Packing Thickness Research Articles

Study of inter-annual variations in surface melting over Amery Ice Shelf, East Antarctica, using space-borne scatterometer data

The widespread retreat of glaciers can be considered as a response to the climate change. Being the largest retreating glacier–ice shelf system in East Antarctica, the Amery Ice Shelf–Lambert Glacier system plays an important role in contributing to sea level rise as well as the surrounding environment and climate. The present study is focused on the investigation of surface melting over the ice shelf using QuikSCAT Ku-band scatterometer data for more than 100 months covering the period from January 2000 to July 2009. The corresponding weather data of Davis Station was obtained from the website of Australian Antarctic Division. Very prominent dips in the backscatter observed in the month of January form a distinct signature caused by physical process of significant melting of the ice/snow surface. The steep increase again in February is attributed to the initiation of the freezing phenomenon. The derived melting index compared well with the passive microwave-based melting index derived by other researchers. A strong relationship was found between the scatterometer-derived melting index and the cumulative monthly mean air temperature. The highest melting was observed in the summer (January) of 2004, and thereafter gradual cooling appeared to take place in the subsequent years. The snow pack thickness, inferred from the backscatter variations, was found to be higher during winters (June) of 2004 and 2005, compared with other years.

An experimental study of structured packing dehumidifier/regenerator operating with liquid desiccant

The present work presents an experimental investigation on the performance of the structured packing cross flow desiccant dehumidification system (DDS). This system is referred as DDS; its heart is the dehumidifier/regenerator. It is used to meet a latent heat load by air dehumidification. Calcium chloride (CaCl 2) solution is used as the working desiccant material in this system. The structured packing has a density (specific surface area) of 390 m 2/m 3, corrugation angle of 60° and void fraction of 0.88. The effect of relevant parameters such as air flow rate, desiccant solution flow rate, desiccant solution temperature and concentration and packing thickness on the performance of the system is studied. The performance of the system is evaluated using the mass transfer coefficient, moisture removal rate (MMR), effectiveness and the coefficient of performance (COP). The remarkable increase of mass transfer coefficient and MRR for both deh/reg is observed by increasing both air and solution flow rates. Eventually, the payback period (PP) of the DDS is 11 months with annual running cost savings (Δ C RC) of about 31.24% compared with vapor compression system (VCS) dehumidification. The overall environmental impacts of DDS are nearly 0.63 of VCS. This may emphasize the need of incorporating a desiccant system along with air conditioning applications.

Performance characteristics of a solar humidification dehumidification unit using packed bed of screens as the humidifier

The aim of the present work is to investigate the main factors affecting the performance improvement of a solar humidification-dehumidification unit (HD), using a packed bed of screens as the humidifi er. The HD unit consists mainly of a flat plate solar collector, humidification section and dehumidification exchanger. The investigation was divided into three main parts which are Part 1: investigation of the main variables affecting the solar collector performance. It was found that the efficiency of solar collector increased by increasing the collector angle of inclination up to 45°, increasing the area of solar collector, and decreasing the inlet water flow rate. Part 2: investigation of the humidification-dehumidification unit separated from the solar collector and using external source of heating. It was found that, the productivity of the unit increased by increasing the saline water inlet temperature, saline water flow rate, and thickness of screen packing. Part 3: the overall system components were...

Modeling of the Precipitation Process in a Rotating Packed Bed and Its Experimental Validation

A mixing-precipitation model based on the modified coalescence-redispersion model was presented to describe the flow, mixing, nucleation and growth in a rotating packed bed (RPB). The model was coupled with population balance, mass balance and crystallization kinetics. It predicted well the influence of coalescence probability, which represents the mixing intensity among droplets, on the particle number density, supersaturation and mean particle size of the produced precipitates. The effects of the radial thickness of packing, liquid flow rate and rotating speed on the product particle size were also investigated. The results indicate that the needed radial length of packing is short for sparingly soluble substance precipitation (about 40-50 mm in this work), and the mean particle size of precipitates decreases with the increase of rotating speed and liquid flow rate, respectively. The validity of this model was verified by experiment on BaSO 4 precipitation in RPB.

