Effect Of Various Arrangements Research Articles

Fluid flow and heat transfer characteristics of a microstructured microchannel heat sink under flow boiling condition

A microchannel heat sink (MCHS) is known as a heat dissipation device from the miniaturized electronic components and devices due to its capability to dissipate high heat flux from smaller surface area. However, the higher pressure drop and the uneven heat removal along the channel length are the noticeable disadvantages of MCHS. Though there are attempts to address these shortcomings, no existing study has been found to study the effect of positions of microstructures (micro-pin fin and blind holes) and combined effect of micro-pin fins and blind holes under flow boiling condition. Therefore, in the present study, an attempt has been made to logically explain the effect of various arrangements and positions of pin fins and blind holes in the selected twenty-four uniformly distributed stations on the thermohydraulic performance of MCHS through numerically predicted results. The objectives of the study have been attained using the following three analyses, flow boiling, (i) with saturated fluid inlet conditions (inlet Re = 500), (ii) with different inlet subcooling (20, 40, and 60 °C), and (iii) with different heat flux conditions (100, 150, 200 and 250 W/cm2). From the study, it is observed that the pin fin enhances heat transfer in single-phase flow and delays the phase change by disturbing the flow. The blind holes act as nucleation sites and help phase change heat transfer. It is also observed that the ratio of single-phase and two-phase length and arrangement of microstructures in these two regions predominately dominate the heat transfer and fluid flow characteristics of the microchannel heat sink. The optimum performance (maximum heat transfer coefficient and minimum pressure drop) is achieved when twelve pin fins are placed in the upstream half and twelve blind holes are located at the downstream half of the channel. However, design improvement is possible through more computational and experimental analysis.

DESIGN OF THE POSITION OF THE BLOCKING MATERIAL IN THE WATERFLOODED HIGH-PERMEABLE INTERLAYER OF OIL RESERVOIR FOR FIVE-SPOT FLOODING SCHEME

The comparative analysis of the effectiveness of various arrangements of blocking material in a thin, high-permeable water-cut layer of an oil reservoir is presented in order to reduce unproductive injection and in- crease oil recovery. Efficiency calculation was performed using high-resolution numerical simulation in the vertical section of the typical stream tube for a five-spot waterflooding scheme. Three types of location of isolation intervals are considered for two representative ratios of the viscosity of the water and oil phases.

Numerical study on the cooling performance of various arrangements of medium-gap-medium for direct evaporative cooling systems

Medium is one of the most critical components in direct evaporative cooling systems. The current study is to investigate the effect of various arrangements of medium-gap-medium (MGM) on the performance of direct evaporative cooling systems, and to find the most practical MGM arrangement for engineering application. Different widths of medium 1 zone, gap zone and medium 2 zone are extensively studied by numerical simulation. Results indicate that: (1) the cooling efficiency and air-side pressure drop at air speed of 1.5 m·s−1 increase from 79.8% to 91.9% and from 14.30 Pa to 14.76 Pa, respectively when the width of gap zone increases from 50 mm to 300 mm; (2) the cooling efficiency and air-side pressure drop at air speed of 1.5 m·s−1 increase from 83.8% to 93.5% and from 14.42 Pa to 25.04 Pa, respectively when the width of medium 1 zone increases from 100 mm to 250 mm; (3) the cooling efficiency and air-side pressure drop at air speed of 1.5 m·s−1 increase from 84.1% to 93.9% and from 14.40 Pa to 25.05 Pa, respectively when the width of medium 2 zone increases from 50 mm to 200 mm; (4) the cooling efficiency gradually tends to its maximum when the sum width (the total width of medium 1 zone, gap zone and medium 2 zone) reaches to 350 mm. Finally, the arrangement of 150 mm medium 1 zone, 100 mm gap zone and 100 mm medium 2 zone is found to be the most practical MGM arrangement.

