bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer and Film Dynamic in Shear-Driven Liquid Film Cooling System of Microelectronic Equipment
Authors: Kabov O. A. , Kuznetsov V. V. , Legros J. C.
Published: December 2008

The conjugated two-dimensional model, based on long-wave theory, of a steady laminar flow of liquid film and co-current gas flow in plane channel with the height varied from 150 to 500 μm is performed. A chip with the several millimeters length is located on the bottom wall of channel. The linearised approximation of the problem is obtained analytically. Numerical calculations are executed for liquid FC-72 and Nitrogen gas flow. In contrast to a case of a large channel, there is essential an influence of liquid film deformations on pressure and velocity in a gas phase.
Constructal Networks for Efficient Cooling/Heating
Authors: Lundell Fredrik , Thonon Bernard , Gruss Jean Antoine
Published: December 2008

Channel networks designed with constructal theory are compared. The efficiency of the networks when used for cooling a uniformly heated surface is compared. Three networks are compared and it is found that the two constructal designs with two and three constructal levels have similar performance. It is shown that for a given pumping power, the constructal designs give a heat transfer coefficient of the surface which is almost a factor of magnitude higher than the one obtained for a parallel channel system.
Simulation of Droplet Formation and Spread in Direct Ceramic Inkjet Printing
Authors: Ponnambalam P. , Rajesh P. K. , Ramakrishnan N. , Prakasan K.
Published: December 2008

Recently, drop on demand inkjet printers have been used to deposit ceramic containing inks to develop ceramic components for several strategic applications (for sensors, fuel cells and for intelligent inks to be used as self assembling particles to interact with incident wave forms). It seems that the availability of literature with respect to the studies on fluid-structure interaction in a drop on demand inkjet printer is limited, though enough information is available on the preparation of ceramic inks. The design of nozzle for drop on demand inkjet printing involves transient interaction between fluids and structures to eject ink droplets. Study of phenomena that contribute to the droplet formation, ejection and deposition on a substrate for several combination of physical properties of constituents of the ink and the characteristics of actuation mechanism is relevant for understanding and effective utilization of direct ceramic inkjet printing (DCIJP). This paper focuses on the simulation of formation and ejection of a ceramic ink droplet (paraffin wax loaded with different volume fraction of alumina particles) from a reservoir using piezoelectric actuation. The properties of ceramic ink are found in literature and they are used for simulation. Simulations were performed with computational fluid dynamics software (CFD-ACE+) which can solve multi-physiscs problems as encountered in DCIJP. This study gives details of the tight interaction among different physical phenomena that contribute to he droplet formation and ejection process. The results from this study will be useful for the preparation of ceramic inks to achieve desired droplet characteristics.
A Numerical Examination of the Inkjet Refilling
Authors: Yang Kai-Shing , Chen Ing-Young , Wang Chi-Chuan
Published: December 2008

A numerical study is conducted to examine the flow characteristics of the inkjet print-head with special attentions on the refilling process. By solving the full set of three-dimensional transient Navier-Stokes equations and considering the process of bubble growth and collapse as a movable membrane, it is found that the double refilling channels can reduce the flow surge phenomenon considerably due to the imposed friction. However, for the additional cylinder obstacle placed at the filling channel, the flow surge phenomenon is still present. This is because of the jet-like flow along the cylinder leading to a collision and eruption of fluid angled towards the plane boundary with the presence of cylinder. The calculated results also indicated the flow surge can be moderately suppressed for fluid having larger dynamic viscosity.
First Local Pressure Drops Measurements in Microchannels With Integrated Micromachined Strain Gauges
Authors: Baviere R. , Ayela F.
Published: December 2008

The knowledge of the fundamental aspects of hydrodynamics at microscales is an exciting challenge. Some authors have published conflicting results concerning the friction and the thermal exchange coefficients, the transition to a turbulent flow regime (Qu et al. 2000, Mala and Di 1999, Papautsky et al. 1999). Some explanations, based on surface effects, have been proposed, but microeffects, if they are, are probably hidden by experimental artefacts. We aim at performing local measurements of pressure drops in monophasic microstreams. Precedent works (Baviere et al. 2003) have shown that a great care has to be taken with the intrepretation of anomalous or unexpected results, and that the metrological set up of these experiments is crucial. We have performed and tested cupro-nickel strain gauges micromachined on different sorts of silicon nitride membranes. The design of the gauges obeys an electrical Wheatstone bridge configuration. The experimental signals are in good agreement with the expected electromechanical response of the bridge. The sensitivity ranges from 50 to 100 μV/V/bar with a thermal drift below 0.011%.°C−1. Such sensors have been integrated along smooth and rough silicon microchannels with hydraulic diameter of 15 μm, and no deviation from the laminar regime has been observed with such local pressure sensors. The micromachining of these devices is described and the first local pressure drops measurements performed with deionized water of low electrical resistivity are presented and discussed.
Crosstalk of Parallel Components for Microfluidic Systems
Authors: Chen Yu-Feng , Tseng Fan-Gang , Chieng Ching-Chang
Published: December 2008

