Array Of Tubes Research Articles

Experimental and numerical study of convective heat transfer in-line tube bundle by acoustic action

This paper proposes the acoustic properties acting on the in-line tube bundles heat exchanger and an analysis of the tube bundle gap flow characteristics and convective heat transfer. In contrast to the reported literature, the present study adds the effect of audible sound on the tube array gap flow, in which the Reynolds number for free flow is Re = 2000, sound frequency is f = 100–1000 Hz, and sound pressure level range is SPL = 127–145 dB. In this paper, a numerical calculated turbulence intensity and Reynolds shear stress of the fluid in the tube bundles gap for acoustic frequency and sound pressure level. Moreover, experiments revealed the effect of acoustic properties on convective heat transfer on the surface of the tube bundles. The results show that the average Nussle number increases by almost 1.8 when the acoustic frequency f = 100 Hz is added, and the sound pressure level reaches 145 dB, compared to no acoustic perturbation. The average Nussle number increases by almost 2.1 when the sound pressure level reaches 145 dB with frequency modulation of f = 1000 Hz. Since the relative error is less than 15% between experimental and numerical calculations, acoustic waves are able to enhance convective heat transfer through the tube array. At the same time, the present study serves as a reference for engineering applications.

Performance of a prototype TORCH time-of-flight detector

TORCH is a novel time-of-flight detector, designed to provide charged particle identification of pions, kaons and protons in the momentum range 2–20 GeV/c over a 9.5 m flight path. A detector module, comprising a 10 mm thick quartz plate, provides a source of Cherenkov photons which propagate via total internal reflection to one end of the plate. Here, the photons are focused onto an array of custom-designed Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs) which measure their positions and arrival times. The target time resolution per photon is 70 ps which, for 30 detected photons per charged particle, results in a 10–15 ps time-of-flight resolution. A 1.25 m length TORCH prototype module employing two MCP-PMTs has been developed, and tested at the CERN PS using a charged hadron beam of 8 GeV/c momentum. The construction of the module, the properties of the MCP-PMTs and the readout electronics are described. Measurements of the collected photon yields and single-photon time resolutions have been performed as a function of particle entry points on the plate and compared to expectations. These studies show that the performance of the TORCH prototype approaches the design goals for the full-scale detector.

Experimental assessment and semi empirical estimation of frost accretion—A case study on a spine-finned inverted-V tube array evaporator

Present work focuses on frost accretion in a spine-finned inverted-V tube array evaporator. An experimental evaluation was performed using a standard issue, vertical top-mount, 18 cubic feet, 0.5 m3, refrigerator. Evaporator temperature distribution, inner airflow velocity, and relative humidity were measured to account for convective phenomena influencing frost distribution. Frost formation and accretion on the surface of the evaporator were visualized using thermal and microscopic imagery. The images were processed using a machine vision algorithm to measure frost thickness. Complementarily, frost density and vapor mass transfer were computed using available correlations. An estimation function was derived from the compiled data using a semi empirical approach, i.e., direct measurements and thermophysical substance properties. The resulting mathematical expression estimated the frost accretion rate within an error expectancy, RMSE, of 0.1479 and displayed a goodness-of-fit, R-Squared, of 0.9029. Based on these results, semi empirical estimation, is proposed as a viable approach to construct adequate limits for new predictions, vis-à-vis evaporator performance, ultimately reducing appliance energy consumption via implementing more effective control strategies regarding internal defrosting.

Oil–Water Separation using Synthetic Trees

Existing oil-water filtration techniques require gravity or a pump as the driving force for separation. Here, we demonstrate transpiration-powered oil-water filtration using a synthetic tree, which operates pumplessly and against gravity. From top to bottom, our synthetic tree was composed of: a nanoporous "leaf" to generate suction via evaporation, a vertical array of glass tubes serving as the tree's xylem conduits, and filters attached to the tube inlets to act as the oil-excluding roots. When placing the tree in an oil emulsion bath, filtrate samples were measured to be 97-98% pure water using gravimetry and refractometry. The spontaneous oil-water separation offered by synthetic trees could be useful for applications such as oil spill cleanup, wastewater purification, and oil extraction.

