Individual Tubes Research Articles

The Neonicotinoid Insecticide Imidacloprid Disrupts Bumblebee Foraging Rhythms and Sleep.

SummaryNeonicotinoids have been implicated in the large declines observed in insects such as bumblebees, an important group of pollinators. Neonicotinoids are agonists of nicotinic acetylcholine receptors that are found throughout the insect central nervous system and are the main mediators of synaptic neurotransmission. These receptors are important for the function of the insect central clock and circadian rhythms. The clock allows pollinators to coincide their activity with the availability of floral resources and favorable flight temperatures, as well as impact learning, navigation, and communication. Here we show that exposure to the field-relevant concentration of 10 μg/L imidacloprid caused a reduction in bumblebee foraging activity, locomotion, and foraging rhythmicity. Foragers showed an increase in daytime sleep and an increase in the proportion of activity occurring at night. This could reduce foraging and pollination opportunities, reducing the ability of the colony to grow and reproduce, endangering bee populations and crop yields.

In-House Viral Transport Medium (VTM) Manufacture in the Time of Shortage, Supply and Crisis of COVID-19 at Veteran Affairs Medical Center (VAMC)

Introduction/ObjectiveWith the outbreak of COVID-19 caused by SARS-CoV-2, there have been challenges in the maintenance of adequate supplies both in terms of PPE and for testing. The shortage of commercial VTM for the transport of specimens for PCR testing has created a situation in which laboratories would need to manufacture their own in-house VTM as commonly used commercial VTM is unavailable. However, there is sparse literature on the emergency manufacture of VTM. Here, we describe the VAMC experience in manufacturing/quality control on its own VTM.ResultsVTM was manufactured by pathology and laboratory medicine using strict aseptic technique with Hanks Balanced Salt Solution (HBSS) 500 ml bottle with phenol red, sterile heat-inactivated fetal bovine serum (FBS) gentamicin sulfate (50 mg/mL) and amphotericin B (250 ug/ml). First, 50 ml of amphotericin B and 50 ml of gentamicin sulfate were mixed. Then 10 ml of FBS was mixed with the HBSS bottle and then 2 ml of the gentamicin/amphotericin B mixture was also mixed into the HBSS bottle. 3 ml aliquots were made from this mixture to constitute individual tubes of VTM for clinical use. Sterility for each batch (after 24-hour incubation at 37o C in the CO2 incubator) was assessed visually and by culture on a blood agar, chocolate agar, and thioglycolate mediums. An efficacy check was performed for each batch by spiking positive and negative controls into the VTM aliquots; RT-PCR for SARS-CoV-2 was executed to verify the medium did not degrade viral RNA and produced expected results for room temperature, refrigerated, and frozen samples. Previously manufactured VTM without phenol red also underwent sterility and efficacy checks.ResultsVTM was successfully manufactured in-house, allowing testing to continue despite the shortage. Sterility and efficacy checks on all lots and bottles from which the VTM aliquots were made passed with no growth detected and efficacy passing with all expected positives and negatives resulting as expected.ConclusionTo the author’s knowledge, this represents the first published abstract on VTM manufacture in this most unprecedented crisis involving COVID-19. In this national emergency with corresponding shortage of testing supplies including commercial VTM, the in-house manufacture of VTM is both feasible and prudent to ensure continuity of testing and quality patient/laboratory care.

New records of mosquito species (Diptera: Culicidae) in La Comarca Lagunera, Durango, Mexico

