Manifold Configurations Research Articles

Experimental investigation of microchannel heat sink performance under non-uniform heat load conditions with different flow configurations

Cooling methods for multiple hotspots with high heat flux pose a reliability threat to electronic devices. This study investigates the microchannel-based heat sink performance under various non-uniform heat load conditions for different geometry with three different flow configurations (I, U and Z). An in-house designed Heater Array Unit (HAU) facilitates the generation of both uniform and non-uniform heat loads using a heater power supply. Two different microchannel geometries were employed, namely, microchannel-1 (MC-1) with channel and fin widths of 0.6 mm and 0.33 mm, respectively, and MC-2 with dimensions of 0.64 mm and 0.572 mm. Each microchannel incorporates three manifold configurations (I, U, and Z). Each flow configuration is regulated by flow control valves. Various non-uniform heat load patterns were considered, including streamline, non-streamline, and across-streamline conditions. To assess the thermal performance of the heat sinks the parameters used are thermal resistance (Rth), Nusselt number (Nu), and temperature non-uniformity (Ѱ). Experimental findings indicate that the MC-2 design with an I flow configuration is more suitable for uniform heat load conditions. On the contrary, for some non-uniform heat load cases MC-1 also showed up as a suitable design over MC-2.

Performance and Thermal Stress Evaluation of Full-Scale SOEC Stack Using Multi-Physics Modeling Method

A three-dimensional computational fluid dynamics (CFD) method coupled with multi-physics phenomena is developed and applied for a 10-cell full-scale SOEC stack in this study. Effects of gas flow patterns, operating temperature, and manifold configurations are simulated and analyzed for stack performance and thermal stress. It is demonstrated the hydrogen production and thermal stress obtained in cross-flow mode stack are about 8% and 36 MPa higher compared to that in other flow cases. Furthermore, it is found the temperature gradient is the predominant factor affecting the thermal stress distribution and failure probability. Lastly, a stack arrangement with 2-inlet and 1-outlet is proposed and analyzed to enhance gas distribution uniformity within the cell channels. The findings of this study hold significance as a reference for investigating the impact on the SOEC stack performance and thermal stress distribution.

Numerical investigation of novel manifold microchannel heat sinks with countercurrent regions

Manifold microchannel (MMC) heat sink is a potential method to dissipate high heat fluxes of electronic devices. Traditional Z-type MMC is a simple configuration but usually encounters high temperature difference and pressure drop. In this work, we introduced countercurrent flows to alleviate these problems by revising the design of manifold configurations. Six cases with different manifold arrangements are numerically investigated using single-phase deionized water at mass flow rates ranging from 0.04 - 0.12 g/s. The results show that the maximum temperature, average temperature, and temperature difference of the revised arrangements are all lower than these of the traditional Z-type manifold arrangement. The cases with countercurrent regions can reduce the maximum temperature around 5 K compared with the original cases with parallel regions. The temperature difference of the ZU-type MMC with double-layer countercurrent flow configuration is lower than 4 K, which is about 25% of the original Z-type MMC. For the revised manifold configuration with countercurrent flows, the pressure drops also decrease due to the split of inlets and outlets of the manifold. The pressure drops of single-layer and double-layer countercurrent manifolds are respectively 27.13% and 33.36% lower than that of the case with traditional Z-type manifold. This leads to a higher comprehensive performance of revised cases with countercurrent flows. Besides the better temperature uniformity, the fluid flow becomes more uniform in the microchannels for the revised case. The improved ZU-type MMC with double-layer countercurrent flow can dissipate 1100 W/cm2 for single-phase flow with a temperature increase of 80 K and a pressure drop of 22 kPa at mass flow rate of 1.2 g/s.