The influence of internal flow on fluidelastic instability of a flexible tube in tube bundles subjected to two-phase cross-flow

This paper investigates the fluidelastic instability of a flexible tube in a rotated triangular tube array subjected to two-phase cross-flow and internal flow. We first established a mathematical model of a flexible tube in the tube bundles conveying flow considering the effect of two-phase cross-flow. Then, the eigenvalue analysis was performed to study the influences of the internal flow on the threshold and mechanism of the fluidelastic instability of the tube system in two-phase cross-flow. The results indicate that the internal flow has a significant effect on the threshold of the fluidelastic instability of the tube system in two-phase cross-flow, and may cause different kinds of instabilities. And, the mechanism of the fluidelastic instability of the tube system subjected to two-phase cross-flow and internal flow is notably affected by the tube boundary condition.

Assessment of The Acoustic Scattering Matrix of a Heat Exchanger Using ssCFD-LNSE Simulation

The risk of thermoacoustic instability is present in any combustion appliance. The instability results from a closed loop feedback between unsteady combustion, heat-transfer and acoustic modes of the system. To predict the system acoustics all constituting elements of the appliance need to be modelled. A heat-exchanger is the element where the gas faces complex fluid dynamics and heat transfer processes. Therefore, modelling of (thermo)-acoustic properties of a heat exchanger is challenging. In this paper, a computational approach is proposed to characterize the acoustic properties of a generic heat exchanger in both laminar and turbulent flow regimes. A hybrid Computational Fluid Dynamics - Computational Aero-Acoustics (CFD-CAA) method is used based on full linearized Navier-Stokes equation, called ssCFD-LNSE. The fundamental idea in this approach is to efficiently model acoustic wave propagation with inclusion of mean flow and temperature fields. ssCFD-LNSE is performed by splitting the quantities of the total field into a mean part (obtained from CFD) and a (acoustic) perturbation part modelled within the LNSE solver. The goal of this research is to assess the two-port acoustic scattering matrix of an array of tubes, as a generic model of heat-exchanger, with a hot cross flow.

Investigations of In-Plane Fluidelastic Instability in a Multispan U-Bend Tube Array—Part II: Tests in Two-Phase Flow

Abstract Tests to study fluidelastic instability (FEI) in an array of U-bend tubes were recently completed in the multispan U-Bend test rig at Canadian Nuclear Laboratories. These tests were sponsored by the Electric Power Research Institute and were designed to study in-plane fluid elastic instability of steam generator tubes in two-phase cross flow. This instability mechanism was first observed in previous experiments by Atomic Energy of Canada Limited. This mechanism was not thought to be a serious practical concern until 2012 when it caused severe damage to tubes in a new replacement steam-generator in a nuclear power plant in the United States. In this study, tests were conducted both with flows of air and two-phase liquid/vapor Refrigerant 134a. The tube bundle consisted of 22 flexible U-bend tubes supported by a configurable flat-bar arrangement. Testing focused on the effects of support geometry and tube-to-support interaction. Data were recorded from 33 dynamic signals from accelerometers, displacement probes, force transducers, and void-fraction probes. Part I of this two-part series presented results of air tests. Part II presents results of tests using two-phase Freon refrigerant (R-134a) as the working fluid.

