Small Diameter Pipes Research Articles

Improving the waste utilisation efficiency of combined heat and power plants by increasing the performance of dry-ash output units

The study aims to improve the efficiency of waste utilisation from the coal-fired power industry based on an analysis of the dry-ash output unit operating at the Novo-Irkutsk Combined Heat and Power Plant, JSC “Irkutskenergo”. The unit was tested under various operating conditions of steam generating blocks following the standard methods adopted at the enterprise. The tests showed that the station steam generating block No. 3 (with a steam load of 409.2 t/h and an electrostatic precipitator efficiency of 90.46%) provided an ash supply efficiency of 7.10 t/h. When the ash is supplied from the steam generating block No. 4, operating at a steam load of 421.8 t/h and an electrostatic precipitator efficiency of 94.72%, the ash supply efficiency amounts to 9.19 t/h. Under the simultaneous operation of the steam generating blocks No. 3 and 4 at a steam load of 397.6 and 380.7 t/h, respectively, and an electrostatic precipitator efficiency of 90.46 and 94.72%, respectively, the unit efficiency was 14.23 t/h. As a result, limitations in the unit operation were identified. Thus, the airspeed in the pneumatic ash pipeline during ash transporting was 8.0-8.5 m/s, which facilitated the operation of the dry-ash output unit in a pulsed cycle. It was, therefore, recommended to increase the airspeed by accelerating the flow rate through the jet pump or by using a smaller diameter pipe. The conducted analysis showed that the efficiency of the dry-ash output unit depends mainly on the steam capacity of steam generating blocks, as well as on the flue gas cleaning efficiency in the steam generator electrostatic precipitators. The obtained results were used to determine the technical state, efficiency and reliability of the dry-ash output unit of the Novo-Irkutsk Combined Heat and Power Plant.

Miniaturised Low-Cost Gamma Scanning Platform for Contamination Identification, Localisation and Characterisation: A New Instrument in the Decommissioning Toolkit.

Formerly clandestine, abandoned and legacy nuclear facilities, whether associated with civil or military applications, represent a significant decommissioning challenge owing to the lack of knowledge surrounding the existence, location and types of radioactive material(s) that may be present. Consequently, mobile and highly deployable systems that are able to identify, spatially locate and compositionally assay contamination ahead of remedial actions are of vital importance. Deployment imposes constraints to dimensions resulting from small diameter access ports or pipes. Herein, we describe a prototype low-cost, miniaturised and rapidly deployable ‘cell characterisation’ gamma-ray scanning system to allow for the examination of enclosed (internal) or outdoor (external) spaces for radioactive ‘hot-spots’. The readout from the miniaturised and lead-collimated gamma-ray spectrometer, that is progressively rastered through a stepped snake motion, is combined with distance measurements derived from a single-point laser range-finder to obtain an array of measurements in order to yield a 3-dimensional point-cloud, based on a polar coordinate system—scaled for radiation intensity. Existing as a smaller and more cost-effective platform than presently available, we are able to produce a millimetre-accurate 3D volumetric rendering of a space—whether internal or external, onto which fully spectroscopic radiation intensity data can be overlain to pinpoint the exact positions at which (even low abundance) gamma-emitting materials exist.

Sand-granulated rubber mixture to prevent liquefaction-induced uplift of buried pipes: a shaking table study

Buried pipelines in liquefiable soils are vulnerable and can float during earthquake excitation. The uplift forces due to pore-water-pressure generation relocate the pipelines in the soil. Therefore, it is essential to measure the liquefaction effects of the backfill materials on buried pipes and make an intelligent choice for the surrounding soil to reduce the applied forces on pipelines during liquefaction. Recently, scrap tire–soil mixtures have been used as a new geomaterial to decrease the adverse effects of liquefaction. This paper investigates the flotation of the buried pipe and the sand–granulated rubber mixture’s effectiveness around the pipe by a series of shaking table tests. Dynamic tests were performed under 1 g conditions on a fully saturated sand–granulated rubber mixture with small-diameter buried pipes. Three different granulated-rubber dimensions of 2.5–5, 5–10, and 10–15 mm and granulated rubber ratios of 10, 20, and 30 percent were examined in the tests. The outcomes of excess pore water pressure, settlement, pipe uplift, and upward pressure during and after shaking were compared. The test results demonstrated that the sand–granulated rubber mixture reduces excess pore water pressure accumulation and prevents liquefaction. Moreover, the effect of pipe diameter, burial depth, consolidation coefficient of the mixture, and uplift initiation time on pore water pressure and load increment below the pipe were combined to predict the buried pipe’s uplift probability.