Introduction: Many mosquitoes are of great medical and veterinary importance because they transmit numerous pathogens which cause diseases in animals and humans; thus, knowing their taxonomy and distribution is pivotal for implementing the correct control strategies. The aim of this study was to determine the occurrence of mosquito species and their distribution in La Comarca Lagunera in the state of Durango, Mexico.Method: Adult mosquitoes were collected at different resting sites in four municipalities between August and November 2018 using Insectzookas. Aquatic habitats were also sampled for immature stages. Adult specimens were killed using lethal chambers with triethylamine vapors; while larvae and pupae were stored in individual tubes to obtain the adult stages and associated exuviae. All material was transported to the Molecular Biology Laboratory of the Parasitology Department of the Universidad Autónoma Agraria Antonio Narro, Unidad Laguna (UAAAN-UL) for mounting and taxonomical identification. Species were identified using taxonomic keys for the region.Results: In total, 689 mosquito specimens (286 males and 403 females) were collected belonging to 15 species, among them Anopheles franciscanus McCracken, Culex erythrothorax Dyar, and Toxorhynchites moctezuma (Dyar and Knab) are new records for Durango State. The most abundant species was Cx. quinquefasciatus Say with 364 (56.2%) specimens, followed by Aedes aegypti (Linnaeus) (21.3%) and Ae. vexans (Meigen) (7.7%).Conclusion: 13 out of 15 species collected are associated with the transmission of an arbovirus of relevant medical or veterinary importance in Mexico. There are now 38 species recorded for Durango. The information in this study is directly relevant for the Health Ministry in Durango State for the control of vector borne diseases in the region.

State of the Art and Trends in the Design and Operation of High- and Low-Pressure Heaters for Steam Turbines at Thermal and Nuclear Power Plants in Russia and Abroad: Part 2. Heater Design and Operation Peculiarities

The modern state of the processes connected with design, calculation, and operation of heaters used in steam turbine regeneration systems is reviewed and analyzed on the basis of data available from domestically published and foreign sources. The existing methods for thermal–hydraulic, strength, and vibration design calculations of apparatuses are described; criteria adopted in designing individual areas of heater heat-transfer surfaces are mentioned, and recommendations on taking into account the heat-transfer surface fouling in analyzing its influence on the apparatus’s thermal-efficiency indicators are given. The possibility of using modern computation tools for designing regeneration system apparatuses is considered. A list of materials from which the apparatus heat-transfer surface tubes are made is given; methods for fixing them in shell-and-tube heaters are mentioned, and the level of stresses recommended for individual tube sections is pointed out. The values of key operating parameters—coolant temperatures, pressures and velocities—are given, which are selected based on the results of designing the apparatuses and with reference to foreign standards and other regulatory documents. Recommendations used by foreign manufacturers of heaters as guidelines for selecting vibration-safe length of free spans and tube fastening methods in the bend zone are given. Failures that most frequently occur during operation of high- and low-pressure heaters are pointed out. Some questions concerned with the technology for repairing the regeneration system heaters used as part of a turbine plant are considered. It is shown that there are differences in arranging the repair system and, especially, in the maintenance of heat-transfer apparatuses as concerns the tools necessary for monitoring the equipment condition. The introduction of new technologies for designing and operating heaters in domestic practice will help keep their efficiency and reliability indicators at a high level.

Fluoride release from different tooth colored restorative materials: An in vitro study

This in vitro study evaluated the amount of fluoride released from fluoride-containing materials over a period of (30) days. Twenty eight disk samples (2.5 mm depth × 10 mm diameter) were prepared and divided into four groups: GroupI Vitremer glass ionomer, group II resin composite Tetric, group III resin composite Definite, and group IV Compoglass. The samples were stored in an incubator at 37°C for (24) hours. Each disk was suspended in an individual plastic tube containing (3) ml of deionized water. The water was changed every (24) hours, fluoride release was determined at each day for (30) days, after buffering the solution with equal volume of TISAB. The fluoride release was measured with a fluoride-ion selective specific electrode previously calibrated from (0.05) to (100) ppm. Fluoride release was expressed in part per million (ppm). ANOVA test was used to evaluate the data. The results revealed that Vetrimer glass ionomer released significantly more fluoride (4l ppm) for the first day than all the other products. This was followed by Compoglass which exhibits more fluoride release than the other two types (32 ppm), the Tetric composite resin Was the third material in the amount of fluoride released (3.75 ppm), and finally the resin composite Definite released fluoride in about (0.75 ppm). All fluoride release was decreased from day (1) to (30) observation period.