Investigations of In-Plane Fluidelastic Instability in a Multispan U-Bend Tube Array—Part I: Tests in Air Flow

Abstract The tubes in the U-bend region of a recirculating type of nuclear steam generator are subjected to cross-flow of a two-phase mixture of steam and water. There is a concern that these tubes may experience flow-induced vibration, including the damaging effects of fluidelastic instability. This two-part series of papers presents the results of flow-induced vibration experiments performed by Canadian Nuclear Laboratories for the Electric Power Research Institute (EPRI) using the Multi-Span U-Bend test rig. The tube bundle is made of 22 U-bend tubes of 12.7 mm (0.5 in.) diameter, arranged in a rotated triangular configuration with a pitch-to-diameter ratio of 1.5. The test rig was equipped with variable clearance flat bar supports at two different locations to investigate a variety of tube and flat-bar support configurations. The primary purpose of the overall project was to study the occurrence of in-plane (or streamwise) fluidelastic instability in a U-tube bundle with flat-bar tube supports with clearances or preloads. Initially, the test rig was configured for tests in air-flow using an industrial air blower. Then tests with two-phase refrigerant (R-134a) were performed. Part I of this two-part series describes the test rig, experimental setup and some of the challenges encountered, and the results of experiments with air flows. Part II will present results of tests using refrigerant two-phase flows.

Effect of fin density and fin height on flow-induced vibration behavior of finned tube arrays subjected to water cross flow

PurposeThe prediction of critical velocity at instability threshold for shell and tube heat exchangers is important to avoid failure of tubes as a result of flow-induced vibrations due to water cross flow. The flow-induced vibration in finned tube heat exchangers is affected by various parameters such as fin height, fin pitch, fin material, tube array, pitch ratio, fin type, fluid velocity etc. In this paper, an experimental investigation of fluid elastic instability in shell and tube heat exchangers is carried out by subjecting normal square finned tube arrays of pitch ratio 1.79 to water cross flow.Design/methodology/approachThe five tube arrays, namely plain array, two finned tube arrays with 3 fpi and 9 fpi fin density, and two finned tube arrays with 3 mm and 6 mm fin height are tested in the experimental test setup with water flow loop and vibration measurement system. The research objective is to evaluate the effect of fin density and fin height on the instability threshold. The critical velocity at instability threshold is determined to characterize the fluid elastic instability behavior of different tube arrays. The vortex shedding behavior of the tube arrays is also studied by determining Strouhal number corresponding to the small peaks before fluid elastic instability.FindingsThe fluid elastic instability behavior of the tube arrays was found to be the function of fin tube parameters. The experimental results indicate that an increase in fin density and fin height results in delaying the instability threshold for finned tube arrays. It is also observed that critical velocity at instability is increased for finned tube arrays compared to plain tube arrays of the same pitch ratio. The design modifications in the outer box have resulted in further reduction in the natural frequency. This enabled to reach clear instability for all the five-tube arrays.Originality/valueThe research data add the value to the present body of knowledge by knowing the effect of fin height and fin density on the fluid elastic instability threshold of normal square finned tube arrays subjected to water cross flow.

Fluid elastic instability and vortex shedding in finned tube arrays: the effects of tube material and fin density

PurposeThe purpose of this paper is to present investigations on the significant influence of the tube material and fin density on fluid elastic instability and vortex shedding in a parallel triangular finned tube array subjected to water cross flow.Design/methodology/approachThe experiment was conducted on finned tube arrays with a fin height of 6 mm and fin density of 3 fins per inch (fpi) and 9 fpi. A dedicated setup has been developed to examine fluid elastic instability and vortex shedding. Nine parallel triangular tube arrays with a pitch to tube diameter ratio of 1.78 were considered. The plain tube arrays, coarse finned tube arrays and fine finned tube arrays each of steel, copper and aluminium materials were tested. Plain tube arrays were tested to compare the results of the finned tube arrays having an effective tube diameter same as that of the plain tube.FindingsA significant effect of fin density and tube material with a variable mass damping parameter was observed on the instability threshold. In the parallel triangular finned tube array subjected to water cross flow, a delay in the instability threshold was observed with an increase in fin density. For steel and aluminium tube arrays, the natural frequency is 9.77 Hz and 10.38 Hz, which is close to each other, whereas natural frequency of the copper tubes is 7.40 Hz. The Connors’ stability constant K for steel and aluminium tube arrays is 4.78 and 4.87, respectively, whereas it is 5.76 for copper tube arrays, which increases considerably compared to aluminum and steel tube arrays. The existence of vortex shedding is confirmed by comparing experimental results with Owen’s hypothesis and the Strouhal number and Reynolds number relationship.Originality/valueThis paper’s results contribute to understand the effect of tube materials and fin density on fluid elastic instability threshold of finned tube arrays subjected to water cross flow.