A Study on flow boiling characteristics in a minichannel and conventional channel

The flow boiling characteristics of minichannel and conventional have been evaluated for the various mass flux and heat flux. The impact of channels heat transfer analysis was carried out by mixture model (MM) of ANSYS Fluent by using water as a working fluid. The aim of this paper to find the better heat transfer in the channels at a different range of mass flow rates (0.020kg/s to 0.040 kg/s) and heat fluxes (1000 W/m2 to 2000W/m2). The analysis was explained with help of output parameters like vapour fraction, heat transfer coefficient, evaporative thin film thickness, temperature difference in channel wall side and film water temperature side, Nusselt number and friction factor. The validation was done with the help of the previous paper. It was observed that friction factor is calculated for various mass flow rate in channels, is lower from smaller diameter pipe but heat transfer is more for the case of bigger diameter. The minimum mass flow rate increases the wall surface temperature as well as high heat flux increase the channel wall temperature. The 4 mm conventional channel is better heat transfer rate compared to 3 mm minichannel.

Comparative experimental study on phased array and X-ray detection of small diameter pipe weld

According to the principle of ultrasonic phased array technology, the phased array inspection technology for butt weld of small-diameter pipe is developed. The ultrasonic phased array and ray inspection tests are carried out on the sample pipe of small-diameter tube with typical specification of heating surface in Inner Mongolia thermal power plant, and the evaluation results obtained by the two inspection methods are compared and analyzed. It can be seen from the comparison of testing results that ultrasonic phased array testing has more advantages than X-ray testing in defect detection rate and defect parameter measurement. At the same time, ultrasonic phased array testing also has the advantages of environmental protection, intuitiveness and high testing efficiency.

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.

Interfacial area transport for bubbly-to-slug transition flows in small diameter pipes

This study aims to experimentally investigate the two-group interfacial area transport in small diameter pipes. Experimental data focusing on the bubbly to slug transition regime, namely one-group to two-group transport region, are collected in a 12.7 mm vertical pipe under adiabatic, air-water conditions. The result shows the intergroup transfer in the small diameter pipe can be drastic, especially under low superficial liquid velocities. The cause of this phenomenon is mainly due to the large relative bubble size comparing to the pipe cross-sectional area. The wake entrainment effect could be enhanced by the small spherical bubbles that are acting like cap or slug bubbles in a medium-size pipe. Based on the experimental observation, a throughout analysis of the dependence of the drastic intergroup transfer is provided in this study. The models predicting the initiation of drastic intergroup transfer in small diameter pipes in terms of the bubble diameter and the void fraction are developed. These models are compared with the two-phase data among the different pipe sizes and the results show a good agreement. These newly developed models are applied to the IATE wake entrainment model by developing a transition function analogous to the sigmoid function. With the transition function, the revised IATE model is given the new ability on predicting the drastic intergroup transfer phenomenon.

Experimental study of the three-dimensional interfacial wave structure of freely falling liquid film in a vertical large pipe diameter

Most of the experimental and theoretical studies on the film thickness of falling liquid films are focussed on either small diameter pipes or flat plates. Almost, all these studies provide time series data of the film thickness measured at single positions around the pipe wall or along the pipe section, which might not reflect the real flow structure in both axial and circumferential directions. This paper reports the interfacial structure of freely falling liquid films (liquid Reynolds numbers, ReL=618–1670) in a vertical large diameter pipe (127mm) using advanced Multi-Probes Film Sensor (MPFS). Unlike smaller diameter pipes where the waves are characterised as coherent rings, the waves found in this paper with larger diameter pipe were much localised around the pipe circumference and evolved with time in the axial direction. Skewness and Kurtosis numbers showed two distinct linear trends with two different slopes intersecting at ReL=960. One of the significant contributions of the current paper is that the new experimental reconstructed three-dimensional wave structure data for the falling liquid film in a vertical large pipe diameter will be available in the literature which would be of interest to many modellers who need such data to validate their CFD models.

