High-performance Packing Research Articles

Improved thermal conductivity of epoxy composites filled with three-dimensional boron nitride ceramics-carbon hybrids

Epoxy (EP) is the preferred packaging materials used as a crucial component in power semiconductor devices. However, its low thermal conductivity (TC) always has negative impact in the heat dissipation of electronic devices. In this paper, we use hole-making method to prepare three-dimensional boron nitride ceramics-carbon (3D-BN-C) hybrids which are filled in EP matrix to improve the TC of the 3D-BN-C/EP composites. The results show that TC values of 3D-BN-C/EP composites are much superior to the BN/EP composite with random distribution of BN and 3D-BN/EP composite without carbon. The improved TC is mainly attributed to the high TC-3D skeleton structure and the low interface thermal resistance (R) due to the carbon connected with BN fillers. Infrared thermal images and Comsol simulation demonstrate that high TC 3D-BN-C/EP composite offers excellent heat dissipation capability of EP composites used as packing insulation materials. In addition, the dielectric loss of 3D-BN-C/EP composite still remains at a relative low level in a wide frequency range, exhibiting good insulation property and great potential to be used as high-performance packing insulation materials in electronic device applications.

Modeling of SO2 seawater scrubbing in countercurrent packed-bed columns with high performance packings

Packed-bed columns with fourth generation random packings offer an attractive way to implement SO2 seawater scrubbing on-board large marine ships because of small two-phase pressure drop, high capacity and high SO2 removal efficiency. SO2 seawater scrubbing was investigated via an Eulerian 3-D model based on the macroscopic volume-averaged continuity, momentum, energy and species balance equations in the liquid and gas phases. The performance of SO2 seawater absorption process in packed-bed column reactors with fourth generation random packings can be enhanced by the increase of liquid flow rate and the decrease of liquid temperature. Consequently, SO2 seawater scrubbing on-board large marine ships improves significantly in the temperate oceans with an average temperatures between 10 and 20 °C. The increase of pressure improves the driving force of gas-liquid mass transfer and subsequently SO2 removal process which becomes completely at lower values of liquid-to-gas ratio. SO2 seawater scrubbing at higher pressure increases the capital cost and energy requirement but offers major improvements such as total removal of SO2 at large sulfur content of fuel and prevention of losing of engine power because of the large counter pressure to the incoming exhaust. The operation with extra packed bed height allows to amplify the gas–liquid contact time and consequently the absorption process performance.

Determining efficiency of removal of dispersed phase from gases and modernization of scrubbers using high-performance packings

A solution to the problem of modeling the removal of a finely dispersed phase from stack gases and process gases at power engineering and petrochemical enterprises using a column apparatus filled with new highly efficient random and structured packings is considered.The use of diffusion and cell models of the flow structure for calculating a concentration profile of particles settling on a liquid fi lm in apparatuses filled with various packings is shown. Accounting for the deposition of finely dispersed particles from gases on the interfacial surface of the liquid fi lm flowing down along the packing is carried out using a bulk source of mass. The model of turbulent-inertial sedimentation of particles is adopted. The main parameters of the model are the coefficient of turbulent migration of particles to the fi lm surface on contact devices, a modified Peclet number with a backmixing coefficient, and the number of complete mixing cells. This approach can be generalized to a wide class of fi lm-type apparatuses for wet gas cleaning with the aim of designing them or choosing modernization options. Expressions are obtained for calculating the efficiency of aerosol separation on packings as well as the required depth of the packed bed for a given efficiency.Results of calculating the efficiency of gas purification from aerosols with the use of various types of packings in scrubbers as well as the required depth of the packed bed for a given efficiency are presented. A graphical dependence of the power spent on gas cleaning in apparatuses with different packings is given. Results of solving the production problem of cleaning pyrogas from coke and tar by circulating water in a modernized scrubber with new highperformance packings are shown.Expressions for calculating the rate of turbulent particle migration for random and structured packings as well as modified Peclet numbers are presented. A distinctive feature of these expressions is the calculation based on the known hydraulic resistance of contact devices.

