Coil Flow Research Articles

Headaches Following Endovascular Treatment of Cerebral Aneurysms: Coil Embolization vs. Flow Diversion (P5.125)

Headaches Following Endovascular Treatment of Cerebral Aneurysms: Coil Embolization vs. Flow Diversion (P5.125)

피복전선의 내부 열화 검출용 센서 개발

In this research, it have developed a sensor that could diagnose inner deterioration of covered wires. With this sensor it observed results from simulation, and the attribute required for realization. For simulation it have used FLUX, it have considered all of geometric and electromagnetic information from coil and base metal that influences eddy current sensor's property in order to predict the final result. It assumed there is no mutual inductance in the coil with N number of turns, because equivalent current flows in coil that is continuously connected in eddy current sensor. It assumed circular coil loop draws a circle, always have self inductance, and they are connected in series and overlapped according number of turns (N) in coil, and bobbin configuration. Actual sensor was produced with consideration of inductance and number of turns (N). In conclusion, it were able to test the dependency through results from simulation, actual measurement, and modeling of simulation. It is considered that attributes of respective base metal and structure can be predicted by simulating in advance.

PIV Characterization of Transient Flow in Pipe Coils

This paper aims to better understand transient flow dynamics by measuring instantaneous velocity profiles in pipes subjected to a water-hammer, using Particle Image Velocimetry (PIV). Measurements were carried out in a coiled copper pipe with 103.2 m length and 20 mm diameter. Velocity profiles for steady flows are asymmetrical in the pipe cross section, with higher velocities in the outer region due to the centrifugal force created by the flow in the coil. Velocity profiles during transient flows have shown regions of flow recirculation and a large flow reversal near the wall, occurring first in the inner side of the pipe. An estimate of wall shear stress is presented and discussed. Wall friction alone appears to be insufficient to describe momentum losses.

Hydrodynamically and thermally developing laminar flow in spiral coil tubes

In this study, steady state combined developing flow and heat transfer in spiral tube coils is numerically investigated. The spiral coil is isothermal and the fluid flow is laminar. The spiral coils with four different curvature ratios of defined as the radius of the spiral at the outlet (Ro) to the radius at the inlet (Ri), Ro/Ri = 2.5, 5, 7 and 17, are simulated for Pr = 0.7 (air) and Pr = 7 (water). The cold fluid is assumed to enter the coil from the innermost turn of the spiral tube. The three-dimensional steady-state continuity, Navier–Stokes and energy equations are solved using the commercially available CFD software—Fluent v6.1.22®. The effects of the spiral tube pitch, curvature ratio, the Prandtl and the Dean number on the friction factor and the heat transfer are investigated for combined developing flow. With increasing Reynolds number, the heat transfer is enhanced 2–4 times over straight tubes of the same length due to secondary flow and centrifugal forces. The friction losses also increase to some extent. As the number of turns is increased, the normalized friction factor tends to decline towards the straight tube values. Useful correlations for the normalized apparent friction factor and the mean axial Nusselt number were generated.

The effect of bubble on pressure drop reduction in helical coil

In the present paper, the effect of bubbles on the pressure drop and drag reduction of air–water two phase flows in vertical helical coils was experimentally investigated. The curvature ratio of the studied coils was 0.06 and 0.095. The ranges of the investigated Reynolds numbers and void fractions were 8000–50,000 and 0–0.09, respectively. The effect of the drag reduction will decrease with the increase of Reynolds number and the amount of drag reduction increases with increasing void fraction. It was found that for helical coil, the drag reduction increases with the decrease of curvature because of the secondary flow increases with the increase of curvature. The average diameter of injected bubbles was 270μm; and as the Reynolds number increased, the diameters of injected bubbles diminished. The experimental results indicate that in this range of void fraction, the maximum reduction of friction drag is 25%, which occurs at low Reynolds numbers. Also, in void fraction 0.01 the drag reduction was 9% which was observed in Reynolds of 11,000.