Effects of saturation temperature on the boiling properties of carbon dioxide in small diameter pipes at low vapour quality: Heat transfer coefficient

The renewed interest in carbon dioxide as a refrigerant stems from both the environmental friendly properties of this fluid and from its extremely favourable performance as compared to most standard refrigerants at the same temperature, in particular for all applications where small size evaporators are required. Since a dependable forecast of heat transfer is crucial for these applications and reliable predictive methods spanning a large temperature range are so far missing, a long-term study has been launched to create a consistent and reliable experimental database studying the peculiarities of boiling carbon dioxide in mini- and micro-channels, aiming at a future improvement of predictive models. This study presents results on the local heat transfer coefficient of boiling carbon dioxide at low vapour quality (0 < x < 0.4) in 200 mm-long stainless steel tubes with inner diameters of 2.15 mm, 1 mm and 0.5 mm. The dedicated test setup equipped with high precision sensors allows to probe a wide range of saturation temperatures (+15∘C to -25∘C) and mass fluxes between 100 and 1800 kg/m2s have been studied under diabatic test conditions for heat fluxes from 5 to 35 kW/m2. The results discussed focus on the influence of the saturation temperature on the two-phase heat transfer coefficient. It is suggested that the combination of shifting physical properties of carbon dioxide and different flow confinement conditions cause a change in the phenomenological behaviour of the flow and that a transition between macro- and micro-scale most likely occurs within the range of tested parameters. Furthermore it is found that a shift in the applicability of existing prediction methods is caused by those effects and no correlation is able to predict the experimental data and trends in the whole temperature range observed. However, a critical performance analysis of selected correlations provides useful hints on the variation of the phenomenological flow boiling features induced by the combined effects of changing saturation temperature and evaporator diameter.

Numerical Assessment of Earth to Air Heat Exchanger with Variable Humidity Conditions in Greenhouses

Earth to air heat exchangers are widely utilized to cool or heat passive buildings for energy savings. They often need to deal with high humidity air conditions, especially in the greenhouse due to plant transpiration, and the condensation phenomenon is frequently observed during the cooling process. To evaluate the effect of humidity and condensation on thermal performance, a three dimensional computational fluid dynamic (3D-CFD) model was developed. The distribution of relative humidity in each pipe was investigated, and the impact of inlet air relative humidity on the integrated performance of the earth to air heat exchanger was discussed. The effects of inlet air temperature and volume flow rate were also analyzed. Moreover, the influence of the heat exchanger configurations on the performance of the air condensation was researched. The results indicated that condensation had few effects on the airflow distribution uniformity of the earth to air heat exchanger, while it acted observably on the thermal performance. In addition, humid air in a small diameter pipe tended to condense more easily. Humidity and condensation should be taken into consideration for the design of earth to air heat exchangers in greenhouses during engineering applications.

Research on on-line ultrasonic testing of small diameter thin wall stainless steel straight welded pipe

In the production process of thin-walled stainless steel longitudinal welded pipe, there are many defects, such as cracks, porosity, partial welding, incomplete penetration, incomplete fusion. In this study, a local coupling water tank and six ultrasonic linear focusing probes with a center frequency of 5MHz were used to realize the defect identification of the straight welded pipe in the twisted state through the combined detection of the ultrasonic shear wave, longitudinal wave and creeping wave, which can meet the on-line inspection requirements of small-diameter thin-walled stainless steel straight welded pipe.

Application of Active-Screen Plasma Nitriding to an Austenitic Stainless Steel Small-Diameter Thin Pipe

Low-temperature active-screen plasma nitriding (ASPN) was applied in this study to improve the bending rigidity and corrosion resistance of a small-diameter thin pipe composed of austenitic stainless steel (SUS 304). The inner and outer diameters of the pipe were ϕ0.3 and ϕ0.4 mm, respectively, and the pipe length was 50 mm. The jig temperature was measured using a thermocouple and was adopted as the nitriding temperature because measuring the temperature of a small-diameter pipe is difficult. The nitriding temperature was varied from 578 to 638 K to investigate the effect of temperature on the nitriding layer and mechanical property. The nitriding layer thickness increased with an increase in nitriding temperature, reaching 15 μm at 638 K. The existence of expanded austenite (S phase) in this nitriding layer was revealed using the X-ray diffraction pattern. Moreover, the surface hardness increased with the nitriding temperature and took a maximum value of 1100 HV above 598 K. The bending load increased with an increase in the nitriding temperature in relation to the thicker nitriding layer and increased surface hardness. The nitrided samples did not corrode near the center, and corrosion was noted only near the tip at high nitriding temperatures of 618 and 638 K in a salt spray test. These results indicated that the bending rigidity of the small-diameter thin pipe composed of austenitic stainless steel was successfully improved using low-temperature ASPN while ensuring corrosion resistance.

