Channel Shape Research Articles

Study of the influence of objective functions on the topology optimization design of battery cold plate

Topology optimization design of cold plate flow channels is a potential approach to improve the performance of battery thermal management systems. In this paper, four objective functions, such as maximum heat exchange, maximum outlet enthalpy, minimum solid domain temperature, and multi-objective function, are used to investigate the effect of the objective function on the topology optimization flow channel shape and cooling performance. The results show that the cold plate channel shape can be adjusted according to the objective function. With the inlet flow rate of 0.002 kg·s−1, the inlet coolant temperature of 25 °C, the ambient temperature of 20 °C, and the 3C-rate discharge, it was found that the topology optimization cold plate with maximum outlet enthalpy as an objective function will give the best cooling performance, in which the maximum temperature of the battery is 29.65 °C, which is 0.48 °C less than the battery with convectional rectangular channel cold plate cooling. For the multi-objective function, the increase in the weighting coefficient of the heat transfer term can improve the cooling capacity of the cold plate, and the increase in the weighting coefficient of the flow term can reduce the flow resistance of the cold plate and enhance the efficiency of energy utilization. In addition, the unsteady battery temperature is calculated during the entire 3C-rate discharge process, and it is found that the topology optimization cold plate can slow down the increase of battery temperature and improve the proportion of battery discharge time at ideal temperature.

Towards shape optimization of flow channels in profile extrusion dies using reinforcement learning

AbstractProfile extrusion is a continuous production process for manufacturing plastic profiles from molten polymer. Especially interesting is the design of the die, through which the melt is pressed to impart the desired shape. However, due to an inhomogeneous velocity distribution at the die exit or residual stresses inside the extrudate, the final shape of the manufactured part often deviates from the desired one [1]. To avoid these deviations, we want to optimize the shape of the flow channel inside the die computationally. This has already been investigated in the literature using conventional optimization approaches [2,3].In this work, we investigate the feasibility of Reinforcement Learning (RL) as a learning‐based approach for shape optimization. RL is based on trial‐and‐error interactions of an agent with an environment. For each action, the agent is rewarded and informed about the subsequent state of the environment, which for this application stems from a high‐fidelity Finite Element Method (FEM) simulation.We will introduce a 2D test case as a proof‐of‐concept, in which an RL agent learns to change the geometry of a flow channel by modifying its representation as computational mesh through a spline‐based deformation method known as Free Form Deformation (FFD) [4]. We will show that an agent can be trained to optimize the geometry for different values of the quantity of interest and that the learning behavior is reproducible, which renders the RL‐based approach promising for further research.

Condensation heat transfer of binary and ternary mixtures inside multiport tubes

This study investigated the condensation heat transfer of pure refrigerants and binary and ternary mixtures inside horizontal multiport tubes with multiple square minichannels. The effects of mass flux, vapor quality, heat flux, channel size, and channel shape were evaluated using pure refrigerants R32 and R1234yf; binary mixtures R32/R1234yf, R32/R1123, R32/R13I1, and R410A; and ternary mixtures R1123/R32/R1234yf and CO2/R32/R1234yf. For pure refrigerants, the heat transfer coefficient in the annular and churn flow regimes decreased monotonically with decreasing vapor quality. By contrast, the heat transfer coefficient in the plug flow regime was higher over a wide vapor quality range because of the thin condensate film formed by surface tension. Smaller channels exhibited higher heat transfer coefficients. The square minichannels exhibited higher heat transfer coefficients than the circular minichannels, except in the region with high mass flux and high vapor quality. For binary and ternary mixtures, the heat transfer coefficients significantly decreased with decreasing mass flux and vapor quality and were strongly deteriorated at lower mass fluxes. Compared with the annular and churn flow regimes, in the plug and slug-annular flow regimes, where heat transfer through the thin liquid film was dominant, the effect of mass diffusion resistance in deteriorating heat transfer was the most pronounced. A new heat transfer model for pure refrigerants inside multiport tubes with multiple rectangular minichannels was developed considering the contributions of vapor shear stress and surface tension. The proposed model was verified using a dataset of pure refrigerants, and a mean absolute percentage error (MAPE) of 11.5% was achieved. Furthermore, a new heat transfer model that considers the heat transfer deterioration of non-azeotropic refrigerant mixtures was proposed, which could predict 508 datapoints with an MAPE of 13.3%.