Direct Numerical Simulations of Liquids on Microstructured Surfaces: Analysing the Fluid Dynamics on Packing

Structured high performance packing for packing columns have macrostructures, e.g., corrugated or folded sheets, and in many cases microstructures or surface topographies with geometrical dimensions in the same order of magnitude as the film thicknesses. For an optimal design of microstructured surfaces and for the development of novel methodologies to predict the mass transfer, a reliable description of the influence of these microstructures is crucial. To research the influence of these microstructures on the liquid film in detail, and later on optimize the geometry, Direct Numerical Simulations applying the Cahn-Hilliard-Navier-Stokes (CHNS) equations were performed for this study. The model and the implementation were validated against analytical solutions for undisturbed laminar film flows. The influence of two single microstructures (triangle and rectangle) on the gas-liquid interface and the velocity in the liquid were systematically investigated. Thereby, it was observed, that small microstructures in comparison to the film thickness have no influence on the gas-liquid interface. In contrast, higher structures could increase the interfacial area. The results indicate, that systematic studies on a wide range of geometries, phase properties and gas velocities can give valuable information on the path to optimal microstructures.

Electrochromatographic behavior of core-shell particles: A comparison study

Core-shell particle is a new generation high performance packing material for liquid chromatography. Through comparison with a classical totally porous silica phase of the same particle size, we studied Ascentis Express 5 μm core-shell particle's electrochromatographic behavior, in terms of voltage-current property, electroosmotic flow (EOF) and van Deemter curve. It was found, due to the nonpermeable solid core, the core-shell particle presented a diminished EOF and efficiency than the totally porous paricle. This on the other hand proved that the intra-particle pore flow extensively exists and plays an important role in electrochromatography on totally porous material. The core-shell particle's high retentivity led to an enhanced resolution for weakly retained hydrophilic peptides, which were poorly retained and co-eluted on totally porous particles. Further exploration has shown the core-shell material can achieve efficient electrochromatography of protein digests, excellent performance in terms of resolution, reproducibility and long term stability have been observed. The results indicate that the core-shell structure may suggest a reasonable design of stationary phase for bioelectrochromatography of peptides and proteins.

Liquid Distribution in a Semi-Industrial Packed Column - Experimental and Theory

The scientific interest in the efficiency of packed bed columns is part of the world-wide pursuit of sustainability of processes. The maldistribution of the phases in the apparatus reduces the efficiency and makes difficult the prediction of process performance and scaling up. In the present work the operation of liquid distribution devices and high performance packings are investigated addressing the reasons for hydrodynamic non-uniformity of the liquid phase, including the formation and development of wall flow. Data are obtained from semi-industrial size experimental studies and mathematical modeling of the liquid flow through a layer of random Raschig Super-Ring packing. The effect of measures for ensuring uniform initial liquid distribution in the column apparatus is evaluated and the parameters in the mathematical model are identified.

Theoretical Analysis for Setting Up a Catalyst-Packing Mixture that Equips a Catalytic Isotopic Exchange Column

Water – hydrogen catalytic isotopic exchange is the front-end detritiation technology that is used in the pilot plant at ICSI Rm. Valcea. It is also chosen as the main technology for the Tritium Removal Facility will be built at the Cernavoda NPP, Romania. The performance of the isotopic exchange process is mainly determined by the composition of the packing used in the catalytic isotopic exchange columns of the installations. In order to have a good working the packing should consist out of two components: i) a catalyst to enable the isotopic exchange and ii) a hydrophilic packing to maximize the fluid surface that can participate in the isotopic exchange. It is important that these two components of the packing are arranged in such a way that a uniform flow along and across the exchange column is ensured. To achieve a high performance packing theoretical and experimental research that took several years was necessary. The impact of the catalyst /hydrophilic packing ratio, the structure of these materials and their mutual arrangement were investigated. Theoretical analyses based on mathematical models contributed were used to select the optimal exchange column compositions for experimental research. This paper presents a theoretical analysis developed to set up a high performance catalyst-packing mixture, as well as the developed graphical and numerical mathematical models that allowed for this analysis.

