Concentric Tube Research Articles

Correction to: Role of Suction/Injection on Natural Convection Flow of Magnetite $$({\text {Fe}}_{ 3} {\text {O}}_{ 4} )$$ Nanoparticles in Vertical Porous Micro-annulus Between Two Concentric Tubes: A Purely Analytical Approach

In the original publication of the article, grant number was published incorrectly in Acknowledgements section.

Design of a multi-arm concentric-tube robot system for transnasal surgery.

Concentric tube robot (CTR) has gradually attracted the attention of researchers on the basis of its small size and curved shape control ability. However, most of current experimental prototypes of CTR are single-arm structure, which can only carry out simple operation such as drug delivery or monitoring. In this paper, design and analysis of a three-arm CTR system is proposed. It has a four-DOF vision arm and two six-DOF manipulator arms, which equipped with special end effectors to achieve different surgical operations. Finally, a mean motion accuracy of 0.33 mm has been obtained quantitatively through teleoperation experiments. Moreover, tissue excision experiment in skull model is carried out to prove the effectiveness and feasibility of the proposed CTR system in nasopharyngeal carcinoma surgery. Graphical Abstract Platform of the proposed Multi-Arm Concentric Tube Robot system. (a) Configuration of the end-effectors with the CTR system. (b) The setup of the tissue removal experiment in a skull model.

Effect of cut-outs on the axial crushing response of cap and open-end hybrid frusta tube

The present paper presents the computational analysis of the crushing response of AA-1080 cap and open end hybrid frusta tube, with and without circular cut-outs subjected to the quasi-static axial loading. The two concentric frusta tubes placed co-axially having different heights of 91.6 mm and 85 mm of inner and outer tubes respectively were considered as hybrid frusta. The frusta tubes thickness and semi-apical angle were assigned constant value as 1.15 mm and 5.71˚ respectively. The effect of radial distance (2.94 mm, 4.44 mm, and 6.94 mm) between two concentric tubes as investigated. The numerical simulations were carried out using finite element code LS-DYNA.The crushing behavior of hybrid frusta tubes was examined based on the response of the peak force (PF), mean force (MF), crush load efficiency (CLE), and energy absorbing capacity (EAC). The radial distance was found to have a major impact on the deformation behaviour and with an increase in radial distance, the CLE decreases. Moreover, the response of cut-outs on the performance of hybrid frusta was presented and analysed. Through having a cut-out on both sets of hybrid frusta, the CLE increased by 3% to 10% whereas the radial distance R3 was insignificant as per CLE perspective. Further, the reduction in PF was found 13% to 23% for cap end while 8% to 19% for open end hybrid frusta.

Permeate flux enhancement with a helical wired concentric tube in air gap membrane distillation systems

Temperature polarization plays an important role in determining the permeate flux of the membrane distillation in an air gap membrane distillation (AGMD) module. This study aimed to increase the pure water productivity of saline water desalination by applying helical wire on the circumference of a concentric-tube AGMD module to reduce the temperature polarization occurring on the smooth annulus tube of an AGMD module with a normal concentric-tube. Modeling equations of heat and mass transfer in the new design of the AGMD device with helical wire winding on the annulus of a concentric tube have been investigated theoretically and experimentally. The mathematical model proposed in this study was used to correlate a simplified equation for estimating the heat transfer coefficient and to predict the permeate flux accordingly. The effects of various operation parameters, including the feed saline water temperature, feed volumetric flow rate, air gap thickness, and helical wire pitch, on the pure water productivity were also delineated. The permeate flux enhancement for helical wire in the AGMD module could provide the maximum relative increment of up to 31.1. The temperature polarization coefficient found in this study is ranging from 0.5527 to 0.5451 for different hot feed temperature and flow rate, respectively. An optimal helical wire module was assessed when considering both permeate flux enhancement and energy utilization effectiveness. © 2020 Desalination Publications. All rights reserved.

Development of heat transfer and pressure drop correlations in twisted tube heat exchangers

Heat transfer in concentric twisted tubes exchangers has several applications in the chemical and food industry mainly due to its compact structure and high transport coefficients, however, its use has been limited as a consequence of drop pressure. This study reports Nusselt number and friction factor correlations as a function of the dimensionless Dean number as well as Prandtl number, and a torsional step parameter. Simulations were carried out using ANSYS CFX® V16.0 software at workstations belonging to Grupo de Investigación en Materiales Avanzados y Energía of Instituto Tecnológico Metropolitano. Six geometries were developed with SolidEdge® ST9 academic license. Geometry modification, cleanup, and repair were made although DesignModeler® 2019 academic license. Finally Meshing® for discretization. The mesh size independence, and incidence of the turbulence model, and twisting step validated the computational tools use. Correlation numerically showed an increase of 60% average respect to smooth bending tube.