Constrained Motion Planning Networks X

Constrained motion planning is a challenging field of research, aiming for computationally efficient methods that can find a collision-free path on the constraint manifolds between a given start and goal configuration. These planning problems come up surprisingly frequently, such as in robot manipulation for performing daily life assistive tasks. However, few solutions to constrained motion planning are available, and those that exist struggle with high computational time complexity in finding a path solution on the manifolds. To address this challenge, we present Constrained Motion Planning Networks X (CoMPNetX). It is a neural planning approach, comprising a conditional deep neural generator and discriminator with neural gradients-based fast projection operator. We also introduce neural task and scene representations conditioned on which the CoMPNetX generates implicit manifold configurations to turbo-charge any underlying classical planner such as sampling-based motion planning methods for quickly solving complex constrained planning tasks. We show that our method finds path solutions with high success rates and lower computation times than state-of-the-art traditional path-finding tools on various challenging scenarios.

Numerical and experimental investigation of exhaust manifold configurations of turbo-charged diesel engines

The exhaust energy recovery is significant for engine fuel efficiency. However, the exhaust gas interference and the loss of flow affect the utilization of exhaust energy of multi cylinder turbocharged diesel engine seriously. In this paper, through Particle Image Velocimetry experiment and computational fluid dynamics simulation of exhaust T-junction flow field, the characteristics of junction local flow field and the law of energy loss are obtained. Based on the one dimensional simulation of engine working process, the exhaust available energy analysis is carried out, and the transmission of available energy of exhaust valve and various pipe systems under typical operating conditions is obtained. On this basis, five exhaust systems are designed, and the steady-state and transient performances are compared by bench tests. The results show that the shrinkage rate and the intersection angle of T-junction are the key factors affecting exhaust energy transmission and exhaust gas interference suppression. Reducing the branch pipe shrinkage rate leads to an increase in branch pipe flow loss, but it will also reduce the main pipe flow loss and exhaust gas interference. Reducing the angle between the main pipe and branch pipe is beneficial to the exhaust flow and exhaust energy recovery. The pulse converter exhaust system has a high exhaust available energy transmission rate; the Modular Pulse Converter system has superior fuel efficiency and transient response performance from the perspective of the entire engine operation range. The 90% response time difference between the five studied exhaust systems is about 0.41 s.

Manifold configurations for uniform flow via topology optimisation and flow visualisation

The current study proposes compact and adaptable manifold configurations for achieving uniform flow distribution with minimal pressure drop, for electronics cooling and many other industrial applications. Two-dimensional topology optimisation generates new manifold configurations, referred to as mini-baffle and baffle. Both configurations use proportionately sized obstructions to regulate flow distribution and achieve excellent uniformity. Elliptical pins, with parametrically optimised diameters, are adopted to represent the mini-baffle configuration and tested using a three-dimensional model and flow visualisation experiments. Computational results show that introducing these pins reduces the variation of normalised channel flow rates from 19% to 1% with only an 8% increase in the pressure drop, at a Reynolds number of 200. Experimental results support this, with variation reduced from 20% to 7%, the slight increase due to manufacturing limitations. Results also show the influence of vortices, formed at the inlet, on flow distribution. A test section printed in a single piece demonstrates a streamlined and cost-effective manufacturing method for milli-fluidic devices. Coupling topology with parameter optimisation provides a method for accurately extracting discrete optimised geometries for physical manufacturing.

Effects of Inlet/Outlet Manifold Configuration on the Thermo-Hydrodynamic Performance of Recharging Microchannel Heat Sink

Abstract Thermal performance of microchannel heat sink can be augmented by designing inlet/outlet manifolds such that fluid flow distribution is uniform across microchannels. In this work, the effect of inlet/outlet manifold configurations on the thermo-hydrodynamic performance of recharging microchannel heat sink (RMCHS) is investigated numerically. For this purpose branched, rectangular, trapezoidal, and triangular manifold configurations are considered. All the numerical simulations are performed for channel Reynolds number of 50–300 and constant heat flux of 10 W/cm2 applied on the substrate bottom surface of the RMCHS. The results reveal that branched manifold configuration shows uniform fluid flow distribution across all the microchannels of heat sink and also shows uniform temperature distribution on the substrate bottom surface of RMCHS. Branched manifold configuration reduces thermal resistance by 16% and enhances average Nusselt number by 9.5% compared to rectangular manifold configuration. However, branched manifold configuration shows higher pressure drop in spite of enhancements in thermal performance and flow distribution uniformity. Overall performance analysis indicates that RMCHS with branched manifold configuration can be advantageous for high heat flux removal applications if there is no restriction on pumping power requirement.