Experimental investigation of roll bond liquid cooling plates for server chip heat dissipation

High-performance data centers have high heat dissipation requirements. In order to solve the problems such as complex structure, high manufacturing cost, and long manufacturing cycle in the technology of server cooling, roll bond liquid cooling plates (RBLCP) for server chip heat dissipation were proposed in this work. A performance test platform for RBLCP was set up. The influence of bending, flow channel shape, flow rate, and heating power on RBLCP performance was investigated via experiences. The results show that bending has little effect on its heat transfer performance. However, with the increase in flow rate, the flow characteristics of RBLCP after bending is worse than that of RBLCP before bending. The heat transfer performance and flow characteristics of the RBLCP are mainly determined by the bending degree of the flow channel. Compared with the RBLCP which bending to “Z” shape (Z-RBLCP), the RBLCP which bending to “N” shape (N-RBLCP) has better comprehensive performance. The heat transfer performance of the RBLCP improves with the increase in flow rate, but the variation is small at a high flow rate. The total temperature uniformity of the cooling plate decreases with the increase of flow rate and heating power, while its local temperature uniformity increases with the increase of flow rate and decreases with the increase of heating power. To ensure that the temperature and temperature difference of heat source are low, RBLCP should be avoided working at a low flow rate. When the heating power is 100 W, and the flow rate is 35 L/h, N-RBLCP has a minimum thermal resistance Rt = 0.0613 K/W. RBLCP has a low cost and can meet the heat dissipation requirements of server chips.

ANN model with feature selection to predict turbulent heat transfer characteristics of supercritical fluids: Take CO2 and H2O as examples

Heat transfer deterioration of supercritical fluids is difficult to predict accurately due to the numerous influencing factors. Traditional correlations failed to fit the relationships between many parameters over a wide range of experimental conditions. To this end, we developed a general artificial neural network model for simultaneously predicting the Tw and Nu of supercritical H2O and CO2, which is the first model currently available for multi-fluid prediction. To maintain the compactness of the model feature space, redundant features are eliminated by feature selection. This model was trained with circle tube data but still maintained high accuracy on the non-circle tube data, demonstrating its strong generalization and independence of channel shape. High accuracy, applicability, and convenience over a wide range of applications are embraced in the ANN model, which lays a solid foundation for engineering application of the ANN model. The generalizability of the ANN model could be further improved by incorporating other fluid data.

Influence of surface chemistry and channel shapes on the lithium-ion separation in metal-organic-framework-nanochannel membranes

Metal-organic-framework-based channel (MOFC) membranes have great potential in ion separation due to their high flexibility than polycrystalline MOF membranes. Although a few single-MOFC membranes with high ion selectivity and permeability have been reported, the scale-up of MOFC membranes from single-channel membranes to multichannel membranes remains a challenge as defects with the system are escalated, limiting their practical application. Minimizing defects in multichannel MOFC membranes is the key to solving this scale-up challenge. Herein, the surface chemistry of polyethylene terephthalate (PET) nanochannel substrate was firstly tuned by a chemical modification to enhance the binding between the PET nanochannel walls and UiO-66-(COOH)2 MOF crystals. Further investigation of the influences of PET nanochannels' size, shape, and channel density on the selectivity revealed that the cylindrical and ethylenediamine (EDA)-functionalized single PET-UiO-66-(COOH)2 MOFC membrane exhibited an ultrahigh Li+/Mg2+ selectivity of 3077-fold over those of previous single-MOFC works. Furthermore, cylindrical, EDA-functionalized, multichannel UiO-66-(COOH)2 MOFC membranes with a channel density of 106/cm2 have been fabricated to achieve 50-fold Li+/Mg2+ selectivity and a vast enhancement of Li + conductance for 6 orders of magnitude. As the first example of scaling up the MOFC membrane, this work provides a fundamental basis and experimental techniques for MOF membrane synthesis and lithium-ion extractions.

