Effect Of Channel Size Research Articles

Controlling the pore size of carbonate apatite honeycomb scaffolds enhances orientation and strength of regenerated bone

To restore functions of long bones and avoid reconstruction failure, segmental defects should be quickly repaired using abundant amounts of regenerated bone with high mechanical strength and orientation along the bone axis. Although both bone volume and bone matrix orientation are important for faster restoration of long bones with segmental defects, researchers have primarily focused on the former. Artificial bone scaffolds with uniaxial channels, (e.g., honeycomb (HC) scaffolds), are considered adequate for regenerating bone oriented along the bone axis. The channel size may affect the orientation, amount, and strength of the regenerated bone. In this study, we investigated the effects of channel size in carbonate apatite HC scaffolds on the orientation of bones regenerated in segmental bone defects and determined the adequate channel size. Carbonate apatite HC scaffolds, with different channel sizes (350, 550, 730, and 890 μm in length on the side of the square aperture), were fabricated by extrusion molding of a mixture of calcium carbonate and organic binder, debinding, and subsequent phosphatization to convert the composition from calcium carbonate to carbonate apatite. No significant difference in the amounts of regenerated bones was observed for different channel sizes. However, bone along the bone axis was formed in the channels ≤550 μm in size but not in channels ≥730 μm. The HC scaffolds with a channel size of 350 μm regenerated bone with higher bending strength than those with a channel size of 890 μm. However, bone regenerated with the HC scaffolds having channel sizes of 350, 550, and 730 μm showed equal bending strength. Thus, the adequate channel size for fast regeneration of high-strength bone, oriented to the bone axis, is ≤730 μm. To the best of our knowledge, this is the first study to report the effect of channel size on bone orientation and strength. The findings of this study are relevant to the fast repair of segmental bone defects.

Thermal and Structural Analysis of A Vascular Cooled Composite Radome

To increase the efficiency of aircraft radome structures, the potential to integrate structural, cooling, and electromagnetic (EM) transmission functions into a composite radome is being investigated. The radome configuration includes micro-channels, used for flow of cooling fluids, and embedded copper layers, used to alter the EM transmission characteristics, incorporated into a composite panel. Concepts have been developed using low dielectric loss composite for manufacturing the multilayer structure required to incorporate these multifunctional characteristics. Structural analyses and conjugate heat transfer analyses have been performed to assess the effects of channel size and position on load-carrying capability and cooling capability. Results from the analyses have been used to identify candidate configurations that will be fabricated. Fabrication concepts and results of the structural and thermal analyses are presented.

Unraveling the influence of channel size and shape in 3D printed ceramic scaffolds on osteogenesis

Bone has the capacity to regenerate itself for relatively small defects; however, this regenerative capacity is diminished in critical-size bone defects. The development of synthetic materials has risen as a distinct strategy to address this challenge. Effective synthetic materials to have emerged in recent years are bioceramic implants, which are biocompatible and highly bioactive. Yet nothing suitable for the repair of large bone defects has made the transition from laboratory to clinic. The clinical success of bioceramics has been shown to depend not only on the scaffold's intrinsic material properties but also on its internal porous geometry. This study aimed to systematically explore the implications of varying channel size, shape, and curvature in tissue scaffolds on in vivo bone regeneration outcomes. 3D printed bioceramic scaffolds with varying channel sizes (0.3 mm to 1.5 mm), shapes (circular vs rectangular), and curvatures (concave vs convex) were implanted in rabbit femoral defects for 8 weeks, followed by histological evaluation. We demonstrated that circular channel sizes of around 0.9 mm diameter significantly enhanced bone formation, compared to channel with diameters of 0.3 mm and 1.5 mm. Interestingly, varying channel shapes (rectangular vs circular) had no significant effect on the volume of newly formed bone. Furthermore, the present study systematically demonstrated the beneficial effect of concave surfaces on bone tissue growth in vivo, reinforcing previous in silico and in vitro findings. This study demonstrates that optimizing architectural configurations within ceramic scaffolds is crucial in enhancing bone regeneration outcomes. Statement of significanceDespite the explosion of work on developing synthetic scaffolds to repair bone defects, the amount of new bone formed by scaffolds in vivo remains suboptimal. Recent studies have illuminated the pivotal role of scaffolds’ internal architecture in osteogenesis. However, these investigations have mostly remained confined to in silico and in vitro experiments. Among the in vivo studies conducted, there has been a lack of systematic analysis of individual architectural features. Herein, we utilized bioceramic 3D printing to conduct a systematic exploration of the effects of channel size, shape, and curvature on bone formation in vivo. Our results demonstrate the significant influence of channel size and curvature on in vivo outcomes. These findings provide invaluable insights into the design of more effective bone scaffolds.