Numerical simulations based on first principle equations is used to study the crosstalk phenomena and elimination mechanism for the parallel microchannel systems as microarray. The cases of this study focus on the surface tension driven flow include inkjet printing system, stamping by stamper protein microarray with embedded microchannels and the filling of H-shaped parallel microchannels. The parallel arrangements of microfluid components in terms of configuration as well as the parallel operation mode are the key issues to ensure the least crosstalk.
The Effect of Reynolds Number on Microfan Performance
Authors: Quin David , Grimes Ronan , Walsh Ed , Davies Mark , Kunz Stefan
Published: December 2008

Miniaturisation of modern electronics means that future compact electronic systems are likely to be too hot to be held in the users hand. Simultaneous increases in heat dissipation will also require the development of novel compact cooling technologies. In systems such as mobile phones and palmtop computers, macro scale fans cannot be used to overcome this problem, as they are too large. As a solution, the implementation of micro fan technology is proposed. Previous investigators have shown that reduction of the Reynolds number of turbomachinery results in reduced efficiency. To experimentally investigate this predicted phenomenon, a series of geometrically similar axial flow fans have been fabricated. These range in size from the macro to the micro scale with the Reynolds numbers varying linearly with fan dimensions. Through detailed Particle Image Velocimetry (PIV) measurements and pressure flow characterization of these fans, this investigation aims to quantify the reduction in efficiency, which occurs as the Reynolds number is reduced. This paper concludes that the extent to which fan efficiency is reduced by Reynolds number is in surprisingly good agreement with relatively simple predictions developed by the authors in previous investigations. Reduced Reynolds number was also seen to alter the velocity distribution at the fan outlet. This is an important point as it indicates a change in the physics of the flow with reducing scale.
A Numerical Case Study of Fluid Mixing in Microchannels: The Electro-Osmotic Driven Micro-Mixer
Authors: Kang Kai , Chevray Rene
Published: December 2008

Flow in microchannels is usually slow and the mixing of several fluids is poor if only relying on diffusion. A microchannel mixer with a simple design that is capable of rapid mixing is important for practical applications such as biochemistry analysis. In this study, a general numerical approach to analyze microchannel flow is proposed. The method is based on numerical particle tracking and computer graphics techniques. As a case study, an electro-osmotic driven microchannel mixer is considered with four geometric configurations. The microchannel has a repeated oblique-angled stripe pattern of zeta potential coatings on its floor. The comparison of the particle residence time distributions gives some indication of the mixers’ performances. The efficiency of mixing two flow streams at Pe´clet numbers 2 × 105 and 2 × 104 is then evaluated using the developed procedure. The results indicate that the stripe length ratio is one of the parameters that can be optimized for better mixing. Of the three stripe length ratios evaluated, the configuration with the stripe length ratio 2.0 is found to be the best. In addition, this case study demonstrates that the developed numerical technique is suitable for expeditious parametric optimization of mixer design.
Convective Mixing and Its Application to Micro Reactors
Authors: Engler Michael , Kockmann Norbert , Kiefer Thomas , Woias Peter
Published: December 2008

This work shows the application of convective fluid flow caused by flow-induced secondary vortices to fluidic single-phase micro mixers. As an example we used simple static T-shaped micro mixers. The convective flow was observed both by simulations and by experiments and is suitable for enhancing the mixing quality. Concerning micro reactors, it is necessary that the mixing is faster than the chemical reaction to be induced so that the creation of unwanted side products is minimized. The mixing model by Bourne is slightly modified for continuous flow reactors and applied to our mixers. Using this model, timescales for the mixing in our micro mixers are calculated. A first test reaction — the iodide-iodate reaction by Villermaux and Dushman — to check the validity of the timescales is outlined. These overall results will help to achieve a deeper understanding of micro reactors.
Characterization of Mixing Efficiency in Narrow Channels by Using the Iodide-Iodate Reaction System
Authors: Trippa Giuliana , Jachuck Roshan J. J.
Published: December 2008

Microreactors and narrow channel reactors have found an increasing number of applications in the last few years for their enhanced heat and mass transfer properties if compared to traditional process equipment. In this investigation, mixing efficiency in a narrow channel reactor system has been studied by using the iodide-iodate scheme of parallel competing reactions that leads to the formation of iodine. The tested system is constituted by two reactors machined in Perspex. The two channels have identical configuration and a square cross section with diagonal lines of 1·10−3 m and 2·10−3 m respectively. Influence of flow rate on the selectivity towards iodine has been studied for both reactors. This allows the characterization of mixing intensity at varying operating conditions. The results obtained reflect the expected influence of flow rate and channel characteristic dimension on mixing efficiency. This investigation has been carried out on the same reactor system that had been previously used for studying the precipitation of calcium carbonate from solutions of sodium carbonate and calcium nitrate. In fact, a study on mixing efficiency is particularly useful in the case of precipitation reactions as poor mixing can lead to a final product that does not respect marketing requirements in terms of particle size and particle size distribution. The information acquired in the two investigations can constitute the basis for the design of modules based on narrow channel technology for the production of powders and slurries with controlled properties.
Numerical and Experimental Studies on Electrical Potential Distribution of Pressure Driven Flow in Parallel Plate Microchannels
Authors: Lu Fuzhi , Yang Jun , Kwok Daniel Y.
Published: December 2008