Cationic polymerization in rotating packed bed reactor: Experimental and modeling

AbstractOn the basis of analysis of key engineering factors predominating in cationic polymerization, butyl rubber (IIR) as an example was synthesized by cationic polymerization in the high‐gravity environment generated by a rotating packed bed (RPB) reactor. The influence of the rotating speed, packing thickness, and polymerization temperature on the number average molecular weight (Mn) of IIR was studied. The optimum experimental conditions were determined as rotating speed of 1200 r min−1, packing thickness of 40 mm and polymerization temperature of 173 K, where IIR with Mn of 289,000 and unimodal molecular weight distribution of 1.99 was obtained. According to the experimental results and elementary reactions, a model for the prediction of Mn was developed, and the validity of the model was confirmed by the fact that most of the predicted Mns agreed well with the experimental data with a deviation within 10%. © 2009 American Institute of Chemical Engineers AIChE J, 2010

Dual Polarization Interferometric Analysis on the Interaction between Fullerene Grafted Polymer and Nonionic Surfactants

The interaction between polyelectrolyte grafted fullerenes and surfactants was elucidated using a dual polarization interferometer (DPI). The deposition of poly(2-(dimethylamino)ethyl methacrylate) (PDMA(50)-b-C(60)) at pH 6 on the surface of silicon oxynitride induced by electrostatic interaction between charged PDMA segments and negatively charged surface revealed an adsorption thickness similar to the diameter of a fullerene molecule. A second deposition of poly(acrylic acid)-block-C(60) (PAA(83)-b-C(60)) on adsorbed PDMA(50)-b-C(60) at pH 6 was facilitated by electrostatic interaction between negatively and positively charged PAA and PDMA segments, respectively. A monolayer of PAA(83)-b-C(60) adsorbed on PDMA(50)-b-C(60) layer yielded a thickness twice the diameter of C(60) molecules. As a comparison, a two end-capped C(60)-PAA(83)-C(60) was examined, where the packing thickness and mass were smaller than the monocapped system due to steric hindrance effect of fullerene molecules. The adsorption of two nonionic surfactants (i.e., polyoxyethylene 9 lauryl ether (Brij 76) and octyl phenol ethoxylate (Triton X-100 or TX100)) on the adsorbed PDMA-C(60) layer was examined. Both Brij 76 and TX100 interacted with the PDMA-C(60) layer. For TX100, the interaction was promoted by pi-pi interaction between the C(60) headgroup and phenyl ring of the surfactant. Beyond the critical micellar concentration of TX100, the adsorption was greatly reduced. The concentration effect of first layer PDMA-C(60) was evaluated, where the PDMA-C(60) molecules adsorbed on the chip at higher density, resulting in a larger layer thickness. The densely packed fullerene headgroup hindered the penetration of TX100 aromatic ring into the first layer.

A New Method for Measuring Cake Thickness by a Powder Pressure—Displacement System

An on-line powder pressure–displacement measurement system was developed based on a static measurement instrument (vernier caliper). This system consists of a pressure sensor and a displacement subsystem, and has the on-line capability to measure the thickness of powder packing with different powder sizes. The design principle employs a pressure sensor to determine the thickness by different signals generated when the pressure sensor contacts the free surface zone of powder packing and when it contacts the other powder zone. The powder materials adopted to validate this newly developed system were glass beads, sand and dust. This measurement technique can be applied under different measurement conditions.

