced Thermoacoustic Waves in Supercritical Fluids: Experimental and Numerical Studies

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Nusair Hasan ◽  
Bakhtier Farouk
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluid ◽  
Thermal Energy ◽  
Acoustic Waves ◽  
Electrical Heating ◽  
Temperature Perturbation ◽  
Energy Propagation ◽  
Numerical Predictions ◽  
Supercritical Carbon

Thermoacoustic waves in near-critical supercritical carbon dioxide are investigated experimentally on acoustic time scales using a fast electrical heating system along with high speed pressure measurements. Supercritical carbon dioxide (near the critical or the pseudocritical states) in an enclosure is subjected to fast boundary heating with a thin nickel foil and an R-C circuit. The combination of very high thermal compressibilities and vanishingly small thermal diffusivities of the near-critical fluid affect the thermal energy propagation, leading to the formation of acoustic waves as carriers of thermal energy (the so called piston effect). The experimental results show that under the same temperature perturbation at the boundary, the strength of the acoustic field is enhanced as the initial state of the supercritical fluid approaches criticality. The heating rate, at which the boundary temperature is raised, is a key factor in the generation of these acoustic waves. The effect of different rates of boundary heating on the acoustic wave formation mechanism near the critical point is studied. The thermoacoustic wave generation and propagation in near-critical supercritical fluid is also investigated numerically and compared with the experimental measurements. The numerical predictions show a good agreement with the experimental data.

Dynamic solubility measurement of substances in supercritical fluids

2019 ◽  
Vol 60 (12) ◽  
pp. 96-103
Author(s):  
Lenar Yu. Yarullin ◽  
◽  
Farizan R. Gabitov ◽  
Insaf I. Zamaliev ◽  
Lyudmila Y. Sabirova ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Phase Equilibria ◽  
Supercritical Fluid ◽  
Supercritical Fluids ◽  
Raw Materials ◽  
Plant Materials ◽  
Fluid Media ◽  
Tea Leaf ◽  
Supercritical Carbon

The study of currently known methods and devices for processing plant materials has shown that during the study period, the greatest interest (about 31%) of patent holders is manifested in increasing the yield of extractive substances. If we take as an example a tea leaf, then indeed, the formation of conditions for a more complete release of the target components into the aqueous phase during brewing can provide a more profitable and economical consumption of tea raw materials. The study of the thermodynamic principles of the use of supercritical fluid media and carbon dioxide, in particular, in the processing of plant materials and the processing of tea raw materials, as well as the development of methods for intensifying mass transfer to the aqueous phase when “brewing” tea leaves, are uniquely relevant tasks. An important section of thermodynamics is the concept of phase equilibria in systems of different composition. And one of the key characteristics of phase equilibria is such a thing as the solubility of a substance, including in supercritical fluid media. Since solutions of substances in supercritical fluids are diluted, the dependence of the solubility of substances on temperature, pressure, and density of a pure solvent near its critical point is of practical interest. The results of experimental studies of measuring the solubility of tannin in supercritical carbon dioxide by the dynamic method at a temperature of 308 and 333 K, in the pressure range from 8 to 26 MPa, are presented. The data obtained, firstly, indicate a low solubility of tannin in supercritical carbon dioxide, which is a positive moment for the implementation of the tea leaf pretreatment process in order to improve its biological potential, and secondly, a clear suppression of isolines is observed, which in turn indicates the presence of crossover behavior on solubility isotherms. Based on the results of the obtained experimental data on the solubility of tannin in supercritical carbon dioxide, a mathematical description of the solubility of tannin was carried out by the Peng-Robinson equation of state.

The Influence of Temperature and Concentration on Copper Deposition Kinetics in Supercritical Carbon Dioxide

2004 ◽  
Vol 812 ◽  
Author(s):  
Yinfeng Zong ◽  
James J. Watkins
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
Zero Order ◽  
Copper Deposition ◽  
Deposition Kinetics ◽  
Zero Order Kinetics ◽  
Concentration Interval ◽  
Kinetics Of ◽  
Supercritical Carbon

AbstractThe kinetics of copper deposition by the hydrogen-assisted reduction of bis(2,2,7- trimethyloctane-3,5-dionato)copper in supercritical carbon dioxide was studied as a function of temperature and precursor concentration. The growth rate was found to be as high as 31.5 nm/min. Experiments between 220 °C and 270 °C indicated an apparent activation energy of 51.9 kJ/mol. The deposition kinetics were zero order with respect to precursor at 250 °C and 134 bar and precursor concentrations between 0.016 and 0.38 wt.% in CO2. Zero order kinetics over this large concentration interval likely contributes to the exceptional step coverage obtained from Cu depositions from supercritical fluids.

scholarly journals SPATIAL NONUNIFORM DISTRIBUTION OF 235U ISOTOPE AT SUPERCRITICAL FLUID EXTRACTION WITH CARBON DIOXIDE IN A GRADIENT TEMPERATURE FIELD

2021 ◽  
pp. 98-103
Author(s):  
B.V. Borts ◽  
S.F. Skoromnaya ◽  
Yu. G. Kazarinov ◽  
I.M. Neklyudov ◽  
V.I. Tkachenko
Keyword(s):  
Carbon Dioxide ◽  
Temperature Field ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluid ◽  
Separation Factor ◽  
Natural Uranium ◽  
Nonuniform Distribution ◽  
Spatial Redistribution ◽  
Granite Samples ◽  
Supercritical Carbon

The spatial redistribution of the 235U isotope of natural uranium in a gradient temperature field along the height of the reactor in supercritical carbon dioxide has been experimentally investigated. The scheme of the reactor is given and the principle of operation of the reactor is described. The method of preparation of initial samples from granite samples containing natural uranium and the procedure of extraction are described. The conclusion about the spatial redistribution of 235U isotopes in supercritical carbon dioxide is based on the analysis of gamma spectra of extracts. It is shown that the concentration of the 235U isotope in a supercritical fluid is maximal near the lower heated flange of the reactor, and decreases with approaching the upper, cooled flange. It was concluded that the separation factor of the 235U isotope in supercritical carbon dioxide can be about 1.2 ± 0.12.

Design Principles of Surfactants for Polymerization in Supercritical CO2

2016 ◽  
Vol 852 ◽  
pp. 766-769
Author(s):  
Shi Ping Zhan ◽  
Qing Chun Qi ◽  
Qi Cheng Zhao ◽  
Shu Hua Chen ◽  
Wei Min Hou ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
Design Principle ◽  
Design Principles ◽  
Supercritical Carbon

In recent years, supercritical carbon dioxide, as a green chemical solvent, is widely used. The surfactants for polymerization in supercritical fluids have become one of the important issues. This paper mainly discusses the mechanism and influence of the surfactants in supercritical carbon dioxide system. The choice and design principle of surfactants and the recent development of surfactants were introduced in detail.

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