Relativistic finite temperature multifluid hydrodynamics in a neutron star from a variational principle

We develop a relativistic multifluid dynamics appropriate for describing neutron star cores at finite temperatures based on Carter's convective variational procedure. The model includes seven fluids, accounting for both normal and superfluid/superconducting neutrons and protons, leptons (electrons and muons) and entropy. The formulation is compared to the non-variational relativistic multifluid hydrodynamics of Gusakov and collaborators and shown to be equivalent. Vortex lines and flux tubes, mutual friction, vortex pinning, heat conduction and viscosity are incorporated into the model in steps after the basic hydrodynamics is described. The multifluid system is then considered at the mesoscopic scale where the currents around individual vortex lines and flux tubes are important, and this mesoscopic theory is averaged to determine the detailed vortex line/flux tube contributions to the macroscopic "effective" theory. This matching procedure is partially successful, though obtaining full agreement between the averaged mesoscopic and macroscopic effective theory requires discarding subdominant terms. The matching procedure allow us to interpret the magnetic $H$-field inside a neutron star in a way that is consistent with condensed matter physics literature, and to clarify the difference between this interpretation and that in previous astrophysical works.

Calculating the Efficiency of Complex Shaped Fins

In the calculation of heat exchangers with individual finned tubes or continuous fin heat exchangers, i.e., plate-fin and tube heat exchangers (PFTHEs), it is necessary to determine the efficiency of complex fins. Usually, these are circular or rectangular fins mounted on circular, elliptical, or oval tubes as well as flattened tubes. In case of PFTHEs, the continuous fin is divided into virtual fins, which are rectangular for an inline pipe layout or hexagonal for a staggered pipe arrangement. This paper presents a procedure based on the finite element method for determining the efficiency of fins of any shape placed on tubes of any shape. The article shows examples of calculating the efficiency of virtual fins in most commonly used PFTHEs. The research also assesses the accuracy of determining the efficiency of complex-shaped fins using approximated methods such as the equivalent circular fin method (Schmidt’s method) and the sector method. The efficiency of a fin as a function of heat transfer coefficient for four different, most common geometries in PFTHEs was depicted. An example of determining the efficiency of a hexagonal fin using various methods for air velocities measured at the exchanger inlet was presented.

Mass spectrometric sample identification with indicator compounds introduced via labeled sample tubes.

The risk of sample confusion continues to be a challenge for the pre-analytical part of the overall testing process. We here describe a novel system to track samples based on a chemical code labeling of test tubes with unique combinations of indicator compounds, which are naturally not present in specimens of human origin. As part of the sample vessel filling, the liquid specimens are permanently labeled with the compound code that can be tracked back to the primary tube. As a proof of concept we used 10 stable-isotope-labeled derivates of medical drugs as indicator substances to create a combinatory 10-digit binary number ID for individual test tubes, i.e. presence/absence of the respective compound. For this purpose, combinations of indicator compounds were provided in evaporated form in polypropylene tubes prior to filling with anonymized patient whole blood and corresponding plasmas subjected to liquid chromatography tandem-mass spectrometry designed to detect the 10 indicator compounds. In the blind analysis, we correctly identified 307 different whole blood samples by readout of a 10-digit binary number ID based on the detection of indicator compounds with respect to their presence and number. We have demonstrated the feasibility of an internal labeling procedure for diagnostic samples with mass spectrometry-based readout of dissolved indicator compound combinations as a binary number ID. With an increasing number of coding compounds (≫10) a vast number of combinations for sample labeling can be realized beyond the proof of concept setting studied herein.

3-D Multi-Tubular Reactor Model Development for the Oxidative Dehydrogenation of Butene to 1,3-Butadiene

The oxidative dehydrogenation (ODH) of butene has been recently developed as a viable alternative for the synthesis of 1,3-butadiene due to its advantages over other conventional methods. Various catalytic reactors for this process have been previously studied, albeit with a focus on lab-scale design. In this study, a multi-tubular reactor model for the butadiene synthesis via ODH of butene was developed using computational fluid dynamics (CFD). For this, the 3D multi-tubular model, which combines complex reaction kinetics with a shell-side coolant fluid over a series of individual reactor tubes, was generated using OpenFOAM®. Then, the developed model was validated and analyzed with the experimental results, which gave a maximum error of 7.5%. Finally, parametric studies were conducted to evaluate the effect of thermodynamic conditions (isothermal, non-isothermal and adiabatic), feed temperature, and gas velocity on reactor performance. The results showed the formation of a hotspot at the reactor exit, which necessitates an efficient temperature control at that section of the reactor. It was also found that as the temperature increased, the conversion and yield increased whilst the selectivity decreased. The converse was found for increasing velocities.

