Pipe Mode Research Articles

Control of low-frequency guided elastic wave modes in a hollow pipe using a meta-surface

A locally resonant meta-surface for preferential excitation of a guided mode in a hollow pipe can improve ultrasonic guided wave inspection of pipelines. The proposed meta-surface comprises a periodic arrangement of bonded prismatic rod-like resonators in the circumferential and axial directions of the pipe. We demonstrate the presence of bandgaps for the low-frequency axisymmetric longitudinal modes L(0,1) and L(0,2) and the torsional mode T(0,1). The generated bandgaps can be used to filter the higher harmonics associated with the system nonlinearity to improve nonlinear ultrasonic measurements on pipes. These bandgaps exist even for the non-axisymmetric flexural modes but with their hybridized dispersion curves exhibiting mode-coupling for higher circumferential orders. Moreover, a “partial” bandgap is obtained where preferential transmission of the L(0,2) mode over L(0,1) is possible. We discuss the potential advantages of this partial bandgap to improve pipeline inspections using the L(0,2) mode. Time-domain finite element analyses are used to validate the presence of these bandgaps under radial, circumferential, and axial excitation that mimics the excitation using a ring of piezoelectric transducers. Finally, we discuss the influence of resonator spacing, filling fraction, and the number of resonator rings on the bandgaps for an informed meta-surface design.

Scattering of guided waves propagating through pipe bends based on normal mode expansion

The scattering of guided waves propagating through pipe bends is studied by means of normal mode expansion. First, the bi-orthogonality relationship for normal modes in pipe bends is derived, based on which the displacement and stress fields at the interfaces between the straight and curved parts are expanded with the normal modes in both parts. Then, based on the displacement and stress field continuity principle, the scattering problem is regarded as an eigenproblem of a transfer matrix, the solution of which gives the mode conversions at the interfaces. A case study is presented of the low-frequency longitudinal mode incident on a pipe bend, and it is found that the dominant mode conversions are L(0,1) reflection and mode conversion from L(0,1) to F(1,1). Finite element simulations and experiments are also conducted. L(0,1) bend reflection and mode-converted F(1,1) are clearly observed, which agrees well with the theoretical predictions.

Analysis and investigation of the leakage failure on the shale gas gathering and transmission pipeline

There is an accident that a shale gas gathering and transportation pipeline suffer corrosion and leakage within less than 10 months of its operation, which is rare for pipelines to have corrosion faults in such a short time. In this paper, through a series of experiments such as macroscopic observation, wall thickness measurement, physical and chemical inspection, optical microscope (OM), scanning electron microscope (SEM) as well as energy dispersive spectrometry techniques (EDS), the failed pipeline was analyzed, and subsequently the water quality analysis and bacterial counts were performed on the gas field produced water in the transmission medium. Consequently, according to the experimental results and field investigation, the root cause was identified that the failure mode of seamless steel pipe was corrosion leakage caused by local corrosion. The main reason for corrosion and leakage is that the metal on the inner wall of the pipeline is first corroded by sulfate-reducing bacteria (SRB) in the transmission medium, and a layer of black corrosion biofilm is deposited at the bottom of the steel pipe. If the corrosion biofilm has defects such as damage, the exposed metal and black corrosion biofilm will form the electrode corrosion with large cathode and the small anode, which will accelerate the corrosion rate and eventually lead to rapid corrosion failure of steel pipe. For the purpose of avoiding similar accidents, suggestions to prevent such failures were proposed in this paper.

