Rectangle Channel Research Articles

Case study on thermal management of planar elements with various polymeric heat exchangers: experiment and simulation

A reliable battery thermal management system (BTMS) is essential to ensure proper performance, a long life span and high electric vehicle safety. The primary objective of BTMS is to maintain the cells’ temperature in the range of 15–35 °C while limiting the temperature spread between cells to below 5 °C. Active thermal management with polymeric hollow fibers (PHFs) has been reported in a few articles, but its tremendous flexibility is mainly advantageous for cylindrical cells. Extruded polymeric cold plate heat exchangers with rounded rectangle channels (RRCs) are proposed as a more elegant solution for planar batteries. Heat exchangers using PHFs and RRCs were experimentally compared, with a strong focus on minimizing the maximum temperature and temperature spread of the experimental setup while simultaneously achieving minimal pressure drops. The system behavior with different parameters, including materials, geometry and thermophysical properties, was further studied using properly validated CFD models.

Syntheses, crystal structures, and fluorescence properties of two new copper phosphonates from hydroxy-functionalized bisphosphonic acid ligand

Exploring metal phosphonates with new crystal structures is of significance for the development of metal-organic frameworks (MOFs). In this work, two new copper phosphonates, [tetraauqa-1,4-phenylenebis(hydroxymethylene))bisphosphonate biscopper(II)] bishydrate [Cu2(H2L)(H2O)4]·2H2O (1) and 1,4-phenylenebis(hydroxymethylene))bisphosphonate-(4,4’-bipy) copper(II) [Cu(H4L)(4,4’-bipy)] (2) (4,4’-bipy = 4,4’-bipyridine), have been synthesized from a hydroxy functionalized bisphosphonate ligand, H6L = (1,4-phenylenebis(hydroxymethylene))bis(phosphonic acid). The introduction of a hydroxy group can regulate the crystal structures. The bisphosphonate ligand in 1 is hexadentate, binding six copper ions with its six phosphonate oxygen atoms and two hydroxy oxygen atoms, forming a three-dimensional framework structure with rectangle channels running along the b-direction. For 2, the bisphosphonate ligands are double deprotonated and chelate or bridge two copper ions, showing a two-dimensional layered crystal structure. These compounds have interesting fluorescence properties with emission maxima (307 and 410 nm) lying in the blue region.

A mathematical model for predicting crystallization fouling in narrow rectangle channel incorporating crystal growth effect

Crystallization fouling is an ongoing concern for many heat transfer systems, and simulating fouling formation under various flow and heat transfer conditions is crucial for predicting fouling resistance and improving energy efficiency. This paper proposes a mesoscopic model for predicting crystallization fouling in narrow rectangle channels accounting for the realistic crystal growth. A hybrid lattice Boltzmann and finite difference model is established to predict the coupled process of fluid flow, heat transfer, concentration diffusion and crystallization fouling. The second-order mass deposition rate is solved and transformed to the surface-reaction boundary condition in lattice Boltzmann (LB) scheme, and the volume of pixel (VOP) method is employed to simulate the dynamic crystal growth. The scheme and the sub-models are verified systematically by the analytical solution of a linear diffusion-reaction problem, the semi-theoretical fouling models, and the experimental data. The results indicate that the present model can effectively predict the crystallization fouling controlled by either surface integration or mass transfer, and show its capability to simulate the non-uniform fouling growth process in heat transfer channels, providing insight towards full understanding and mitigation design of crystallization fouling.

Effects of geometrical confinement on the generation of droplets at microfluidics T-junctions with rectangle channels

Effects of geometrical confinement on the generation of droplets at microfluidics T-junctions with rectangle channels

Three coordination networks of Cd(II) with 2-hydroxy-trimesic acid and their photoluminescence properties

With a rigid carboxylic acid ligand, 2-hydroxy-trimesic acid (H4L), coordination polymers {[Cd3(L)2(H2O)6]·4H2O}n (1), [Cd2(H2L)2(pdp)0.5(µ-H2O)]n(2) azobispridine (pdp) and [Cd(4,4ʹ-bipy)2(H2O)2]n·[H2L]n (3) 4,4’-bipyridine (4,4’-bipy) were synthesized. Compound 1 is a three-dimensional network of linear trinuclear clusters [Cd3(μ2-COO)2(μ1-COO)2]. Compound 2 can be simplified as a 3.12-connected 3-nodal net with a new topological point symbol of {4.52}4{416.516.626.88}. Compound 3 features a two-dimensional grid cationic architecture with rectangle channels encapsulating [H2L]2− anions. The powder X-ray diffraction, the thermal stabilities, and solid-state luminescence properties were studied for 1–3. Furthermore, compound 1 shows high selectivity and sensitivity for detecting both NB and Fe3+.