A number of papers have been published on the computational approaches to electrokinetic flows. Nearly all of these decoupled approaches rely on the assumption of the Poisson-Boltzmann equation and do not consider the effect of velocity field on the electric double layers. By means of a charge continuity equation, we present here a numerical model for the simulation of pressure driven flow with electrokinetic effects in parallel-plate microchannels. Our approach is similar to that given by van Theemsche et al. [Anal. Chem., 74, 4919 (2002)] except that we assumed liquid conductivity to be constant and allows simulation to be performed in experimental dimension. The numerical simulation requires the solution of the Poisson equation, charge continuity equation and the incompressible Navier-Stokes equations. The simulation is implemented in a finite-volume based Matlab code. To validate the model, we measured the electrical potential downstream along the channel surface. The simulated results were also compared with known analytical solutions and experimental data. Results indicate that the linear potential distribution assumption in the streaming direction is in general not valid, especially when the flow rate is large for the specific channel geometry. The good agreement between numerical simulation and experimental data suggests that the present model can be employed to predict pressure-driven flow in microchannels.
Modeling and Visualizing Electroosmotic Microchannel Flow With Joule Heating Effects
Authors: Xuan Xiangchun , Sinton David , Xu Bo , Li Dongqing
Published: December 2008

Electroosmotic flow with Joule heating effects was examined numerically and experimentally in a micro capillary. Fluorescence-based thermometry and velocimetry techniques were employed to visualize the liquid temperature and the electroosmotic velocity profile, respectively. Sharp temperature drops close to the two ends and a high-temperature plateau in the middle of the capillary were observed. Correspondingly, concave-convex-concave velocity profiles were observed in the inlet-middle-outlet regions of the homogeneous capillary. The measured liquid temperature distributions and electroosmotic velocity profiles along the capillary agree well with the predictions of a theoretical model developed in this paper.
Influence of the 3D Heterogeneous Roughness on Electroosmotic Flow in Microchannels
Authors: Hu Yandong , Werner Carsten , Li Dongqing
Published: December 2008

Surface roughness has been considered as a passive means of enhancing the species mixing in electroosmotic flow through microfluidic systems. It is highly desirable to understand the synergetic effect of the 3D roughness and the surface heterogeneity on the electrokinetic flow through microchannels. In this study, we developed a three-dimensional, finite-volume-based numerical model to simulate electroosmotic transport in a slit microchannel (formed between two parallel plates) with numerous heterogeneous prismatic roughness elements arranged symmetrically and asymmetrically on the microchannel walls. The results showed that, the rough channel’s geometry and the electroosmotic mobility ratio of the roughness elements’ surface to that of the substrate, εμ, have dramatic influence on the induced pressure field, the electroosmotic flow patterns and the electroosmotic flow rate in the heterogeneous rough microchannels. The associated sample species transport in the heterogeneous rough microchannels presents tidal-wave-like concentration field at the intersection between four neighboring rough elements when under low εμ values, and presents the concentration field similar to that of the smooth channels when under high εμ values.
Numerical Simulation on the Electrophoretic Motion of Multiple Particles in Microchannels
Authors: Ye Chunzhen , Li Dongqing
Published: December 2008

This paper considers the electrophoretic motion of multiple spheres in an aqueous electrolyte solution in a straight rectangular microchannel, where the size of the channel is close to that of the particles. This is a complicated 3-D transient process where the electric field, the flow field and the particle motion are coupled together. The objective is to numerically investigate how one particle influences the electric field and the flow field surrounding the other particle and the particle moving velocity. It is also aimed to investigate and demonstrate that the effects of particle size and electrokinetic properties on particle moving velocity. Under the assumption of thin electrical double layers, the electroosmotic flow velocity is used to describe the flow in the inner region. The model governing the electric field and the flow field in the outer region and the particle motion is developed. A direct numerical simulation method using the finite element method is adopted to solve the model. The numerical results show that the presence of one particle influences the electric field and the flow field adjacent to the other particle and the particle motion, and that this influences weaken when the separation distance becomes bigger. The particle motion is dependent on its size, with the smaller particle moving a little faster. In addition, the zeta potential of particle has an effective influence on the particle motion. For a faster particle moving from behind a slower one, numerical results show that the faster moving particle will climb and then pass the slower moving particle then two particles’ centers are not located on a line parallel to the electric field.
Spatio-Temporal Evolution of a Spot Under the EDL Effect
Authors: Tardu Sedat , Shiu Huan-Ruei
Published: December 2008