Optimization of Heat Losses of Concentric Coaxial Glass Tube Solar Air Collector

Optimization of Heat Losses of Concentric Coaxial Glass Tube Solar Air Collector

A Stiffness Adjustable 6-DOF Robotic System for Pituitary Tumor Resection Under MRI

Magnetic resonance imaging offers better visualization for tumors present in the delicate parts of the human body. A pituitary tumor is one of the common types of brain-related tumors located underside the brain. It can be accessed through the nostrils and visualized better using magnetic resonance imaging (MRI). In this work, we present a 6-degree-of-freedom (DOF) robotic system for pituitary tumor resection via a transsphenoidal approach designed specifically for a commercially available 3T MRI scanner. The robotic system is designed to follow the anatomical and surgical constraints and to work inside the bore of the MRI to allow image acquisition during the surgical procedure. It has a 6-DOF manipulator consisting of a concentric tube and a tendon-driven bendable section. Both mechanisms are merged to have stiffness changing capability, and payload capacity to aid the surgical task. The manipulator is attached to a flexure shaft to bend it at the desired surgical angles. The materials used for development are analyzed in MRI and exhibit signal-noise ratio (SNR) reduction of less than 10%. The experimental results show that the stiffness can be changed more than ten times for safe navigation to the surgical site without damaging the surrounding tissues. Also, it can provide a maximum lifting force of more than 2N. The presented system is the preliminary version of the pituitary tumor resection system under development and shows the feasibility to be used in a real surgical environment.

Convective heat transfer in pipe flow for glycolated water-based carbon nanofluids. A thorough analysis

The exceptional thermal properties of graphene are maintained in a few orders of magnitude in its multi-layered structure, graphene nanoplatelets, with a considerably lower production cost. Ethylene glycol and water binary mixtures are commonly used as working fluids in different applications, such as the automotive sector, industrial cooling systems, renewable domestic heating systems, or solar and wind power plants, due to the protection provided against low freezing temperatures. In this work, the heat transfer performance of different-loaded sulfonic acid functionalized graphene nanoplatelet nanofluids (0.25, 0.50 and 1.0 wt%) based on an ethylene glycol:water 50:50 vol% mixture was experimentally assessed. Firstly, thermophysical and rheological evaluations for base fluid and nanofluids were developed in a wide temperature range (293.15 to 333.15 K). Densities, isobaric heat capacities, thermal conductivities and dynamic viscosities for base fluid and nanofluids were determined by vibrating tube, differential scanning calorimetry, transient hot wire and rotational rheometry methods, respectively. Subsequently, convective heat transfer coefficients and pressure drops/pumping powers were experimentally determined through a test rig with a concentric tube heat exchanger as main element at different working temperatures (from 298.15 to 318.15 K) and flow rates (from 300 to 700 dm3·h−1). Furthermore, a dimensionless analysis from the obtained results was carried out. The proposed new 0.25 wt% nanofluid achieves the higher convective heat transfer performance. Finally, a summary and a comparison of the results for different glycolated water-based carbon nanofluids evaluated in the same experimental facility are reported.

3D CFD Simulation of Gas Hold-up and Mass Transfer in a Modified Airlift Reactor with Net Draft Tube

Abstract This paper documents CFD simulations of the gas hold-up (ɛg) and volumetric mass transfer coefficient (KLa) for three kinds of airlift reactors (ALRs) namely, conventional ALR, ALR with net draft tube (ALR-ndt), and packed-bed ALR with net draft tube (PBALR-ndt). The 3D two-fluid Eulerian-Eulerian model was adopted to predict the influence of superficial gas velocity on ɛg and KLa. The simulation results were consistent with the trends described previously in the experimental work regarding ɛg and KLa values and a good agreement was obtained (absolute error less than 20 %). Based on the simulation results, axial flow is the dominant flow in the conventional ALR while in ALR-ndt and PBALR-ndt radial flow streamlines are appeared in the reactors due to the presence of concentric net draft tube which improves their performance. The effective role of the net draft tube is proven since consequence of generation of small bubbles by passing through net draft tube is the entrainment of a larger percentage of gas bubbles from the riser into the downcomer which results in improvement of gas holdup and the KLa values. An exponential correlation is used for relating gas hold-up and mass transfer coefficient. Higher power obtained for ALR-ndt and PBALR-ndt (n ≈ 1.22) compared to ALR (n = 0.95) was indicative of high sensitivity of KLa value to gas hold-up in these reactors due to presence of the concentric net draft tube. The CFD modeling is considered to be an invaluable tool allowing us to analyze and visualize the impact of fluidic forces on hydrodynamic properties and consequently, reactor performance.