3D‐printing carbon nanotubes/Ti3C2Tx/chitosan composites with different arrangement structures based on ball milling for EMI shielding

AbstractConductive macroscopic MXene‐based architectures receive tremendous attention for various potential applications. In this paper, the rheology and printing suitability of MXene ink were optimized by ball milling method to ensure good structural integrity and electrical conductivity of the printing structure. Porous CNT/Ti3C2Tx/CS composites were prepared by 3D printing, and the effects of various arrangements on electromagnetic interference shielding (EMI SE) were studied in depth. Since Ti3C2Tx can produce TiO2 under the action of high‐energy ball milling, it provides more heterogeneous interfaces and dipole effects. At the same time, Ti3C2Tx and CNT are evenly dispersed and can construct a complete conductive network, which greatly enhances its conductivity loss. In collaboration with the 3D‐printed framework, it can also extend the propagation path of electromagnetic waves and enhance their multiple reflection losses. The results show that the EMI SE of the composite material can reach 26 dB in X‐band, and EMI SE can be affected by the different arrangement. This work lays a solid foundation for the construction of heterogeneous interfaces by ball milling and the free construction of EMI shielding materials by 3D printing.

Computational modeling of porous medium inside a channel with homogeneous nanofluid

In the present study, the flow field and heat transfer have been simulated numerically inside a channel. The channel is under the constant heat flux. The main objective of this research is investigating the effect of the arrangement of the porous medium in water/Al2O3 nanofluid inside the channel on the flow and heat transfer characteristics. The effect of various arrangements of porous medium with two porosities and different volume fractions of nanoparticles has been investigated in a constant cross section of the porous medium. The results are validated with other references, and excellent consistency has been seen. The results show that using the porous medium has more effect on heat transfer than using nanofluid, and the arrangement of the porous medium has a strong influence on temperature profile and heat transfer. Based on the results, using stair arrangement of porous medium with the distance of 30 cm from each other and the length of 30 cm and using nanofluid with 0.02 volume fraction of Al2O3 nanoparticles have better performance than other considered arrangements.

Experimental investigation on thermo-physical characteristics of fluid flow in circular tube enhanced with circular rings with different arrangements

This paper studies the effect of various arrangements of circular rings on thermal performance in a circular tube. A wall attached circular rings were configured with the different inner diameter to achieve flow blockage area of 30%, 40%, and 50%. These rings were fitted inside the tube to obtain the different arrangements as diverging sections, converging sections and converging-diverging sections. The effect of these various arrangements of the ring on heat transfer rate and fluid friction were studied. Parameters varied during the tests were the pitch-diameter ratio (PDR) and Reynolds number. Air with ambient temperature was used as working fluid in a test tube in which inner wall is maintained at uniform heat flux. The Reynolds number and pitch diameter ratio was varied from 6000 to 24,000 and 2 to 4 respectively. Significant enhancement in heat transfer rate up to 2.75 times that of the smooth tube was observed with these inserts along with an increase in friction loss. Also, inserts with diverging sections found effective than the inserts with converging and converging-diverging sections for a particular PDR. Insert with a diverging section with PDR 2 gives the highest overall performance factor in the range 0.94–1.17 for a tested range of Reynolds number.

Effect of Response Related Weighting Matrices on Performance of Active Control Systems for Nonlinear Frames

In this paper, the effect of various arrangements of displacement, velocity and acceleration related weighting matrices on the performance of active control systems on nonlinear frames has been studied. Different arrangements of weighting matrices and feedback combinations of the response have been considered to design the active controllers using a single actuator for reducing the response of an eight-storey bilinear hysteretic frame under white noise excitations. The nonlinear Newmark-based instantaneous optimal control algorithm has been used, where the distributed genetic algorithm (DGA) is employed to determine the proper set of weighting matrices. For each set of feedback and weighting matrices, the active control system has been designed with the optimal weights determined. Here, the objective is to minimize the maximum control force required to reduce the maximum structural drift to a value below the desired level. The numerical results of simulation show that, for the cases studied, the use of different arrangements of weighting matrices in the proposed method for the performance index of the active control law has no significant impact on the performance of the active control system. However, the type of response feedback combination included in the control law considerably affects the performance, and the controllers designed based on velocity feedback have been found to be more effective. It was also shown that for all the weight-cases, using the full feedback of response can lead to design controllers that require minimum control force to reduce the structural response with more online measurements. The robustness of the designed controllers for different weighting matrices arrangements and feedback combinations has also been tested under a number of real earthquake excitations with the results discussed.