Influence of guide tubes on configuration and heat-up behaviour for PHWR specific suspended debris bed – An analytical assessment

The estimation of accident source term and hydrogen generation is dependent on the core heat-up under postulated accident scenarios. The uncertainty of such estimations increases as the accident severity increases due to complexity in the determination of i) evolving degraded core configurations, and ii) associated suitable physical models for heat-up and degradation simulation. Analysis of postulated severe accidents for PHWR is essential for emergency planning and severe accident management guidelines from a plant licensing perspective. The study presents the order of uncertainty that is present as of today in deciding the size and shape of the suspended debris bed, which in turn decides the exposed core heat up, hydrogen generation as well as fission product release. The study reveals that the location and integrity of reactivity mechanism guide tubes significantly impact the exposed core heat-up, channel disassembly pattern and shape and size of the suspended debris bed. Nevertheless, the experimental study on the guide tube behaviour on asymmetric heat-up condition and their failure will further substantiate the postulation of suspended debris bed configuration.

Effects of Asymmetric Channel on the Convective Heat Transfer: A Computational Study

In the fields of engineering, especially in the heat transfer area, the contribution of the fluid flows through different channels is remarkable. Among the different available shapes in the channel, the sinusoidal wavy channels are considered more efficient in the heat transfer areas such as cooling of electronic devices, boilers, biomedical applications, etc., due to their increased recirculation capability of mixing the flowing fluids - which increases the heat transfer performance, consequently. The optimization of channel design and modelling has been an engineering problem in recent years. In this research, flat, symmetric sinusoidal, and asymmetric sinusoidal channels were designed - using ANSYS 2020 - to investigate the effects of channel shape, amplitude, and aspect ratio of sinusoidal wavy walls on the overall heat transfer performance. Several designs have been considered in the present study at different Reynolds numbers and different aspect ratios, keeping the wall temperature as constant. The results of this study exhibit that at an aspect ratio of 0.4, the asymmetric channel shows the highest heat transfer effect due to increased recirculation tendency.

Heat Transfer and Pressure Loss of Additively Manufactured Internal Cooling Channels With Various Shapes

AbstractAdditive manufacturing (AM) provides the ability to fabricate highly customized internal cooling passages that are relevant to gas turbine components. This experimental study examines the pressure loss and heat transfer performance of a range of fundamental channel shapes that were produced using direct metal laser sintering. Circular, hexagonal, pentagonal, elliptical, diamond, square, rectangular, trapezoidal, and triangular channel cross sections were investigated. To maintain the same convective surface area between shapes, the wetted perimeters of the channel cross sections were kept constant. Parallel computational fluid dynamic simulations were performed to understand the relationships in cooling performance between several channel shapes. Several characteristic length scales were evaluated to scale the pressure loss and heat transfer measurements. Among the channel shapes investigated, the diamond channel showed the lowest Nusselt number and friction factor. The pentagon exhibited a similar Nusselt number as the circular channel despite having a lower friction factor. There was no difference in scaling the friction factor or Nusselt number results of the different channel shapes between using the square root of cross-sectional area compared to hydraulic diameter as the characteristic length scale

Efficient coarse-grained simulations of multiple Piezo channels in flat membrane and vesicles.

The unique dome shape of mechanosensitive Piezo channels has inspired biophysical studies on whether and how Piezos should cluster under various cell types and physiological conditions. Molecular dynamics (MD) simulation can, in principle, capture Piezo diffusion and clustering stemming from interactions at the near atomistic level. However, due to their very large size, sampling spontaneous inter-channel Piezo interactions is inaccessible by standard MD techniques based on all-atom or Martini coarse-grained (CG) force fields. To overcome this challenge, we developed a minimal CG model for simulating the dynamics of multiple Piezo channels at the submicron scale in membranes and vesicles. In addition, our model enables tuning the shape and mechanical properties of both channel and membrane. Using this model, we investigated the propensity and topology of Piezo clustering under different channel densities, protein conformations, membrane bending rigidity, and membrane curvature. This work provides new insights into the interplay between protein and membrane deformation energy on Piezo clustering, hence bridging the gap between continuum elasticity theory and high-resolution imaging techniques.