Experimental and numerical study of a solar collector using phase change material as heat storage

Abstract The present work present numerical and experimental investigations to study the performance of a small-scale parabolic trough solar concentrator integrated with thermal energy storage system. A new design of receiver which uses the phase change material to store the thermal energy is built. A parabolic-trough solar concentrator was proposed and constructed using a concentric absorber tube with phase change material. The absorber is considered as a temporary thermal heat storage component. The heat storage-recovery mechanism will act as a thermal compensator that allows the parabolic trough solar concentrator to stabilizing energy output during the absence of intense radiation or for short time cloudy conditions. The PCM used a binary salt composed of a mixture of 60% NaNO3 and 40% KNO3, filling the annular space of the absorber tube. Solar energy is converted to heat, stored in the phase change material and is discharged to cold water, which is the final heat transfer fluid in the inner pipe of the receiver. The simultaneous testing of the receiver with and without phase change material is investigated. A commercial computational fluid dynamics model of the whole system is presented and numerical results are compared to experimental results, which were conducted with and without phase change material in the receiver tube. The maximum outlet water temperature achieved using phase change material in the receiver tube is about 16.80% and 14.86% higher than the simple tube for 21 July and 21 October respectively. The daily thermal efficiency of the parabolic trough solar concentrator increases by 6.56% and 8.32 respectively for a both days using a receiver with a phase change material concentric tube. The phase change material showed good heat retention of 2 h to 1 h 40 min for water inlet temperature 30°C and 40°C respectively.

Investigation of the influences of kaolin-deionized water nanofluid on the thermal behavior of concentric type heat exchanger

Different strategies have been proposed to improve the efficiency of the energy conversion systems. One of the outstanding technics for heat transfer increment is utilizing nanofluid as working fluid. This experimental study investigates the effect of using kaolin/deionized water nanofluid that is comprise various kinds of metal oxides in different ratios, on thermal behavior of counter flow concentric tube (CFCT) heat exchanger and parallel flow concentric tube (PFCT) heat exchanger. The prepared kaolin/deionized water nanofluid solution has 2% (wt/wt) nanoparticle concentration. Also, to prevent flocculation and to enhance stability of the prepared nanofluid, sodium dodecyl benzene sulfonate surface-active agent has been mixed into the solution. The experiments have been conducted in various conditions to investigate the influence of using nanofluid. Utilizing kaolin/deionized water nanofluid as working fluid caused maximum improvement of 37% and 12% in overall heat transfer coefficient in CFCT and PFCT heat exchangers respectively, in comparison with deionized water.

High Amplitude Combustion Instabilities in an Annular Combustor Inducing Pressure Field Deformation and Flame Blow Off

Abstract This article reports experiments carried out in the laboratory scale annular combustor MICCA-spray equipped with multiple swirling spray injectors. The experimental setup consists in an air plenum connected to a combustion chamber formed by two concentric cylindrical quartz tubes, allowing full optical access to the flames. A new injection system is introduced and characterized. For a wide range of operating conditions, strong combustion instabilities are observed, but the focus of this article is placed on very high amplitude combustion instabilities coupled by a standing azimuthal mode. New results are obtained using a higher order reconstruction method for the pressure field: its shape is shown to be modified during high amplitude oscillation, leading to asymmetries of the pressure distribution in the system. Flame blow off occurs near the pressure nodal line when a critical level of oscillation is reached. A method is proposed to reconstruct the acoustic velocity field just before blow off occurs and in this way determine the blow off threshold. It is found that the pressure distribution, velocity field, and blow off pattern become asymmetric as the amplitude of oscillation increases and that this process is accompanied by a rapid shift in frequency of oscillation. Another notable result is that the heat release rate in the flames on the same side of the nodal line is not perfectly in phase and that the phase differences become larger as the amplitude of oscillation increases.