Deformation at continuous forming of longitudinal welded pipes

One of the effective methods for studying any process is its physical modeling, during which it is possible to verify the concepts and hypothesis obtained previously by theoretical modeling. In the laboratory of metal forming of NUST “MISIS” there is ERW mill 30 – 50 for the production and simulation of processes for the continuous forming of longitudinal welded pipes of small and medium diameter, their welding and calibration. This article discusses the deformation zone of a pipe billet, using the first two stands of a molding mill as an example with a calibration of a roll tool for a pipe diam. 50×1.5 mm. Based on the analysis of methods for calculating the parameters of real roll calibers, a model of contact interaction of the pipe billet with the first and second roll open stands was developed and areas of the deformation zone were determined including their sizes: non-intensive and intense impact; input and output contact zones; springing up. Analyzing the conditions of contact interaction of the pipe billet with roll calibers, parameters of the pipe billet in contact with the first-caliber rolls were determined in seven sections, taking into account the features of continuous forming. An analysis of the results has shown that the maximum longitudinal deformation occurred at the edge of the billet in section B – B and was equal to 1.04 %, and for the pipe billet bottom it was 0.92 %. For the experiment, a grid was applied to the pipe billet using a laser engraver. During forming, the trajectory deviation of the pipe billet bottom from horizontal axis was recorded, and sizes of the forming sections were determined. Comparison of theoretical and experimental values has shown that the discrepancy between them does not exceed 7 %.

Clamp-On Measurements of Fluid Flow in Small-Diameter Metal Pipes Using Ultrasonic Guided Waves

Clamp-on ultrasonic transit time difference is used extensively to calculate the volumetric flow rate of a fluid through a pipe. The operating principle is that waves traveling along a path that is generally against the flow direction take longer to travel the same path than waves traveling along the same path in the opposite direction. The transit time difference between the waves traveling in opposite directions can be used to calculate the flow rate through the pipe, by applying suitable mathematical correction factors. The approach is non-disruptive and noninvasive and can be retrospectively fit to pipes and easily relocated to different positions. When ultrasonic clamp-on transducers are attached to pipes with diameters of less than 30 mm and a wall thickness of less than a few millimeters, the resulting guided waves can appear confusing and produce very different signals to those observed on larger diameter pipes. The experimentally observed behavior of these guided waves in fluid-filled, small-diameter pipes is analyzed, modeled, and explained. Experiments are performed in copper pipes of sizes that are commonly used in buildings, and accurate measurements of water flow rates are taken down to a few milliliters per second. This technique presents new possibilities for smart metering of water supplies, where the positioning of the small clamp-on transducers is not sensitive to the variations in water temperature, and low-power electronics can be used.

MEASUREMENT OF VOID FRACTION DISTRIBUTION WITH SMALL WIRE MESH SENSOR IN WATER-AIR TWO-PHASE BUBBLE AND SLUG FLOWS IN VERTICAL SMALL DIAMETER PIPE

MEASUREMENT OF VOID FRACTION DISTRIBUTION WITH SMALL WIRE MESH SENSOR IN WATER-AIR TWO-PHASE BUBBLE AND SLUG FLOWS IN VERTICAL SMALL DIAMETER PIPE

Verification of Flow Regime Difference for Measurement of Void Fraction Distribution with Small Wire Mesh Sensor in Water-Air Two Phase Flow in Vertical Small Diameter Pipe

Verification of Flow Regime Difference for Measurement of Void Fraction Distribution with Small Wire Mesh Sensor in Water-Air Two Phase Flow in Vertical Small Diameter Pipe

A Small Diameter Ultrasonic Water Meter With Self-Diagnosis Function and Self-Adaptive Technology

