U-shaped Pipe Research Articles

Fluid-Conveying Flexible Pipes Modeled by Large-Deflection Finite Elements in Multibody Systems

The modeling and simulation of flexible multibody systems containing fluid-conveying pipes are considered. It is assumed that the mass-flow rate is prescribed and constant and the pipe cross section is piecewise uniform. An existing beam element capable of handling large motions is modified to include the effect of the fluid flow and the initial curvature of the pipe. The modified element is incorporated in a finite-element based multibody system dynamics program, which takes care of the connection with other parts of the system and the simulation. The element is applied in several test problems: the buckling of a simply supported pipe, the flutter instability of a cantilever pipe, and the motion of a curved pipe that can rotate about an axis perpendicular to its plane. As a three-dimensional example, a Coriolis mass-flow rate meter with a U-shaped pipe is considered.

The Vibration Characteristics Analysis of U-Shaped Pipe Based on Finite Element and Modal Experiment

The U-shaped pipe located in the compressor piping system of the lyophilizer is studied in this paper. Its finite element modal analysis is carried out through the software ABAQUS, and at the same time, the experimental modal analysis is conducted by the software LMS Test.lab and its corollary equipment. Through the comparison between the finite element modal analysis results and the experimental modal results, it can be seen that the two results have good consistence, which verifies that the finite element model is reasonable. This paper provides reference for the further studies of the curving pipe vibration.

Numerical sensitivity study of thermal response tests

Thermal conductivity and thermal borehole resistance are basic parameters for the technical and sustainable design of closed ground source heat pump (GSHP) systems. One of the most common methods to determine these parameters is the thermal response test (TRT). The response data measured are typically evaluated by the Kelvin line source equation which does not consider all relevant processes of heat transfer in the subsurface. The approach only considers conductive heat transfer from the borehole heat exchanger (BHE) and all transport effects are combined in the parameters of effective thermal conductivity and thermal borehole resistance. In order to examine primary effects in more detail, a sensitivity study based on numerically generated TRT data sets is performed considering the effects of (1) the in-situ position of the U-shaped pipes of borehole heat exchangers (shank spacing), (2) a non-uniform initial thermal distribution (such as a geothermal gradient), and (3) thermal dispersivity. It will be demonstrated that the shank spacing and the non-uniform initial thermal distribution have minor effects (less than 10%) on the effective thermal conductivity and the determined borehole resistance. Constant groundwater velocity with varying thermal dispersivity values, however, has a significant influence on the thermal borehole resistance. These effects are even more pronounced for interpreted effective thermal conductivity which is overestimated by a factor of 1.2–2.9 compared to the real thermal conductivity of the saturated porous media.

A Study on the Fatigue Life Prediction for Bending Pipe

Mechanical structures with power sources experience repeated force produced by motors. As a result, the life of the pipes reduces and ultimately, the pipes collapse. In most cases, the U-shape pipe is made from a straight pipe by complicated bending work. During this work process, plastic deformation of the pipe produces residual stress in the pipe. The residual stress significantly affects the fracture behavior of the pipe. In this paper, fatigues tests of U-shape bending pipe are performed by uniaxial testing machine and residual stresses were evaluated by FEM analysis. So we established the relation between residual stress and fatigue life. And we suggested new equation for fatigue life prediction using the residual stress of U-shape bending pipe.

Effect of roadway turnings on gas explosion propagation characteristics in coal mines

In order to reveal the effect of turnings on explosion propagation, experiments were performed in three different pipes (single bend, U-shaped pipe and Z-shaped pipe). Flame and pressure transducers were used to track the velocity at the explosion front. When the pipes were filled with methane, the explosion strength was significantly enhanced due to the turbulence induced by increasing the number of turnings, while the flame speed ( S f ) and peak overpressure (Δ P max) increased dramatically. In addition, the strength of the explosion increased in violence as a function of the number of turnings. However, when the bend was without methane, the turnings weakened the strength of the explosion compared with the ordinary pipe, shown by the decrease in the values of Δ P max and S f . In addition, the propagation characteristics in a U-shaped pipe were similar to those in a Z-shaped pipe and the values of Δ P max and S f were also close. The results show that the explosion propagation characteristics largely depend on gas distribution in the pipes and the number of turnings. The different directions of the turnings had no effect.