The effect of the electric double layer (EDL) on the bypass transition mechanism in the linear evolution stage is explored through direct numerical simulations. An initial perturbation velocity field consisting of a pair of counterrotating vortices is introduced in Poiseuille and EDL flows and the time-space evolution of the perturbed field is analysed for short times at half the critical Reynolds numbers (3000 for Poiseuille and 150 for EDL). The wall normal and spanwise perturbation velocities development are both quantitatively and qualitatively similar in macro and micro flows. The streamwise velocity, which is initially zero and set up by the generation of the wall normal vorticity is twice larger under the EDL effect. Both flows develop inclined strong streamwise shear layers. Overall is the close similarity of the disturbance evolution showing that the three dimensional linear mechanism in EDL flow lead to the structures that are at least as strong as in Poiseuille flow.
Sample Manipulation in Microfluidic Devices With Electrical Conductivity Gradients
Authors: Ren Carolyn L. , Li Dongqing
Published: December 2008

A common application in microfluidic devices is on-chip capillary electrophoresis (CE). In this process, sample species are transported by electroosmotic flow and separated based on their electrophoretic mobilities. Separated analytes are typically detected using laser-induced fluorescence. It has been found that the sample shape and size, which is critical to the later detection processes or the quality of other analytical techniques, depends on many parameters, such as the sample diffusion coefficient, the applied voltages, and the electrical conductivity difference between sample and buffer. The conductivity difference can alter the electric field strength, which is the driving force behind both the electroosmotic bulk flow and the electrophoretic velocity of individual species. Therefore, the manipulation technique is required to consider the transport processes with conductivity differences. A numerical model presented in this paper is used to simulate the sample transport process with the consideration of conductivity gradient in order to develop the sample manipulation techniques. There are two situations studied here, which are sample pumping (where bulk transport is increased and analyte separation is delayed using a relatively high conductivity sample), and sample stacking (where bulk transport is decreased and analyte separation is expedited using a relatively low conductivity sample). The effects of applied electrical potential, sample diffusion coefficient and the extent of conductivity difference on the sample control are investigated through the developed model. The simulation results show that the sample transport with the consideration of conductivity gradient differs significantly from that of uniform conductivity case.
Micro-Electrical Impedance Spectroscopy for Particle Detection
Authors: Wu Jie , Chang Hsueh-Chia
Published: December 2008

Microfludic devices with integrated electrical detection will enable fast, low-cost or portable sensing and processing of biological and chemical samples. As an inherent property of microfabrication, micro-electrical impedance spectroscopy detectors can take advantage of AC electrokinetics for particle manipulation, leading to enhanced sensitivity. Preliminary experiments on particle detection were carried out using microelectrode pairs, and impedance spectra are compared with respect to opposite effects of dielectrophoresis and electrode polarization. The values of cell equivalent circuit are extracted for electrode optimization.
Mechanisms of Coupled Heat Transfer and Flow of High Heat Flux Pulsating Heat Pipe
Authors: Qu Wei , Qu Yantao , Ma Tongze
Published: December 2008

The mechanisms of coupled heat transfer and flow are modeled to describe the looped pulsating heat pipe of high heat flux. The latent heat transfer produces the pressure difference between the heating section and cooling section. This can provide the operational driving force to overcome the total flow resistances. While the sensible heat transfer contributes more to the transferred power. The results demonstrate that the circulation flow velocity can balance the heat and mass transfers automatically. And the ratio of latent heat transfer to sensible heat transfer is within 30 percent.
Thermocapillary Flow and Evaporation Near Contact Lines in Micro Heat Pipes
Authors: Ajaev Vladimir S. , Gebresilassie M. Markos
Published: December 2008

We develop a mathematical model for heat transfer and fluid flow near a contact line on a heated surface in the presence of thermocapillary flow and evaporation. The coupled heat transfer and flow problem is reduced to an equation for local thickness, which is then solved numerically. The steady-state results indicate that thermocapillary stresses act to reduce the rate of liquid flow towards the contact line and increase interfacial curvature there. We also discuss solutions than involve moving contact lines, applicable to studies of start-up and shut-down operations of heat pipes. The velocity of the contact line and the apparent contact angle are found as functions of the Marangoni number. Thermocapillary effect is shown to reduce contact line speed and increase the apparent contact angle. Finally, the local solution is incorporated into global solutions for curvature variations of an evaporating three-dimensional meniscus in a corner. This configuration is typically encountered in proposed designs of micro heat pipes. Interface curvature is found as a function of the axial coordinate for the case of linear axial temperature variation in the corner.
MC Simulation of Radiative Heat Transfer Between Planar Semi-Infinite Media and Nano-Spheres With Near Field Effect
Authors: Huang Yong , Liang Xin-Gang
Published: December 2008

