Pipe Mode Research Articles

温暖地における地中熱の利用に適した空調用サイクル

A ground source heat is one of a renewable energy. The ground source heat has been applied for melting snow and a heat source of a air conditioner. When a groun source heat is used for heat source of a air conditioner, a ground temperature is lower than a required temperature in Summer in most part of Japan. Therefore only heat pipe is required for air conditioning at that conditon. In winter, the ground temperature is higher than a required temperature. Then heat pump system is required for air conditioning in winter. We consider the cycle that can operate as both of heat pipe mode and heat pump mode, and made experiment about the cycle with R407C as refrigerant. By the experiment result, the heat transfer and the work decreased with the increase of the refrigerant charge amount. COP took the maximum value in 2700g for refrigerant charge amount and 19 kg/h for mass flow rate.

The efficiency of plate tectonics and nonequilibrium dynamical evolution of planetary mantles

AbstractConsideration of the structure of dynamical equilibria in terrestrial planets using simplified descriptions of the relevant heat transport processes (rigid‐lid convection, plate tectonics, and heat pipe volcanism) reveals that if the efficiency of plate tectonic heat transport decreases at higher mantle temperature, then it cannot govern quasi‐equilibrium dynamical evolution, and the system is always evolving away from the plate tectonic regime. A planet on which plate tectonics is less efficient at higher temperature stays in heat pipe mode longer, spends less time undergoing plate tectonics, and has a low and ever‐decreasing Urey number during this phase. These conclusions are based solely on the structure of the equilibria in a system with less efficient plate tectonics in the past and are independent of the mechanisms leading to this behavior. Commonly used quasi‐equilibrium approaches to planetary thermal evolution are likely not valid for planets in which heat transport becomes less efficient at higher temperature.

EFFECT OF SOIL CORROSION IN FAILURES OF BURIED PIPELINES

Over the last few years, several failures in transmission and distribution water/gas pipelines have been reported around the world. The failure of buried pipeline is controlled by several factors, such as pipe material, soil corrosion, internal and external loading, etc. Among these, soil corrosion makes a significant contribution towards failure mode and mechanisms in buried pipes, yet few studies have been done. Although a number of corrosion models have been developed over the years, the applicability of the model predominantly depends on the type of soil and its moisture change over time at the pipe depth. By incorporating a corrosion model, the remaining life of the pipe can be estimated on the basis of applied traffic and pressure loads, which determine the stresses in the pipe segment. Depending on the model, the estimation can show significant variability, and consequently affect the pipe renewal and rehabilitation plans that ultimately have economic impacts. Therefore, it is important for the pipeline asset owners to understand the effect of corrosion models in the remaining life calculation. This paper reviews briefly the available corrosion models and the sensitivity of each parameter in pipe corrosion pit properties and in the remaining life estimation. Finally, a comparison among the corrosion models on the basis of the remaining life estimation is provided to improve the renewal plan.

On the scattering of elastic waves from a non-axisymmetric defect in a coated pipe

Viscoelastic coatings are often used to protect pipelines in the oil and gas industry. However, over time defects and areas of corrosion often form in these pipelines and so it is desirable to monitor the structural integrity of these coated pipes using techniques similar to those used on uncoated pipelines. A common approach is to use ultrasonic guided waves that work on the pulse-echo principle; however, the energy in the guided waves can be heavily attenuated by the coating and so significantly reduce the effective range of these techniques. Accordingly, it is desirable to develop a better understanding of how these waves propagate in coated pipes with a view to optimising test methodologies, and so this article uses a hybrid SAFE-finite element approach to model scattering from non-axisymmetric defects in coated pipes. Predictions are generated in the time and frequency domain and it is shown that the longitudinal family of modes is likely to have a longer range in coated pipes when compared to torsional modes. Moreover, it is observed that the energy velocity of modes in a coated pipe is very similar to the group velocity of equivalent modes in uncoated pipes. It is also observed that the coating does not induce any additional mode conversion over and above that seen for an uncoated pipe when an incident wave is scattered by a defect. Accordingly, it is shown that when studying coated pipes one need account only for the attenuation imparted by the coating so that one may normally neglect the effect of coating on modal dispersion and scattering.