Performance analysis of two-stage evaporative coolers

An experimental rig of two-stage evaporative cooling unit is constructed and tested in the Kuwait environment. The system is formed of an indirect evaporative cooling unit (IEC) followed by a direct evaporative cooling unit (DEC). The system is operated during the summer season of Kuwait with dry bulb temperatures higher than 45 °C. The system is operated as a function of the packing thickness and water flow rate of the DEC unit. Other parameters include the water flow rate to the IEC unit and the mode for operating the IEC heat exchangers. Results show that the efficiency of the IEC/DEC varies over a range of 90–120%. Similarly, the efficiency of the IEC unit is varied over a range of 20–40%. The efficiency of the DEC unit varies over a range of 63–93%. The data is used to correlate the Nusselt number for the air stream outside the IEC heat exchange unit. Results show that the Nusselt number varies over a range of 150–450, which corresponds to a heat transfer coefficient of 0.1–0.4 kW/m 2 K. These results are consistent with literature data and should be of great value in designing of IEC units. In summary, the results and analysis presented here indicate the attractiveness of the EC systems for indoor air conditioning. High efficiency is obtained irrespective of the high intake air temperature. It is highly recommended to continue research investigations in this area in search for low energy consumption air conditioning units as these would contribute to a cleaner environment and would conserve the limited resources of fossil fuel.

Siberia snow depth climatology derived from SSM/I data using a combined dynamic and static algorithm

One of the major challenges in determining snow depth (SD) from passive microwave measurements is to take into account the spatiotemporal variations of the snow grain size. Static algorithms based on a constant snow grain size cannot provide accurate estimates of snow pack thickness, particularly over large regions where the snow pack is subjected to big spatial temperature variations. A recent dynamic algorithm that accounts for the dependence of the microwave scattering on the snow grain size has been developed to estimate snow depth from the Special Sensor Microwave/Imager (SSM/I) over the Northern Great Plains (NGP) in the US. In this paper, we develop a combined dynamic and static algorithm to estimate snow depth from 13 years of SSM/I observations over Central Siberia. This region is characterised by extremely cold surface air temperatures and by the presence of permafrost that significantly affects the ground temperature. The dynamic algorithm is implemented to take into account these effects and it yields accurate snow depths early in the winter, when thin snowpacks combine with cold air temperatures to generate rapid crystal growth. However, it is not applicable later in the winter when the grain size growth slows. Combining the dynamic algorithm to a static algorithm, with a temporally constant but spatially varying coefficient, we obtain reasonable snow depth estimates throughout the entire snow season. Validation is carried out by comparing the satellite snow depth monthly averages to monthly climatological data. We show that the location of the snow depth maxima and minima is improved when applying the combined algorithm, since its dynamic portion explicitly incorporate the thermal gradient through the snowpack. The results obtained are presented and evaluated for five different vegetation zones of Central Siberia. Comparison with in situ measurements is also shown and discussed.

Effets des illutations de boue thermale sur la microcirculation cutanée

Objectives. – The objective of this study was to conduct a laser–Doppler flowmetry investigation of skin microcirculation changes induced by mud pack therapy. The magnitude of the changes, potential remote effects, and potential influence of mud pack thickness were studied. Results. – The patients were volunteers receiving Spa therapy and free of diabetes mellitus, vaso-active drug treatment, and inflammatory shoulder disease. Two mud packs, 15 and 30 mm in thickness, respectively, were applied at an interval of 48 h, at the same time of day in a given patient, and at a distance from other spa treatments. The packs were centered on the deltopectoral groove. The side and order of application of the 2 packs were determined at random. Superficial skin blood flow was measured by laser–Doppler flowmetry (Perimed ® PF4001, wavelength 82 nm) and recorded by the Perisoft ® computer program with a 3 s time constant downstream from a broadband filter (12 MHz). Methods. – Twenty female spa therapy patients aged 28 to 67 years (median, 51 years) participated in the study. The reason for spa therapy was lower limb venous insufficiency in 14 patients and osteo-arthritis in 6 patients, none of whom had involvement of the shoulders. Mud pack treatment was associated with a significant elevation in skin temperature, by 1.8 ± 0.2 °C and 1 ± 0.2 °C with the 30 mm and 15 mm packs, respectively ( P <0.001 for both comparisons; nonsignificant difference between the 2 packs). Skin blood flow increased significantly, by 619 mV ± 82 and 410 ± 124 mV with the 30 mm and 15 mm packs, respectively ( P <0.0001 for both comparisons; nonsignificant difference between the 2 packs). The vasomotion score increased markedly on the treated side, by 16.7 ± 2.8 and 13 ± 1.6 with the 30 mm and 15 mm packs, respectively ( P <0.005 for both comparisons; no significant difference between the 2 packs). Furthermore, low-frequency vasomotion waves of a type not described previously were recorded. The microcirculatory changes lasted longer than did the temperature increase. No significant changes were noted in the other shoulder or in central body temperature. Conclusion. – These results suggest that the vascular changes induced by mud pack therapy are not fully explained by vasodilation in response to local temperature elevation. Further studies are in order to identify the other mechanisms involved.

