Taper Geometry Research Articles

An experimental investigation on the performance of TEGs with a compact heat exchanger design towards low-grade thermal energy recovery

Thermoelectric generator (TEG) is a promising technology for low-grade heat recovery, whereas the scalability of TEGs remains challenging. Modular design with an ideal thermal design provides a potential solution for large scale application of TEG system in harvesting low-grade thermal energy. In this paper, a concept of modular design with a compact thermal design was proposed for the cold and hot sides of TEG system. A compact heat exchanger was fabricated by using diffusion welding technique for the TEG system. The inlet and outlet of the heat exchanger are designed with a tapering geometry to achieve a uniform fluid flow and temperature distribution among the flow channels, and the inlets of the hot-side heat exchangers and the outlets of cold-side heat exchangers can be arranged at the same side to realize a counter-flow thermal design. With the design of compact heat exchanger, the modularization assembly of a TEG system can be achieved and the TEG system can be scaled up by alternately arranging hot- and cold-side heat exchangers. To evaluate the TEG performance with current design, a single unit with five TEG modules was tested at various temperature differences. Despite that a thermoelectric conversion efficiency of 1.64% was obtained at a temperature difference of 96.4 °C, the unit exhibited a high volumetric power density (86.4 kW/m3) and a negligible power consumption (0.64% of the total power output). Furthermore, the measurements were also carried out to evaluate the temperature distribution across the contacting surface of the heat exchanger and the flow resistance between inlet outlet of the heat exchanger. A low temperature variation (<1.76 °C) across the heating surface was indicated at the temperature differences from 26.4 to 96.4 °C with a relatively low flow resistance (1.00–4.34 kPa) at the flow rates from 0.026 to 0.06 kg/s. The current design of the heat exchanger realizes a relatively uniform temperature distribution and a low flow resistance, leading to a better performance of the developed TEG and making it feasible for the large-scale applications towards low-grade thermal energy recovery.

Thermohydraulic performance and second law analysis of a tube embedded with multiple helical tape inserts

ABSTRACT The present investigation deals with the analysis of the heat exchanger tube by inserting the multiple helical tape geometry to determine the heat transfer, friction factor, thermal performance, and entropy generation experimentally. The helical tapes designed for current investigation are analyzed in terms of geometrical parameters namely number of tape (1,2,3), twist ratio (2,3,4), and width ratio (0.4). The experiments are conducted in the range of Reynolds number lying in turbulent region from 5000 to 29000. The experimentation affirms an enhancement of the thermal performance. The experimental data reveal that there is 3.95 times enhancement in the heat transfer for twist ratio of 2 and number of tapes of 3. The thermal performance factor is enhanced by 1.23 times over smooth tube for the twist ratio of 2 and number of tapes of 1. It is observed that the maximum heat transfer enhancement is found for low and high values of twist ratio and number of tapes, respectively. The rate of entropy generation is less for the tube equipped with helical tape inserts for all possible cases than smooth tube. The minimum entropy generation value of 0.27 is observed for twist ratio of 2 and number of tapes 3. The developed empirical correlations for Nusselt number, friction factor, and thermal performance factor are in good agreement with experimental results.

Analysis of tall chimney with piled raft foundation under wind load using ANSYS

Chimneys are the principal structures in any industry that emits pollutants to higher parts of the atmosphere. The geometrical traits of the chimney are so unique that it has slender dimensions and tapering geometry and therefore the analysis and design of chimney and other forms of tower structures should be carried out individually. Nowadays chimney heights have gone up from 100 m to more than 400 m according to the purpose that it serves. These tall chimneys are very sensitive to wind loads. Wind load is one of the most important parameters that affect the response of tall building’s chimneys. When tall chimneys are subjected to wind load, it may undergo lateral deflection. It also leads to the development of radial and tangential moments along with base moments. The dynamic wind effects on chimneys by analytical procedures are intricate and take a great amount of time. To analyze and further improve the response of chimneys, analysis using commercial finite element (FE) software ANSYS is carried out. Chimney with and without providing stiffeners is analyzed using ANSYS and the lateral deflection and bending moment found from the chimney models are compared. This method is more economical and time-saving.