Studies on convective heat transfer through helical coils

An experimental investigation on steady state convection heat transfer from vertical helical coiled tubes in water was performed for laminar flow regime. Three coils with curvature ratios as 0.0757, 0.064, 0.055 and range of Prandtl number from 3.81 to 4.8, Reynolds number from 3,166 to 9,658 were considered in this work. The heat transfer data were generated from 30 experiments conducted at constant water bath temperature (60 °C) for different cold water flow rates in helical coils. For the first time, an innovative approach of correlating Nusselt number with ‘M’ number is proposed which is not available in the literature and the developed correlations are found to be in good agreement with the work of earlier researchers. Thus, dimensionless number ‘M’ was found to be significant to characterize the hydrodynamics of fluid flow and heat transfer correlations in helical coils. Several other correlations based on experimental data are developed. To cover wide range of industrial applications, suitable generalized correlations based on extended parameters beyond the range of present experimental work are also developed. All these correlations are developed by using least-squares power law fit and multiple-regression analysis of MATLAB software. Correlations so developed were compared with published correlations and were found to be in good agreement. Comparison of heat transfer coefficients, friction factor and Nusselt number for different geometrical conditions is presented in this paper.

Flow Characteristics of Power-Law Fluids in Coiled Flow Inverter

A novel device coiled flow inverter (CFI) has shown great potential as a heat exchanger and inline mixer.(1-3) The device offers negligible thermal and concentration gradient in the radial directio...

PRESSURE DROP AND HEAT TRANSFER INSIDE THE COILED FLOW CHANNEL OF SMOOTH TUBES AND INTERNALLY HELICAL-GROOVED TUBES

In this study, we investigated ways of improving the performance of heat exchangers, which are the heat pumps for use in hot-water supply systems on the hot-water supply side. Therefore, we verified experimentally the pressure drop and the heat transfer characteristics within the coiled flow channel. Five smooth copper tubes and five internally helical-grooved copper tubes with an outside diameter of 12.7 mm and coil diameters of 100 mm, 120 mm, 140 mm, 160 mm and 180 mm were used as the heat-transfer coiled tubes in the experiments. Experiments were conducted under conditions of constant isothermal heating and fluid flow inside coiled tubes with an inlet temperature of 20°C, and the flow rates of the fluid flow inside the coiled tubes were adjusted and varied to change the Reynolds number within the range of 900 to 25,000. Based on the experimental values, we proposed prediction equations to systematically calculate the friction factor and the heat transfer coefficient for different curvature radius ratios.

Numerical Simulation the Temperature Field of the Multi-Coil Batch during Annealing Process in Bell-Type Furnace

In this paper temperature field of multi-coil during batch annealing process in strong forced convective hydrogen atmosphere of Bell-type furnace was simulated, and the influences of heat transferring between steel coil and air flow under a given condition on the temperature field of the steel coil were studied. And then, the temperature field of a single and three coils steel plate were calculated during reheating, holding and cooling process according to the measured annealing curves. The simulated results show that the same trend of temperature in different steel coils. However, considering the heat radiation of steel coil, temperature variation in the topside of coil is higher than that in the bottom of coil.

Protecting the Leads of a Powered Magnet That is Protected With Diodes and Resistors

MRI magnets and other magnets that have a low current and high self-inductance are passively quench-protected with a system that includes sub-divided coils with resistors and diodes that are in parallel with sections of the coils. The primary purpose of coil sub-division is to protect the coil from the high voltages that can occur during a quench. In the event of a lead failure (conventional or superconducting) between the coil and its power supply or its persistent switch, the total current in the coil flows through the diodes and resistors in parallel with the coil. When a lead fails, the current decay time constant for the coil current can be quite long. It is desirable that the coil quench in a time that is short compared to the coil current decay time constant. Experience shows that the heating from the resistors and diodes will eventually quench the magnet. This paper presents methods for shortening the time between a lead failure or a persistent switch failure and the eventual magnet quench.

Can the Dean number Alone Characterize Flow Similarity in Differently Bent Tubes?

Although flows of fluids in curved channels belong to a classical problem of fluid dynamics, most publications are restricted to investigations of flows in tube coils, or in single bends. This paper presents experimental and numerical (CFD) results concerning Newtonian flows in a set of multiple S-type bends of various orientations. Investigations were conducted for a wide range of Re values (0–3500) and for a significant curvature ratio lying between 0.05 and 0.29, which corresponds to De value falling within the range 0.02–1200. A coiled tube was also examined and treated as the reference geometry. It was shown, that despite a completely different velocity pattern, the nonlinear dependence of normalized flow resistance of wavy tubes and coiled tube of the same curvature ratio overlap within a significant range of De. A novel, close phenomenological formula to estimate the nonlinear flow resistance of tortuous tube in a wide range of De was proposed and compared with those in the literature. The conditions were also determined in which the De might be the only dimensionless group that characterizes such flows.