Ultrasonic water meters have current widespread problems of poor site adaptability, low measurement accuracy, and poor stability. A high-precision intelligent ultrasonic water meter with self-diagnosis function and adaptive technology was proposed in this paper, which is focus on improving the measurement accuracy and repeatability of the small pipe diameters. The hardware circuit design of the ultrasonic water meter studied in this paper adopts the low-power STM32L053 microcontroller with Cortex-M0 core architecture and the high-precision 11 ps time resolution timing chip TDC-GP30 to complete the metering function. The software combines pulse width ratio and amplitude voltage measurement technology to make the water meter have self-diagnosis function, avoid measurement errors caused by accidental factors, improve adaptability and measurement accuracy, also the application of adaptive measurement period method is used to improve measurement repeatability. The software adopts the moving average filtering algorithm, which effectively reduces the fluctuation of the time-of-flight(ToF) difference and improve the measurement accuracy of the flow point in the low zone (between the minimum flow and the boundary flow). The experimental verification results show that the accuracy of the small-caliber ultrasonic water meter can reach within ±1.5 %, and the repeatability is less than 0.5 %. In the face of fluid disturbances, adaptive technology is used in this water meter to adjust the measurement period and carry out self-diagnostic function research, and automatically respond to deal with abnormal faults, thereby realizing the demand for intelligence.

In-Pipe Inspection Robot Capable of Actively Exerting Propulsive and Tractive Forces With Linear Antagonistic Mechanism

In this study, the authors comprehensively evaluated the traveling performance of a flexible pipe inspection robot (PI-RO) that can actively output both propulsion and traction forces. Household pipes must be frequently inspected for cracks and corrosion to ensure continuous provision of water and gas. As these pipes are essential for our everyday life, it is difficult to suspend their usage for long periods; hence, inspection should be conducted for short durations. In addition, inspecting entire pipelines using existing methods is challenging because the pipes are constructed over long distances and have complex structures. Therefore, we developed a flexible robot that can actively output propulsion and traction forces to inspect long-distance complex pipelines, such as household pipelines. Herein, we describe the flexible structural design of a PI-RO that inspects thin one-inch pipes (inner diameter of approximately 28 mm) typically present in household piping. We also evaluated the characteristics of each PI-RO unit. Finally, we confirmed that the PI-RO is not significantly affected by the traveling environment, such as long distances and complex small-diameter pipes, by conducting traveling experiments on small pipes (inner diameter 28 mm) and long-distance (up to approximately 11.7 m) complex pipes composed of horizontal, vertical, and 90° bend pipes.

The application of a reflected non-axisymmetric torsional guided wave model for imaging crack-like defects in small-diameter pipes

Crack imaging of a pipe can provide detailed information about defects within the pipe such as the circumferential and axial position of the defect and its circumferential coverage. Due to the complicated propagation characteristics of a non-axisymmetric guided wave within a small pipe and the limited surface area available to install the transducer, crack imaging within a small-diameter pipe is difficult. This paper reports a reflected non-axisymmetric torsional guided wave model for imaging a crack in a small pipe. First, the reflected non-axisymmetric torsional guided wave model was proposed based on the theory of the normal mode expansion method. Then, the crack imaging algorithm was determined based on the theoretical reflected non-axisymmetric torsional guided wave model. Subsequently, the relationships between the angular profiles of the reflected T(M,1) and the axial distance of the cracks, the relationships between the angular profiles of the reflected T(M,1) and the circumferential length of the cracks predicted by the theoretical model were supported by the simulation results and the experimental data. Next, the crack imaging based on the proposed reflected non-axisymmetric torsional guided wave model was carried out for four pipes to verify its practicability. The axial position and circumferential range of the cracks within the four pipes were different. The experimental and numerical results demonstrated that the reflected non-axisymmetric torsional guided wave model has the potential to image cracks within a small pipe.

Study of a Noncontact Flow Transducer Using Semicylindrical Capacitive Sensor

The fluid flow rate through a pipeline is a very important process variable in any process plant that is required to be measured accurately. In this article, a new noncontact semicylindrical capacitive flow sensing technique has been developed and studied. The proposed capacitive sensor consists of two semicylindrical curved copper plates mounted on the outside surface of an insulating pipeline near the turbulence region produced at the junction of a larger diameter pipe and a smaller diameter pipe. Here the insulating pipeline section between the copper plates along with the flowing fluid acts as a composite dielectric material of the sensing capacitor. The semicylindrical curved copper plates along with two lead wires are rigidly mounted without any air gap on the larger diameter pipe using a thin layer of araldite. A mathematical relation between the sensor capacitance and flow rate is derived in this article. This capacitance is found to vary nonlinearly with flow rate and is measured using an op-amp-based DeSauty bridge-type transducer circuit where a similar capacitor with the same fluid at zero flow is used as a dummy capacitor. A prototype unit of the proposed transducer is designed, developed and tested experimentally. The static characteristic curves drawn from the experimental results are found to follow the derived mathematical equation to a very good extent with good repeatability.