Assessing Taper Geometry, Head Size, Head Material, and Their Interactions in Taper Fretting Corrosion of Retrieved Total Hip Arthroplasty Implants

BackgroundDecreased fretting and corrosion damage at the taper interface of retrieved ceramic-on-polyethylene total hip arthroplasty (THA) implants has been consistently reported; however, resultant fretting corrosion as a function of femoral head size and taper geometry has not been definitively explained. MethodsEight cohorts were defined from 157 retrieved THA implants based on femoral head composition (n = 95, zirconia-toughened alumina, ZTA vs n = 62, cobalt-chromium alloy, CoCr), head size (n = 56, 32mm vs n = 101, 36mm), and taper geometry (n = 84, 12/14 vs n = 73, V40). THA implants were evaluated and graded for taper fretting and corrosion. Data were statistically analyzed, including via a 23 factorial modeling. ResultsFactorial-based analysis indicated the significant factors related to both resultant (summed) fretting and corrosion damage were head material and taper geometry; head material–taper geometry interaction was also a significant factor in resultant corrosion damage. Lower rates of moderate-to-severe fretting and corrosion damage were exhibited on ZTA heads (ZTA = 13%, CoCr = 38%), smaller heads (32mm = 18%, 36mm = 26%), and 12/14 tapers (12/14 = 13%, V40 = 35%). ZTA+32mm heads demonstrated the lowest rates of moderate-to-severe fretting and corrosion damage (12/14 = 2%, V40 = 7%), whereas CoCr heads with V40 tapers demonstrated the greatest rates of moderate-to-severe damage (32mm = 47%, 36mm = 59%). ConclusionIn this series, retrieved implants with ZTA, 32-mm heads paired with 12/14 tapers exhibited lower rates of moderate-to-severe damage. Factorial analysis showed head material, taper geometry, and their interactions were the most significant factors associated with resultant damage grades. Isolating implant features may provide additional information regarding factors leading to fretting and corrosion damage in THA. Level of EvidenceIV (case series).

Defect Tolerant High-Temperature Superconducting Cable for the Central Solenoid of Compact Fusion Reactor

The future compact fusion reactors, will feature very high, >16 tesla, magnetic fields, which can be only created by magnet coils wound with the second generation (2G) superconducting wire. The 2G wires are currently manufactured with a thin (1-2 μm) YBCO layer deposited on a ~100 μm thick metal substrate. The substrate makes up a considerable portion of the cross-section, thus reducing the engineering current density. It also prevents effective inter-filament current sharing, and the wide tape geometry is responsible for high magnetization loss. We report on the recent progress in the development of a new type of high-temperature superconducting cable architecture for the central solenoid of a high-field fusion reactor. The new architecture combines two recent innovations: (i) Reduction of AC loss by bundling narrow, 1-2 mm, exfoliated YBCO filaments into a cable, (ii) continuous winding and parallel slicing technologies, which eliminate labor-intensive and expensive handling of narrow filaments, critical for the central solenoid, which operates under pulsed load.

Optical confinement in the nanocoax: coupling to the fundamental TEM-like mode.

The nanoscale coaxial cable (nanocoax) has demonstrated optical confinement in the visible and the near infrared. We report on a novel nanofabrication process which yields optically addressable, sub-µm diameter, and high aspect ratio metal-insulator-metal nanocoaxes made by atomic layer deposition of Pt and Al2O3. We observe sub-diffraction-limited optical transmission via the fundamental, TEM-like mode by excitation with a radially polarized optical vortex beam. Our experimental results are based on interrogation with a polarimetric imager. Finite element method numerical simulations support these results, and their uniaxial symmetry was exploited to model taper geometries with both an electrically large volume, (15λ)3, and a nanoscopic exit aperture, (λ/200)2.

Cubic Spline-Based Genetic Algorithm Optimization for Millimeter and Microwave Integrated Circuits

A clamped cubic spline profile taper of an air-filled substrate integrated waveguide (SIW) transition was optimized to search for the optimal design of taper in this paper. The optimization technique involved a combination of the multi-objective genetic algorithm (MOGA) and full-wave analysis of the waveguide. The data from the return and transmission losses provides a basis for the optimization of the transition tapers design. The simulation results show the efficacy of our proposed strategy, where the optimal taper geometry yields an improvement of the return loss while maintaining its original transmission loss at Ka-band (26–40 GHz) frequencies.