Directional emissivity from two-dimensional infrared waveguide arrays

Fabrication and optical characterization of surfaces covered with open-ended metallic waveguides are presented along with numerical modeling of these structures. Both modeling and measurement of the structures indicate that the 2-D array of 3D metallic waveguides modify both the direction and spectral content of the emissivity, resulting in directionality normal to the surface due to the optical axis of the waveguides and spectrally narrow emissivity due to the lateral dimensions of the waveguides. Furthermore, the optical behavior of these structures is placed in the broader context of other structured emission/absorption surfaces such as organ pipe modes, surface plasmon modes, and coherent thermal emission from gratings.

Ultrasonic guided waves in elliptical annular cylinders.

This paper studies the influence of cross-section ovalness or ellipticity on lower order axisymmetric guided wave modes in thin pipes. The second longitudinal mode L(0,2) and the fundamental torsional mode T(0,1) are studied, as these are of interest to current pipe inspection. The semi-analytical finite element (FE) method is mainly used, with three-dimensional FE simulations for visualization and cross-validation of results. The studies reveal that even a small degree of ovalness can affect mode shapes and velocities. The effect is more pronounced on the L(0,2) mode than on T(0,1) and this may be important for practical inspection applications.

Exploring the Sensitivity of Fatigue Analysis with Regard to Design Parameters in PVC Pipes Subjected to Cyclic Transient Pressures

Abstract Experimental studies show that the parameters that contribute to fatigue in PVC pipes include the number of pressure cycles, the amplitude of the transient pressures, and the average pressure to which PVC material is exposed during the transient. Based on such experimental studies, design standards have been set to provide the required data for calculating the permissible number of pressure cycles below which the PVC pipes are considered safe against fatigue. However, the key challenge is to determine the amplitude and the number of transient pressure cycles, values which should be the outcome of a thorough transient analysis. Using a quite simple concept, the Plastic Pipe Institute developed the computer program PACE for the analysis of the fatigue failure mode in PE and PVC pipes. However, the concept behind this program disregards the intensity of the transient in the system, and thus its results are questionable in more realistic systems. The current research aims to explain and improve on the underlying concept of the program PACE. To this end the fatigue analysis of a hypothetical pumping system is made by the aid of both the program PACE and the results of a thorough transient analysis considering different mode of operation of the pumping system. The results show, somewhat predictably, that the analysis of fatigue in PVC pipes is a crucially system dependent; thus, the concept utilized by the PACE program is overly simplistic. In addition, the numerical results obtained imply that PVC pipes are safe against fatigue failure in a wide verity of operational conditions and that a reliable fatigue analysis can be only achieved through utilizing the data obtained from a though transient analysis.

Torsional mode magnetostrictive patch transducer array employing a modified planar solenoid array coil for pipe inspection

In recent investigations, the application of the transducers used in plates has been extended to pipe inspection with circumferential arrays because of the similar particle displacement patterns of some modes between plate and pipe, such as SH and torsional modes. Motivated by the configuration of magnetostrictive patch transducer (MPT), in which a planar solenoid array (PSA) coil was adopted to generate SH waves in plates, we proposed a MPTs array employing a modified planar solenoid array (MPSA) coil, i.e. MPSA coil-MPTs array, for generating and receiving the torsional mode in pipes. The configuration of the MPSA coil modified from PSA coil is suitable to be arranged on the pipe surface and can generate high-power waves. In the suggested configuration of MPT, because the direction of the actuating dynamic magnetic field produced by the MPSA coil is orthogonal to the direction of the static magnetic field produced by the permanent magnets in the magnetostrictive patch, the shear deformation induced by the magnetostriction in the patch will be delivered to the pipe, thus generating the torsional mode. First, it was experimentally verified that the fundamental torsional mode, T(0,1), could be effectively generated and received in pipes with the developed MPSA coil-MPTs array. Then, we studied the relationship between the frequency response characteristic of the developed MPSA coil-MPTs array and the interval defined by the distance of adjacent solenoids in the MPSA coil. Simultaneously, the circumferential crack defects in pipe were successfully identified. Finally, the performance of the MPSA coil-MPTs array was compared with that of previous meander coil-MPTs array. The comparison results demonstrated that the developed MPSA coil-MPTs array could enhance the power of the torsional mode.