Based on the principle of electric dipole radiation and the Planck’s spectral distribution of emissive power, the enhancement of thermal radiation between two planar semi-infinite media or two nano-spheres was studied in this paper by the Monte Carlo method. By this simple method, some parameter’s influence on the radiative heat transfer was investigated, such as the distance between two semi-infinite media, the particle’s radius, the distance between two particles and the difference in temperature between two particles, and so on. This solution is not rigorous but simple. The results show that heat transfer can be enhanced by several orders of magnitude for the near field effect. And the radiative heat transfer is decreasing sharply with the increasing of the distance.
Anomalous Capillary Wetting Dynamics of Blood Suspensions
Authors: Zhou Ronghui , Lastochkin Dmitri , Chang Hsueh-Chia
Published: December 2008

When blood suspension penetrates a capillary radius by wetting, the advancing meniscus decelerates rapidly when the blood cell volume fraction is above a certain critical concentration. Below the critical concentration, blood suspension behaves like a homogeneous liquid and the wetted length increases as the 0.5 power of time. We attribute the former deceleration dynamics to a unique packing mechanism behind the meniscus that is driven by radial migration of the deformable blood cells. Unlike rigid particle suspensions, a concentrated slug develops behind the meniscus of blood suspension and its concentration increases linearly with respect to the meniscus position downstream due to this packing mechanism. As the suspension viscosity blow up with a −2 power with respect to blood concentration φ at maximum packing, viscous dissipation at the slug quickly controls the meniscus speed if the slug length is comparable to the total wetted length, thus significantly delaying the meniscus penetration dynamics. The critical concentration is measured empirically and shown to be a linear function of the capillary radius R with a simple scaling theory. For 40% whole blood, penetration rate is too slow, in the order of μm /s at 2cm from the entrance, to be widely used in sample loading for miniature diagnostic kits with diameter less than 26 micron.
Velocity Measurements in Microchannels With a Laser Scanning Microscope and Particle Linear Image Velocimetry
Authors: Chao S. H. , Holl M. R. , Koschwanez J. H. , Carlson R. H. , Jang L. S. , Meldrum D. R.
Published: December 2008

A novel velocity measurement method for microscale flow field characterization is reported, particle linear image velocimetry (PLIV). The method records a series of one-dimensional images that represent the trace of particles in the flow across a one-dimensional imager. Linear imaging results in a faster frame rate than planar imaging, allowing observation of larger microscope magnification or measurement of faster flow rates in real-time than comparable techniques. In contrast to particle image velocimetry (PIV), PLIV does not require high-speed cameras or shutters. Furthermore, PLIV is adaptable to multiple linear imager formats and, as one example, can use laser scanning confocal microscopes (LSCM) that acquire images slowly but with high spatial resolutions and optical sectioning ability. Higher resolution can be obtained for flows where in-plane velocity gradient in the direction of the optical path (z-direction) is important. This paper presents the PLIV algorithm, and demonstrates its utility by measuring Poiseuille flow with 1-μm resolution in a microfluidic environment.
Effect on Heat Transfer of Particle Migration in Suspensions of Nanoparticles Flowing Through Minichannels
Authors: Wen Dongsheng , Ding Yulong
Published: December 2008

Thermal management is one of the greatest challenges in maintaining the functionality and reliability of high-speed micro-electronic systems such as MEMS and NEMS. This requires development of high performance heat transfer media, which can not only flow through micro- and nano-channels under local operating conditions, but also carry as more heat as possible out of the system. Recent work has shown that suspensions of nanoparticles with a size considerably smaller that 100nm but with thermal conductivity orders of magnitudes higher that the base liquids have a greater potential as a high energy carrier for the micro- and nano-systems. However, it is also known that particles in a suspension undergoing a shearing action may migrate, hence lead to non-uniformity. This indicates that the efficiency of heat transfer in the micro- and nano-channels may not be as superior as expected, which bears significance to the system design and operation. This work aims at addressing this issue by examine the effect of particle migration on heat transfer in small channels. This involves development of both flow and heat transfer models, and numerical solution to the models. The flow model takes into account the effects of the shear-induced and viscosity gradient-induced particle migrations, as well as self-diffusion due to the Brownian motion, which is coupled with an energy equation. The results show that particle migration leads to concentration of particles in the wall region can be much lower than that in the core region. Particle migration is also shown to increase the Nusselt number under both constant temperature and constant heat flux conditions.
Proteinaceous Bubbles and Nano Particle Flows in Microchannel
Authors: Jung Jung-Yeul , Byun Ki-Taek , Hong Jae-Ho , Kwak Ho-Young
Published: December 2008