Study of action mechanisms and properties of Cr3+ cross-linked polymer solution with high salinity

Performance characteristics of partially hydrolyzed polyacrylamide (HPAM) and cross-linked polymer (CLP, Cr3+ as the cross linker) solutions have been investigated. A Brookheld viscometer, rheometer, dynamic light scattering system, and core flow device have been used to measure the viscosity, viscoelasticity, polymer coil dimensions, molecular configuration, flow characteristics, and profile modification. The results show that, under conditions of high salinity and low HPAM and Cr3+ concentrations, cross-linking mainly occurred between different chains of the same HPAM molecule in the presence of Cr3+, and a cross-linked polymer (CLP) system with a local network structure was formed. Compared with an HPAM solution of the same concentration, the apparent viscosity of the CLP solution increased slightly or remained almost unchanged, but its viscoelasticity (namely storage modulus, loss modulus, and first normal stress difference) increased, and the resistance coefficient and residual resistance coefficient increased significantly. This indicates that the CLP solution exhibits a strong capability to divert the sequentially injected polymer flood from high-permeability zones to low-permeability zones in a reservoir. Under the same HPAM concentration conditions, the dimensions of polymer coils in the CLP solution increased slightly compared with the dimensions of polymer coils in HPAM solution, which were smaller than the rock pores, indicating that the cross-linked polymer solution was well adapted to reservoir rocks. Core flood experiments show that at the same cost of reagent, the oil recovery by CLP injection (HPAM-1, Cr3+ as the cross linker) is 3.1% to 5.2% higher than that by HPAM-2 injection.

유로저항에따른 속도제어를 통한 Zone별 유량특성 연구

We use floor radiant heating system in the house of commons in winter Floor radiant heating system, which transfer heat by radiation, is one of the energy efficient and comfortable systems that. Floor radiant heating system is configured to be controlled by the room for energy-saving. Proper flow rate to a comfortable heating in the room is important. However, Using a constant speed circulation pump in separate rooms, heating system may cause an imbalance because of the difference of length of coil when operating in the rooms. In this study, our Research team examined heating imbalance due to the variation length through the coil length changes and flow control of the circulation pump.

Liquid–Liquid Mixing in Coiled Flow Inverter

The mixing of liquids is a common operation in process industries such as refineries and chemical and pharmaceutical industries, etc. However, the problem of mixing of different liquids has not been rigorously characterized. Therefore, the objective of this paper is to investigate liquid–liquid mixing in a novel coiled flow inverter (CFI). The device works on the principle of flow inversion which is achieved by bending a coiled tube to 90° at equidistant length. In the present study, velocity field and scalar concentration distribution of liquids were characterized. The mixing performances and pressure drop in CFI was investigated and compared with that of a straight, coiled tube and helical element mixer (HEM) for a liquid flow range of 98 ≤ Re ≤ 1020. CFI exhibits significant mixing of two liquids with negligible change in pressure drop as compared to a coiled tube as well as a HEM. The present study reveals that CFI is an efficient device for the mixing of two liquids in process industries.

Single and two-phase pressure drop in serpentine mini-channels

The pressure differential of single and two-phase flow in mini-channel serpentine geometries was investigated to determine the effects of flow patterns and radius of curvature of the serpentine on pressure drop. The friction factor for single phase flow through a straight channel was comparable to existing literature, while that in the serpentine geometry fell between conventional theory for straight channels and fully developed flow in helical coils. Extension of the single phase results to two-phase flow using a separated flow model led to the development of empirical correlations for two-phase pressure drop in the straight and serpentine configurations. Five operating regions were identified within the serpentine, each with distinct pressure drop characteristics dependent on the flow pattern and extent of bubble deformation. Two of the operating regions corresponded to bubbly and slug/unstable-annular flow, while the boundaries between the three remaining regions occurred at We LG L C = 2.7 and 15.5; corresponding to the onset of mild cap deformation and continuous bubble breakup, respectively.