Effects of mud pack treatment on skin microcirculation

Objectives. – The objective of this study was to conduct a laser-Doppler flowmetry investigation of skin microcirculation changes induced by mud pack therapy. The magnitude of the changes, potential remote effects, and potential influence of mud pack thickness were studied. Methods. – Twenty female spa therapy patients aged 28–67 years (median, 51 years) participated in the study. The reason for spa therapy was lower limb venous insufficiency in 14 patients and osteoarthritis in six patients, none of whom had involvement of the shoulders. Mud pack treatment was associated with a significant elevation in skin temperature, by 1.8 ± 0.2 and 1.0 ± 0.2 °C with the 30- and 15-mm packs, respectively ( P < 0.001 for both comparisons; nonsignificant difference between the two packs). Skin blood flow increased significantly, by 619 ± 82 and 410 ± 124 mV with the 30- and 15-mm packs, respectively ( P < 0.0001 for both comparisons; nonsignificant difference between the two packs). The vasomotion score increased markedly on the treated side, by 16.7 ± 2.8 and 13.0 ± 1.6 with the 30- and 15-mm packs, respectively ( P < 0.005 for both comparisons; no significant difference between the two packs). Furthermore, low-frequency vasomotion waves of a type not described previously were recorded. The microcirculatory changes lasted longer than did the temperature increase. No significant changes were noted in the other shoulder or in central body temperature. Results. – The patients were volunteers receiving spa therapy and free of diabetes mellitus, vasoactive drug treatment, and inflammatory shoulder disease. Two mud packs, 15 and 30 mm in thickness, respectively, were applied at an interval of 48 h, at the same time of day in a given patient, and at a distance from other spa treatments. The packs were centered on the deltopectoral groove. The side and order of application of the two packs were determined at random. Superficial skin blood flow was measured by laser-Doppler flowmetry (Perimed ® PF4001, wavelength 82 nm) and recorded by the Perisoft ® computer program with a 3-s time constant downstream from a broadband filter (12 MHz). Conclusion. – These results suggest that the vascular changes induced by mud pack therapy are not fully explained by vasodilation in response to local temperature elevation. Further studies are in order to identify the other mechanisms involved.

Experimental models of 'Basement'-controlled salients - application to the proterozoic fold-thrust belt of the quadrilátero ferrífero (Minas Gerais, Southeastern Brazil)

Scaled sandbox models are used to simulate the development of ´basement´-controlled, salients. We investigate the controlling factors on the development of closed curvatures in map-view, considering constant both the sand pack thickness and the space between obstacles. These models are compared with the Fundão-Cambotas Fault System in the Proterozoic fold-thrust belt in the Quadrilátero Ferrífero region, along the southeastern margin of the São Francisco craton. In the experiments, a pronounced curvature resulted from the margin-controlled salient process in the presence (i) of a basal ductile detachment, or (ii) of pre-existing structures. The results suggest that the convex-to-the-foreland, west-vergent Fundão-Cambotas Fault System that borders the Archean basement highs and displaced older Transamazonian structures westward, is partly a consequence of interaction of propagating thrusts with obstacles in the foreland.