Dynamic behavior of direct spring loaded pressure relief valves in gas service: Model development, measurements and instability mechanisms

A synthesis of previous literature is used to derive a model of an in-service direct-spring pressure relief valve. The model couples low-order rigid body mechanics for the valve to one-dimensional gas dynamics within the pipe. Detailed laboratory experiments are also presented for three different commercially available values, for varying mass flow rates and length of inlet pipe. In each case, violent oscillation is found to occur beyond a critical pipe length, which may be triggered either on valve opening or closing. The test results compare favorably to the simulations using the model. In particular, the model reveals that the mechanism of instability is a Hopf bifurcation (flutter instability) involving the fundamental, quarter-wave pipe mode. Furthermore, the concept of the effective area of the valve as a function of valve lift is shown to be useful in explaining sudden jumps observed in the test data. It is argued that these instabilities are not alleviated by the 3% inlet line loss criterion that has recently been proposed as an industry standard.

Transfer characteristics of vehicle air conditioners’ booming noise

Vehicle air conditioners generate a booming noise when pressure pulsation in the compressor is generated and transmitted to vehicle interiors through the attached pipes and chassis, which constitute a typical noise transfer path between the compressor and the interior. In this study, the transfer path analysis and operational deflection shape methods were employed for analyzing the characteristics of noise transfer paths, and acoustic intensity was measured through empirical experiments for analyzing the characteristics of the response system. The rigid body mode of the double pipe influences the dynamic behaviors of the liquid pipe, which is the major noise contribution path. The force exerted on the liquid pipe generates not only structure-borne noise but also air-borne noise in a heating, ventilation and air-conditioning system. An experiment was carried out to reduce such noise by distributing the high noise contribution to the low one. Through this experiment, we propose a path coupling method for noise reduction that modifies the contribution of each transfer path from the source to the receiver.

Copper–water loop heat pipes for energy-efficient cooling systems of supercomputers

An implementation of a cooling system with a loop heat pipe for thermal control of supercomputers is considered. For this purpose two copper–water loop heat pipes (LHPs) with an effective length of 400 mm and ID/OD diameters of the vapor lines of 3/4 and 4/5 mm correspondingly were designed and tested. The LHPs were equipped with a flat-oval evaporator with one-sided heat supply. The evaporator had a thickness of 7 mm, a length (including the compensation chamber) of 80 mm and a width of 42 mm. The influence of the cooling temperature of the condenser on the LHP operating characteristics was the central issue of this research. Tests were conducted in the range of the cooling temperature from 20 to 80 °C. The heat load supplied to the evaporator was varied from 20 to 600 W. A mathematical model for prediction of the LHP's operating temperature has been developed. It takes into consideration three operating modes of a loop heat pipe. Modeling results and their analysis are presented.

Fundamental modes in a waveguide pipe twisted by inverted nonlinear double-well potential

We study the fundamental modes trapped in a rotating ring with the local strength of the linear and nonlinear potentials modulated as V (θ − ωz) and − V (θ − ωz), respectively, where θ is the azimuthal angle and the modulation pattern is V (θ) ∼cos2θ, which is a double-well profile in the domain of − π ≤ θ < π. The model, based on the nonlinear Schrödinger equation with periodic boundary conditions, applies to light propagation in a twisted waveguiding pipe, and to a Bose–Einstein condensate loaded into a toroidal trap under the action of a rotating π-out-of-phase linear potential and nonlinear pseudopotential, induced by means of a rotating optical field and the Feshbach resonance, respectively. In the case of self-focusing, three types of fundamental trapped modes are identified, one symmetric and two asymmetric. This is different from the recently considered setting with purely linear or nonlinear rotating potential. In that setting, only two fundamental modes can be found. The shapes and stability of these modes, together with the transitions between them, are investigated in the first rotational Brillouin zone. The symmetry breaking, which transforms the symmetric mode into the asymmetric ones, is strongly affected by the modulation depth and the rotation speed of V (θ, ω). The ground-state mode is identified among these three types, and the evolution of an unstable asymmetric mode, which is chiefly trapped in one potential well, features Josephson oscillations between the two wells.