An Influence of Air Volume Flow Rate and Temperature Set Point on Performance of Inverter Split-Type Air-Conditioner

This paper presents an experimental and analytical study on the inverter split-type air-conditioner for the purpose of energy saving and a proper balance between sensible and latent capacity. Performance of an inverter split-type air-conditioner is investigated at varied refrigerant mass flow rates, air volume flow rates, and set point temperatures. The performance investigated for a 2.54-kW inverter split-type air-conditioner includes cooling capacity, power consumption, the value of coefficient of performance (COP), and equipment sensible heat ratio (SHR). An increase of electrical frequency input to compressor from 34 to 66 Hz results in an increase of cooling capacity by 0.88 kW, a decrease of COP by 0.84, and a decrease of SHR by 0.11. An increase in cooling coil flow rate from 4.14 to 8.2 m3/min results in an increase in cooling capacity by 0.16 kW, an increase in COP by 0.10, and an increase in SHR by 0.15. An increase of set point temperature from 24 to 26°C results in an increase of the value of COP by 0.13 and a decrease of SHR by 0.03. The study offers guidelines for the application of small-size inverter split-type air-conditioners in hot and humid climates.

Pressure Drop and Heat Transfer inside the Coiled Flow Channel of Internally Helical-Grooved Tubes

Pressure Drop and Heat Transfer inside the Coiled Flow Channel of Internally Helical-Grooved Tubes

A New High-Performance Ion Source Based on Magnetically Neutral Loop Discharge

We have developed a new high-performance ion source on the basis of the high-density plasma formation method known as magnetically neutral loop discharge (NLD). The ion source consists of three separate electromagnetic coils, an ion extraction electrode, and a quartz vessel plasma chamber with a one-turn RF antenna coil, which is the main component of conventional RF ion sources. The three electromagnetic coils are located around the periphery of the plasma chamber. The current in the middle coil flows opposite to the currents in the top and bottom coils. With this configuration, our source produces a high plasma density of 1011 cm-3, which is about ten times higher than that of a conventional source under a low gas pressure of 0.1 Pa. In addition, it is possible to control both the ring like plasma diameter and the high-density plasma generation position in the plasma chamber. As a result, we achieved a high ion current density of up to 1 mA/cm2 at 50 V of ion extraction voltage, which is almost five times higher than the conventional source. Furthermore, we also obtained a high ion current uniformity of ±5% over a 6-in.-diameter wafer using the source's plasma space controllability. A processing system that uses this ion source will contribute to faster processing, high-quality processing, and excellent-uniformity processing for ion beam etching, ion beam deposition, and ion beam sputter deposition. Many other applications are also expected.

Experimental study and optimization of heavy liquid hydrocarbon thermal cracking to light olefins by response surface methodology

Response surface methodology coupled with central composite design (CCD) was used to investigate the effects of operating variables, namely, coil outlet temperature (COT), flow rate and steam ratio, on the yield of light olefins (ethylene and propylene) in thermal cracking of heavy liquid hydrocarbon. From the CCD studies the effects of COT and flow rate were concluded to be the key factors influencing the yield of light olefins. Based on this experi- mental design, two empirical models, representing the dependence of ethylene and propylene yields on operating con- ditions, were developed. The single maximum response of ethylene and propylene yields and simultaneous maximiza- tion of both responses have also been obtained at the corresponding optimal independent variables. The results of the multi-response optimization could be used to find the suitable operating conditions.

Mathematical modeling of dispersion in single interface flow analysis

This work describes the optimization of the recently proposed fluid management methodology single interface flow analysis (SIFA) using chemometrics modelling. The influence of the most important physical and hydrodynamic flow parameters of SIFA systems on the axial dispersion coefficients estimated with the axially dispersed plug-flow model, was evaluated with chemometrics linear (multivariate linear regression) and non-linear (simple multiplicative and feed-forward neural networks) models. A D-optimal experimental design built with three reaction coil properties (length, configuration and internal diameter), flow-cell volume and flow rate, was adopted to generate the experimental data. Bromocresol green was used as the dye solution and the analytical signals were monitored by spectrophotometric detection at 614 nm. Results demonstrate that, independent of the model type, the statistically relevant parameters were the reactor coil length and internal diameter and the flow rate. The linear and non-linear multiplicative models were able to estimate the axial dispersion coefficient with validation r(2)=0.86. Artificial neural networks estimated the same parameter with an increased accuracy (r(2)=0.93), demonstrating that relations between the physical parameters and the dispersion phenomena are highly non-linear. The analysis of the response surface control charts simulated with the developed models allowed the interpretation of the relationships between the physical parameters and the dispersion processes.