CFD Analysis of Various Design Aspects in Baffle Tube Heat Exchanger

To improve temperature difference, a computer simulation assessment for a rectangular duct with right angle confounds heat exchanger with small displacements and bewilder height was carried out. A total of 10 There were three separate two half Autocad models of rectangular shaped channel with bewilders spacing of 40 milimetre, 80 milimetre, and 120 milimetre and baffle heights of 10 mm, 12.5 milimetre, and 15 milimetre developed. The major goal of this study is to run computer simulations to see how Cu water nanoparticle affect the architecture and thermally hydrodynamic characteristics of a rectangular duct with baffles exchanger. The bottom walls of the canal, as well as the baffles, are regarded isothermal zones, whereas the sidewalls are termed regular zones. This approach employs a second derivative upwind mass and energy equation. The baffle pitch and height have a significant influence on the temperature distribution from the rectangle shaped channel heating element, with a maximal temperature fluctuations of 9.831oC and a maximum heat transfer of 6.571 KW for baffle spacing 40 mm and height 15 mm for rectangle channel without opposite baffles. In comparison to the base design of rectangle shaped channels exchanger, the temperature difference increases nearly 1.5 times as even the width is decreased.

Analysis of Aspect Ratio in a Miniature Rectangle Channel for Low Frictional Resistance.

We conducted a theoretical investigation of the cross-sectional aspect ratio of a rectangular channel to have sufficiently low frictional resistance under less than 150 of the Reynolds number. From the theoretical consideration, it was clarified that 3.40 or more is recommended as a criterion for determining the aspect ratio. This addresses the problem of determining the interval of rectangle channels, installed in a plate reactor. There is a concern that the real system does not follow the analytical solution, assuming laminar flow, since the higher aspect ratio leads to disturbances of the flow such as the emergence of vortices. However, in the channel’s volume range of (W × H × L) = (7.0 mm × 0.38 mm × 0.26 m), such a turbulence was not observed in the detailed numerical calculation by CFD, where both calculation results were in agreement to within 3% accuracy. Moreover, even in an experimental system with a surface roughness of ca. 7%, friction resistance took agreement within an accuracy of ±30%.

Numerically investigating two-phase reactive transport in multiple gas channels of proton exchange membrane fuel cells

Understanding the coupled mechanisms between two-phase flow and reactive transport in proton exchange membrane fuel cells is important for improving cell performance. In this study, a one-dimensional + three-dimensional model is developed to simulate the air–water two-phase flow, mass transport and electrochemical reaction in the cathode side of proton exchange membrane fuel cells. Dynamic water behaviors affected by several forces in three channels are well captured by the volume of fluid method. Effects of liquid water behaviors on pressure drop, mass flow rate, oxygen concentration distribution, current density and especially the distribution characteristics among different channels are discussed. It is found that the current density increases under certain flow patterns such as droplet detachment and water film on the top wall. Compared with single-phase flow, the two-phase flow magnifies the flow maldistribution in different channels, and such maldistribution in turn leads to different water detachment sequence in the three channels. The change of the mass flow rate in the second channel is more sensitive to that in the third channel. Effects of the gas channel wall wettability and channel structures are also investigated. The results show that changing the gas channel as hydrophobic will lead to higher pressure drop, lower current density and poorer flow distribution among different channels, which thus is not desirable in application. Modified structures of rectangle channel and tapered channel are finally explored. Compared with the base case, the tapered channel results in increased flow uniformity and averaged current density by 65.9% and 1.5%, respectively.