Analysis of anisotropy mechanism in relation with slip activity in near α titanium alloy pipe after Pilger cold rolling

Understanding of anisotropy mechanism for Pilger rolling Ti80 (Ti-6Al-3 Nb-2Zr-1Mo) alloy pipe is of great significance to improve its service performance. In this work, the strength, plasticity and fracture mode of Ti80 alloy pipe with rolling texture in three different directions (RD, TD and 45°) were comparatively investigated. Firstly, the tensile strength is in the descending order of TD, RD and 45°, and plasticity shows the opposite trend. According to the statistics of a large number of deformed grains, the underlying mechanism of anisotropy was revealed by analyzing the slip activation, slip transfer, damage and fracture for three different loading directions. The results show that prismatic<a> slip is the dominant deformation mechanism in RD, and the basal<a> slip is mostly activated in TD. In 45°, the number of activated prismatic<a> slip and basal<a> slip is almost the same. Meanwhile, the pyramidal<a> slip plays an important role in accommodating the plastic deformation. A method for predicting the yield strength was established based on the critical resolved shear stress (CRSS) of basal<a> slip, prismatic<a> slip and pyramidal<a> slip, accompanying by different SFs distributions of activated slip systems. Subsequently, slip transfer, which can relieve the incompatible deformation, occurred between adjacent α grains when the slip transfer factor (m) and Schmidt factor (SF) are at a high value. Slip transfer was prone to occurring between the same slip systems, such as between prismatic<a> slip or basal<a> slip. However, it is discovered that the slip transfer between prismatic<a> slip and basal<a> slip is also likely to occur, when the adjacent α grains maintain 90° variant relationship. The slip transfer between 90° variants in 45° have higher probability than that in RD and TD due to high SFs of activated basal<a> slip and prism<a> slip, resulting better plasticity. Lastly, the micro-defects are uniformly distributed and the fracture mode is microvoids coalescence in RD. More basal<a> slip induces the cleavage cracks and cause the shear fracture in 45°. In TD, a mixed fracture mode of microvoids coalescence and cleavage is presented due to the heterogeneous deformation.

Non-planar motions due to nonlinear interactions between unstable oscillatory modes in a cantilevered pipe conveying fluid

Cantilevered pipes conveying fluid with an end mass exhibit rich post-critical nonlinear behaviors and have attracted the interest of many researchers. In the present paper, we focus on non-planar motions due to nonlinear interactions between two unstable oscillatory modes. By applying the orthogonality condition between the eigenfunction and its adjoint function to governing equations, evolution equations governing mixed-mode non-planar motions are analytically derived. In a certain range of flow velocity, mixed-mode non-planar motion can be produced. In this region, second- and third-mode oscillations are in distinct planes, which intersect perpendicularly. In particular, three-dimensional non-contacting measurements were conducted to verify the theoretical predictions, and hidden nonlinear modal interactions were extracted from experimental data. We observed mixed-mode non-planar motion that qualitatively agrees with the theoretical predictions. Moreover, in further experiments with a long pipe for future study, a sequence of bifurcating non-planar motions was observed.

Performance of a mechanically-driven loop heat pipe heat recovery system

A mechanically-driven loop heat pipe heat recovery system by booster and refrigerant pump was proposed to match the all-year fresh air load varying greatly with ambient temperature in an energy recovery ventilation unit and enhance its energy-saving potentials. The system prototype was developed and the experimental setup established in which the booster and pump can operate together or separately. Namely, the prototype could be running in pump-driven loop heat pipe (PLHP) mode, booster-driven loop heat pipe (BLHP) mode or booster combining with pump-driven loop heat pipe (CLHP) mode. The heat transfer characteristics of the prototype running in these three modes under winter and summer conditions were studied, respectively. The results showed that the temperature effectiveness of CLHP was greater than that of PLHP or BLHP under all-year conditions. When outdoor temperature is −15 °C, the temperature effectiveness of CLHP is 78.0% and 52.5% higher than that of PLHP and BLHP, respectively, and the heating EER of CLHP is 29.6% higher than that of BLHP. When outdoor temperature is 40 °C, the CLHP has 19.5% higher of temperature effectiveness and 21.7% higher of cooling EER comparing with the BLHP, respectively. In winter, BLHP performs better when outdoor temperature is greater than 7.5 °C while CLHP performs better when outdoor temperature is lower than 7.5 °C. And BLHP has better performance when outdoor temperature is lower than 35 °C in summer while CLHP performs better when outdoor temperature is higher than 35 °C. The composite system can switch its operating mode according to the fresh air load, which can improve effectively the year-round performance of the system to recover heat in building ventilation.