Investigation of the effect of the taper geometry on the sensitivity of tapered-fibre gas sensors

In this paper, a comprehensive study is conducted to determine the optimum geometry for tapered fibre-optic gas sensors. A staircase concatenation method is introduced to investigate the effects of taper angle and fibre taper diameter on the sensitivity of the tapered-fibre sensors. The simulations show that the sensitivity of the tapered fibre-optic sensor increases by increasing the taper angle and reducing the taper diameter. To evaluate the predictions of the presented model, different tapered-fibre sensors have been fabricated and tested. The surface of the tapered fibres has been coated with palladium in order to determine the sensitivity of the sensors to hydrogen exposure. By increasing the percentage of the hydrogen in the surrounding environment, a shift of the output interference spectrum is observed. The experimental results confirm the simulation results obtained for the effect of geometry on the sensitivity of the sensors.

EXPERIMENTAL INVESTIGATIONS TO STUDY THE INFLUENCE OF TWISTED TAPE INSERT ON HEAT TRANSFER EQUIPMENTS – AN EXTENSIVE REVIEW

Heat transfer augmentation with compact and effective manner are the recent developments of the heat exchangers. Considering cost reduction, simplicity, compact size etc were the parameters considered for the design and development of heat exchangers. Use of passive techniques like creating fins, rough surface on the flow path, wire coil inserts, generation of swirl on the flow path and mounting inserts like blocks, winglets and twisted tapes were the impressive methods of heat transfer intensification in heat exchanger design. Twisted tape is the technique that supports to enhance the heat transfer in heat exchanging devices. Many investigators involved on the experimentation to enhance the rate of heat transfer employing twisted tapes by varying the twisted tape geometry , twisted tape shape and the size of the duct etc. This extensive review emphases on the argumentation of heat transfer by twisted tape insert with varying twisted tape geometry, is discussed and disclosed in detail. This review revealed the outcomes of the literatures reported for the past decade.

Genetic Algorithm-Based Approach for Minimising Losses in Substrate-Integrated Waveguide

The transitions in air-filled substrate-integrated waveguide (SIW) are studied here for millimetre-wave applications. A good design of an air-filled SIW (AFSIW) must allow for minimum losses in its interconnects between the air-filled and dielectric-filled regions of the SIW. This paper assesses the influence of the geometry of transition taper in an AFSIW on the return and insertion losses using full-wave analysis of a complete AFSIW structure. The data from the return and transmission losses provide a basis in the optimisation of the design of the transition tapers. The optimisation approach uses the multi-objective genetic algorithm (GA) with full-wave analysis to find an optimum profile of the transition. Defining the profile of the transition taper with a clamped cubic spline as a phenotype, the developed procedure shows that further losses are possible within the prescribed frequency bands. Furthermore, the length of the transition taper can be significantly reduced while maintaining an optimal quality of signal transmission in the transition. The simulation results show the efficacy of the proposed strategy where the optimal taper geometry is shown to provide a wider band of operating frequencies with lower return loss compared to a more established taper geometry.

Microfluidics control the ballistic energy of thermocavitation liquid jets for needle-free injections

Illuminating a water solution with a focused continuous wave laser produces a strong local heating of the liquid that leads to the nucleation of bubbles, also known as thermocavitation. During the growth of the bubble, the surrounding liquid is expelled from the constraining microfluidic channel through a nozzle, creating a jet. The characteristics of the resulting liquid jet were imaged using ultra-fast imaging techniques. Here, we provide a phenomenological description of the jet shapes and velocities and compare them with a boundary integral numerical model. We define the parameter regime, varying jet speed, taper geometry, and liquid volume for optimal printing, injection, and spray applications. These results are important for the design of energy-efficient needle-free jet injectors based on microfluidic thermocavitation.