Finite element modeling of borehole heat exchanger systems: Part 1. Fundamentals

Single borehole heat exchanger (BHE) and arrays of BHE are modeled by using the finite element method. The first part of the paper derives the fundamental equations for BHE systems and their finite element representations, where the thermal exchange between the borehole components is modeled via thermal transfer relations. For this purpose improved relationships for thermal resistances and capacities of BHE are introduced. Pipe-to-grout thermal transfer possesses multiple grout points for double U-shape and single U-shape BHE to attain a more accurate modeling. The numerical solution of the final 3D problems is performed via a widely non-sequential (essentially non-iterative) coupling strategy for the BHE and porous medium discretization. Four types of vertical BHE are supported: double U-shape (2U) pipe, single U-shape (1U) pipe, coaxial pipe with annular (CXA) and centred (CXC) inlet. Two computational strategies are used: (1) The analytical BHE method based on Eskilson and Claesson's (1988) solution, (2) numerical BHE method based on Al-Khoury et al.'s (2005) solution. The second part of the paper focusses on BHE meshing aspects, the validation of BHE solutions and practical applications for borehole thermal energy store systems.

Detection of axial crack in the bend region of a pipe by high frequency electromagnetic waves

High frequency electromagnetic guided waves are used to detect axial narrow slit or crack in bend-section of the U-shape pipe. In the previous studies performed by the authors, electromagnetic waves (EM-waves) of TM 01- and TE 11-modes have used to detect circumferential and axial crack in straight section of a pipe, appropriately. In this paper to show potential of this technique for detection of any shape of piping system, especially bend-section of the steam generator (SG) and feeder pipe of pressurized water reactor (PWR), axial crack in bend-section is investigated. Due to axial orientation of the crack, TE 11-mode, a suitable mode for detection of axial crack is implied for this purpose. To excite TE 11-mode in the test pipe, microwave signals generated by the network analyzer, are sent to the inspected pipe by a coaxial line and a mode converter. Presence of the crack causes change in the reflection coefficient of the reflected signals from the crack. The behavior of the crack characteristic signals as a function of time is studied to estimate time of flight of the reflected wave and consequently crack position. Suitable frequency range is chosen in order to generate only TE 11-mode in the test pipe. To show effect of frequency range of the electromagnetic waves to the crack, crack positions are also evaluated for several smaller frequency ranges. Two crack positions were examined and comparisons of measurement results with theoretical calculations indicate that the microwave guided waves technique has high capability to detect defect in bend-section of a piping systems.

Effective pipe-to-borehole thermal resistance for vertical ground heat exchangers

The effective pipe-to-borehole thermal resistance of a vertical ground heat exchanger is investigated numerically. An analysis is carried out to determine the dimensionless geometrical parameters affecting such resistance. The heat transfer rates between the U-shaped pipes and the borehole are determined numerically and compared with some well-known limiting analytical solutions. A best-fit correlation for the effective pipe-to-borehole thermal resistance is presented in dimensionless form. The results are compared against approximate analytical solutions that represent the U-shaped pipes as a single pipe of equivalent diameter and against experimental data available in the literature. It is found that the available models do not accurately represent the effective pipe-to-borehole thermal resistance.

EVALUATION OF RESIDUAL STRESS OF COPPER PIPE BY USING RAMAN SPECTROSCOPY

In most cases, a straight pipe is used after complicated bending work in a mechanical system. In this work process, the plastic deformation of the pipe produces residual stress in the pipe. This residual stress significantly affects the behavior of pipe fracture. For this reason, residual stress must be evaluated. Measuring the residual stress of a U-shaped copper pipe is difficult with existing destructive and nondestructive measurement methods. In this paper, the residual stress of a U-shaped copper pipe (99.9% pure copper) was evaluated from the Raman shift by Raman spectroscopy and FEM analysis. Also, the results of the bending test by FEM analysis and experiments are compared. The analyzed results of Raman spectra had a similar tendency with the results of the FEM analysis in regard to the residual stress distributions in the U-shaped pipes. Also, the results of the bending tests were shown resemblance.