Effect of channel size on the performance of a PCHE-based supercritical [formula omitted] thermoacoustic engine

Thermoacoustic engine is a promising energy conversion device. Recently, supercritical CO2 has been successfully employed as the working fluid in a standing-wave thermoacoustic engine operating under transcritical temperature conditions. The core components of the device are integrated as a printed circuit heat exchanger (PCHE), where the CO2 channel size plays a vital role in the performance of the device. In the present work, guided by approaching two to four times thermal penetration depth, a PCHE module with improved channel size is designed, fabricated, and tested. Results suggest improvements are achieved in pressure amplitude Δp (the highest record increases from 0.419 to 0.455 MPa) and onset temperature difference (the lowest record drops from 14.8 to 11.2 °C), which are attributed to the enhanced thermally-driven expansion and contraction during one oscillation period. This paper shows that the average thermal penetration depth is a notable variable generally positively correlated to the applied temperature difference. By studying the transition and saturation in operation mode observed in the experiments, it is revealed that three to four times the average thermal penetration depth is the best interval for the CO2 channel size. Beyond this interval, the power law relation between dimensionless pressure amplitude and the temperature difference holds. Below this interval, the saturation becomes so strong that the growth of pressure amplitude with temperature difference decelerates significantly.

Scale and shear investigation of the viability and consequences of controlling viscous heating for Argon flows in nano-channels

Molecular dynamics (MD) is used to investigate the combined effects of channel size and wall shear stress on force-driven Argon flows in nanochannels. The adaptive wall thermostat (AWT) is used to automatically adjust wall temperature refraining the viscous heating upsurge with the increased body force from increasing mean fluid temperature. AWT is functional up to “wall shear stress limit” (WSSL), classifying wall shear stress range into controllable and uncontrollable viscous heating ranges (CVH and UVH) before and beyond WSSL, respectively. With increasing wall shear stress in CVH, liquid Argon at ∼119.9 K exhibits more non-uniform temperature profile in larger channels. Consequently, further shear dependence of density profile and fluid molecular layering which leads to controversial size-dependent slip length. Within UVH, supercritical Argon emerges from the significant increase of temperature and pressure exceeding critical state; consequently, density profile and molecular layering decrease noticeably drifting toward walls which results in minor and proximate values of slip length in all channels approaching no-slip condition. The apparent viscosity is higher in larger channels with decreasing and increasing trends within CVH and UVH, respectively, associated with changing fluid state and phase. Finally, the continuum solution suggests the possibility of estimating the mass flow rate with reasonable accuracy relative to MD if implemented with appropriate properties and slip boundary condition.