Large area 3He tube array detector with modular design for multi-physics instrument at CSNS

Large area 3He tube array detector with modular design for multi-physics instrument at CSNS

Tube-Sponge-Inspired Hierarchical Electrocatalysts with Boosted Mass and Electron Transfer for Efficient Oxygen Evolution.

Hindered gas bubble release and limited electron conducting process represent the major bottlenecks for large-scale electrochemical water splitting. Both the desorption of bubbles and continuous electron transport are achievable on the surfaces of biomimetic catalytic materials by designing multiscale structural hierarchy. Inspired by the tubular structures of the deep-seasponges, an exceptionally active and binder-free porous nickel tube arrays (PNTA) decorated with NiFe-Zn2+ -pore nanosheets (NiFe-PZn ) are fabricated. The PNTA facilitate removal of bubbles and electron transfer in the oxygen evolution reaction by reproducing trunks of the sponges, and simultaneously, the NiFe-PZn increase the number of catalytic active sites by simulating the sponge epidermis. With improved external mass transfer and interior electron transfer, the hierarchical NiFe-PZn @PNTA electrode exhibits superior oxygen evolution reaction performance with an overpotential of 172mV at 10mAcm-2 (with a Tafel slope of 50mVdec-1 ). Furthermore, this electrocatalytic system recorded excellent reaction stability over 360h with a constant current density of 100mAcm-2 at the potential of 1.52V (versus RHE). This work provides a new strategy of designing hierarchical electrocatalysts for highly efficient water splitting.

Efficiency and Wave Run-Up of Porous Breakwater with Sloping Deck

In order to protect fragile shoreline and coastal assets during extreme storms, a combined floating breakwater-windbreak has been proposed to reduce both wind and wave energies in the sheltered area. The 1 km-long breakwater has a porous hull with internal tubes to allow free passage of water; thereby further dissipating wave energy. The deck of the structure is designed to have a slope of 25 degrees facing the upstream side, and arrays of cylindrical tubes are placed on the sloping deck to form a windbreak. A reduced-scale (1:50) model test was carried out in a wave flume to examine wave sheltering performance under significant wave heights Hs = 3.0 m to 7.5 m and peak wave periods Tp = 9.4 s to 14 s sea states. Both regular and random wave conditions with different wave heights were considered. It is found that transmission coefficients ranging from 0.4 to 0.6 can be achieved under tested wave conditions. Porous breakwater hull increases the wave dissipation coefficients and is effective in reducing the wave reflection at the upstream side. The wave run-up length is dependent on the Iribarren number if the reduction induced by vertical freeboard is considered. Based on experimental data, empirical formulae have been proposed to predict the wave run-up responses in regular waves, probability of non-zero wave run-up occurrence, modified Weibull distribution of the wave run-up peaks and extreme wave run-up in random waves.

Design and construction of a novel energy-loss optical scintillation system (ELOSS) for heavy-ion particle identification.