Nonconservative pipes conveying fluid: evolution of mode shapes with increasing flow velocity

When the velocity of fluid flow in a cantilevered pipe is successively increased, the vibration characteristics of the system may vary remarkably. This paper is concerned with exploring the evolution of the actual mode shapes of the pipe with increasing flow velocity. Results show that the mode shapes of the cantilevered system may dramatically change due to the increment of flow velocity. At higher flow velocity, these mode shapes, indeed, differ much from those of the classical cantilevered beam. When a critical mass ratio at which the so-called ‘mode exchange’ phenomenon occurs was chosen, the corresponding two modes of the cantilevered pipe would have the same shape. In addition, the nonlinear responses of the system have also been linked to the lowest three mode shapes by comparing the calculated mode shapes with the limit-cycle motions obtained experimentally.

Frequency-domain simulation of logging-while-drilling borehole sonic waveforms

Numerical simulation of sonic logging-while-drilling (LWD) borehole measurements is challenging because of significant wave propagation effects due to the massive drilling collar occupying a large portion of the borehole. In addition, the internal structure of the LWD tool can have a significant impact on the measured dispersions of Stoneley and quadrupole modes. The collar is typically constructed with a set of inner periodic grooves, which act as a mechanical filter to attenuate undesirable collar modes. Reliable numerical simulation and interpretation of LWD sonic waveforms requires that all features and dimensions of the drilling collar be included in the simulation model. Furthermore, the presence of the drilling collar can prompt numerical instabilities due to backward propagating modes in the perfectly matched layer (PML) commonly used to truncate the computational domain. This problem can be circumvented with the implementation of artificial viscoelastic attenuation in the collar whenever the simulations are intended to reproduce only wave propagation within the surrounding rock formations. In addition, reliable modeling of borehole wave propagation in the presence of high contrasts in material properties and the internal structure of the LWD collar requires a numerical method capable of accurately and stably resolving all spectral scales present in the model. We implemented an automatic [Formula: see text]-adaptive finite-element method in the frequency domain combined with a PML technique to simulate LWD sonic logging measurements. Examples of the application verified the accuracy and reliability of the simulated borehole and formation propagation modes in the presence of casing and internal structures in the LWD collar. The presence of steel casing and quality of casing/formation bond significantly influence the propagation modes excited in a borehole. However, it is still possible to estimate the formation shear slowness using monopole and quadrupole sources regardless of the quality of cement bond in fast formations. Assessment of the formation compressional slowness was significantly impeded by the strong pipe mode. Estimation of formation shear slowness in slow formations is practically impossible due to the presence of casing and a strong annulus mode when the quality of casing bond is poor.

Finite Element Analysis of Buried Polyethylene Pipe Subjected to Seismic Landslide

Polyethylene (PE) pipes are widely used in natural gas transportation systems in urban areas nowadays. As landslide caused by earthquake would cause destructive damage to buried pipes, increasing attention is attracted to the safety of buried PE pipes under seismic load. In this paper, the deformation behavior of PE pipe subjected to seismic landslide was investigated and a related failure criterion due to yielding was proposed. Based on extensive uniaxial tensile tests, a rate-dependent constitutive model of PE was applied to simulate the mechanical behavior of PE pipes. The extended Drucker-Prager model was used for surrounding soil. In our proposed finite element model, a quartic polynomial bending deflection displacement normal to the pipeline was loaded along the axial direction of PE pipe. The numerical simulation results revealed that the main failure mode of buried PE pipe subjected to seismic landslide shifted from bending deformation to ovalization deformation with increasing bending deflection. On the basis of deformation behavior analysis, failure criterion curves were put forward, which depicts the maximum relative deflection of the pipe cross-section, and the maximum displacement of the pipe versus pipe length subjected to seismic landslide. The results may be referable for design and safety assessment of PE pipes due to seismic landslide.