Experimental investigation of intermediate compressor duct

The intermediate duct connects high-pressure and low-pressure compressors. It comprises flow channels and struts that fix the relative positions of the hub and shroud. The mechanism of airflow movement around the struts in the downstream intermediate ducts is experimentally investigated based on four cases, including two types of struts and two shapes of meridional flow channels. The measurement parameters of the intermediate duct under the same conditions are measured in the wind tunnel, including the total pressure loss coefficient at the outlet and axial wall pressure distribution. In addition, the flow characteristics near the wall are obtained through the oil flow test, and the frequency of the shedding vortex is captured by the dynamic pressure probes. The results demonstrate that the strut and channel with the modified profile can reduce the total pressure loss and eliminate wake oscillation by changing the flow characteristic. The total pressure losses of the modified profile at 0.2, 0.25, 0.3, 0.35, 0.4, and 0.45 Ma conditions are reduced by 60%, 63%, 83%, 89%, 85%, and 87%, respectively.

Modeling and Performance Analysis of a Split-Gate T-Shape Channel DM DPDG-TFET Label-Free Biosensor

This article proposes, for the first time, a split-gate T-shape channel dielectrically modulated (DM) double-gate TFET (DGTFET) with a drain pocket (DP). This device can be used as a label-free biosensor. The analytical model for DM DPDG-TFET has been developed and it has been validated against commercial simulation software (Silvaco TCAD). This article intends to focus both on the sensitivity of the biosensor and its performance as a tunnel field-effect transistor (TFET) device. This has been accomplished by improvisations in the channel shape. The performance of the device has thoroughly been investigated in terms of threshold voltage, subthreshold slope, ON current, and OFF current. Due to the novel design, the proposed TFET possesses higher sensitivity, higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{ {\text{ON}}}/{I}_{ {\text{OFF}}}$ </tex-math></inline-formula> current ratio, and lower subthreshold slope. The inclusion of DP at the drain–channel junction proves to be a successful way to remove the ambipolarity completely. The high ON current without any ambipolarity has been achieved by optimizing the DP length and its doping concentration. The proposed T-shape DM DPDGTFET proves itself to be superior to several reported devices in terms of both biosensor as well as field-effect transistor (FET) device. The presence and absence of charge of various biomolecules are taken into consideration for evaluation of device sensitivity as a label-free biosensor.

Quantitative analysis of irregular channel shape effects on charge-trapping efficiency using massive 3D NAND data

The randomly fluctuating trap efficiency of taper-etched nanowire thin-film transistors was investigated by measuring a very large statistical ensemble of three-dimensional NAND flash memory cells. We made trapping in n-bit multi-level cells using incremental step pulse programming and observed the widening of the threshold voltage distribution caused by abnormal program cells. Further, we classified the components that broaden the threshold voltage distribution in both chip- and wafer-level measurements to analyze behaviors of the randomly fluctuating abnormal program cell. The variations in reading and programming operations are difficult to separate because they act simultaneously in the data reading and writing operations. For each pulse of the programming, the variations occur in reading for verification, in programming itself, and in reading after program completion. To analyze the inseparable variation, we used a method to extract only the intrinsic over-programming by removing variations in the read operation from the entire abnormal program cell. Using this extraction method, we could distinguish between the simultaneous read variation and over-programming. In particular, the unpredictable effect of the three-dimensional structure, such as the irregular shape and different radius due to the tapered channel hole profile from the nonideal etching process, was calculated and verified using experimental data. We quantitatively analyzed the experimental data one by one for each cell within the entire distribution, and each pulse of dozens in the programming scheme. This analysis provides quantitative information on the variations in charge-trapping efficiency and the threshold voltage distribution width by irregular-shaped tunneling layers.