Reef forming Serpula vermicularis from Scotland and Ireland: Tube structure, composition and implications

Serpula vermicularis, as with many other serpulid species, is normally found as separate individual tubes. A limited number of exceptions to this have been recorded where S. vermicularis forms isolated vertically oriented ‘reef’-like structures, of agglomerated intertwined tubes, up to ∼35 cm in height. Such reefs have mainly been noted from freshwater influenced sea lochs along the west coast of Ireland and Scotland. The ultrastructure of the tubes of reef forming S. vermicularis described herein, is more diverse than that previously described of tubes from solitary S. vermicularis from fully marine environments, and bears many similarities to that of Spirobranchus triqueter (as Pomatoceros triqueter). The tube comprises a mixture of ordered (O), unordered (U) and spherulitic-prismatic (SPHP) fabrics, with composition varying from Mg-calcite to aragonite. Ordered and unordered fabrics are used as replacements for previously used lamello-fibrillar and irregularly oriented prismatic fabrics, based on their more complex nano-structure, and in the case of ordered vs lamello-fibrillar fabrics, the latter should be restricted to usage amongst the Mollusca as originally described; as the two are likely to have had divergent origins/modes of formation. Both changes follow previous work on Spirobranchus and Spirorbis, and resurrect the descriptive terminology of ‘ordered chevron structure’ and ‘unordered chevron structure’. Examination of the detailed nano-structure of the lath-like components of ordered and unordered fabrics illustrates that both comprise previously unrecognised spherical calcitic structures, arranged into bundles of parallel to sub-parallel rods. The latter has important implications for mode of formation for both S. vermicularis and other serpulid tubes with similar microfabrics such as Spirobranchus, reopening the debate over a simple plastering mode of tube formation versus that of an organic sheet or organic matter mediated origin.

Linking mean pore velocity and dispersivity to pore velocity distribution by advection–dispersion and stream tube modeling

A large set of experimental solute tracer breakthrough data (corresponding to more than 350 individual tracer breakthrough curves) in eight granular filter materials, were used to investigate the links between solute dispersivity and the shape of the pore velocity—relative pore area distributions for the materials. Solute dispersivity values and the shape of the pore velocity—relative pore area distributions were determined by fitting the breakthrough data to the advection–dispersion equation and to the stream tube modeling (STM), respectively. For the STM calculations, stream tube diameter and average stream tube flow rate were allowed to vary between individual stream tubes. Shape parameters e.g., mean, coefficient of variation, skewness and excess kurtosis for the STM-based pore velocity—relative pore area distributions were subsequently calculated. Comparisons between dispersivity and shape parameter values showed strong correlation between dispersivity, coefficient of variation, skewness and excess kurtosis. These results also indicated a universal relationship between dispersivity, skewness and excess kurtosis across all materials and breakthrough curves. This relationship will assist in modelling of experimental data which cannot be characterized by a single or a limited number of pore velocities but require continuous pore velocity distributions. Results further indicated, that the shape of the observed pore velocity—relative pore area distributions could be well approximated by a log-normal distribution.

Validation of Chronic Restraint Stress Model in Young Adult Rats for the Study of Depression Using Longitudinal Multimodal MR Imaging.