Effect of Channel Size on Air-Cooling Performance in Interior Permanent Magnet Motor Driving Aviation Fans at High Altitude

Abstract To enhance worldwide environmental conditions, the air transport industry must drastically reduce carbon dioxide emissions. Electrification of aircraft propulsion systems is one way to meet this demand. In particular, the focus is on obtaining single-aisle aircraft with partial turbo-electric propulsion and approximately 150 passenger seats by the 2030s. To develop a single-aisle aircraft with partial turbo-electric propulsion, an air-cooled interior permanent magnet (IPM) motor with an output of 2 MW is desired. One of the most difficult problems in air cooling is that air-cooling performance decreases with increasing altitude because the air density decreases. To investigate the effect of altitude on air-cooling performance in the IPM motor, the authors formulated mathematical system equations to describe heat transfer inside the target air-cooled IPM motor, and mathematical analytical solutions were obtained. The most severe condition is the top-of-climb condition. For this condition, a designer should choose cooling air mass flow rates that keep the temperature of the permanent magnets below the maximum temperature limit of 100 °C and the temperature of the coils below the maximum temperature limit of 250 °C. Here, the sizes of the air-cooling channels strongly affect air cooling with the IPM motor. In this paper, the authors briefly review the mathematical formulations and their solutions, investigate the effect of channel size on air-cooling performance in an IPM motor, and explore the optimum configuration and settings for the air cooling channels.

Effects of channel size, wall wettability, and electric field strength on ion removal from water in nanochannels

Molecular dynamics simulations are employed to estimate the effect of nanopore size, wall wettability, and the external field strength on successful ion removal from water solutions. It is demonstrated that the presence of ions, along with the additive effect of an external electric field, constitute a multivariate environment that affect fluidic interactions and facilitate, or block, ion drift to the walls. The potential energy is calculated across every channel case investigated, indicating possible ion localization, while electric field lines are presented, to reveal ion routing throughout the channel. The electric field strength is the dominant ion separation factor, while wall wettability strength, which characterizes if the walls are hydrophobic or hydrophilic has not been found to affect ion movement significantly at the scale studied here. Moreover, the diffusion coefficient values along the three dimensions are reported. Diffusion coefficients have shown a decreasing tendency as the external electric field increases, and do not seem to be affected by the degree of wall wettability at the scale investigated here.

Design optimization and experimental investigation of CPU heat sink cooled by alumina-water nanofluid

In this study, an experimental evaluation on the use of Al2O3 nanoparticles in a circular structure of minichannel heat sink is conducted for heat dissipation from electronic components such as Central Processing Unit (CPU). The experiments are prepared for various hydraulic diameter of channels and different values of coolant flow rates. After a hydro-thermal analysis on the obtained data, as a main outcome, findings indicate that decreasing the channel diameter and increasing the flow rate of Al2O3-water as working fluid are the most effective approaches to improve the cooling performance of heat sinks. An optimization study using Response Surface Methodology (RSM) based on Central Composite Design (CCD) is performed due to complex effect of channel size, nanofluid volume flow rates and channel numbers on pressure drop and heat transfer to reach the best operating design.

Modeling and Analysis of Heat Dissipation for Liquid Cooling Lithium-Ion Batteries

To ensure optimum working conditions for lithium-ion batteries, a numerical study is carried out for three-dimensional temperature distribution of a battery liquid cooling system in this work. The effect of channel size and inlet boundary conditions are evaluated on the temperature field of the battery modules. Based on the thermal behavior of discharging battery obtained experimental measurements, two temperature control strategies are proposed and studied. The results show that the channel width of the cooling plates has a great influence on the maximum temperature in the battery module. It is also revealed that increasing inlet water flow rate can significantly improve the heat transfer capacity of the battery thermal management system, while the relationship between them is not proportional. Lowering the inlet temperature can reduce the maximum temperature predicted in the battery module significantly. However, this will also lead to additional energy consumed by the cooling system. It is also found that the Scheme 5 among various temperature control strategies can ensure the battery pack working in the best temperature range in different depths of discharge. Compared with the traditional one with a given flow rate, the parasitic energy consumption in Scheme 5 can be reduced by around 80%.