Experimental in vivo canine model for gastric prolapse of laparoscopic adjustable gastric band system

Background The most prevalent long-term complications in patients undergoing laparoscopic adjustable gastric band (LAGB) surgery are symmetric pouch dilation and gastric prolapse (slippage). However, no published data or a reliable model are available to evaluate the actual mechanism of band slippage or how to prevent it. The objective of the present study was to construct an animal model of anterior gastric band prolapse and to use this model to evaluate the effectiveness of various arrangements of gastrogastric sutures and gastric wraps in preventing prolapse. Methods The esophagus of male mongrel dogs was accessed through the left chest, and a pressure transducer and an insufflation catheter were introduced. An AP-S Lap-Band (Allergan, Irvine, CA) filled to 10 cm 3 was placed using the pars flaccida technique. A standardized cut of meat was placed into the esophagus to simulate food impaction at a tight LAGB. After the placement of multiple different gastrogastric suture configurations, air was insufflated into the gastric pouch by way of the esophagus. Results Prolapse, identical to that seen in clinical practice, was reliably reproduced in this model by increased esophageal pressure acting on a LAGB outlet obstruction. In addition, prolapse was reproduced with all gastrogastric configurations that did not secure the anterior gastric wall to within 1.5 cm of the lesser curve. Conclusion The results of the present study support the theory that prolapse is caused by esophageal peristalsis against an occlusion at the level of the LAGB. In this canine model, gastrogastric sutures encompassing the anterior gastric wall were integral to preventing prolapse.

Measuring Circuits with Preset-Power Generators

The principles of the construction of measuring circuits containing a measuring generator of preset power are considered. A qualitative estimate of the effectiveness of various arrangements is presented.

Correlation of dynamic characteristics of a super‐tall building from full‐scale measurements and numerical analysis with various finite element models

AbstractThe Di Wang Tower located in Shenzhen has 79 storeys and is about 325 m high. Field measurements have been conducted to investigate the dynamic characteristics of the super‐tall building. In parallel with the field measurements, seven finite element models have been established to model the multi‐outrigger‐braced tall building and to analyse the effects of various arrangements of outrigger belts and vertical bracings on the dynamic characteristics and responses of the Di Wang Tower under the design wind load and earthquake action. The distributions of shear forces in vertical structural components along the building height are also presented and discussed. The results from detailed modelling of group shear walls with several types of finite elements are addressed and compared to investigate various modelling assumptions. Finally, the performance of the finite element models is evaluated by correlating the natural frequencies and mode shapes from the numerical analysis with the finite element models and the field measurements. The results generated from this study are expected to be of interest to professionals and researchers involved with the design of tall buildings. Copyright © 2004 John Wiley & Sons, Ltd.

Multiple antigen peptide: A novel approach to increase detection sensitivity of synthetic peptides in solid-phase immunoassays

We describe a novel approach to detect antibodies to synthetic peptide antigens in solid-phase radioimmunoassays, using a multiple antigen peptide (MAP) system. The MAPs consist of multiple copies of peptides that are synthesized as single units on a branching lysyl matrix using a solid-phase peptide synthesis method. The efficacy of the MAP approach in solid-phase immunoassays was compared with the conventional approach using a monomeric peptide of the immunodominant epitope of the circumsporozoite proteins of two species of malaria. Two monomeric peptides with 12 and 17 residues were found to bind poorly to plastic surfaces at a concentration up to 30 μg/ml, and showed no immunoreactivity to specific polyclonal or monoclonal antibodies, while the corresponding MAP-containing peptides showed excellent binding capacity and immunoreactivity at a concentration of 0.11 μg/ml. The immunoreactivity of MAP-containing peptides was also superior to that of monomeric peptides conjugated to a protein carrier. The effects of various arrangements of lysyl branching of MAP on antigenicity were also studied, and the optimal number for lysyl branching of MAP was found to be octameric. Thus, the MAP, by enhancing the coating and the avidity of synthetic peptides, provides increased sensitivity and reliability for the use of synthetic peptide to study antigen-antibody interactions on solid surfaces.