A comparative numerical study on two-phase boiling fluid flow and heat transfer in the microchannel heat sink with different manifold arrangements

The manifold microchannel (MMC) heat sink system has been widely used in high-heat-flux chip thermal management due to its high surface-to-volume ratio. Two-phase, three-dimensional numerical methods for subcooled flow boiling have been developed using a self-defined solver based on OpenFOAM. Four different types of manifold arrangements (Z-type, C-type, H-type and U-type) have been investigated at a fixed operational condition. The numerical results evaluate the effects of flow maldistribution caused by different manifold configurations. Before simulating the two-phase boiling flow in MMC metamodels, single-phase liquid flow fields are performed at first to compare the flow maldistribution in microchannels. It can be concluded from the flow patterns that H-type and U-type manifolds provide a more even and a lower microchannel void fraction, which is conducive to improving the temperature uniformity and decreasing the effective thermal resistance. The simulation results also show that the wall temperature difference of H-type (0.471 K) is only about 10% of the Z-type (4.683 K). In addition, the U-type manifold configuration show the lowest average pressure drop at the inlet and outlet of the MMC metamodel domain. However, H-type manifold also shows an impressive 59.9% decrease in pressure loss. Results indicate that both the H-type and the U-type manifolds for flow boiling in microchannels are recommended due to their better heat transfer performance and lower pressure drop when compared with Z-type and C-type.

A tapered inlet/outlet flow manifold for planar, air-cooled oblique-finned heat sink

Flow maldistribution compromises thermal and hydraulic performances of heat sinks. The oblique-finned heat sink is a multichannel heat sink comprising parallel (primary) and collinear oblique (secondary) channels and it was reported to suffer from a self-induced flow migration in liquid and air cooling. In this study, a novel tapered inlet/outlet flow manifold was proposed for the planar oblique-finned heat sink. Two heat sink configurations (oblique angles of 30° and 45°) and three flow manifold configurations (of 5%, 10%, and 20% wider flow domains) were investigated. Flow migration characteristics were studied via numerical simulations. Wind tunnel measurements, supported by infrared thermography, were performed to characterize thermal and hydraulic performances on a wide range of air flow rates. The flow manifold was observed to provide a favorable distribution of secondary flows in the spanwise direction of the heat sink. Up to 50% increase in Nusselt number with a negligible increase in pressure drop was observed with the 45° oblique-finned heat sink once the flow manifold was incorporated. 30° oblique angle −10% flow manifold combination provided the lowest heat sink temperature and the most uniform wall temperature. The novel tapered inlet/outlet flow manifold is the first effort reported in the literature to reduce the adverse effects of flow migration through the planar oblique-finned heat sinks.

An experimental study on microchannel heat sink via different manifold arrangements

The current experimental study performed the overall performance of the microchannel heat sink using the heat transfer coefficient, Nusselt number, and pressure drop for three novel manifold configurations. These selected manifolds have a rectangular (R), rectangle with semicircular (RSC) and divergent–convergent (DC) shapes for inlet and outlet. The heat transfer coefficient for all three types of microchannel was reported for the Reynolds number range of 342–857. The experiments were tested at four different heat inputs ranges between 50–125 W. R-type microchannel heat sink showed the worst performance, while the performance of DC-type microchannel heat sinks was the best. At Re of 342, the lowest Nusselt number was observed to be 2.8 at lower Reynolds number 342 for R-type manifold. RSC manifolds MCHS seems to be a better choice compared to R-type and DC-type MCHS with respect to pressure drop and Nusselt number. Compared to R-type microchannel heat sink, 24–32% and 7–10% augmentation in heat transfer coefficients were reported for DC-type and RSC-type microchannel heat sinks, respectively. Based on the released experimental results, it can be stated that DC-type microchannel heat sink is more beneficial in terms of heat transfer enhancement.