Experimental research and model development on interfacial drag in rectangle channel bubbly and slug flow

As one of the most important constitutive models, interfacial drag determines the phase distribution directly and impose significant influences on pressure drop and heat transfer. Due to the limited study on interfacial drag for rectangle channel, experimental research and model development were performed in this paper. The air-water flow experiments in rectangular channels were carried out to obtain local parameters such as void fraction, interfacial area concentration and bubble chord length. These parameters were all characterized with core peak distribution except for the situations of void fraction at lower gas velocity and interfacial area concentration at higher gas velocity. The development of interfacial drag model in bubbly and slug flow was proposed based on the experimental data. The drag coefficient and interfacial area concentration in bubbly and slug flow were modified for distorted bubble, Taylor bubble and liquid slug respectively. Further validation was performed with system analysis codes. Better prediction of interfacial area concentration and void fraction, as well as numerical stability were obtained, proving the validity of interfacial drag model developed for rectangle channel bubbly and slug flow.

Study on Flow Boiling Characteristics in Rectangle Channel After Formation of Blisters

Plate-type fuel elements is one of the first fuel structure choice for the novel integrated PWR, however, blisters will appear on the cladding induced by irradiation and fission. In this work CFD method was used to investigate the subcooled boiling characteristic of the water in rectangle channel with round and pillow blisters, the modified RPI model was also proposed, we can draw conclusions as follows: In the channel with round blister, as the blisters will increase the local flow resistance and more fluid will flow through center of the channel. Boiling occurred only in the area near the edges, nearly no vapor appeared at the center of the channel. The boiling region in channel with pillow shape blisters is wider and concentrated between two pillow blisters and downstream of the non-blisters side. The dry out area are both in the downstream region of blisters for the two types of channels.

Resolved CFD–DEM simulation on hydrodynamic bridging in a bend rectangle channel

Resolved CFD–DEM simulation on hydrodynamic bridging in a bend rectangle channel

Plasmonic Biosensor for Low-Index Liquid Analyte Detection Using Graphene-Assisted Photonic Crystal Fiber

We report a sensitive D-shaped photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensor with linear sensing performance and a broad detection range for low refractive index (RI) liquid analytes ranging from 1.27 to 1.37 with possible extension beyond this range. We examine three combinations of materials (silver only, graphite on silver, and graphene on silver) as plasmonic nanofilm for the PCF-SPR and demonstrate that graphene-assisted PCF has the best overall performance. We show that graphene coating of silver nanofilm improves the sensitivity and the overall figure of merit of the sensor, besides the practical benefit of protecting the silver nanofilm from surface oxidation. Furthermore, we propose two distinct ways of analyte sensing based on filling patterns where the liquid analyte can be filled internally into the top two air holes of the PCF, or externally into a rectangle channel at the top of the fiber. In the internal filling detection scheme, the graphene-assisted PCF-SPR sensor demonstrates ultra-linearity, a detection range of 0.1 refractive index unit (RIU) between 1.27 and 1.37, an average linear spectral sensitivity of 2320 nm/RIU, and a maximum amplitude sensitivity of 192 RIU−1 for 1150 nm excitation. In the external filling detection scheme, the PCF-SPR exhibits extremely large sensitivities with a maximum spectral sensitivity of 22,400 nm/RIU close to analyte RI of 1.33, and a maximum figure of merit (FOM) of 127 which is approximately five times larger than that of the similar reported PCF-SPR sensors in the literature. The combination of a broad detection range for low-index analytes, large sensitivities, design flexibility, and stability against surface oxidation renders our proposed sensor as an interesting candidate for biosensing applications in chemistry, biology, and medicine.

Structural diversity and luminescence sensing of cadmium coordination polymers derived from 5-(bis(4-carboxybenzyl)amino) isophthalic acid

Reactions of cadmium ions with the flexible tetracarboxylic ligand, 5-(bis(4-carboxybenzyl)amino) isophthalic acid (H4L) gave rise to four complexes, namely {[(Me2NH2)2Cd3(L)2]∙10H2O)}n (1), {[Cd2(L)(pdp)(H2O)2]∙2DMF·4H2O}n (pdp = 4-[(E)-4-Pyridinylazo]pyridine) (2), {[Cd2(L)(bpe)(H2O)2]∙2DMF·4H2O}n (bpe = 1,2-bi(4-pyridyl)ethene) (3) and {[Cd4(L)2(bpmp)3]∙2H2O}n (bpmp = N,Nʹ-bis-(4-pyridyl-methyl) piperazine) (4). Compound 1 features a three-dimensional anionic architecture constructed by triangular Cd3 cluster and ligands, with rectangle channels encapsulating [Me2NH2]+ cations. Compounds 2 and 3 present similar structures, exhibiting the 2D polythreading layer. Compound 4 possesses a 3D structure with 4,6-connected new topology. The powder X-ray diffraction, the thermal stabilities, and solid-state luminescence properties were studied for 1–4. Furthermore, the luminescent sensing of compounds 1 and 4 toward nitrobenzene has also been investigated.

