Inlet Pipe Research Articles

Stratified-to-annular gas-liquid flow patterns transition in a horizontal pipe

Air-water flow in a 20 mm horizontal pipe is studied using side-view visualization with a background image and Brightness-Based Laser-Induced Fluorescence technique. The investigation is focused on the transition from stratified to annular flow patterns. Stratified flow is organized at the pipe inlet, and the dynamics of liquid lifting up the pipe walls is investigated. During the transition to annular flow, the liquid film is spread over the pipe walls in a stable and gradual manner; the spreading begins before the disturbance waves are formed. Two transition regimes are identified. At large gas and low liquid flow rates, the film is spread up the pipe walls reaching a stable height unaffected by the passing waves. At low gas and large liquid flow rates, the liquid can be lifted by the large-scale waves, but it promptly drains downwards between the waves. Secondary flow in the gas phase is considered the main mechanism of liquid lifting and the only mechanism able to create a stable annular film. The processes of formation and development of disturbance waves are qualitatively the same as previously observed in vertical pipes. Namely, the disturbance waves are formed due to the coalescence of high-frequency initial waves appearing near the inlet; the disturbance waves undergo coalescence and grow in amplitude and speed. Quantitatively, the disturbance wave formation occurs at larger distances from the inlet compared to the vertical flow, and the acceleration rate is much lower. An estimation of circumferential shear stress due to secondary flow is made based on the roughness of the liquid film surface at the bottom of the pipe. An increase in this shear stress increases the height of the liquid film on the pipe walls.

Research on Visualization of Inducer Cavitation of High-Speed Centrifugal Pump in Low Flow Conditions

Inducer is often used to improve the cavitation performance of pump. In order to study the cavitation characteristics of inducer under low flow condition of high-speed pump, high-speed photography technology was employed in this paper to carry out visual experiments on the inducer of a high-speed centrifugal pump. In low flow rates, Cavitation distribution and evolution among the inducer were captured. The experimental results revealed that a band-shaped backflow vortex in the inlet pipe would occur when the flow rate was less than 0.3 Qd. Moreover, the backflow vortex in the inlet pipe rotated with the inducer and the rotational speed of backflow vortex was approximately half of the inducer. The visualization test of 0.27 Qd was carried out: when the NPSH was greater than 6.72 m, the bubbles in the inlet pipe were asymmetrical; When the NPSH dropped to 5.41 m, the cavitation was becoming less asymmetrical; When NPSH dropped to 3.81 m, cavitation evolved to the deteriorating stage, plenty of bubbles entered into the main impeller, resulting in a rapid decline of pump performance. Furthermore, the cavitation performance was worse at an extreme flow rate, and the NPSH value of 0.27 Qd was 7.5% greater than that under design condition.

Influence of asymmetric airflow on the cooling performance of brake disc of railway vehicle

The main objective of this article is to discuss the influence of asymmetric airflow on the cooling performance of the brake disc. This asymmetry might be caused by the air inlet pipe curvature of the UIC test bench for frictional components, whereas in reality this asymmetry might be caused by various factors. In the first part of the paper, a brief summary of effects of heat and temperature changes on the brake disc is presented. Additional information about UIC test bench is given with the focus on cooling effects of airflow on the disc. In the second part, a CFD simulation was made, and its settings and results are presented in detail. In the last part, temperature differences in various time points and positions on the brake disc are compared graphically in order to assess the influence of airflow from the inlet pipe and its curvature on the cooling performance of the brake disc.

Research of condensation induced water hammer under filling a horizontal pipe with subcooled water

Experiments at the KGU test facility, devoted to condensation induced water hammers (CIWH) were analysed with the WAHA code. Test section of the KGU test facility is slightly inclined horizontal pipe of 3 m length and of 64 mm inner diameter. Subcooled water was supplied to the pipe inlet, pipe outlet was connected to separator vessel. Upper part of separator vessel was connected to steam source. Experiments were performed for different system pressure, different water subcooling and different mass flow rate of water supply. The performed experimental study of CIWH showed that in the investigated range of parameters, the development of CIWH occurs in different ways. At the stage of water propagation along the filled with steam horizontal pipe, water hammer was not observed. At the stage of free drainage of water from the outlet end of the pipe, water hammer was realized only when the water was sufficiently subcooled. At the stage of the water level rise in the horizontal pipe, water hammer occurred in all tests. At the last stage of filling the upper part in the separation vessel, there were small water hammers due to the collapses of the remaining steam bubbles. Numerical modelling of these experiments with the WAHA code revealed the shortcomings of the interphase heat transfer model developed for this code, which have a noticeable effect on the numerical solution.