Process Engineering Evaluation of Modern High Performance Packings for Mass Transfer Apparatus

Modern packing technology is presented in terms of correlations and criteria for an extensive evaluation of up-to-date packing design used in current mass transfer operations. The corresponding basic information covers the process engineering aspects, e.g. volumetric effectiveness and optimum geometry of the packing, and the techno-economic aspects, e.g. when selecting a packing adopted in practice for a certain application task. The correlations required for this investigation are derived and evaluated on the basis of a comprehensive experimental research by testing and comparison of modern packings, such as Raschig Super-Rings and reference packings. The results thus obtained are correlated and presented in graphic presentation of diagrams, figures and tables.

A new packing ring design – improved sealing efficiency and high durability

This feature provides details of a new high-performance packing ring design that is characterised by both its high sealing efficiency and low wear rate. As this article shows, clarifying the thermo-physical processes in a pressure packing, gaining an understanding of the wear pattern of a packing ring and elucidating the factors governing the sealing efficiency of a packing ring have played key roles in the development of this design.

Polystyrene microcapsules containing Aliquat 336 as a novel packing material for separation of metal ions

The widespread use of chromatography is mainly because of the development of high-performance packing materials and the simultaneous determination of many components in a sample. In this study, polystyrene microcapsules containing Aliquat 336 have been prepared by solvent evaporation method and the chromatographic separation of heavy metal ions with the microcapsules as a new packing material was investigated using Cr(VI), Cd(II) and Zn(II) as solutes. The experimental results show that the base-line separation of Cr(VI)/Cd(II) and Cr(VI)/Zn(II) could be reached at pH = 2.0 and the peaks are sharp and symmetrical at low pH values. The retention time of each metal keeps constant at same mobile phase conditions and the peak area decreases in direct ratio as the concentration of injection decreases. A stability experiment shows that the solvent microcapsules have a sufficient durability for long-term processing. They also have a sufficient rigidity for liquid chromatography operation.

Evaluation of heat and mass transfer coefficients in a gauze-type structured packing air dehumidifier operating with liquid desiccant

In this paper, high performance packing, namely, structured packing that has good heat and mass transfer characteristics, is proposed for dehumidification of air using liquid desiccants and for regeneration of liquid desiccants. In order to design a structured packing tower for liquid desiccant — air contacting operations, heat and mass transfer coefficients for each phase are required. This paper is concerned with the interface transfer of heat and mass when air is brought into contact with the liquid desiccant solution. A theoretical study of evaluating heat and mass coefficients in an air-desiccant contact system employing three liquid desiccants, namely calcium chloride, lithium chloride, and a mixture of 50% calcium chloride and 50% lithium chloride (called cost effective liquid desiccant, CELD) is investigated. Moreover, air phase transfer coefficients are correlated with flow rates of air and liquid and the temperature of air, whereas liquid phase coefficients are correlated with rates of air and liquid flow, and the temperature and concentration of the liquid. The findings for the three liquid desiccants are compared and discussed.

Heat and Mass Transfer in Packed Bed Liquid Desiccant Regenerators—An Experimental Investigation

Liquid desiccant cooling can provide control of temperature and humidity, while at the same time lowering the electrical energy requirement for air conditioning. Since the largest energy requirement associated with desiccant cooling is low temperature heat for desiccant regeneration, the regeneration process greatly influences the overall system performance. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer on the regeneration process are of great interest. Due to the complexity of the regeneration process, which involves simultaneous heat and mass transfer, theoretical modeling must be verified by experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed regenerator using high liquid flow rates. To regenerate the desiccant, it is heated to temperatures readily obtainable from flat-plate solar collectors. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of water evaporation, as well as the effectiveness of the regeneration process is assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, the findings in the present study are compared to findings previously reported In the literature. Also, the results presented here characterize the important variables that impact the system design.