Proteinaceous bubbles of 185 nm in average diameter were synthesized by a sonochemical treatment of bovine serum albumin in aqueous solution and the nanoparticles (TiO2) solution was made by ultrasonic irradiation. To study the macroscopic flow behavior associated with the changes in the state of microparticles, a flow test of these solutions in microchannels was done. Also the size distributions of the proteinaceous bubbles in solution before and after the flow test were measured by a light scattering method. Test results show that the air-filled proteinaceous bubbles in solution adjust their size to reduce the shear stress encountered in the flow through the microchannel. On the other hand, the flow rate of the solution with nanoparticles suspensions becomes smaller than that of deionized water above the flow rate of 6 cm3/min in the microchannel with a dimension of 100×150 μm2.
Novel Connections for Non-Metallic, Flexible, Thin, Microchannel Heat Exchangers
Authors: Pourmohamadian Neema , Philpott Mike L. , Shannon Mark A.
Published: December 2008

Non-metallic, flexible, thin, microchannel heat exchangers made from heat-sealable polyimide films have recently been developed for refrigeration and air-conditioning applications. In order for these heat exchangers to function properly and independently, robust and reliable connectors are needed. The connectors must be easy to manufacture and assemble, hold high pressures without leaking, and have the ability to connect to standard tubing and piping and different heat exchangers together in series and parallel. Three uniquely different connector designs have been developed, manufactured, and tested. The first includes a machined metal connector internally embedded within the heat exchanger that is capable of holding pressures up to 1.03 MPa. The second connector design includes a two-piece polymer assembly containing an O-ring used to seal around the inlet and outlet holes of the heat exchanger. The design incorporates a 10-degree wedge that creates the sealing force when fully assembled with the heat exchanger and has been pressure tested to 2.07 MPa without leaking. A variation of the design allows multiple heat exchangers to connect in series and in parallel. Finally, the third design contains no additional parts and connects two heat exchangers together by thermally bonding the inlet of one heat exchanger to the outlet of another. The thermally bonded connection was able to hold pressures greater than 2.07 MPa.
Catalytic Micro Channels Stacked by Brazing Method
Authors: Yu Sang-Phil , Lee Seung-Jae , Jeoung Nam-Jo , Ryu In-Soo , Kang Sung-Kyu , Song Kwang-Sup
Published: December 2008

Each stack of microstructured stainless steel and aluminum plates was coated and brazed in vacuum. As a supporter of catalyst, the coating layer was formed by solgel method and anodizing respectively. Though the number of brazed plates extended to a hundred, the thickness of coating layer on the respectively coated plate was relatively uniform and the leakage of assembly was effectively minimized. The critical variables for brazing were both thickness and shape of filler metal. Consequently, brazing method had good resolution for 200μm three dimensional multi layer structures. Through these results, coating to support catalysts in highly stacked layers by brazing can be applied to micro catalytic heat exchanger where the reaction and heat transfer occur simultaneously.
Extruded Microchannel-Structured Heat Exchangers
Authors: Gruss Jean-Antoine , Bouzon Christophe , Thonon Bernard
Published: December 2008

In the search for more compact air/liquid heat exchangers, one possible way is to increase the heat transfer coefficient and surface area by a decrease of the size of the fluid channels. A practical example could be air/water cross-flow heat exchangers used in cars. These exchangers are designed so that air pressure drop is minimised at a given thermal power exchanged from water to air. In this case, minimisation of the total volume leads to a very thin structure with a large frontal area, with a lot of small and short air channels. This configuration is very inconvenient for most practical applications and also difficult to manufacture at low cost. Using this rationale, we have designed and patented a cross-flow heat transfer surface with microchannels that has such a structure, but can be manufactured industrially at reasonable cost by extrusion either in aluminium or in polymers. Moreover, the arrangement of the heat transfer surfaces is very flexible and allows for different configurations (accordion, serpentine, cylindrical, star...) so that various geometric configurations, adapted to specific applications, can be obtained. The thermo-hydraulic performance of the structure has been simulated using standard correlations and CFD codes. Prototypic structures made by stereolithography have been manufactured in glass reinforced polymer and are currently being tested on a test bench. In order to validate our simulation code, a single structure and an accordion arrangement heat exchanger are under investigation. Compared to classical heat exchangers, our design is superior in flexibility and compactness for air/liquid applications. An additional interest of our design would be to increase performance in humid air cooling applications, since our structure may drain condensates more easily. We are currently looking for a partnership to develop this design for industrial applications.
Detection of Mechanical Damage Using the Magnetic Flux Leakage Technique
Authors: Clapham Lynann , Babbar Vijay , Byrne James
Published: December 2008