Accolade TMZF trunnion corrosion and mechanical failure 9 yr after primary surgery: A case report and treatment options

Accolade TMZF trunnion corrosion and mechanical failure 9 yr after primary surgery: A case report and treatment options

Comparative study of heat transfer characteristics of a tube equipped with X-shaped and twisted tape insert

In order to investigate the effect of insert tape geometry on the heat exchanger tubes, present study compares thermal characteristic of water flowing in a tube equipped with X-tape and twisted tape. Material of the insert tapes used in the investigation is stainless steel. Thermal performance of heat exchanger tube has been analysed in terms of heat transfer rate (Q), Nusselt Number (Nu), friction factor (f). Significant enhancement in thermal performance was observed for X tape compared to twisted tape insert. Forced turbulence created due to modified geometry of tape played vital role in improvement of heat transfer rate in the tube. The X-shaped tape showed an enhancement of 1.27 times in heat transfer rate with respect to twisted tape. Computational fluid dynamics (CFD) analysis of the proposed tapes was performed to validate the obtained results.

The effect of twisted tape inserts on heat transfer and pressure drop of R1234yf condensation flow: An experimental study

This paper deals with condensation flow inside plain and twisted tape inserted (TTI) tubes with diameter and length of 8.7 mm and 700 mm, respectively. R1234yf, identified as a viable alternative for R134a with low global warning potential (GWP), is examined as the working fluid. The heat transfer coefficient and the pressure drop of the flow are measured in different mass velocities and vapor qualities ranging 160–310 kg m−2 s−1 and 0.12–0.84, respectively. A well-equipped test rig consisting of a test condenser and other necessary equipment is employed to precisely adjust the test conditions. Experimental results for the plain tube are compared with some well-known correlations. As a result, Shah and Souza et al. equations are the most reliable equations to predict the flow heat transfer coefficient and its pressure drop, respectively. Different twisted tape inserts with three twist ratios of 6, 9, and 12 are exploited to study the effect of twisted tape geometry. The results indicate that up to 42% and 235% increment in the heat transfer coefficient and the pressure drop, respectively, is associated with implementing twisted tape inserts. In addition, it was shown that, among some correlations proposed previously in the literature, the experimental heat transfer coefficient and pressure drop in TTI tubes can be predicted by Akhavan Behabadi et al. and Hejazi et al. correlations with reasonable accuracy. According to the results, the twist ratio of 6 gives the highest increase in the heat transfer coefficient, while the ratio of 9 is associated with the highest overall enhancement ratio.

Modern trunnion designs do not affect clinically significant patient-reported outcomes.

Trunnion geometry is known to vary between hip systems. Trunnionosis and the impact of trunnion design on total hip arthroplasty (THA) survival, has gained attention as a failure mechanism. We sought to report the differences in patient-reported outcome measures (PROMs) between the most commonly utilised modern THA trunnions. We reviewed primary unilateral THA patients from May 2007 to October 2011. The most frequently used stems were included. LEAS, HOOS subdomains, and SF-12 were obtained pre and post operatively while satisfaction was measured at 2 years after THA. Trunnions were grouped by taper geometry and manufacturer. The 2-year change in PROMs for each trunnion was compared to the pooled 2-year change in HOOS for all other trunnions. 3950 THA patients were studied. 6 trunnion designs were evaluated from 5 manufacturers. The range in differences between the 2-year change in individual PROMs were as follows: HOOS pain (0.6-2.4), HOOS symptoms (0-3.8), HOOS ADL (0.4-4), and HOOS QOL (0.5-3.6). None of the differences in the 2-year change in PROMs reached a minimal clinically important change (MCIC), which we previously determined to be a minimum of 9 points for all HOOS domains. All of the trunnions designs utilised in our study cohort demonstrated excellent clinical results. Small differences were well below the known MCIC; and were not clinically relevant. The findings of this study should prompt further investigations into the long-term impact of trunnion design on clinical patient-reported outcomes.

Generation of 25 T with an all-superconducting magnet system: field profile and field quality measurements of a layer-wound 4 T REBCO insert coil for a 21 T LTS magnet