Mycoremediation of vinasse by surface response methodology and preliminary studies in air-lift bioreactors.

This work evaluated the degradation of sugarcane vinasse with the production of biomass by Pleurotus sajor-caju CCB020, considering the combination of temperature and pH effects, using surface response methodology (RSM). A 22 complete central factorial composite experiment was used to analyze the results. The optimum temperature and pH values were respectively 27°C and 5.6 for maximum decolorization yield and 20°C and 6.8 for maximum biomass production. In parallel, scale-up experiments under conditions of 30°C and initial pH 5.0 were evaluated in two different air-lift bioreactors of 7.0L. Under these conditions, reductions of 53% and 58% in chemical oxygen demand (COD) and 71% and 58% in biological oxygen demand (BOD) were obtained respectively with the concentric tube type air-lift bioreactor with an increased degassing zone and without an increased degassing zone. Under these conditions, this study concluded that the systematic combination of P. sajor-caju and vinasse can be applied in the biodegradation process of refractory compounds contained in vinasse, concomitant to obtaining biomass and laccase and manganese peroxidase enzymes. Due to the good performance of the air-lift bioreactors, they can be used in scale studies in future industrial vinasse applications, besides it is possible to emphasize that different configurations in the bioreactor can affect the efficiency of the process.

Analytical Behaviour of Stiffened and Unstiffened CFDST Short Column

Concrete filled steel tubular (CFST) members comprise of a hollow steel section of circular or rectangular shape filled with plain or reinforced concrete. Concrete-filled double-skin tubular (CFDST) columns are formed by sandwiching concrete between two concentric hollow steel tubes. When compared to a traditional concrete-filled steel tube (consisting of a single hollow steel tube instead of two), the CFDST column is found to have greater axial, flexural, and torsional strengths as well as improved strength-to-weight ratios. They are widely used in high-rise and multi-story buildings as columns and beam-columns. This paper presents the analytical results obtained by using ANSYS software and to develop various kinds of CFDST columns by varying cross-sections, by providing stiffeners and by changing the position of the reinforcements. And also to plot the load-deformation curve and to evaluate the load-carrying capacity of the different models. From the analysis, it is concluded that the square–squaren CFDST with plain stiffeners attached to the outer steel tube has the best axial load carrying capacity.

Thermal performance characteristics of a triple spiral tube heat exchanger

In the current paper, the thermo fluid characteristics of a new design of curved tube called a triple spiral tube heat exchanger (TSTHE) was achieved with a brave comparative with a double spiral tube heat exchanger (DSTHE) as particular reference. A three-dimensional computational fluid dynamic model was developed using Ansys 14.5 software package. The Realize k–ε model had been applied with enhanced wall treatment to simulate the thermo-fluid characteristics. The governing equations were solved by a finite volume discretization method. The new design was created by adding a third tube to a double concentric spiral tube heat exchanger. The study carried out under consideration of turbulent fluid to fluid heat transfer condition. The influence of different key design parameter such as; inlet hot fluid temperatures, flow arrangements, concentration of Alumina (Al2O3) nanoparticles, and Dean number were the main point of interest. The effect of Alumina-water nanofluid was considered in three different concentrations of 0.5%, 1% and 2% by volume. The results carried out at Dean number ranged from 1100 to 10,500 in the turbulent region corresponding to Reynolds number from 6400 to 57,400. The results presented that the Nusselt number obtained from a TSTHE was higher than that value of DSTHE at the same flow conditions. The results also presented that a significant effect of hot water inlet temperature on the Nusselt number while the increase in pressure drop can be approximately considered neglect. Also, the counter flow arrangement gives better effect on hot fluid Nusselt number compared with the three other flow arrangements. A notice augmentation of heat transfer enhancement occurs due to use Alumina–water nanofluid in TSTHE by 20.8 %. New correlations for inner annulus hot fluid Nusselt number, effectiveness, and friction factor of heat exchanger were presented.

Towards optimal control of concentric tube robots in stereotactic neurosurgery

ABSTRACTWe consider the design and control problem of concentric tubes used in stereotactic neurosurgery. The goal is to optimally reach a configuration of the cannula linking an entry point on the skullcap to a pre-specified region inside the brain. Key issues related to this task are the mechanical behaviour of the cannula and the topography of the brain. We formulate an optimal control problem in order to determine a feasible path while minimizing brain damage caused by missing follow-the-leader behaviour. Numerical results show the potential of the proposed approach.