Since magnetism is strongly stress dependent, Magnetic Flux Leakage (MFL) inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, MFL application to mechanical damage detection faces hurdles which make signal interpretation problematic: 1) the MFL signal is a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. This paper summarizes recent results of experimental and modeling studies of MFL signals resulting from mechanical damage. In experimental studies, mechanical damage was simulated using a tool and die press to produce dents of varying depths in plate samples. Radial component MFL measurements were made before and after selective stress-relieving heat treatments. These annealing treatments enabled the stress and geometry components of the MFL signal to be separated. Geometry and stress effects generate separate MFL peaks — the geometry effects lead to central peak regions while the stress effects produce ‘shoulder’ peaks. In general the geometry peaks tend to scale with depth, while the shoulder peaks remain approximately constant. This implies that deep dents will display a ‘geometry’ signature while shallow or rerounded dents will have a stress signature. Finally, the influence of other parameters such as flux density and topside/bottomside inspection was also quantified. In the finite element analysis work, stress was incorporated by modifying the magnetic permeability in the residual stress regions of the modeled dent. Both stress and geometry contributions to the MFL signal were examined separately. Despite using a number of simplifying assumptions, the modeled results matched the experimental results very closely, and were used to aid in interpretation of the MFL signals.
Advances in the Use of Spaceborne InSAR for Application to Pipeline Route Selection and Integrity Management
Authors: Froese Corey R. , van der Kooij Marco , Kosar Keith
Published: December 2008

Spaceborne Synthetic Aperature Radar (InSAR) is a technique that has been used to measure ground movements associated with slope movements and subsidence since the mid-90’s. Previous applications had utilized either dry terrain with no vegetation cover or have relied on the use of articial targets to quanitify deformations. Recent advances in the processing technology have allowed for sub-millimetre level accuracy movements tracking over long time periods and for detection of movements as small as 2 mm/month in vegetated slopes in northern Canada. The archival data and the active aquisitions allow engineers working in the pipeline industry to both review previous movement rates and patterns for planning of pipeline routes and provides a tool for ongoing monitoring of deformations due to ground subsidence or slope movement for operational pipelines.
Integrity Management: Automated Analysis for Class Location
Authors: Odegard Lori , Humber Jason
Published: December 2008

Class location analysis is a key component of an effective integrity management plan. Application of class location results vary based on the product transported, but regardless of product, the analysis has requirements of audit, reporting, and annual update. Process definition and reengineering as part of the Natural Gas Business Unit (BP Canada) pipeline integrity management system was a driving force behind implementation of an automated class location analysis. The results of the automation effort have been manifested as: • Reduced data acquisition costs; • Improved data workflow; • Increased data reuse; • Cost savings through personnel reduction, and • Consistency in application of rules defined by the pipeline integrity management system.
Integration of the Commercial and Operational Systems for the Supply of Services Related to the Transportation of Natural Gas
Authors: Silva Mauri´cio S. , Varo´n Rene´ , Frisoli Caetano , Carvalho de Faria Jose´ Aure´lio
Published: December 2008

The Bolivia-Brazil Gas Pipeline Project is a major South American pipeline serving the natural gas market in Brazil. TBG the transportation company on the Brazilian side, developed an integrated commercial and operational management system in partnership with Energy Solutions International Inc. to increase the efficiency and quality of natural gas transportation service. TBG needed a field-proven solution to manage commercial procedures and operational tools to evaluate available capacity in the pipeline. To meet the challenge, TBG and Energy Solutions developed a state-of-the-art network that combines a gas contract management system with engineering applications for pipeline monitoring. The resulting network integrated commercial, operational, SCADA, and corporate financial software.
Dynamic Modelling and Real-Time Leak Detection for NGL Pipelines
Authors: Young Brent R. , Cooke J. Greg , Daye Ron E. , Svrcek William Y.
Published: December 2008

This paper describes the development and use of a dynamic simulation model and the implementation of a novel leak detection system. Experiences from the implementation and operation of the system will also be detailed from a user perspective. The dynamic model may be used for the transient simulation of the pipelines. The model was used to test the real-time leak detection system. The results of the simulation also prompted a change in the control scheme of the pipelines that resulted in less transient operation. The leak detection system is based upon rigorous thermodynamics and dynamic mass balance calculations driven by real-time information from field flow, pressure and temperature sensors. This system was successfully implemented to replace a simple volume balance system for NGL pipelines near Empress, Alberta.
The Use of Geotextile Fabric, Anti-Buoyancy Weights for Buried Pipelines
Authors: Connors Geoff W.
Published: December 2008

Buried pipelines have always required a certain level of additional weight to counteract the buoyant force that is often exerted on them from groundwater. Early methods of buoyancy control include the use of cast iron, and later, concrete weighting. In 1993 a new type of weight was introduced to the pipeline industry which addressed many of the pitfalls of earlier weight designs — the geotextile fabric weight (GFW).
Integrity Assessments of Pipelines Using SE(T) Specimens
Authors: Cravero Sebastian , Ruggieri Claudio
Published: December 2008

This work presents a numerical investigation of crack-tip constraint for SE(T) specimens and axially surface cracked pipes using plane-strain, nonlinear computations. The primary objective is to gain some understanding of the potential applicability of constraint designed fracture specimens in defect assessments of pressurized pipelines and cylindrical vessels. The present study builds upon the J-Q approach using plane-strain solutions to characterize effects of constraint on cleavage fracture behavior for fracture specimens and cracked pipes. Under increased loading. each cracked configuration follows a characteristic J-Q trajectory which enables comparison of the corresponding crack-tip driving force. The results provide a strong support to use constraint-designed SE(T) specimens in fracture assessments of pressurized pipes and cylindrical vessels.
Uncertainties in Pipeline Water Percentage Measurement
Authors: Scott Bentley N.
Published: December 2008