Morphology of Nanostructured Films for Environmental Applications: Simulation of Simultaneous Sintering and Growth

A sequential Brownian dynamics approach was used to establish the morphological evolution of a nanostructured particle deposit accounting for random diffusion, particle–particle and particle–surface interactions through van der Waals forces, and sintering of deposited particles. Monodisperse (30nm radius) titanium dioxide particles were used in the simulations. A linear sintering law rate expression was used to account for the decrease in total surface area of the deposit. Characteristics such as packing thickness, total surface area, and fractal dimension are reported as a function of time during the deposition process. Sintering resulted in higher fractal dimensions (as defined) for the deposits, and elevated temperatures resulted in more compact deposits.

Effects of powder bed conditions on the liquid-phase sintering of Si3N4

The effects of the active and passive protection mechanisms of powder beds on the sintering of Si3N4 were investigated. Shrinkage, density, and coloring behavior of sintered samples were analyzed using different compositions and packing conditions of powder beds based on BN and Si3N4 with different additives. Y2O3 additive in the powder bed influences the weight change and phase formation behavior of the samples, although it has a very low vapor pressure at the sintering temperature. When MgO/Y2O3 was used as sintering additives, the packing density and thickness of the powder bed had a much stronger effect than in the case of Al2O3/Y2O3. For the optimization of the powder bed conditions, the vapor pressure and chemical stability of sintering additives at the sintering temperature has to be considered.

Distillation in a Rotating Packed Bed.

This work presents a novel rotating packed bed owing to its applicability in distillation. Distillation experiments were conducted using the methanol-ethanol system at atmospheric pressure and total reflux conditions with two packings. Rotor speeds ranged from 600 to 1600 rpm, which provided 42–298 equivalent gravitational force. Experimental results indicated that 1–3 theoretical plates were achieved with a packing thickness of 8.6 cm. Consequently, the height equivalent of a theoretical plate (HETP) of about 3–9 cm can be obtained in a rotating packed bed, i.e., much lower than that in a conventional packed bed. An empirical correlation was also proposed, implying that the HETP value varied with centrifugal force to the 0.23–0.26 power.

Influence of the pack thickness of the boronizing mixture on the boriding of steel

Boronizing, which involves diffusion of boron atoms into steel substrate to form iron borides, is a well-known diffusion coating process and numerous studies have demonstrated the outstanding tribological properties of boronized steel vis-à-vis carburized or nitrided steels. However, the high cost of the boronizing process has severely limited its applications. One way to bring down the cost of the boronizing process is to reduce the thickness of the boronizing mixture to be packed around the component (called pack thickness) to the minimum required level without compromising on the properties of the boride coating. The present study attempts to estimate the optimum pack thickness required to form boride coating of adequate thickness and property in the case of a low carbon steel boronized at 940°C for 2 h. Low carbon steel samples have been boronized with varying pack thickness in the range 2–25 mm and the resulting boride coatings have been examined for thickness, microstructure, microhardness profile and abrasion resistance. An analysis of the results obtained indicated that a pack thickness of 10 mm is sufficient to obtain boride coatings of adequate thickness and optimum properties.