Experimental study on boiling performance of wetting fluids in three-dimensional rectangle microchannels

A unique boiling heat transfer study of wetting fluids in a vertical three-dimensional rectangle microchannel was carried out in this paper, to develop a novel passive three-dimensional chip stack cooling technology. The base liquids were deionized water and R113, and Sodium dodecagon sulfate (SDS) was used as a surfactant, which is added into the base fluids for developing wetting fluids. The length, gap, and width of rectangle channels were in the range of 30 mm to 100 mm,30 mm to 50 mm, and 0.4 mm to 4 mm, respectively. Metal wires with different numbers were laid in the rectangle channel along the flow direction for forming change in the width of the microchannel. The study results show that using wetting fluids can significantly enhance both heat transfer coefficients and maximum heat flux of thermosyphon boiling in three-dimensional microchannels compared with that found in pure liquids. The enhanced effects have significant relations with the three-dimensional geometric dimensions. The present experimental results provide significant technology support for passive three-dimensional chip cooling.

Effect of lattice structures on heat transfer deterioration of supercritical CO2 in rectangle channels

In view of the heat transfer deterioration of supercritical CO2 under the condition of low mass flow rate and high heat flux, the influence of Body-Centred Cubic (BCC) lattice, Kagome lattice and Pin-fin structure on the heat transfer of supercritical CO2 in rectangular channels were investigated in this article. The results showed that all the three structures can generate arch-shaped vortices near the wall, which increases the wall shear stress and the fluid turbulence intensity, promotes the full mixing of the mainstream and the near-wall fluid, and weakens the heat transfer deterioration. In addition, there was obvious longitudinal vortices distributed between adjacent lattices, which increases the turbulence intensity of the mainstream, facilitates the mixing of high and low speed fluids, so as to improve the heat transfer rate of supercritical CO2 channel and reduce the heat transfer deterioration. In the vertical upward channel, the buoyancy reduces the turbulence intensity of the near-wall fluid and the shear stress of wall, and results in the heat transfer deterioration. In the horizontal channel, the buoyancy leads high-density fluid to settle, thus enhances the turbulence intensity of the fluid near the down-wall surface, and intensifies the heat transfer of the down-wall surface.

A Luminescent Mg-Metal-Organic Framework for Sustained Release of 5-Fluorouracil: Appropriate Host-Guest Interaction and Satisfied Acid-Base Resistance.

It is important to achieve a moderate sustained release rate for drug delivery, so it is critical to regulate the host-guest interactions for the rational design of a carrier. In this work, a nano-sized biocompatible metal-organic framework (MOF), Mg(H2TBAPy)(H2O)3·C4H8O2 (TDL-Mg), was constructed by employing π-conjugated 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4TBAPy) as a ligand and used for 5-fluorouracil (5-FU) loading (28.2 wt %) and sustained slow release. TDL-Mg exhibits a 3D supramolecular architecture featuring a 1D rectangle channel with a size of 6.2 × 8.1 Å2 and a Brunauer-Emmett-Teller surface area of 627 m2·g-1. Channel microenvironment analysis shows that the rigid H2TBAPy2- ligand adopts special torsion to stabilize the channels and offer rich π-binding sites; the partially deprotonated carboxyls not only participate in the formation of strong hydrogen bonds but also create a mild pH buffer environment for biological applications. Suitable host-guest interactions are generated by the synergistic effect of polydirectional hydrogen bonds, multiple π-interactions, and confined channels, which allow 5-FU@TDL-Mg to release 76% of load in 72 h, a medically reasonable rate. Microcalorimetry was used to directly quantify these host-guest interactions with a moderate enthalpy of 22.3 kJ·mol-1, which provides a distinctive thermodynamic interpretation for understanding the relationship between the MOF design and the drug release rate. Additionally, the nano-sized 5-FU@TDL-Mg can be taken up by mouse breast cancer cells (4T1 cells) for imaging based on the dramatic fluorescence change during the release of 5-FU, exhibiting potential applications in biological systems.

