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.

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 Thermoacoustic Waves in Mildly Supercritical Carbon Dioxide

2004 ◽  
Author(s):  
Zhiheng Lei ◽  
Murat K. Aktas ◽  
Bakhtier Farouk ◽  
Elaine S. Oran
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
Stokes Equations ◽  
Heated Surface ◽  
Reference Database ◽  
Computational Domain ◽  
Left Wall ◽  
Square Enclosure ◽  
Supercritical Carbon

The generation and propagation of thermoacoustic waves in mildly supercritical carbon dioxide are investigated by solving the fully compressible form of the Navier-Stokes equations. Mildly supercritical fluids have high thermal conductivity; however the diffusion of heat in such fluids is very slow. Due to the high compressibility of the mildly supercritical fluids, the boundary layer along any heated surface expands and compresses adiabatically the whole fluid. We investigate these interesting phenomena via a high order numerical scheme. A square enclosure filled with supercritical carbon dioxide is considered as the computational domain. Thermally induced pressure waves are generated by heating the left wall. The thermodynamic properties of the slightly supercritical carbon dioxide are calculated via the NIST Standard Reference Database 12 [1].

Numerical Simulation of ‘Piston Effect’ in Supercritical Carbon Dioxide

2005 ◽  
Author(s):  
Zhiheng Lei ◽  
Bakhtier Farouk ◽  
Elaine S. Oran
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Computational Domain ◽  
Piston Effect ◽  
Bulk Fluid ◽  
Left Wall ◽  
Supercritical Carbon

Piston effect is an interesting mechanism of heat transfer in supercritical fluids. It is the result of propagation and damping of a thermoacoustic waves in supercritical fluids. The generation and propagation of a thermoacoustic wave in supercritical carbon dioxide is investigated by solving the fully compressible form of the Navier-Stokes equations. Two infinite plates filled with supercritical carbon dioxide, where the right walls is thermally insulated, is considered as the computational domain. A thermally induced pressure wave is generated by heating the left wall. The wave repeatedly traverses the length between the left and right walls, and its amplitude eventually damps out due to the viscous and thermal losses within the fluid, thus heating the bulk fluid. Results are presented in this paper that shows the heating up of the bulk fluid due to piston effect.

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.

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.

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.

Production of Microsphere Polystyrene Using Solution Enhanced Dispersion by CO2 Supercritical Fluids (SEDS)

2019 ◽  
Vol 805 ◽  
pp. 146-152
Author(s):  
Achmad Chafidz ◽  
Umi Rofiqah ◽  
Sumarno ◽  
Megawati ◽  
Mujtahid Kaavessina ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Size Distribution ◽  
Supercritical Fluids ◽  
Atmospheric Condition ◽  
Average Diameter ◽  
Solution Flow ◽  
Polystyrene Solution ◽  
Annulus Diameter ◽  
Supercritical Carbon

Supercritical fluids (SCFs) process can be considered as an emerging ”clean“ technology for the production of small-size particles (e.g. micron-size). Microsphere is a material in micron scale which has been widely used as adsorbent, catalyst support, and drug delivery system. For advanced application, those materials are formulated in the form of porous microspheres. There are several methods that can be used using SCFs. One of them is Solution Enhanced Dispersion by Supercritical Fluids (SEDS). This method is considered to be suitable in obtaining the porous microsphere polystyrene. In this study, polystyrene was first dissolved into toluene (polystyrene solution) at different concentrations (i.e. 3, 5, 7, 9, 11, 13, 15 wt%) and then blown/sprayed together with supercritical carbon dioxide (CO2) through co-axial nozzle with two differents annulus diameter (i.e. 3.6 mm and 4.6 mm). Co-axial nozzle consists of two concentric pipes, inner pipe and annulus. Inner pipe for polystyrene solution flow and annulus for supercritical carbon dioxide flow. The expansion of these two of fluid was done both in atmospheric condition and in pressurized precipitator (40 bar). The resulted microsphere was analyzed by using SEM (Scanning Electron Microscope) to determine morphology and average diameter of the microsphere. The SEM analysis results showe that the smaller the initial concentration of solution used, the resulted microspheres tend to be smaller and less fibrils formed. Additionally, in the pressurized precipitator, the formed microspheres size was smaller and size distribution more narrow than that of atmospheric condition. Moreover, the use of smaller annulus diameter in co-axial nozzle produced smaller microsphere size and the size distribution was more uniform.

Effect of Flow Acceleration and Buoyancy on Thermalhydraulics of sCO2 in Mini/Micro-Channel

2021 ◽  
pp. 161-182
Author(s):  
Nitesh Kumar ◽  
Dipankar Narayan Basu ◽  
Lin Chen
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluids ◽  
High Efficiency ◽  
Thermal Characteristics ◽  
Flow Acceleration ◽  
Power Cycle ◽  
Numerical Studies ◽  
Major Interest ◽  
Supercritical Carbon

Supercritical fluids have found enhanced applications in several sectors. High efficiency and high compactness associated with supercritical carbon dioxide power cycle are of major interest to the thermal engineers. Additionally, due to environment friendly properties, such as zero ODP, considerably lower GWP, non-toxic and nonflammable supercritical carbon dioxide has emerged as a potential substitute of conventional refrigerants. The peculiar properties of supercritical fluids ensured distinct flow and thermal characteristics of supercritical systems. Therefore, the chapter is aimed to discuss the thermalhydraulic characteristics of supercritical carbon dioxide in minichannel and microchannel. Both experimental and numerical studies on flow and thermal behavior of supercritical carbon dioxide will be discussed. The focus of this chapter is to examine the effect of buoyancy and flow acceleration on heat transfer performance. Considering the widespread applicability, the comprehensive discussion introduced in the chapter will affirmatively help the researchers.

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