We present the development of a novel heavy-ion particle-identification (PID) device based on an energy-loss measurement to be implemented in the focal plane of the S800 spectrograph of the Facility for Rare Isotope Beams (FRIB). The new instrument consists of a multi-segmented optical detector [energy-loss optical scintillation system (ELOSS)] that is filled with xenon at pressures ranging from 400 to 800 Torr. The gas volume is surrounded by arrays of photomultiplier tubes and placed along the direction of the beam for recording the prompt scintillation light. The number of detected photons, which is proportional to the energy deposited by the beam particle along its track in the detector volume, allows one to identify the corresponding atomic number (Z). The ELOSS technology is expected to provide high-resolution ΔE measurements (≤0.6% σ) at a high counting rate (>50kHz). In addition, it has the capability of providing timing information with around 150ps resolution (σ) compared to the lack of useable timing information of the conventional ionization chamber relying on drifting charges. The development of fast, accurate ΔE measurement techniques for present and future nuclear science facilities will have a high impact on the design and implementation of rare-isotope beam experiments at FRIB and their scientific outcome. As such, ELOSS also represents a prototype for the development of PID detector systems of other planned and future spectrometers, such as the high rigidity spectrometer at FRIB.

Development of multichord ion Doppler spectroscopy system for toroidal flow measurement of field-reversed configuration.

A double-chord ion Doppler spectroscopy (IDS) system was developed to measure the ion temperature and flow velocity of field-reversed configuration (FRC) plasmas in the FRC amplification via a translation-collisional merging (FAT-CM) device. Adopting a Czerny-Turner mount monochromator and 16-channel photomultiplier tube array, the developed IDS system achieves high wavelength resolution and fast time response. In addition, two vertically aligned optical paths share the optical system up to the monochromator and then branch just before the detector, successfully reducing crosstalk to <1%. The Doppler broadening was measured at two measurement points in the FAT-CM device, simultaneously, and ion temperatures of ∼50eV were measured. Toroidal spin-up from 7 to 15 km/s and a steady flow velocity of ∼10 km/s were estimated from the Doppler shift obtained by the developed system. The observation of the toroidal flow velocity and the spatial profile of the ion temperature of the FRC plasma in the FAT-CM device were realized. These spectroscopic diagnostic's double chord capabilities will aid in understanding and improving the FRC plasmas.

Tuning the Roundabout of Four-Point-Star Tiles with the Core Arm Length of Three Half-Turns for 2D DNA Arrays.

By rationally adjusting the weaving modes of point-star tiles, the curvature inherent in the tiles can be changed, and various DNA nanostructures can be assembled, such as planar wireframe meshes, perforated wireframe tubes, and curved wireframe polyhedra. Based on the weaving and tiling architectures for traditional point-star tiles with the core arm length at two DNA half-turns, we improved the weaving modes of our newly reported four-point-star tiles with the core arm length at three half-turns to adjust their curvature and rigidity for assembling 2D arrays of DNA grids and tubes. Following our previous terms and methods to analyze the structural details of E-tiling tubes, we used the chiral indices (n,m) to describe the most abundant tube of typical assemblies; especially, we applied both one-locus and/or dual-locus biotin/streptavidin (SA) labelling strategies to define the configurations of two specific tubes, along with the absolute conformations of their component tiles. Such structural details of the DNA tubes composed of tiles with addressable concave and convex faces and packing directions should help us understand their physio-chemical and biological properties, and therefore promote their applications in drug delivery, biocatalysis, biomedicine, etc.

Fluidelastic instability of a curved tube array in single phase cross flow

Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6x9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability.

Energy reconstruction for large liquid scintillator detectors with machine learning techniques: aggregated features approach

Large-scale detectors consisting of a liquid scintillator target surrounded by an array of photo-multiplier tubes (PMTs) are widely used in the modern neutrino experiments: Borexino, KamLAND, Daya Bay, Double Chooz, RENO, and the upcoming JUNO with its satellite detector TAO. Such apparatuses are able to measure neutrino energy which can be derived from the amount of light and its spatial and temporal distribution over PMT channels. However, achieving a fine energy resolution in large-scale detectors is challenging. In this work, we present machine learning methods for energy reconstruction in the JUNO detector, the most advanced of its type. We focus on positron events in the energy range of 0–10 MeV which corresponds to the main signal in JUNO – neutrinos originated from nuclear reactor cores and detected via the inverse beta decay channel. We consider the following models: Boosted Decision Trees and Fully Connected Deep Neural Network, trained on aggregated features, calculated using the information collected by PMTs. We describe the details of our feature engineering procedure and show that machine learning models can provide the energy resolution sigma = 3% at 1 MeV using subsets of engineered features. The dataset for model training and testing is generated by the Monte Carlo method with the official JUNO software.