Experimental study of ventilation system with heat recovery integrated by pump-driven loop heat pipe and heat pump

To improve the thermal performance of the air-to-air energy recovery devices in cold climates, especially in low temperature conditions, a novel integrated system with heat recovery combining pump-driven loop heat pipe and heat pump is proposed and studied. The energy recovery device can operate separately at three modes: pump-driven loop heat pipe mode, heat pump mode or integrated mode. Results show that the temperature effectiveness and energy efficiency ratio of the integrated system are higher than that of heat pump system in whole conditions, and the heat transfer capacity of the integrated system has a positive correlation with the fresh air load. In addition, the system can switch its operating modes according to the different outdoor temperature. In test conditions, when outdoor temperature is greater than 8.7 °C or lower than 35.8 °C, heat pump system performs better, otherwise the integrated system is more suitable. Compared with others systems, the novel integrated system has better performance in all-year, especially in low temperature conditions. The novel integrated system shows a good application prospect in energy-saving buildings.

An exploratory review on heat transfer mechanisms in nanofluid based heat pipes

The current study reviews the research on nanosuspension-enhanced heat pipe technologies. The reviewed studies are categorized based on the nanosuspension type incorporated in the heat pipe i.e., mono &amp; hybrid. The study attempts to identify the heat transport modes in heat pipes and explore their dominance among each other. The dominance of the identified mech-anisms was found to be a strong function of the heat pipe type investigated and get signifi-cantly influenced by the operating conditions. The current review paper will aid in properly understanding the thermal mechanisms prevalent in heat pipes filled with nanosuspensions and to further optimizing their thermal response.

Data-Driven Models for Forecasting Failure Modes in Oil and Gas Pipes

Oil and gas pipelines are lifelines for a country’s economic survival. As a result, they must be closely monitored to maximize their performance and avoid product losses in the transportation of petroleum products. However, they can collapse, resulting in dangerous repercussions, financial losses, and environmental consequences. Therefore, assessing the pipe condition and quality would be of great significance. Pipeline safety is ensured using a variety of inspection techniques, despite being time-consuming and expensive. To address these inefficiencies, this study develops a model that anticipates sources of failure in oil pipelines based on specific factors related to pipe diameter and age, service (transported product), facility type, and land use. The model is developed using a multilayer perceptron (MLP) neural network, radial basis function (RBF) neural network, and multinomial logistic (MNL) regression based on historical data from pipeline incidents. With an average validity of 84% for the MLP, 85% for the RBF, and 81% for the MNL, the models can forecast pipeline failures owing to corrosion and third-party activities. The developed model can help pipeline operators and decision makers detect different failure sources in pipelines and prioritize the required maintenance and replacement actions.

Guided Wave Transducer for the Locating Defect of the Steel Pipe Based on the Weidemann Effect

The electromagnetic guided wave transducer has been widely used in pipeline detection in recent years due to its non-contact energy conversion characteristics. Based on the Weidemann effect, an electromagnetic guided wave transducer that can realize the locating defect of the steel pipe was provided. Firstly, the principle of the transducer was analyzed based on the Weidemann effect. The basic structure of the transducer and the basic functions of each part were given. Secondly, the key structural parameters of the transducer were studied. Based on the size of the magnets and the coils, a protype electromagnetic guided wave transducer based on Wiedemann effect was developed. Finally, the experiments were carried out on the steel pipe with a defect using the developed transducer. The results show that the transducer can actuate and receive the T(0,1) and T(1,1) modes in the steel pipe. The axial positioning of the defect is located by moving the transducer axially. The circumferential positioning of the defect is located by rotating the transducer. Additionally, missed detection can be effectively avoided by rotating the transducer.