Using Local Gravel to Control Sand Production in a Saudi Oil Field

Sand production from oil and gas reservoirs is most commonly associated with unconsolidated and poorly cemented sandstones. Sand production problems are encountered throughout the world and recently are detected in Saudi Arabia. Several techniques could be used to minimize sand production such as drawdown control, installing screen liners, applying resin consolidation, gravel packing, etc. This work was conducted to investigate the possibility of using gravel packs made from gravel deposited in the central province of Saudi Arabia. Optimum gravel size, shape, crushing resistance and solubility in acids were tested. The results of the above analysis showed that the selected Saudi gravel properties meet the recommended API requirements. Furthermore, a physical model has been constructed to simulate sand control process. This model was used to study the effect of drawdown pressure, confining pressure and gravel-pack thickness on rate of fluids and sand production in a Saudi oil field. The experimental results showed that sand and fluid production are affected by the gravel pack thickness, drawdown pressure and confining pressure. Therefore, it is recommended to utilize the tested Saudi gravel in sand control applications after performing an economical feasibility study.

In‐Well Hydraulics of the Electromagnetic Borehole Flowmeter

AbstractPrevious studies have suggested that head losses associated with the application of the electromagnetic borehole flowmeter (EBF) can have important and detrimental effects on the use of the instrument for measurement of hydraulic conductivity (K) profiles. Head losses associated with flow through the meter may cause bypass flow around the packer if the well is gravel packed. In any type of well, changing head losses with meter position can cause changes in flow into the well that are not related directly to the K distribution. Such flow changes, or redistribution, can cause errors in the calculation of the K profile.Numerical simulations, based on measured head losses, indicate that bypass flow in gravel packed systems increases with increasing flow rate through the meter, increasing gravel pack conductivity, and increasing gravel pack thickness. Ideally, the EBF should not be used in gravel packed wells, due to the occurrence of bypass flow.Investigations into the flow redistribution phenomenon indicate that the top portion of the aquifer is where the greatest over‐estimation of K occurs. The portion of the well below the flowmeter is isolated from the observed drawdown as measured from the surface. In this region, the well experiences a reduced drawdown, which differs from the observed drawdown by an amount equal to the head loss at that meter position. Flow redistribution causes a more pronounced effect in more highly conductive mediums and may be almost negligible in mediums of low conductivity.

Experimental Investigation of the Performance of Two-Stage Evaporative Coolers

Experiments have been conducted to investigate the thermal effectiveness and the air-side pressure drop of single- and two-stage evaporative coolers. Two different configurations of the two-stage evaporative cooler have been tested. The first one uses an external cooling tower to cool the water required to precool the air in the indirect water-to-air precooler. In the second design the cooled water in the direct-contact evaporative cooler is used as the cooling medium in the air precooler. Tlie variables considered are packing thickness, mass flow rate of water to the precooler, and mass flux of water irrigating the packing. The data obtained indicate that the thermal effectiveness of the two-stage evaporative cooler with a cooling tower is high compared to that of the system without a cooling tower, which in turn is superior to that of the single-stage, direct-contact evaporative cooler. Increasing the mass flow rate of water to the air precooler improves the effectiveness of the two-stage evaporative coolers. The effectiveness of the two-stage cooler without a cooling tower dimensions uniformly with the increase in the mass flux of water irrigating the packing. The effectiveness of the single-stage and the two-stage design using a cooling tower was found to be independent of the mass flux of water flowing over the packing. For the three configurations tested, the thermal performance increases with the packing thickness, and the air-side pressure is nearly constant.

Thermal and hydraulic performance of a modified two-stage evaporative cooler

The thermal and hydraulic performance of a modified two-stage evaporative cooler is evaluated. Variables considered are the mode of operation, packing thickness, mass flow rate of the water flowing to the precooler, and the mass flux of water flowing over the packing media. The effectiveness of the system increased with the increase of the mass flow rate of water flowing to the precooler, decreasing the mass flux of water flowing to the packing, and with the increase of the packing thickness. The effectiveness of the system with structured packing was higher than that with sheathy leaf base or natural fiber packing. The air-side pressure drop per unit length in the direction of air flow was nearly constant when the structured packing was used. For the sheathy leaf and natural fiber packings, the air pressure drop increased at a uniform rate as the mass flux of water flowing over the packing increased. The air pressure drop was lowest for the setup with the structured packing.