Local buckling resistance of Pultruded FRP columns: Theoretical predictions vs. Experimental study

Fiber-Reinforced Polymer (FRP) in the form of thin-walled plate structures are widely used in different engineering applications due to their outstanding features such as: high strength-to-weight ratio, excellent fatigue and corrosion resistance, etc. Due to the low stiffness, design of FRP material is usually governed by deformations or instabilities, rather than strengths. The development of a technical specification for design of FRP composite structures requires the understanding on buckling behaviour of FRP components. Local buckling of pultruded FRP column is a type of structural instabilities, occurs when the compressive stress reaches to the level that form waves in the flanges or web plates, causing the plastic deformation in the fiber which ultimately reduces its strength and stiffness. This study focuses on the local buckling resistance of pultruded FRP columns by experimental work. The test data were compared to current theoretical and numerical predictions. It is found that the difference of &lt;15% between experiment and predictions can be acceptable. The author recommends that the Kollar’s equations to be used when predicting local buckling of Pultruded FRP column of I or channel shapes.

Experimental study of printed-circuit heat exchangers with airfoil and straight channels for optimized recuperators in nitrogen Brayton cycle

• The recuperator has been reported as the largest component in nitrogen Brayton cycles. • The compactness and economics can be enhanced by adopting advanced channel shapes. • Experiments of advanced channel shapes, such as airfoil and straight, were performed. • New correlations for the airfoil channel were developed to design the recuperator. • Optimal design results of recuperator were discussed in terms of flow channel shapes. In this study, experiments with straight and airfoil channels of printed-circuit heat exchanger (PCHE) are conducted within a 3 % heat balance difference to investigate thermal-hydraulic performances for nitrogen (N 2 ) Brayton cycle recuperator. The results reveal that the airfoil PCHE has higher heat transfer performance and pressure drop than the straight PCHE. In the case of straight PCHE, the Gnielinski correlation for heat transfer and Blasius correlation for pressure drop show sufficient predictability. For airfoil PCHE, new correlations for Nusselt number and friction factor are developed to predict the experimental data with a maximum error of 2 % for heat transfer and 8 % for pressure drop. Subsequently, the newly developed and other previous correlations for different channel configurations are used to compare the comprehensive performances. The results indicate that airfoil PCHE has the highest comprehensive performance rather than straight, zigzag, and S-shape PCHE channels under the given hydraulic diameter and pumping power conditions. With the validated PCHE 1-D code, the optimal volumes are calculated for target conditions considering the PCHE channel configuration effect. The design result of the airfoil type has the smallest volume compared with other PCHE channel types, which was almost 21 % reduced volume than that of zigzag PCHE.

Thermal conversion of infinite coordination polymers to europium-doped yttrium oxide microspheres

• •Y 2 O 3 :Eu 3+ microspheres were obtained by calcinating infinite coordination polymers. • •A relatively low temperature (550 °C) could be used for the thermal conversion. • •An increase of luminescence intensity could be observed after calcination. • •The particles were sliced using focused ion beam (FIB) and studied by SEM. We report the synthesis and thermal conversion of an infinite coordination polymer (ICP) based on the pyrazole-3,5-dicarboxylate linker, malonate coordination modulator, and Y 3+ metallic matrix doped with 5 % of Eu 3+ . The ICP particles exhibited spherical morphology and diameters between 1.0 and 3.0 µm. Then, this sample was subjected to a calcination process in order to obtain luminescent Y 2 O 3 :Eu 3+ particles with the same spherical morphology but with smaller diameters overall (<1.5 µm). A focused ion beam (FIB) was used to slice the particles and observe their insides using SEM. While the precursor ICP particles exhibit a smooth and massive interior, the calcinated Y 2 O 3 :Eu 3+ particles show internal channels and cracks due to the combustion of the organic components. The combination of excellent luminescent behavior, spherical shape, microsize, and presence of internal channels can lead to multifunctional Y 2 O 3 :Eu 3+ microparticles for biomedicine, photonics, and catalysis applications.