Optimization design of the octagonal water diffuser with uniform flow orifice plate

Energy storage technology has been widely used in many fields, mainly due to the continuous development of social economy, resulting in increasing power consumption and peak valley load difference. This technology can play the role of adjusting the electric network load. Among them, water storage technology is the most representative. Naturally stratified technology is the most economical and effective method in chilled water storage technique and its core is the design of water diffuser. Octagonal water diffuser with the uniform flow orifice plate is a more effective water distribution mode in the naturally stratified chilled water storage system. In order to get the higher chilled water storage efficiency, the fluid dynamics software was used to make an optimization research on its parameters. Based on the scheme of octagonal diffuser and uniform flow orifice plate, the simulation analysis of the outlet mode of water distribution pipe and the opening parameters of orifice plate were carried out. According to the numerical simulations on the different volume water storage tanks, the comprehensive analysis showed that the diffusion performance of circular opening was better than slot opening, and the thickness of thermocline was thinner when the opening ratio of the orifice plate was 20% than the case of 30% and 45%. In addition, it was pointed out that the porous media model could almost replace the two-dimensional actual opening model under the low opening rate.

Experimental investigation on vortex-induced vibration and solid-structure impact of a near-bottom horizontal flexible pipeline in oblique shear flow

Vortex-induced vibrations and solid-structure impacts of a horizontal flexible pipeline in the vicinity of a bottom wall boundary are experimentally investigated in a water flume. A neutrally-buoyant submerged pipe, with a length-to-diameter ratio of about 87 and fixed end supports, is subject to a shear flow with an oblique angle of 30°. The initial gap-to-diameter ratio between the wall and the pipe is equal to 0.2. A non-intrusive measurement with high-speed cameras is employed to simultaneously capture the space–time varying in-line and cross-flow vibrations in the normal flow reduced velocity range of 3–15 with a maximum Reynolds number of about 2780. Experimental results highlight new pipe equilibrium profiles and modal response branches being significantly broadened due to the wall proximity. Two solid-pipe impact features are discussed, including single-segment and two-segment alternating impacts depending on the dominant oscillation mode of the flexible pipe. Both the response amplitude and frequency increase with the reduced velocity, resulting in a more frequent impact with a greater impact force. A temporal evolution from a single point contact to a segment contact is observed for the two-segment alternating impact. Nevertheless, the lengths of the two contact segments are different as a result of the asymmetric response profile. In all cases, the pipe transversely impacts the bottom wall introducing a perturbation transmission along the pipe, which leads to the multi-mode, multi-frequency and asynchronous in-line and cross-flow oscillations with a 1:1 and 2:1 resonance. Due to a momentum energy consumption, the pipe experiences a slow post-impact bouncing phenomenon, contributing to a longer temporal period of the fluid–pipe interaction with a wall impact.

Study on operation strategy of evaporative cooling composite air conditioning system in data center

To solve the problems of high energy consumed by the cooling system in the data center, this article puts forward a composite air conditioning system. The simulation platform for system operation performance is established, and the accuracy of the simulation platform is verified by experiments. The influence of operation parameters on system performance is analyzed by simulation. Finally, the optimal operation control parameters are determined. The results show that the system can adjust the condenser wind speed and the refrigerant pump operating frequency to meet the cooling requirements and solve the problem of low evaporation temperature in the heat pipe. The evaporative cooling effectively expands the working range of the heat pipe mode and raises the upper limit of outdoor temperature from 8 °C to 15 °C. In the vapor compression mode, when the ambient temperature is lower than 26 °C, the performance of the air-cooled mode is better than that of the evaporative-cooled mode. The condensation temperature can be ensured within a reasonable range by adjusting the condenser cooling wind speed and the compressor frequency. When the outdoor temperature is not less than 26 °C, the evaporative cooling can effectively improve the operation performance