Image Formation in the Scanning Microscope

Fourier imaging in the scanning microscope is considered. It is shown that there are two geometries of the microscope, which have been designated Type 1 and Type 2. Those of Type 1 exhibit identical imaging to the conventional microscope, whereas those of Type 2 (confocal microscopes) display various differences. Imaging of a single point object, two-point resolution and response to a straight edge are also considered. The effect of various arrangements using lenses with annular pupil functions is also discussed. It is found that Type 2 microscopes have improved imaging properties over conventional microscopes and that these may be further improved by use of one or two lenses with annular pupils.

Reply to a paper by C. G. A. Harrison: "Comments on a paper by Watkins and Richardson: 'Intrusives, Extrusives and Linear Magnetic Anomalies'"

Harrison agrees with us on the following points: that extrusives exist on the sea floor; that triangular cross-sections are probably realistic for such extrusives; and that it is worthwhile to consider their magnetic effect. For example, Hamson states that formation of a dyke causes spreading: on the contrary, it is quite conceivable, or even probable, that spreading is the cause, rather than the result of dike injection. The major disagreements involve the models employed. In our original publication we were careful to point out that our computations were for what we considered to be a probable net configuration of some extrusives on some parts of the ocean floor. These models were based on speculations and bathymetric data by several authors. By no means was the possibility of other configurations excluded. To do so would be (to say the least) a claim to substantial intuitive powers. Harrison negates our conclusions, however, completely on the basis of an inferred universal applicability of his model, thus rejecting all other alternatives. Such confidence, while impressive, is in our opinion somewhat unrealistic. Our model deliberately employed a minimum of artistic liberties, whereas Hamson invokes a relatively complex (though elegant) configuration. As he emphasizes, the models have constant upper and lower surfaces, and normal polarity fraction, and our model does not. (We find ourselves unhappy at the use of flat upper surfaces for detailed analyses, however reasonable such a practice may be for large scale conventional crustal spreading analyses) . This is quite true. But why should our models suffer these limitations, which Hamson believes are obvious? Nature has not provided these restrictions, so we do not understand why Harrison should, particularly when we were not attempting to explain the magnetic effect of all extrusive configurations. We were clearly not considering the magnetic effects of various arrangements of a fixed volume of material, but rather the effect of extrusive accumulations of different volumes, but similar shapes. It is a fact that the extrusives in our models produce a sharpening of the surface magnetic anomaly, relative to that due to a dike alone, provided the widths do not exceed one ocean depth. Harrison’s extrusives do not produce this effect. We do not believe that our point is invalidated because Harrison has a different model, unless he has evidence to show that his models are realistic and ours are not. While we find the geometry of Hamson’s models attractive, we cannot readily accept the detailed extrusiveintrusive relationships, particularly in his model 3. Hamson emphasizes that it is impossible to describe the sharpness of the magnetic anomaly produced by a group of extrusives and intrusives, by examining the anomaly produced by one. In our original paper, we clearly stated that ‘ The body could of course be composed of a series of smaller units. This would be likely to be the case, as

The detection and damping of overhead-line conductor vibration

Overhead-transmission-line conductors are peculiarly prone to aeolian vibration generated by eddy vortices formed as the wind passes across the conductor. Unless steps are taken to reduce this vibration, failure of the conductor by fatigue wear at the clamp may occur after a few years' service.The various methods of detecting vibration are reviewed. These include vibrating-mass recorders, directly-coupled pen recorders, electromagnetic transducers, resistance and piezo-electric strain gauges, and piezo-electric accelerometers. The dampers described include:(a) Tuned dampers: pneumatic, hydraulic, spring and suspended-weight (Stockbridge) types.(b) Impact dampers: vibrating-pad, vibrating-lever, plastic-tube and plastic-spiral types.(c) Reinforcing devices: armour rods, festoons, cable absorbers, tape and springs.(d) Special conductors.Details are given of experimental work performed on 33, 132, and 275/380kV lines to detect and damp vibration. For convenience, vibrating-mass recorders were used. The damping efficiencies of several types of damper are given, the vibration of twin-conductor bundles is compared with that of single similar conductors, and the vibration characteristics of special steel-cored-aluminium conductors are examined. Data are also given on the effectiveness of various arrangements of dampers fitted to the very long spans across the Rivers Usk and Severn, and a method is suggested for damping such long spans with multiple Stockbridge dampers.