Ceramic microchannel reactors with channel sizes less than 100 μm prepared by a mesh-assisted phase-inversion process

Microchannel reactors show fast mass transfer and heat transfer while limited active surface area, which can be greatly increased by reducing channel sizes. However, conventional extrusion makes honeycomb ceramics with channel sizes above 100 μm. This study has prepared ceramic microchannel reactors with channel sizes in the range of 1–100 μm by a one-step phase-inversion process, and channels are formed through the convection between coagulant and solvent. The effect of channel size on reaction performance was investigated by comparing two reactors with different channel sizes in dry reforming of methane. In addition, the microstructure of the reactors can be further tuned via sintering temperature to achieve high catalytic performance owing to the balanced active surface and mass transfer. Therefore, the microchannel reactors developed in this study represent a diagram-shift in the preparation of microchannel reactors by making channels with sizes less than 100 μm, which has potential applications in many catalytic reactions.

Thermo-osmosis in hydrophilic nanochannels: mechanism and size effect.

Understanding thermo-osmosis in nanoscale channels and pores is essential for both theoretical advances of thermally induced mass flow and a wide range of emerging industrial applications. We present a new mechanistic understanding and quantification of thermo-osmosis at nanometric/sub-nanometric length scales and link the outcomes with the non-equilibrium thermodynamics of the phenomenon. The work is focused on thermo-osmosis of water in quartz slit nanochannels, which is analysed by molecular dynamics (MD) simulations of mechano-caloric and thermo-osmotic systems. We investigate the applicability of Onsager reciprocal relation, irreversible thermodynamics, and continuum fluid mechanics at the nanoscale. Further, we analyse the effects of channel size on the thermo-osmosis coefficient, and show, for the first time, that these arise from specific liquid structures dictated by the channel size. The mechanical conditions of the interfacial water under different temperatures are quantified using a continuum approach (pressure tensor distribution) and a discrete approach (body force per molecule) to elucidate the underlying mechanism of thermo-osmosis. The results show that the fluid molecules located in the boundary layers adjacent to the solid surfaces experience a driving force which generates the thermo-osmotic flow. While the findings provide a fundamental understanding of thermo-osmosis, the methods developed provide a route for analysis of the entire class of coupled heat and mass transport phenomena in nanoscale structures.

Single event upset for monolithic 3-D integrated 6T SRAM based on a 22 nm FD-SOI technology: Effects of channel size and temperature

The single event upset (SEU) for monolithic 3-D (M3D) 6T SRAM with different channel sizes was investigated based on a 22 nm fully-depleted silicon-on-insulator (FD-SOI) technology over a temperature range from 210 K to 390 K. Compared with planar SRAM, M3D SRAM exhibits higher SEU sensitivity and increasing the transistor size does not work in mitigating the SEU in M3D. It is also demonstrated that the SEU sensitivity of M3D 6T SRAM enhances with temperature rising after the incident of 127I while it decreases after the striking of 209Bi. The reason can primarily be explained by the different influence ranges of striking heavy ions, which affect the ionized charge transport.

Effect of channel size and shape on condensation heat transfer of refrigerants HFO-1234yf and HFC-134a in rectangular microchannels

Refrigerant HFO-1234yf has similar properties to HFC-134a but much lower GWP value. It is possible to replace HFC-134a by directly drop into the air-condition systems and expected to be an appropriate replacement for these systems. Microchannel heat exchangers have been commonly used in the vehicle air-condition systems attributed to their less weight and low air side pressure drops. However, there is no experimental study on condensation heat transfer performance of HFO-1234yf in microchannel with hydraulic diameter lower than 1 mm. This study provides an experimental comparison on condensation heat transfer and pressure drops of refrigerants HFO-1234yf and HFC-134a in multiport microchannels. The experimental results show that the effect of surface tension drainage force is important on condensation heat transfer in square channels especially for very small channels. The surface tension drainage force pulled the condensate to the corner of the square microchannels. This caused a very thin liquid film left on the tube wall and liquid conductivity became the major controlling property on the condensation heat transfer. Since the liquid conductivity of HFO-1234yf is 27% less than that of HFC-134a, the condensation heat transfer coefficients of HFO-1234yf are 15% to 23% lower than those of HFC-134a at various mass velocities and vapor qualities. The surface tension drainage force is in the direction of normal to the liquid and vapor flow. The experimental two-phase pressure drops are not affected by surface tension force and can be predicted reasonably well by using conventional correlations.