High temperature superconductors, especially rare-earth barium copper oxide (REBa2Cu3O7−x or REBCO) tapes are an enabling technology for magnetic fields beyond 23.5 T, the limit of the existing technology based on the low temperature superconductors (LTS) niobium–titanium (NbTi) and niobium–tin (Nb3Sn). Due to their higher prices, REBCO tapes are in general only employed as insert coils in an LTS outsert. Due to the tape geometry, the effect of the screening currents is high in REBCO insert coils. The resulting screening current-induced field (SCIF) can distort the shape and magnitude as well as affect the temporal stability of the field after charging. Their influence has to be well understood and it can be a limiting factor in field quality critical applications such as nuclear magnetic resonance magnets. In this work, we present the test results of a layer-wound 4 T REBCO insert coil operated in the background of a 21 T LTS outsert reaching a combined field of 25 T. Using an array of 13 calibrated Hall sensors, we investigate the spatial and temporal effects of the SCIFs at different background fields. Series expansion is employed to separate the contributions of the insert and of the outsert. We present in this work the characterization of the effect of the SCIF on the shape of the field and on its temporal stability in background fields from 0 T up to 19 T. We compare the experimental results with existing simulation models for the validation of the model at high magnetic fields, which had never been done for layer-wound REBCO coils. Based on the experimental data, we demonstrate the necessity of SCIF-aware simulations for REBCO insert coils, regardless of the insert’s relative operating current. Before summarizing and concluding the work, we give a short overview of proposed methods for SCIF reduction in REBCO coils from the literature.

The effect of manufacturing tolerances on the mechanical environment of taper junctions in modular TKR

Taper design is known to influence corrosive behavior in taper junctions used in modular orthopaedic devices. Manufacturing tolerance of bore-cone tapers is a critical design parameter due to the effect on taper fit, but the effect of variations in manufacturing tolerance on the mechanics of taper junctions has not been well characterized, particularly in modular total knee replacement (TKR). The purpose of this study was to investigate the effect of manufacturing tolerance on stress and micromotion of modular TKR taper junctions. A 3D finite element (FE) model of a modular TKR taper junction was developed and assigned elastoplastic material properties. Model taper geometry was varied by perturbing the angle mismatch by 0.05° between ±0.25° and represented expected variation in manufacturing tolerance. Stress and micromotion were calculated during dynamic FE simulations for each taper junction geometry under varying activity loads and material combinations. Although an increase in angle mismatch generally resulted in higher stress and micromotion, plastic material behavior disrupted this trend for larger angle mismatches. Model predictions corresponded with corrosion behavior evident in vitro. If the FE results obtained here apply in vivo, the absence of elastoplastic material properties in a taper model may grossly overestimate the micromotion and underestimate corrosion behavior and ion release. It is recommended that manufacturing tolerances of bore-cone tapers in modular TKR designs should produce angle mismatches within 0.1° at the taper junction.

Ultrahigh sensitivity with different taper geometries of thin-core fiber modal interferometer for refractive index sensing

A highly sensitive refractive index sensor based on a fiber in-line Mach–Zehnder interferometer sensor based on single-mode–tapered thin-core–single-mode fiber is proposed. We developed a theoretical model using wide-angle beam propagation method in cylindrical coordinates to simulate light propagation performance of such fiber devices. Tapered structures using different taper geometries (linear, exponential, and parabolic taper) with waist diameters as low as 30 μm are presented. The proposed sensor has an ultrahigh sensitivity of 996.4 nm/refractive index unit in glycerin solution with different concentrations in water using the linear taper geometry. The designed structure presents the merits of high sensitivity, which is 6 times higher than that of the thin-core fiber modal interferometer and makes it an excellent candidate for biochemical sensing applications.

Global fitting equation for constant-loss inverted taper.

Building on the Lagrangian approach to inverted taper coupler design, the constant-loss inverted taper geometry is calculated for rectangular waveguide systems with a range of core refractive indices (3.0 - 3.6), cladding refractive indices (1.0 - 1.6), and waveguide thicknesses (200 - 300 nm). A new approach to describing these taper devices is proposed based on the normalized effective index. This results in an empirical equation that accurately describes the geometry of all simulated constant-loss inverted tapers.

Optimization of a supercontinuum source based on tapered ordinary fibers

In this paper the generation of visible spectrum via optimized supercontinuum generation (SCG) in tapered ordinary fibers by ultrashort laser pulses is presented. The tunability of the visible part of the spectra is achieved by changing the pump pulse duration during operation. The optimization of the SCG is carried out by the investigation of the taper geometry with the emphasis on the downtapering section length. Its increase is found to be correlated to higher intensity in the visible part of the spectra. This is further supported by the results on spectra evolution before it enters the taper waist where an important transfer of the pump power to the shorter wavelengths is found.