Effect of manifold flow configuration on two-phase ultra-high flux cooling

A two-phase, one-dimensional model for the pressure drop and flow distribution in a manifold-microchannel system was developed. The model was run with three different manifold configurations and trends were observed. First, the effect of mass flow rate was investigated in single-phase mode, and it was shown that while z-type manifolds provide superior flow distribution to that of c-type manifolds at low mass fluxes, at high mass fluxes c-type manifolds provide a superior flow distribution, due to the alignment of the inlet and outlet pressure gradients. In addition, due to the lack of an outlet pressure gradient, h-type manifolds were found to provide a more uniform flow distribution across the board. Next, the effects of low and high vapor qualities were investigated. In the end, it was shown that in z-type and c-type manifolds, the flow distribution worsens as vapor quality increases, while for h-type manifolds, the flow distribution improves. Accordingly, h-type manifolds are significantly simpler and less computationally expensive to design, requiring only single-phase computational fluid dynamics simulations, while z-type and c-type manifolds require both single-phase and two-phase computational fluid dynamics simulations.

Numerical analysis of flow distribution behavior in a proton exchange membrane fuel cell

The flow distribution of a proton exchange membrane fuel cell within a manifold plays an important role on its performance. This study presents a numerical analysis of the flow distribution behavior within different manifold configurations. A two-dimensional model with 75 cells was employed to study the flow behavior. The variation in the stoichiometry and number of cells was also studied. Three different flow configurations were considered with different numbers of flow inlets and outlets. The flow characteristics, such as the pressure and velocity variations in the manifold and cells, were measured to determine the effects of the different flow configurations. The results indicated that the double inlet/outlet configuration had the best flow distribution when using 75 cells. Moreover, increasing the stoichiometry resulted in a better flow distribution to the cells in a stack.

Issues, patterns and strategies in the development of event portfolios: configuring models, design and policy

ABSTRACTWhilst the use of event portfolios as a multi-purpose policy tool is increasing worldwide, academic attention on this phenomenon remains sparse. In response, the purpose of this review paper is to identify the major issues in the use of portfolios by host communities and destinations aspiring to become eventful and delineate the emergent development patterns and strategies. The paper postulates the core dynamics that can enable capacity-building in event portfolio development and suggests a network framework for setting up a holistic portfolio policy with systemic management properties. This framework provides a theoretical scaffolding to contextualize the first formalized city portfolio strategies. Based on this discussion, four major issues are identified: portfolio configurations, leveraging, sustainability, and community capacity-building. Policy implications are drawn that theorize the surfacing portfolio development models, design logics and strategic approaches. The effects on social structures are considered in terms of how they determine the longevity, legitimation, and institutional embeddedness of event portfolios. The paper proffers that event portfolios represent a multi-dimensional phenomenon and highly versatile policy tool with manifold configurations. Their sustainable growth requires a shift in event-tourism thinking from the hitherto focus on single major events to managing multiple events for achieving multiple purposes.

Effects of Geometry, Temperature, and Inlet Conditions on the Flow Split in Spheroids Manifold

A Computational Fluid Dynamics CFD study was conducted on the mal-distribution problem occurring within the pipe network upstream of pairs of spheroids gravity separators used in the oil industry. The series of simulations were conducted using the Euler-Euler multiphase and the k-e turbulence models. The cases studied reflect different scenarios of oil production capacity in addition to the effect of seasonal variations of temperature increasing from 10?C during winter to 24?C during summer. The inlet conditions were varied so that they permitted to elucidate the effects of the flow rates and temperatures at the inlet of the piping network on the multiphase flow behavior and hence the mal-distribution within the pairs of spheroids considered. Two manifold configurations were taken from real installations in the oil industry. They contain T-junctions with different orientations. Averages of 2.2 million computational cells were generated for each case studied. The main source of mal-distribution was found to be the sequence and cascading of the existing T-junctions inside the pipe network that are known to act like phase separators. A mal-distribution between the risers of each spheroid was, also, noticed. The relatively large number of T-junctions used, as well as the structure of the downstream piping network employed, led to complex multiphase flow behavior. The mal-distribution, generated by different flow scenarios, were less than 12 for the manifold referred to as Configuration 1. Configuration 2 caused more noticeable mal-distribution reaching up to 40%. The symmetry of the piping networks and the arrangement of the T-junctions were found to be a key parameter among the causes of the mal-distribution