A review on dryout and Post-dryout heat transfer inside tubes and tube bundles

• Detailed review on dryout mechanism and dryout and post-dryout heat transfer. • Summarizing the dryout criterions and models of dryout and post-dryout heat transfer. • Elaborating the methods of dryout and post-dryout heat transfer enhancement. • Proposing further research suggestions of dryout and post-dryout heat transfer. The working medium changes from subcooled liquid through flow boiling to superheated vapor in actual once-through thermal equipment (such as once-through steam generators, once-through boilers). Dryout heat transfer deterioration inevitably occur in this vapor-liquid two-phase flow and heat transfer process. After dryout occurs completely, vapor almost completely covers the wall, resulting in a rapid deteriorating heat transfer performance and a sharp rising wall temperature, which puts forward higher requirements on the design, manufacture, and operation of the equipment. The mechanism of dryout is elaborated, and the dryout criterion is summarized in this paper. The three methods that are used to describe the mathematical model of dryout and post-dryout heat transfer are arranged, and the dryout and post-dryout heat transfer in the straight channel is introduced. Furthermore, the methods of enhancing dryout and post-dryout heat transfer are introduced such as changing the geometric structure (including changing the shape of the flow channel and processing the surface of the flow channel) and injecting liquid droplets, etc.

Effect of Working Coefficient on Induced Breakdown Characteristics of Plasma-Triggered-Based Gas Gap Switch in Fast Bypass Conditions

Gas gap switch (GGS) has obvious advantages in fast bypass operation, quick response, simple structure, and strong controllability. The working coefficient (i.e., the ratio of the main gap working voltage to the steady-state breakdown voltage) of GGS is mainly affected by the working voltage, the main gap distance, the type of trigger gas, and the pressure. However, the research mostly focuses on the influence of the above single factors on the trigger performance of GGS. There is a lack of studies on the induced breakdown characteristics of GGS considering the variation of the working coefficient under different factors. In this article, a research platform about the induced breakdown of GGS is established. It is shown that the working process of the GGS trigger cavity is divided into the high voltage pulse prebreakdown stage in the first cavity, the discharge ablation stage in the first cavity, and the discharge ablation stage in the second cavity. With the increase of the working voltage, the critical trigger capacitor voltage is lower, and the plasma jet characteristic parameters are decreased gradually during the critical conduction. The conduction time delay and time delay jitter are decreased rapidly, the triggering stability is significantly improved. Changing the main gap distance, the discharge channel shape is a significant difference at the moment of GGS-induced breakdown. And the electric characteristics of plasma jets are varied obviously. The high trigger gas pressure hinders the development of the plasma jet and causes a greater trigger jitter. With the increase of SF6 content in the trigger environment, the characteristic parameters of GGS decrease obviously. The strong insulation and electronegative gas seriously constrain the plasma jet capability. The research results can provide theoretical guidance for the improvement of trigger stability and the selection of trigger condition parameters of plasma-triggered-based gas switches used in fast bypass conditions.

Comparative analysis of various channel shapes for a plate-fin heat exchanger of a small-sized gas turbine power plant

Comparative analysis of various channel shapes for a plate-fin heat exchanger of a small-sized gas turbine power plant

The Effect of Using Different Cross-Sectional Shapes of Steel on the Flexural Performance of Composite Reinforced Concrete Beams

Various types of structures can be constructed using reinforced concrete, including slabs, walls, beams, columns, foundations, frames, and more. The incorporation of structural steel and reinforcements in concrete enhances the strength and durability of structural elements while compensating for the tensile weaknesses in the concrete material. This study aimed to investigate the behavior of reinforced concrete beams utilizing structural steel of different shapes. Four types of concrete beams were prepared: a standard beam with normal reinforcement, and three composite beams, each featuring structural steel with different sectional shapes – T-section, I-section, and channel section. The consistent parameters included the cross-sectional area of the specimens, each measuring 100x150x450 mm, a steel reinforcement percentage of 2% of the total volume, and the compressive strength of the concrete. The conducted tests involved applying a concentrated load at the mid-span of each beam to examine the specimens’ behavior in terms of strength, flexural load capacity, deflection, crack patterns, and failure mode. The results of this study reveal that, given the same steel ratio, the load capacity of beams reinforced with structural steel of a channel shape has surpassed that of the other beams. Additionally, specimens with structural steel plates exhibited higher maximum deflections before failure compared to the beams with conventional reinforcement.