Planning High-Quality Motions for Concentric Tube Robots in Point Clouds via Parallel Sampling and Optimization.

We present a method that plans motions for a concentric tube robot to automatically reach surgical targets inside the body while avoiding obstacles, where the patient's anatomy is represented by point clouds. Point clouds can be generated intra-operatively via endoscopic instruments, enabling the system to update obstacle representations over time as the patient anatomy changes during surgery. Our new motion planning method uses a combination of sampling-based motion planning methods and local optimization to efficiently handle point cloud data and quickly compute high quality plans. The local optimization step uses an interior point optimization method, ensuring that the computed plan is feasible and avoids obstacles at every iteration. This enables the motion planner to run in an anytime fashion, i.e., the method can be stopped at any time and the best solution found up until that point is returned. We demonstrate the method's efficacy in three anatomical scenarios, including two generated from endoscopic videos of real patient anatomy.

Analysis of Shell and Double Concentric Tube Heat Exchanger Using CFD Application

This study focuses on CFD analysis in the field of the shell and double concentric tube heat exchanger. A commercial CFD package was used to resolve the flow and temperature fields inside the shell and tubes of the heat exchanger used. Simulations by CFD are performed for the single shell and double concentric tube.
 This heat exchanger included 16 tubes and 20 baffles. The shell had a length of 1.18 m and its diameter was 220 mm. Solid Works 2014, ANSYS 15.0 software was used to analyze the fields of flow and temperature inside the shell and the tubes. The RNG k-ε model was used and it provided good results. Coarse and fine meshes were investigated, showing that aspect ratio has no significant effect. 14 million elements were used in the mesh. A comparison was made between the profiles of temperature and velocity for the experimental and results of the model and it had an acceptable adaptation.

Convective heat transfer of nanofluids TiO2/Thermo Oil XT 32 in concentric tube heat exchanger

This research was conducted to examine the heat transfer characteristic of nanofluids TiO2/Thermo XT 32 oil on a concentric tube heat exchanger. TiO2 nanoparticles with nominal diameter of 21 nm were dispersed in Thermo XT 32 oil as base fluid at three different particles concentration of 0.1%, 0.3%, and 0.5%, respectively. A straight horizontal stainless-steel tube of 1.2 m length, 0.012 m inner diameter, and 0.022 m outer diameter were used as a test section. Collecting data by varying the temperature of the heat transfer nanofluids and nanoparticle volume fraction. Nanofluids prepared using the method of two steps without the addition of a surfactant by using a magnetic stirrer for 1 hour then ultrasonic cleaner for 3 hours. The results of research conducted, the coefficient convection heat transfer of nanofluids TiO2/Thermo XT 32 oil increases along with the addition of fraction volumes; this is due to the increased thermal conductivity of the fluid as well with the rise of temperature against nanofluids TiO2/Thermo oil XT 32. So it is very worthy of nanofluids applied in industries related to heat transfer processes.

Analysis on thermal and flow behavior of triple concentric tube heat exchanger handling MWCNT-water nanofluids

Design of heat exchangers and heat transfer enhancement methods are struggling to meet out the cooling demand of present scenario. Many researchers suggested that the addition of nanosized solids particles into traditional base fluids resulting the higher heat transfer rate than the existing coolants and named the new fluids as nanofluids. In this investigation, the effect of microwave carbon nanotube (MWCNT)-water nanofluids on heat transfer rate, pressure drop and pumping power of a triple concentric tube heat exchanger are experimentally investigated and compared the results of MWCNT-water nanofluids with water. The MWCNT-water nanofluids were prepared by two step method at the volume concentrations of 0.2%, 0.4%, and 0.6%. The range of target fluid mass-flow rate is in the range of 0.026 to 0.039 kg per second and the constant heat flux condition is considered. On experimentation, it is noted that the effectiveness and presure drop of 0.6% MWCNT-water based nanofluids are 27% and 21% greater than water at the maximum mass-flow rate. The reason for improved heat transfer rate of nanofluids is because of higher thermal conductivity, Brownian motion, lower boundary-layer thickness, and lower specific heat capacity of nanofluids. Also found that the pumping power increases with increasing volume concentration and pumping power is 25% higher than water at the 0.6% nanofluids. Therefore, the MWCNT-water nanofluids are good choice for replacing water as coolant in triple concentric tube heat exchanger.