Влияние единичного граничного ловушечного заряда на подпороговый ток стока FinFET-транзистора с различной формой канала

The influence of the FinFET channel shape to the RTN amplitude induced by single charge trapped at interface is simulated. The transistors with both rectangle and trapeze channel cross section are considered. It is shown, single charge trapping at the channel top induce lower RTN amplitude in trapeze than in rectangle channel cross section in the subthreshold region. However, the single charge trapping at side wall of the channel induce essentially higher RTN amplitude in trapeze cross section of the channel.

A stochastic method in simulating particles transport and deposition in wall-bounded turbulent flow

Aiming at the coolant leakage monitor in the containment of a nuclear power plant, a quick numerical method of simulating radioactive aerosols transport and deposition in the near-wall region is studied in this paper. A stochastic method basing on turbulence statistics is proposed to generate anisotropic turbulent fluctuations and track particles motion separately. The model of interactions between airflow and particles is established, and the algorithm of air velocity generation is developed and validated by comparison with DNS statistical results. The longtime transport and diffusion of aerosols in a rectangle channel are simulated in this paper, particles trajectories and instantaneous distribution can be obtained. Due to the nonuniform distribution of velocity fluctuations in wall-bounded flow, the phenomenon of turbophoresis is found from the evolution of particles concentration distribution. Five kinds of particle diameters ranged from 0.1 to 10 μm and three particle densities of 500, 1000, 2500 kg/m3 are considered to compare the deposition characteristics, accordingly, the dimensionless particle relaxation time (τ+) is ranged from 10−6 to 10−1. According to statistical analysis, the dimensionless deposition velocities (Vd+) versus τ+ are obtained and well agree with the Wood’s predictions basically within the error scope of ±30%. It is proved that the method employed in this paper is accurate in tracking particles motion in wall-bounded flow fluids.

An inverse optimization of convection heat transfer in rectangle channels with ribbed surface based on the extremum principle of entransy dissipation

The ribbed surface is a widely used convection heat transfer enhancement technology. The geometric parameters of the ribbed surface have great influences on its heat transfer performance. It is crucial to determine the optimum geometric parameters. In the present work, the optimal arrangement of ribs mounted in a rectangular channel is provided by solving the inverse optimization problem with the entransy dissipation as the objective function. The parameter analysis based on the direct solution is firstly carried out to get an approximate range near the optimal pitch ratio which can provide the initial value for the inverse optimization problem; afterwards, the inverse optimization problem is solved by a modified simplified conjugate gradient method, and the accurate optimal pitch ratio is obtained; finally the optimization results are discussed in detail. The results indicate that, (1) the inverse optimization analysis presented in this paper can provide an accurate optimal value of the pitch ratio; (2) taking the entransy dissipation as the objective function could lead to a faster converge process and give a more stable result than taking the temperature data as the objective function; (3) the optimal value under the fixed heat flux boundary condition is slightly larger than that under the fixed temperature boundary condition.

Numerical simulation of dynamic behavior of compound droplets on solid surface in shear flow by front-tracing method

The dynamic behavior of compound droplets on the wall of a rectangle channel by the action of an imposed shear flow is simulated using our developed three-dimensional front-tracking method combined with generalized Navier boundary condition. The validity of the present method was confirmed by comparing results of the compound droplet spreading under gravity force with analytical solutions. To determine the physical condition required for detaching/pinching-off the compound droplet, we have performed a large number of simulations with varying capillary numbers of two interfaces and obtained a phase diagram of compound droplets on solid surface in shear flow. The deformation and motion of the compound droplet including its contact line motion are investigated. It is found that the behavior of the compound droplet is controlled by two dimensionless parameters, the capillary numbers of the outer interface and the inner interface. Moreover, we also analyze the deformation and migration of the inner droplet and discuss its effect on the compound droplet. The simulation demonstrate that the lateral migration of the small inner droplet could accelerates the pinch-off process and the large inner droplet could promote the detachment for a moderate capillary number of the outer interface.