Fracture analysis on dissimilar metal welding zone of vessel CPP power pipe

The power oil pipe of a vessel adjustable pitch propeller fractured after running for about 25,000 h. The fracture causes were analyzed by macro fracture morphology, micro fracture morphology, chemical composition, metallographic analysis, numerical simulation analysis, mechanical property and hardness test. Fractographic analysis shows that the fracture mode of oil pipe is high cycle fatigue fracture. The crack starts from the intergranular brittle fracture zone in the heat affected zone of dissimilar metal welding. The intergranular crack is mainly formed in the welding process of dissimilar metals, which is caused by intergranular embrittlement due to the deep diffusion of low melting point welding fluid mainly composed of Cu along the grain boundary in the heat affected zone of steel. The temperature gradient of the welding zone is analyzed by finite element method, and the reason why the low melting point welding fluid can diffuse to the farthest depth of 1 mm on the steel side is explained. The fracture mechanics analysis shows that when the crack depth reaches 1 mm, the crack has a greater probability to continue to expand forward, which leads to the risk of unstable fracture. Therefore, both experiments and numerical simulation show that the intergranular brittle crack formed by the diffusion of liquid metal to the heat affected zone of the steel side is the cause of fatigue crack initiation and propagation.

Thermal performance analysis of compact-type simulative battery module with paraffin as phase-change material and flat plate heat pipe

The thermal management of lithium-ion batteries is crucial for electric vehicles because of the optimum operating temperature and safety issues. Herein, we propose two types of compact battery thermal management systems (BTMS), which utilize a phase-change material (PCM), i.e., paraffin and flat plate heat pipes with liquid water cooling. The configurations are classified using the heat pipe installation method as the detached heat pipe (DHP) mode and attached heat pipe (AHP) mode. The thermal performance of the proposed BTMSs is characterized experimentally, and it is verified that the proposed AHP installation mode successfully managed the thermally stable operating conditions of the BTMSs. PCM melting is predicted using computational fluid dynamics and verified via experimental visualization. At a low heat generation rate of 2 W (544.39 W/m2), the PCM remained in the solid state. Melting occurred at higher heat generation rates of 4 and 6 W (1088.79 and 1633.18 W/m2, respectively). At the coolant inlet temperature, the module's maximum temperature decreased significantly; however, the temperature difference within the module increased, which can cause thermal imbalance in the battery module.

A Special Thermal Fatigue Failure Mode of Pipe in Nuclear Power Plant and Its Countermeasures

Thermal fatigue phenomenon is well known and feedbacked in the nuclear power industry. Targeted screening principles has been developed and applied. However, a thermal fatigue failure, “Swirl Penetration” of small-diameter pipeline, was identified through a Reactor Coolant System (RCS) leakage in a nuclear power plant. Unexpectedly, this failure is not within the scope of previous screening principles of thermal fatigue. It is characterized in that the high-temperature main piping is connected downward with a certain length of vertical small-diameter piping, and then the vertical piping turns horizontally through an elbow. The reactor coolant in the lower pipeline does not flow under normal operation conditions. Subject to long-term cyclic thermal fatigue, cracks initiate and propagate in the elbow. Through researches, corrective measures are put forward to prevent, mitigate or discover it.

Visualization study on boiling heat transfer of ultra-thin flat heat pipe with single layer wire mesh wick

In this paper, an experimental study on the ultra-thin flat heat pipe with a single-layer wire mesh core is carried out through a visual experimental platform. Combined with the analysis of temperature and phenomena, it is found that the peak value of temperature fluctuation of ultra-thin flat heat pipe is affected by thermal load, and the period of temperature fluctuation is an integral multiple of the working fluid flow. The working modes of the ultra-thin flat-plate heat pipe under different heat loads include evaporation heat transfer, subcooled boiling heat transfer, nucleated boiling heat transfer and the drying zone beyond the heat transfer limit. When the boiling working medium in the ultra-thin finite cavity enters the nucleate boiling zone, the thermal resistance in the evaporation section will decrease and the thermal resistance in the condensation section will increase slightly. The overall thermal resistance shows certain regularity, with the minimum value about 21.7% lower than the maximum value. Under the condition of sufficient condensation reflux, the heat resistance of the ultra-thin flat heat pipe reaches the minimum when the oscillation intensity of the vapor-liquid two-phase working medium reaches the maximum.