Prior research suggests that the neurobiological underpinnings of depression include aberrant brain functional connectivity, neurometabolite levels, and hippocampal volume. Chronic restraint stress (CRS) depression model in rats has been shown to elicit behavioral, gene expression, protein, functional connectivity, and hippocampal volume changes similar to those in human depression. However, no study to date has examined the association between behavioral changes and brain changes within the same animals. This study specifically addressed the correlation between the outcomes of behavioral tests and multiple 9.4 T magnetic resonance imaging (MRI) modalities in the CRS model using data collected longitudinally in the same animals. CRS involved placing young adult male Sprague Dawley rats in individual transparent tubes for 2.5 h daily over 13 d. Elevated plus maze (EPM) and forced swim tests (FSTs) confirmed the presence of anxiety-like and depression-like behaviors, respectively, postrestraint. Resting-state functional MRI (rs-fMRI) data revealed hypoconnectivity within the salience and interoceptive networks and hyperconnectivity of several brain regions to the cingulate cortex. Proton magnetic resonance spectroscopy revealed decreased sensorimotor cortical glutamate (Glu), glutamine (Gln), and combined Glu-Gln (Glx) levels. Volumetric analysis of T2-weighted images revealed decreased hippocampal volume. Importantly, these changes parallel those found in human depression, suggesting that the CRS rodent model has utility for translational studies and novel intervention development for depression.

A Novel Omnidirectional Self-Locked Energy Absorption System Inspired by Windmill

Abstract Impact accidents cause great damage to lives and properties because the destructiveness, direction, and action mode of impact loadings can hardly be predicted. Ordinary thin-walled tube systems for energy absorption require outside constraints or inside fasteners to avoid tube splashing, which affects the modifiability of the systems and limits their application in emergencies. In an effort to break through this limitation, inspired by windmill, a novel omnidirectional self-locked energy absorption system has been proposed. The proposed system is made up of thin-walled tubes with windmill-liked cross section, which are specially designed to interlock with adjacent tubes and thus provide constraints among individual tubes to resist impact loadings in spatial arbitrary directions. The spatial omnidirectional self-locking capability of the windmill-inspired system is demonstrated under distributed and concentrated impact loadings. Moreover, the windmill-inspired system shows higher energy absorption efficiency than that of the widely used round tube system and previous self-locked system under loadings in various directions, and their energy absorption properties can be further improved by combining with the round tube system, adjusting the geometric parameter of each tube and designing the arrangement of tubes with different properties in the system. This work may shed light on the energy absorption system design and expand the application of self-locked energy absorption systems.

In Situ Monitoring of the Seeding and Growth of Silver Metal-Organic Nanotubes by Liquid-Cell Transmission Electron Microscopy.

Metal-organic nanotubes (MONTs) are highly ordered one-dimensional crystalline porous frameworks. Despite being nanomaterials, virtually all studies of MONTs rely on characterization of the bulk crystalline material (micron-sized) by single-crystal X-ray diffraction. For MONTs to achieve their raison d'être as tunable one-dimensional nanomaterials, individual tubes or small finite bundles of tubes must be synthesized and characterized. Therefore, to directly observe their formation under a variety of reaction conditions in solution, we employ liquid-cell transmission electron microscopy (LCTEM), which allows the early stages of MONT assembly to be monitored in real time. Notably, changing the metal-to-ligand ratio alters the local concentrations of reactant monomers, resulting in multiple nucleation and growth pathways and diverse morphologies at the nanoscale. These various initial seeds grow to form the same nanocrystalline needle phase. This approach of employing LCTEM to study these nanomaterials is analogous to monitoring typical homogeneous solution phase reactions by NMR for controlled nanomaterial formation.

Development and evaluation of a list mode neutron coincidence collar for spatial response measurements of fresh fuel assemblies