Experimental Study of the Heat and Mass Transfer in a Packed Bed Liquid Desiccant Air Dehumidifier

Desiccant cooling systems have the ability to provide efficient humidity and temperature control while reducing the electrical energy requirement for air conditioning as compared to a conventional system. Naturally, the desiccant air dehumidification process greatly influences the overall performance of the desiccant system. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer are of great interest. Due to the complexity of the dehumidification process, theoretical modeling relies heavily upon experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed absorption tower using high liquid flow rates. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of dehumidification, as well as the effectiveness of the dehumidification process are assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, a comparison between the findings in the present study and findings previously reported in the literature is made. The results obtained from this study make it possible to characterize the important variables which impact the system design.

R&D on High Efficiency CO2 Separation Processes for Enhanced Oil Recovery at University of Regina

Introduction In order to sustain the current production capacity of crude oil in Western Ganada, enhanced oil recovery (EOR) techniques such as utilizing carbon dioxide (CO2) must be used. According to Saskatchewan Department of Energy and Mines, a large amount of crude oil worth multi-billion of dollars can be recovered using these techniques. At, the same time, a large amount of carbon dioxide (CO2) is, being produced by industrial plants in the region. This, tremendous quantity of carbon dioxide is discharged into the atmosphere and could be causing an enhanced greenhouse effect nd global warming. To overcome the CO2 emission problem, here is great interest to capture the carbon dioxide and utilize it as a flooding agent for EOR processes. The concept of recovering O2 and utilizing it as an EOR flooding agent or chemical feedstock will provide two important benefits. First, we can market the captured O2 as a commodity chemical which would generate revenue. Second, we will be able to reduce CO2 emissions to the atmosphere and help alleviate a serious environmental problem, at minimum cost. The ultimate goal of this research and development program is to develop better and more effective CO2 separation processes which can be used to recover CO2 from industrial sources such as fossil fuel fired power stations, coal gasification plants and hydrogen production units for EOR applications at the lowest possible apital and operating costs. Research Facilities and Personnel We have initiated a research program on high efficiency separation process technologies for carbon dioxide removal from industrial sources at the Process Systems Laboratory, University of Regina since 1991. We have acquired and built a number of pieces of research apparatus, equipment and pilot plants over the past five years. These include three pilot plant units for testing high efficiency gas treating systems which consists of different sizes of absorption and regeneration towers packed with a variety of high performance packings. The pilot plants are also equipped with microprocessor-based infrared gas analysers, state-of-the-art gas chromatograph units and a high speed digital data logging system. We are in the process of acquiring an ion chromatographysystem and a GC/MS mass detector for comprehensive analysis of solvent compositions and their activities. In addition, a number of embrane reactors have been constructed which can be used as very high capacity absorbers, as well numerous pieces of research apparatus have been built for solvent absorption capacity testing, corrosion studies and gas/liquid diffusivity determination. In terms of computer applications, our laboratory now is well equipped with and has access to high performance computing facilities. including three high speed Pentium work-stations (each has 64 MB memory and 2.5 GB Hard Drive), a number of 486 PCs, a Silicon Graphics work station (32 MB memory. 1 GB Hard ive) and a very large Silicon Graphics Server (12 of 150 Mhz processor, 1 GB memory, 22 GB Hard Drive). These computing facilities are also equipped with state-of-the-art real time intelligent systems development tools such as G2, GDA, NeurOn-Line, COMDALEIX and COMDALE/C, as well as advanced computeraided process engineering simulators including ASPEN.

Comparison and evaluation of HIC columns of different hydrophobicity

Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.

Gel permeation chromatography of cationic polymers on pw gel columns

Universal calibration studies show that several cationica polyelectrolytes can be characterized by aqueous exclusion chromatography, without adsorption effects using PW (Toyo Soda) hydrophilic gel columns. No. other commercially available, high-performance packings are suitable for polycations, primarily because of charge-induced adsorption. In the case of the present columns, such interactions are minimized by 0.2 M NaCl in the mobile phase, which also provides an ionic strength sufficient to suppress Donnan equilibrium salt peaks.