Experimental and numerical evaluation of an elongated plate-fin heat sink with three sections of stepwise varying channel width

The performance of a novel design of a three-section plate-fin heat sink employing channels of stepwise decreasing hydraulic diameter is numerically and experimentally evaluated. Prototype heat-sink and inlet–outlet manifold configurations have been manufactured and characterized, in terms of thermal resistance and induced pressure drop, in a closed fluid loop experimental rig and for flow rates in the range of 20–40mL/s. The flow development and particularly the secondary flow pattern inside the heat sink are investigated by means of a numerical three-dimensional model. The findings of the study establish that the induced pressure drop, which does not exceed 1000Pa for the considered flow rates, is primarily attributed to the flow friction in the third-heat sink section, which is of microscale dimensions and the effect of the inlet–outlet manifold system is very small (0.5% of the total). In terms of heat transfer, the effect of buoyancy in the first heat-sink section has a beneficial impact on thermal performance maintaining the thermal resistance constant, at a value approximately equal to 0.015K/W, regardless of the flow rate of the cooling fluid. Heat transfer is also enhanced in the successive sections due to the effect of contraction-induced longitudinal vortices. Finally, it is proven that the heat sink wall exhibits a more uniform temperature distribution with the decrease of the Reynolds number.

Manifold configurations of the director field formed by topological defects in free and confined geometry in smectic films.

We study the topology of the c-director field near topological defects with point core and with a droplet in the core of the defect in nonpolar smectic-C and ferroelectric smectic-C* freestanding films using polarized optical microscopy. Free and confined geometry of topological defects and droplets with strong outer boundary condition are compared. The c-director field can be remarkably different around a point defect and a droplet with the same topological charge S=+1. In ferroelectric films, splay deformation of the c-director transforms into bend deformation after droplet nucleation. Heating a ferroelectric film with an S=+1 droplet leads to a dramatic change of the c-director topology from bend to splay. In confined geometry we found spiral structures in which the c-director has opposite direction of rotation along the inner and outer boundaries of the island. Our observations are discussed on the basis of theories taking into account both the influence of polarity and of confined geometry on elasticity and topology of the c-director field.

Improvements on maldistribution of a high temperature multi-channel compact heat exchanger by different inlet baffles

The multi-channels plate heat exchangers are recommended to be used in the high-efficiency power and propulsion systems. The present study analyzes the large fluid flow maldistribution occurring at the inlet manifold configurations of a high temperature heat exchanger with CFD (computational fluid dynamics) method. Four modified inlet manifolds are proposed, including inclined baffle, segmental baffle, helical baffle and improved helical baffle. It turns out that all the proposed designs have more or less improvement of uniform flow distribution among each channel. By comparing the flow nonuniformity, the Nusselt number and the friction factor, the inlet manifold with equidifferent helical baffles is the best, whose flow nonuniformity can be decreased by 52% averagely. Comparing with the baseline design, meanwhile, the optimal modified design which inducts the spiral fluid flow has effect on the comprehensive performance. The Nusselt number can be increased by 24% averagely due to the produced spiral fluid flow while the pressure drop is in an acceptable range. Furthermore, the corresponding correlation of Nu and f are obtained according to CFD results.

Investigation of the heat transfer behaviour of a polymer solar collector for different manifold configurations

In order to further promote the utilization of solar thermal systems, solar collectors need to become more efficient and cost effective. This can be accomplished by a variety of methods, either by using lower cost materials, or/and by increasing their thermal efficiency by novel design. The current work presents such an effort dealing with the investigation of the heat transfer behaviour of a novel polymer solar collector for different manifold configurations with computational fluid dynamics (CFD).A CFD model that has previously been developed and validated is used to investigate different collector manifold configurations in order to optimize flow field development and to increase collector thermal efficiency.The investigation was carried-out for a wide range of inlet temperature conditions covering the expected operational range of the solar collector and the proposed collector's manifolds provided a considerable increase of the solar energy exploited by the collector without any increase in the manufacturing cost.