A water-level controlled wind instrument developed by a team-based project for an undergraduate acoustic class

During an introductory undergraduate class of acoustics, a team-based project was given to design and implement their own musical instrument, after studying basic concepts of resonance, standing wave, and modes of string, pipe, bar, membrane, and plate. One of the teams designed and implemented “W.L.C WINDY (Water-Level Controlled Wind Instrument),” which the length of the pipe can be adjusted by water level inside the pipe. The lengths satisfies the modes of a stopped pipe (open-closed end) with end correction. There are several advantages of this instrument for education of acoustics; cheap, easy to make, and easy to understand the principles of modes. It costs less than one dollar (a transparency hose, a syringe, an O-ring) to make “W.L.C WINDY”. This is how to make the instrument; 1. Connect a transparent hose with a syringe without needle using an O-ring. 2. Fill the hose with colored water for easy visualization. 3. Press the thumb rest of the syringe to make various sounds by controlling the water level. Even though W.L.C WINDY is not optimized to play music, it may contribute to easy demonstration of the principles of the modes for education of acoustics. [Supporting program: NIPA-2013-H0401-13-1007.]

Heat Simulation Analysis of Heat Exchangers with Inclined Boreholes in Ground-Source Heat Pump Systems

Heat exchange tube with inclined boreholes is a new method that it is efficient and the exploitation and utilization of the underground thermal energy. This method can enhance the buried pipe heat intensity and reduce the area of drilling. This paper set up the model of heat exchange tube with inclined boreholes . Using the FLUENT to simulate the buried pipe mode of the three different direction in ground-source heat pump systems.

Inexpensive Pipelines Health Evaluation Techniques Based on Resonance Determination, Numerical Simulation and Experimental Testing

In this paper, a non-destructive, reliable, and inexpensive vibration-based technique for evaluating Carbon steel pipes structure integrity. The proposed techniques allow a quick assessment of pipes structures at final pipe manufacturing stages and/or just before installation. A finite element modelling (FEM) using ABAQUS software was developed to determine the resonance mode of healthy Carbon steel pipe and a series of experiments were conducted to verify the outcomes of the modelling work. Consequently, the effects of quantified seeded faults, i.e., a 1 mm, 2 mm, 3 mm, and 4 mm diameter holes in the pipe wall on these resonance modes were determined using modelling work. A number of common used vibration analysis techniques were applied to detect and to evaluate the severity of those quantified faults. The amplitudes and frequencies of vibration signals were measured and compared. There were found to be in good agreement with the modelling work and provide important information on pipe construction condition and fault severity.

The Gas Flow Simulation of Tokamak’s Inflatable Pipeline

Inflatable pipe is an important part of the tokamak's experimental device. This paper first introduces the composition, functions and working mode of the inflatable pipe. Then it's based on the fluid dynamics to establish model of the inflatable pipeline and the nodes. Finally, using the finite volume method to complete a numerical analysis of gas flow in the tokamak's pipeline. The results show that, if it needs to get the gas flow of the H2 that is 400 Pa•m3/s at the valve in the Pipeline, it needs to set the value of the inlet pressure that is 1.5 bar. The larger diameter of the pipeline, the more increase rate of gas flow in the pipeline.

GREEN'S FUNCTION OF THE CONVECTIVE WAVE EQUATION FOR THE RIGIDWALLED PIPE

Green’s function of the three-dimensional wave equation for an infinite straight rigid-walled pipe of circular cross-section with mean flow is found. This function is written in terms of the series of the pipe acoustic modes, and is periodic in the azimuthal coordinate and symmetric about the pipe axial section of the unit point impulse source location. Each term of the series is a sum of the direct and reverse waves propagating in the corresponding pipe mode downstream and upstream of the noted source. In the found Green’s function, the mean flow effects are reflected in the direct manner. The effects become more significant as the flow Mach number increases, causing, in particular, the appearance and further growth of the function asymmetry about the pipe cross-section of the source location. And vice versa, the decrease of the Mach number results in the decrease of the ef-fects and, in particular, the decrease of the indicated asymmetry of the function. In the case of mean flow absence the obtained Green’s function is symmetric about the indicated cross-section and coincides with the corresponding Green’s function for the investigated pipe, which is available in the scientific literature.