Phase‐contrast velocimetry with hyperpolarized 3He for in vitro and in vivo characterization of airflow

This paper describes a technique that combines radial MRI and phase contrast (PC) to map the velocities of hyperpolarized gases ((3)He) in respiratory airways. The method was evaluated on well known geometries (straight and U-shaped pipes) before it was applied in vivo. Dynamic 2D maps of the three velocity components were obtained from a 10-mm slice with an in-plane spatial resolution of 1.6 mm within 1 s. Integration of the in vitro through-plane velocity over the slice matched the input flow within a relative precision of 6.4%. As expected for the given Reynolds number, a parabolic velocity profile was obtained in the straight pipe. In the U-shaped pipe the three velocity components were measured and compared to a fluid-dynamics simulation so the precision was evaluated as fine as 0.025 m s(-1). The technique also demonstrated its ability to visualize vortices and localize characteristic points, such as the maximum velocity and vortex-center positions. Finally, in vivo feasibility was demonstrated in the human trachea during inhalation.

Numerical Simulation of Developing Pulsating Flow (Low Re Number Flow) in a U-shaped Pipe

This paper concerns the secondary flow due to pulsating flows with various frequencies in a U-shaped pipe, solved by a finite difference method with CIP and fractional step methods in a general coordinate system. The streamwise velocity distributions obtained are confirmed with experimental results. The resultant secondary flow is complicatedly changed by the induced secondary and third vortex cores. The intensity of the secondary flow does change throughout the curved pipe, indicating the flow is still developing even at the exit. The overall intensity of the secondary flow within the pipe increases with an increase in the pulsating frequency.

Study on diffusion and natural circulation of two component gases. (1st Report, Experiment and analysis with a reverse U-shaped pipe).

When a primary coolant pipe of a high temperature gas-cooled reactor (HTGR) ruptures, air is expected to ingress into the reactor core from the broken part by natural circulation and diffusion. In order to study the basic features of the air ingress during the early stage of the primary pipe rupture accident in a high temperature gas-cooled reactor, the conjugate problem of natural circulation and diffusion of the He-N2 two-component gas was studied experimentally and analytically. The study was performed on the phenomenon in a reverse U-shaped round pipe with one pipe heated and the other cooled. The analytical and experimental results were in good agreement on gas concentration change in the tube and initiation time of natural circulation of N2 single component gas.

Observation and numerical modelling of density currents resulting from thermal transients in a non rectilinear pipe

In a U-shaped pipe, are studied the density effects following a change in the inlet temperature. When the flow rate is small and the temperature difference high, thermal stratifications appear. The two-dimensional numerical modelling uses finite difference methods with a curvilinear grid, and k-∊a models for turbulence. The computation allows to predict with good accuracy the phenomena which are observed from experiment.

Oil-based and water-based Ciodrin sprays for fly control on dairy cattle.

Tests were conducted during the summer of 1964 to compare the effectiveness of oil-based and water-based sprays containing 2% Ciodrin® ( alpha -methylbenzyl 3-hydroxycrotonate dimethyl phosphate) against flies on dairy cows. Major species infesting the animals were the face fly, Musca autumnalis DeGeer; the stable fly, Stomoxys calcitrans (L.); and the horn fly, Haematobia irritans (L.). Forty lactating and 10 dry Holstein cows on the Pennsylvania State University Farm were employed as treated animals and untreated controls. The sprays were applied by a newly developed “pushbutton“ spraying device, manually operated and especially designed to give thorough coverage of the faces of the cows. The major parts of the device included an inverted U-shaped pipe system plus an extension in front, 4 nozzles each connected to a solenoid valve, a pump and motor assembly, and an extension wire terminating in a push-button switch. Counts of flies were made daily. Effectiveness of treatments was evaluated on the basis of average reduction percentages in fly populations on treated animals calculated by comparing numbers of flies on treated and control groups. Eight applications were made during 6 weeks in July and August. Results of the tests show that both the oil-based and water-based sprays provided good control against face flies and stable flies for 28 hours and significant reductions of fly populations for 52 or 76 hours following spray application. Both sprays gave near-perfect control of horn flies for 124 hours or longer. The oil-based spray showed greater initial toxic effect than the water-based spray against the face fly but the latter demonstrated a more lasting residual effect. Significant reductions in fly populations were noted on the untreated control group that was milked in the same barn as the treated cows, but in a separate section. The groups were grazed in separate pastures.