Measurement of the quantity, density, average temperature and water percentage in petroleum pipelines has been an issue of prime importance. The methods of measurement have been investigated and have seen continued improvement over the years. Issues of pipeline integrity, product loss and production balances are placing further demands on the issues of accurate measurement. Water percentage measurement, often called water cut, is one area that has not received the attention necessary to understand the uncertainty of measurement. Work done with three major oil companies on pipeline measurement problems will be discussed. Spot sampling comparisons over a two-year period will be shown and uncertainty analysis for this data will be presented. Composite sampling versus on line water cut analyzer results will be described.
Risk Reduction Measures Applied to Horizontal Directional Drilling of a Complex Pipeline River Crossing in Canada
Authors: Cocciolo Peter P. , Zeleny Bob
Published: December 2008

In August and September of 2003, Terasen Pipelines (Trans Mountain) Inc. successfully completed the Horizontal Directionally Drilled [HDD] replacement of it’s NPS 24” pipeline crossing at the Fraser River from Surrey to Coquitlam in southwestern British Columbia. The pipeline replacement was necessary to mitigate the high seismic risk from liquefaction induced lateral spreading of soils on the north and south shores of the Fraser River. The high level of urban development and the close proximity of major linear infrastructure on both sides of the river created spatial restrictions which increased the complexity and risk of the HDD crossing. Measures to reduce construction risks and limit Terasen’s exposure to claims for changed subsurface conditions, environmental damage due to frac-outs, delays, pipe and coating damage, and inability to complete the crossing, were applied. Important strategies used during planning and construction of the crossing included: proper selection of the pipeline route and laydown corridor, site specific geotechnical investigation, HDD annular pressure monitoring, HDD electronic drilling recording, and a contractor pre-qualification process. The final result was that the contractors successfully drilled and installed the 1293m long HDD crossing over a period of one month, without incident. This paper presents the challenges and solutions implemented by the project team to bring the project to its successful conclusion.
Validation of EMAT In-Line Inspection Technology for SCC Management
Authors: Kothari Meera , Tappert Stephan , Strohmeier Uwe , Larios Jose , Ronsky N. Daryl
Published: December 2008

TransCanada has a need to manage sections of the pipeline that are susceptible to stress corrosion cracking (SCC) failure by periodically performing hydrostatic testing. Since hydrostatic testing requires a complete service interruption, In Line Inspection technologies (operating in gas pipelines without liquid couplant) are being investigated as an alternate method to managing this hazard. This requirement resulted in a joint technology and tool development project involving GE Energy and TransCanada. The EmatScan® Crack Detection (CD) tool is designed to detect and size longitudinally oriented external SCC features in gas-filled pipelines. During autumn 2002, the EmatScan® CD tool was run in a 64 km section of the TransCanada system. In 2003, field correlation excavations were conducted to assess the accuracy of the tool. This paper describes the results from the correlation program conducted to validate GE Energy’ 36 inch (914 mm) diameter EMAT (Electro Magnetic Acoustic Transducer) crack detection tool.
A Review of the Time Dependent Behaviour of Line Pipe Steel
Authors: Cosham Andrew , Hopkins Phil
Published: December 2008

It is good practice to reduce the pressure in a pipeline prior to inspecting damage. One of the purposes of this pressure reduction is to prevent a ‘time dependent failure’ whilst inspecting the damage. The EPRG (European Pipeline Research Group) guidelines for the assessment of mechanical damage recommend that the internal pressure be reduced to 85 percent of the pressure at the time of damage to prevent time dependent failures. The PRCI (Pipeline Research Council International) Pipeline Repair Manual recommends a pressure reduction to 80 percent of the pressure at the time of damage. Failures that occur under a constant load are time dependent failures. This means that a defect in a pipeline could fail sometime after the damage was caused, even though there has been no increase in the applied load, or an active growth mechanism such as corrosion or fatigue. They have been observed during hydrostatic test hold periods, during operation and under laboratory conditions. Failures under constant load occur because plastic deformation occurs in the material surrounding a defect subject to a load, and because plasticity is time dependent. Time dependent behaviour is relevant to: (1) the safe working practices in the vicinity of a damaged pipeline, (2) pressure reversals, (3) the margin between the operating pressure and the hydrostatic test pressure, and (4) the minimum duration of a hydrotest. The results of experimental and analytical studies of time dependent behaviour reported in the published literature are reviewed in this paper, to understand the background to the above recommended pressure reductions. This paper is based on the findings of the Pipeline Defect Assessment Manual (PDAM) project, a Joint Industry Project sponsored by sixteen international oil and gas companies.