Failure analysis of heat pipe in hydrogen production unit

After two months of service, the heat pipe of hydrogen production unit bulged and fractured. The observation and measurement of the deformation of the pipeline was performed. The failure mode of heat pipe was analyzed by observing the macro and micro morphology of the fracture surface, and by Energy Dispersion Spectrum (EDS) analysis. Through the analysis of the metallographic structure of the pipeline, it is found that the pearlite is seriously spheroidized, which indicates that the pipeline has failed under long-term overheating working condition.

Physics-Driven Machine-Learning-Based Borehole Sonic Interpretation in the Presence of Casing and Drillpipe

SummaryInterpretation of sonic data acquired by a logging-while-drilling (LWD) tool or wireline tool in cased holes is complicated by the presence of drillpipe or casing because those steel pipes can act as a strong waveguide. Traditional solutions, which rely on using a frequency bandpass filter or waveform arrival-time separation to filter out the unwanted pipe mode, often fail when formation and pipe signals coexist in the same frequency band or arrival-time range. We hence developed a physics-driven machine-learning-based method to overcome the challenge. In this method, two synthetic databases are generated from a general root-finding mode-search routine on the basis of two assumed models: One is defined as a cemented cased hole for a wireline scenario, and the other is defined as a steel pipe immersed in a fluid-filled borehole for the logging-while-drilling scenario. The synthetic databases are used to train neural network models, which are first used to perform global sensitivity analysis on all relevant model parameters so that the influence of each parameter on the dipole dispersion data can be well understood. A least-squares inversion scheme using the trained model was developed and tested on synthetic cases. The scheme showed good results, and a reasonable uncertainty estimate was made for each parameter. We then extended the application of the trained model to develop a method for automated labeling and extraction of the dipole flexural dispersion mode from other disturbances. The method combines the clustering technique with the neural-network-model-based inversion and an adaptive filter. Testing on field data demonstrates that the new method is superior to traditional methods because it introduces a mechanism from which unwanted pipe mode can be physically filtered out.This novel physics-driven machine-learning-based method improved the interpretation of sonic dipole dispersion data to cope with the challenge brought by the existence of steel pipes. Unlike data-driven machine learning methods, it can provide global service with just one-time offline training. Compared with traditional methods, the new method is more accurate and reliable because the processing is confined by physical laws. This method is less dependent on input parameters; hence, a fully automated solution could be achieved.

Experimental study on novel pulsating heat pipe radiator for horizontal CPU cooling under different wind speeds

Herein, a horizontal CPU cooler with a pulsating heat pipe for cooling desktop computer was developed. In the experiment, an electric heating block was used to heat a copper plate to simulate the heating process of CPU. The cooling system consists of a cooling fan and a pulsating heat pipe cooler. The influence of cooling wind speed and heat load on heat transfer performance, start-up performance, and temperature uniformity of the pulsating heat pipe cooler was analyzed by controlling variable method. The wind speed was set to be 0 m/s, 0.1 m/s, 0.3 m/s, 0.5 m/s, and 0.7 m/s, respectively. The contour plots were used to analyze the uniformity of temperature distribution due to cooler. The results show that the start-up of the pulsating heat pipe led to a decrease in temperature of CPU. As the cooling wind speed increased, the start-up time of the pulsating heat pipe dropped, the start-up temperature dropped, and its stability was also improved. The operation at different cooling wind speeds also changed the start-up mode of the pulsating heat pipe. The start-up performance was best at cooling wind speed of 0.3 m/s. The contour plot for temperature showed that the temperature distribution of the pulsating heat pipe cooler became more uniform with increased cooling wind speeds. There was excellent temperature uniformity at the cooling wind speeds of 0.3 m/s and 0.7 m/s. When the cooling wind speed was 0.7 m/s, the minimum average thermal resistance was 0.51 K/W.