Hexagonal reciprocating pump: advantages and weaknesses

This paper reports the 1-D fluid transient simulation results of the discharge flow conditions in a 6-cylinder reciprocating slurry pump. Two discharge manifold configurations are studied comparatively; a case with a hexagon shaped discharge manifold where each cylinder discharges at a single vertex, and a case where all the cylinders discharges are lumped together into a tank shaped manifold. In addition, the study examines the effect of two pulsation mitigation measures in the case of hexagonal manifold; a single inline orifice in one of the hexagon sides and a volumetric dampener at the manifold outlet. The study establishes the pressure and flow fluctuation characteristics of each configuration and decouples the pulsation characteristics of the pump and the discharge manifold. 1. Summary Reciprocating pumps produce flow variations in their discharge end that may excite severe pressure pulsation in their discharge manifolds and piping systems. Therefore, developing of new designs of such pumps or introduction of novel configurations of discharge manifold warn an investigation of their flow dynamic characteristics and their susceptibility to acoustic and mechanical resonance. Numerical transient flow simulation is an effective front-end engineering measure to assess the susceptibility to detrimental pulsation flow acoustic performance. This paper reports the simulation results of the discharge flow conditions in a 6-cylinder hexagon shaped reciprocating slurry pump (Hexagonal pump). Two discharge manifold configurations of the same pump are studied comparatively; a case with a hexagon shaped discharge manifold where each cylinder discharges at a single vertex, and a case where all the cylinders discharges are lumped together into a tank shaped manifold. The study establishes the discharge pressure fluctuation characteristics of each configuration, quantifies the flow and pressure pulsation, and decouples the pulsation characteristics of the pump and the discharge manifold. In addition, the study examines the effect of two pulsation mitigation measures in the case of hexagonal pump with hexagonal manifold; a single inline orifice in one of the hexagon sides and a volumetric dampener at the manifold outlet. Finally, it compares the discharge pulsation characteristics of a reciprocating hexagonal pump with those of similar capacity triplex pumps conventionally used in oil wells drilling and in the mining industry. A one-dimensional transient flow simulator is used to investigate the pumping hydrodynamic of a slightly-compressible homogeneous slurry flow. The Hexagonal pump analyzed is based on an emerging industrial product design where the vertical reciprocating motion of the pistons is driven by a rotating cam, and where the kinematic of the piston motion is carefully configured, by the cam profile, to smooth the compound pump discharge flow/pressure. The simulation results of the common discharge tank case show that, under realistic conditions of delays in valves actions, severe discharge pulsation occurs. This pressure pulsation is in the same level of severity as in the crankshaft driven triplex pump used conventionally in drilling oil and gas wells. Furthermore, the simulations of the hexagonal manifold revealed that a complex alternating flow condition prevails in the six sides of the hexagons in response to the six reciprocating pistons actions. Simulation results suggest that the Hexagonal manifold provides certain level of damping when compared with the case of discharging to a common tank manifold. However, it generates multiple high energy frequency spikes over a wide frequency range, some of them at the high frequency range, with tendencies to excite the piping system and the mechanical frame of the pump.

Size and configuration syntheses of rigid-link mechanisms with multiple rotary actuators using the constraint force design method

This study presents a new synthetic approach for path-generating or function-generating rigid-body mechanisms in the framework of a new hybrid genetic algorithm. In spite of some advantages of synthesis methods in designing rigid-body mechanisms, some inherent issues remain in determining optimal sizes and configurations of rigid links with multiple rotary actuators. To alleviate these difficulties and limitations, we improve our previous contribution, called the constraint force design method, by parameterizing and optimizing the existence of links, the x–y locations of joints modeled by unit masses (particles), and the kind of selection between rigid and string links, using binary, integer, and binary design variables, respectively. This new genotype coding system for GA for the integer and binary phenotypes makes it possible to use a smaller number of unit masses to synthesize manifold configurations of rigid-body mechanisms. In addition, the locations and types of rotary actuators are parameterized with additional integer design variables for the synthesis of realistic rigid-body mechanisms. Furthermore, for efficient optimization of GA, a new h-GA integrated with the Sequential Quadratic Programming (SQP) optimization algorithm is also developed to optimize the locations of joints. To demonstrate the validity of the present constraint force design method, several mechanism synthesis problems are solved.