Experimental and numerical investigations of cold-formed austenitic stainless steel unlipped channels under bearing loads

While mechanical properties and material stress-strain response of different families of stainless steel (known as austenitic, duplex and ferritic) are different from each other, current cold-formed stainless steel standards do not generally take into account these differences as they provide single equations for any loading scenario to cover all groups of stainless steel. This may lead to inaccurate results, especially for austenitic steel which is a high performance material increasingly used in modern construction, due to its higher ductility and ultimate-to-yield strength ratio. This research aims to investigate the web bearing performance of cold-formed steel channels fabricated with austenitic stainless steels subject to concentrated transverse forces experimentally and numerically. The experimental programme consists of 16 thick unlipped channel specimens with different internal fillet radius and web depth to thickness ratios. For the numerical investigations, 88 detailed nonlinear quasi-static finite element models are used and validated against experimental data. Complementary parametric investigations are then conducted to ascertain the web bearing strengths in terms of various channel sizes, web thicknesses and internal fillet radius. It is found that the equations proposed by current stainless steel standards are unreliable for austenitic steel as they can lead to significantly un-conservative results (up to 43%) under both one- and two-flange loading scenarios. Other equations suggested in the literature for ferritic stainless steel are also shown to provide overestimated results (up to 34%) for austenitic steel channel sections. Based on the experimental and analytical results from this study, new equations are proposed to estimate the web bearing strength of cold-formed austenitic stainless steel channels and their reliability is demonstrated. • Performance of austenitic stainless steel channels subject to bearing loads is investigated. • 16 thick unlipped channels are tested under one- and two-flange loading scenarios. • 88 validated FE models are developed to assess the effects of channel size, web thickness and internal fillet radius. • Current design equations up to 43% overestimate the web bearing strength of austenitic stainless steel channels. • New design equations are proposed and their reliability is demonstrated under IOF, EOF, ITF and ETF loading scenarios.

Numerical study of heat and mass transfer by reverse water-gas shift reaction in catalyst-coated microchannel reactor

Reverse water-shift reaction (RWGS) is well known as an endothermic reaction to convert carbon dioxide and hydrogen to carbon monoxide and water vapor at an elevated temperature above 600 °C and also considered as a syngas production process before Fischer-Tropsch (FT) synthesis in generating the synthesis of liquid fuels. Unlike the conventional reactor types, micro-structured reactor has various advantages such as enhanced heat and mass transfer, flow uniformity, higher surface-to-volume ratio, safe processing and easier scale-up. In particular, this paper aims to invesitgate the conversion performance of RWGS reaction in catalyst-coated microchannel reactor whose inside surface is coated with Ni-catalyst by utilizing CFD simulations including chemical kinetics. The analytical model is developed to describe heat and mass transfer with chemical reaction in catalyst-coated microchannel. The effect of channel size, gas velocity, operating temperature, inlet gas composition (molar ratio of H2/CO2) and catalytic area ratio is evaluated by displaying CO2 conversion, temperature distribution, heat transfer, and reaction rate.