Effects of tube-support clearance and preload on in-plane fluidelastic instability of tube arrays

The effects of tube-support clearance and preload on In-Plane (IP) or streamwise Fluidelastic Instability (FEI) in tube arrays are investigated in this paper.First, experiments were conducted on an array of straight tubes fixed at one end and supported by flat bars in the out-of-plane (OOP) or transverse direction, at the other end. The array was made of half inch (12.7 mm) outer diameter tubes, arranged in a parallel triangular configuration with a pitch-to-diameter ratio P/D of 1.5. Tube-support clearance and preload were varied to study the precise effect of these parameters on the IP FEI behaviour of the tube array. The tests were conducted in single-phase air and water flows as well as two-phase flow. For each setup and volumetric quality, the flow rate was incrementally increased and the tube vibration response monitored until the tube bundle became unstable. The IP FEI threshold was found to be constant or only slightly increasing with decreasing support gaps in liquid and two-phase flows. As for the effect of preload, the IP FEI threshold was found to be nearly constant for preloads lower than 0.1 N and linearly increasing with preload beyond 0.1 N in two-phase flows. In single-phase liquid flow, the effect of preload was much more significant as a small preload was enough to suppress the IP FEI. In liquid flow, it was also found that, for centred tubes and at a flow velocity much higher than the IP FEI threshold, the motion of the tubes switched from the streamwise (IP) to the transverse (OOP) direction. It appeared that FEI of the second transverse mode caused the first IP mode to become stable.Second, a time-domain, nonlinear, numerical model was developed to simulate fluidelastic instability of the tube bundle, including the effects of the loose supports. The focus of this numerical study was the ability of the model to accurately represent the effects of the tube-support clearance and preloads. The results of the model were consistent with the experimental results: the variation of the instability threshold versus tube-support gap was found to be small and the trend of the results versus preload was generally linear beyond a certain threshold. The agreement between the predictions of the model and the experimental results of a loosely supported, multi-span, U-bend tube bundle subjected to two-phase Freon was found to be very good (within 22%), demonstrating the capability of the model to simulate IP FEI of a realistic tube bundle.

High Zinc Utilization Aqueous Zinc Ion Batteries Enabled by 3D Printed Graphene Arrays

The commercialization of aqueous zinc ion batteries requires good reversibility and high zinc utilization of zinc anode. For commonly applied 2D zinc anodes (zinc foils), their electrochemical performance and reversibility are often negatively correlated with the zinc utilization owing to the formation of zinc dendrites at the electrode-separator interphase. To overcome the disadvantages of 2D geometric design of zinc anode, this work fabricated two types of 3D printing graphene arrays (3DGs), tube arrays and pilar arrays, to simultaneously improve the reversibility and utilization of zinc anodes. The highly ordered 3D printed tubes/pillars array structures can accommodate the significant volume change during the zinc reversibly deposition/dissolution process and modify the zinc deposition on 3DGs. The array structures can also buffer the interaction between the metallic zinc and separator to protect AZIBs from short circuits. Consequently, the 3DGs showed considerable columbic efficiencies at current densities of 10–80 mA cm−2. The 3DGs@Zn anode delivered a lifespan of 1100 h in zinc symmetric cell at 2 mA cm−2 (1 mAh cm−2). The pouch cells fabricated with 3DGs@Zn anodes and V2O5 cathode delivered areal capacity (3.76 mAh cm−2) and zinc utilization (47.12%) under a practical N/P ratio (1.74:1). This work will overcome the limitations of the 2D geometric design of anodes for next-generation battery technologies.