The capabilities of current safeguards neutron instrumentation can be expanded by acquiring and analyzing data in new ways. A new List Mode Collar (LMCL) was created by retrofitting a traditional safeguards neutron coincidence counting system, the Neutron Coincidence Collar, with newly developed preamplifiers on each of its 18 3He tubes in active interrogation mode. By applying list mode data acquisition (LMDA) and analysis, a signal from each 3He tube can now be recorded and analyzed to determine the neutron count rate measured in each individual 3He tube. Further, the count rate distribution across all 3He tube locations in the system can be determined. This is the first time that a full list mode method has been implemented using a traditional neutron coincidence collar and spatial response data has been obtained.The objective of this research was to develop and evaluate a laboratory demonstration list mode neutron coincidence collar (LMCL) that can extract a greater number of useful signatures than are currently generated using the current collar. A new analysis method called the “List Mode Response Matrix” has also been developed for use in combination with these measurements to improve the detection of missing fuel pins (partial defects) during the nondestructive assay of fresh nuclear fuel assemblies, although analysis algorithms will be reported separately from this experimental evaluation. In this paper, 18 channel spatial response data are presented for a 252Cf source moving within the LMCL detector cavity. LMDA, combined with the addition of multiple preamplifiers, facilitates this capability by increasing the number of signals that can be measured simultaneously; allowing for in-depth analysis of neutron coincidence events to determine the location and distribution of nuclear material within the measurement geometry. This approach enables a spatial response measurement to form a “pattern” or item signature unique to the fissioning source’s distribution; in the case of the LMCL, the distribution of fresh low-enriched uranium fuel within the assembly. A major benefit provided by LMDA is that this can all be achieved from a single measurement pulse train in offline analysis.To experimentally demonstrate this concept, a Mirion Technologies (Canberra) model JCC-71 Neutron Coincidence Collar has been retrofitted with new electronics designed at Oak Ridge National Laboratory. This paper presents the results from the experimental evaluation of the laboratory demonstration system. The results indicate equivalent performance of the LMCL to the original collar in addition to improved spatial response capabilities, while maintaining the original system footprint.

Hexagonal Boron Nitride As an Ideal Substrate for Carbon Nanotube Photonics

Hexagonal boron nitride is widely used as a substrate for two-dimensional materials in both electronic and photonic devices. Here, we demonstrate that two-dimensional hexagonal boron nitride is also an ideal substrate for one-dimensional single-walled carbon nanotubes. Nanotubes directly attached to hexagonal boron nitride show bright photoluminescence with narrow linewidth at room temperature, comparable to air-suspended nanotubes. Using photoluminescence excitation spectroscopy, we unambiguously assign the chiralities of nanotubes on boron nitride by tracking individual tubes before and after contact with boron nitride. Although hexagonal boron nitride has a low dielectric constant and is attached to only one side of the nanotubes, we observe that optical transition energies are redshifted as much as ~50 meV from the air-suspended nanotubes. We also perform statistical measurements on more than 400 tubes, and the redshifts are found to be dependent on tube diameter. This work opens up new possibilities for all-solid-state carbon nanotube photonic devices by utilizing hexagonal boron nitride substrates.

A flexion-based approach for the simulation of turbulent flows

Turbulent flows at high Reynolds numbers are dominated by vortex filaments and/or sheets with sharp gradients in the vorticity field near the boundaries of the vortical structures. Numerical simulations of high Reynolds number flows are computationally demanding due to the fine grid required to accurately resolve these sharp gradient regions. In this paper, an alternative approach is proposed to improve the computational efficiency of Navier–Stokes solvers by reformulating the momentum equations as a set of equations for the time-dependent evolution of the flexion field. The flexion vector represents the curl of the vorticity field and is better able to resolve nonlinear effects in regions with large vorticity gradients. The improved resolution capabilities of the flexion-based approach are illustrated through the pseudospectral computations of the rollup of a perturbed 2D shear layer and the transition to a turbulence/viscous decay of the three-dimensional (3D) Taylor–Green vortex. The flexion-based formulation also provides further insight into the dynamics of turbulence through the evolution of the mean-square flexion or palinstrophy. Analysis of data from the Taylor–Green vortex simulations shows that the observed rapid growth of small-scale features and palinstrophy in 3D turbulent flows is primarily associated with flexion amplification by the curl of the vortex stretching vector. Consequently, we hypothesize that the primary physical mechanism responsible for energy cascade from large to small scales is the curl of the vortex stretching vector of interacting vortex tubes, as opposed to the stretching of individual vortex tubes.