Characterization of optical diffraction by single nanochannel for aL–fL sample detection in nanofluidics

Nanofluidics which integrates analytical systems in 101–103 nm space provides ultra-sensitive analyses at a single-cell and single-molecule level. One of the key technologies for nanofluidics is the ultra-sensitive detection method; however, the ultra-small volume at aL–fL scale makes it challenging. Recently, we have developed a non-fluorescent molecule detection method for nanofluidics called photo-thermal optical diffraction (POD) which utilizes the photo-thermal effect of target molecules and optical diffraction by a single nanochannel. To improve the performance of such diffraction-based detection methods, the design and optimization of optical diffraction are essential. However, it is unknown whether the optical diffraction by a single nanochannel follows general diffraction theory because liquid properties change in the ultra-small space. In this study, we elucidated optical diffraction by a single nanochannel from theoretical calculations and experiments. Our experiments revealed the effect of channel size, channel position, and solvents in the nanochannel, which showed good agreement with proposed theoretical calculations. We also revealed no or little change of refractive index of water in the nanochannel compared with that in the bulk. Finally, we confirmed that the POD signal was proportional to the diffracted light intensity, and the calculated limit of detection of POD was 7.0 × 10–7 RIU in a detection volume of 0.23 fL. Our theoretical calculations and experimental results can be widely applied to the design and optimization of detection methods using optical diffraction by nanochannels and nanostructures.

Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

Acoustic cavitation and ultrasound-assisted nitration process in ultrasonic microreactors: The effects of channel dimension, solvent properties and temperature

Experimental studies on acoustic cavitation and ultrasound-assisted nitration reaction were systematically investigated in two laboratory-built ultrasonic microreactors by tuning the microchannel dimension, solvent properties and temperature. Under ultrasound irradiation, acoustic cavitation microbubbles were generated and underwent violent oscillation in microchannel. With the decrease of channel size, acoustic cavitation was largely confined, and channel size 1 × 1 mm2 was recognized as the critical size to eliminate the confinement effect. Acoustic cavitation was also highly dependent on the properties of sonicated liquids. The onset of surface wave oscillation on gas bubble was obviously promoted with decreasing solvent viscosity and surface tension. Additionally, ultrasound-assisted nitration process of toluene was studied in a temperature-controlled ultrasonic microreactor. The effects of channel size as well as liquid properties on ultrasound intensification agreed well with the finding in cavitation research. Under ultrasound power 50 W, toluene conversion was enhanced by 9.9%–36.3% utilizing 50 vol.% ethylene glycol aqueous solution as ultrasound propagation medium, exhibiting ultrasound applicability on intensifying fast reaction processes in microreactors.

A FFT-based numerical implementation of mesoscale field dislocation mechanics: Application to two-phase laminates

In this paper, we present an enhanced crystal plasticity elasto-viscoplastic fast Fourier transform (EVPFFT) formulation coupled with a phenomenological Mesoscale Field Dislocation Mechanics (MFDM) theory here named MFDM-EVPFFT formulation. In contrast with classic CP-EVPFFT, the model is able to tackle plastic flow and hardening due to polar dislocation density distributions or geometrically necessary dislocations (GNDs) in addition to statistically stored dislocations (SSDs). The model also considers GND mobility through a GND density evolution law numerically solved with a recently developed filtered spectral approach, which is here coupled with stress equilibrium. The discrete Fourier transform method combined with finite differences is applied to solve both lattice incompatibility and Lippmann-Schwinger equations in an augmented Lagrangian numerical scheme. Numerical results are presented for two-phase laminate composites with plastic channels and elastic second phase. It is shown that both GND densities and slip constraint at phase boundaries influence the overall and local hardening behavior. In contrast with the CP-EVPFFT formulation, a channel size effect is predicted on the shear flow stress with the present MFDM-EVPFFT formulation. The size effect originates from the progressive formation of continuous screw GND pile-ups from phase boundaries to the channel center. The effect of GND mean free path on local and global responses is also examined for the two-phase composite.

On the Thermal and Pressure Characteristics of Sport Compression Garments

In this study, various knitted fabric structures were designed to help preventing muscular difficulties in sports. The samples, containing channels in widthwise direction, were produced by jacquard knitting technique. The effects of channel size and quilted inlay design were investigated in terms of pressure behaviour, thermal and water vapour resistance. Increasing of channel size and adding inlay yarns provided higher thermal resistance, as well as an increase in water vapour resistance, they also significantly affected pressure characteristics of samples.