A validated discretized thermal model for application in bare tube evaporative coolers and condensers

A discretized modelling method for evaporative coolers is presented in this paper. This study aims to validate the modelling method which can then be applied to any bare tube evaporative cooler/condenser and specifically to model the bare tube bundle of a hybrid (dry/wet) dephlegmator (HDWD), used in direct dry cooling for thermal power plants. The model discretizes a bare tube bundle into single tube control volumes to numerically integrate the governing differential energy equations for the three working fluids. The discretized modelling method presented here allows for evaluation of the fluid/vapour flow in individual tubes of an evaporative cooler/condenser or HDWD system and therefore offers an additional and valuable level of detail when compared to existing integral models.The model presented here is validated against experimental results from a stainless-steel evaporative cooler with water as process fluid and also compared to experimental results of two other evaporative coolers from literature. The cooler consists of a bare tube bundle (inlet area 1.5 m × 1.5 m) with 20 rows of do = 19.8 mm tubes in a staggered 2.27 × do arrangement. Nine intermediate process fluid temperature measurements are recorded throughout the height of the tube bundle as well as the mean outlet processes water temperature to critically compare the measured and modelled values. Intermediate deluge water temperature is also measured with five thermocouples located in deluge water traps below selected tubes.A total of 16 test points, over a range of air and deluge water flow rates, are analyzed and the average error between the predicted and bulk measured process fluid outlet temperature is 0.62% while the maximum error is 1.45%. The results demonstrate that the intermediate processes water temperatures per tube, the bulk outlet processes water temperature and the deluge water temperature could be accurately predicted with the discretized analytical model. The valuable insight of each tube row indicates the trend of the heat transfer rate throughout the height of the tube bundle where the first tube row from the top, which is the air outlet side, has the highest heat transfer rate where after the heat transfer rate decreases to a minimum, at tube 13 from the bottom, and then increases again in the lower portion of the bundle. The discretized model can be adapted to model the HDWD or other evaporative condensers by employing appropriate steam side heat transfer correlations which will enable the analytical model to predict the rate of heat transfer and associated pressure drops in each tube.

Experimental investigation of the condensation mechanisms in the shell side of spiral wound heat exchangers

An experimental investigation of the water vapor condensation mechanisms occurring in the shell side of spiral wound heat exchangers was conducted. Eight different test sections with varying structures were fabricated, each with an observation window, to investigate the effects of the geometric parameters on the condensation process. The experimental results indicated that there is a minimum condensation heat transfer coefficient for the top tube as the inclination of tube increases because of the changes in the film thickness. A comparison of the heat transfer coefficient between each individual tube and the entire test section was conducted and indicated that the heat transfer in the lower tubes dominate the overall heat transfer of the test section. While increases in the tube pitch changes the velocity field in the shell side, it also results in a decrease in the shell-side condensation heat transfer coefficient and the overall heat transfer of the test section.

A comparative study of the tensile failure of carbon nanotube, Dyneema and carbon fibre tows over six orders of strain rate

Manufacturing carbon nanotube (CNT) fibres on a large scale with properties that are a significant fraction of those measured for individual tubes or smaller bundles is crucial to achieving greater impact in industrial applications. We describe three macrostructured morphologies produced on a laboratory scale: CNT ribbons, ropes and tows, wherein tows are the most suitable for industrial scale-up, comprising a bundled structure of thousands of individual micro-fibres. For each morphology, we present the tensile failure mechanisms and mechanical performance observed over six orders of magnitude of strain rate. The tests were conducted on a conventional Hounsfield tensile tester (10─4 to 10─1 s─1 strain rate) and a modified split-Hopkinson tensile bar tester (30–150 s─1 strain rate). To avoid the problem of clamp failure, we present a novel method of testing loops, rather than uniaxial samples, as-produced from our chemical vapour deposition reactor. For material benchmarking and validation, we also tested unsized carbon fibre (Hexcel AS4) and Dyneema tows (SK25). All materials were used ‘dry’, i.e. not as a composite, for raw material and structure comparison. We show here that CNT tows exhibit both a mechanical performance and fracture behaviour which combines the ductility of Dyneema with the tenacity of carbon fibre.