The effect of inlet flow conditions upon thermal mixing and conjugate heat transfer within the wall of a T-Junction

This paper investigates the effects of different inlet velocity profiles on thermal mixing and conjugate heat transfer (CHT) within a T-junction. The flow domain is modelled using the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model implemented within the commercial CFD software STAR-CCM+ 2020.1.1. The thermal analysis of the solid domain is also addressed within the CFD simulations. The OECD/NEA-Vattenfall experimental benchmark database is used to validate the CFD model. The effect of mesh sensitivity within the CFD simulations is also studied qualitatively and quantitatively. The influence of different inlet flow profiles on the CFD simulations is then assessed. Different combinations of inlet flow profiles, uniformly distributed and fully developed, are considered. Compared to the flow profile at the main pipe inlet, the flow profile at the branch pipe inlet presents a much more significant effect on the mean temperature distribution downstream of the T-junction. It is found that the flat flow profile at the branch inlet causes a higher temperature at the top wall, therefore a larger temperature gradient, and may lead to higher thermal stresses due to thermal stratification. The temperature distribution is more uniform for cases with the fully developed flow profile at the branch inlet. The variance of temperature is high at the sides of the pipe, regardless of the velocity profile used. The combination of flat flow profiles at both inlets causes the highest temperature variance. Moreover, the regions of maximum variance of temperature are located at different positions along the pipe section, depending on the combinations of inlet flow profiles.

The Design and Evaluation of a Portable Extracorporeal Centrifugal Blood Pump.

In recent years, blood pumps have become the bridge to heart transplantation for patients with heart failure. Portability and wearability of blood pumps should be considered to ensure patient satisfaction in everyday life. To date, the focus has been on the development of portable and wearable peripheral components, little attention has been paid to the portable and wearable performance of the blood pump itself. This study reported a novel design of a wearable and portable extracorporeal centrifugal blood pump. Based on an in-house centrifugal maglev blood pump, the wearable and portable blood pump was designed with parallel inlet and outlet pipes to improve the wearable performance. A ring cavity was set at the inlet to convert the circumferential velocity of the inlet pipe to an axial velocity. The hydraulic and hemolytic performance of the baseline and portable blood pumps were analyzed and compared. Compared with the baseline pump, the hydrodynamic and hemolytic performance of the portable pump has been maintained without serious degradation. The results of this study will improve the life quality of patients with heart failure, and enhance the clinical benefits of artificial heart.

Research on Heat Transfer Characteristics and Typical Parameters Sensitivity Analysis of the Deep Borehole Heat Exchanger Combined With the Geothermal Wells

Abstract Based on abundant hydrothermal geothermal resources at the depth of 1000–2000 m formation in the basin of the BoHai Bay, the deep borehole heat exchanger (DBHE) combined with the geothermal wells is proposed. According to the modified thermal resistance and capacity model (MTRCM), the heat transfer models inside and outside borehole are established. The transient analytical solutions which are the vertical temperature profiles in the inlet (outlet) pipe and the grout of the DBHE and the corresponding dimensionless form are obtained by deducing and solving the heat transfer models inside the borehole. The mathematical model and the analytical solutions are validated by the experimental data and existing studied data. This paper utilizes respectively the Matlab2012 and the Feflow7.1 to solve the heat transfer models inside and outside the DBHE. The sensitivity analysis is performed to examine the influence of typical parameters on the DBHE heat transfer characteristics, including the quantity of geothermal water exploitation, the well distance between the pumping well and the DBHE, the DBHE inlet temperature, the DBHE depth, and the flowrate of circulating water. Under the action of geothermal wells, the heat transfer mechanism is changed in the thermal reservoir, and the DBHE heat transfer capacity can effectively enhance while the quantity of geothermal water exploitation increases and the well distance decreases. However, with the change of the quantity of geothermal water exploitation, the growth rate of the DBHE heat transfer capacity reduces and the sensitivity of the change of the typical parameters on the DBHE heat transfer performance reduces.

Scale resolving simulations of a high-temperature turbulent jet in a cold crossflow: Comparison of two approaches

A high-temperature turbulent jet in a cold crossflow is investigated with the help of two scale-resolving simulation approaches. This work aims at improving the methodologies used to predict the thermal footprint of exhaust gases issuing from helicopter engines onto the fuselage. Specific attention is brought to the capability of scale resolving simulations to correctly reproduce flow dynamics and turbulent mixing. Mean flow features, turbulent quantities and temperature fields are compared and validated against wind tunnel test measurements. In addition, the present work highlights the importance of synthetic turbulence injection at pipe inlet to obtain a fair prediction of both flow dynamics and temperature field.

Heat transfer efficiency of energy tunnel influenced by inlet temperature, flow rate and pipe spacing

Energy geostructures can be used in urban Heating Ventilating and Air Conditioning (HVAC) system to save energy and reduce emissions. Energy tunnel can extract shallow geothermal energy economically and efficiently without pollution. Based on the utility tunnel in Nanjing, China, heat transfer pipes are buried in the utility tunnel on the non-constant temperature zone to be an energy tunnel. Field test and numerical simulation on the heat exchange efficiency of energy tunnel are carried out. The inlet/outlet temperature and thermal induced stresses are measured and discussed. The results show that the unit heat area transfer efficiency of the energy tunnel is about 63W/m2, the heat transfer efficiency is positively correlated with the inlet temperature and flow rate, and negatively correlated with the pipe spacing.

An Efficient No-Shutdown Pipe-Fixing Freezing Design for Water Management System in Hospitals during COVID-19: A Case Study

Ensuring the uninterrupted flow of the complex piped water distribution networks to combat the COVID-19 pandemic in Taiwan’s hospitals has become a priority. The process involved in the no-shutdown pipe fixing freezing method depends on the water supply system design and the conditions of the environment. Before carrying out repair works onsite, two experiments were undertaken to estimate the liquid nitrogen supply rate and make sure of its adequacy in relation to the fixing system’s heat transfer performance. Using an iron exhaust pipe and galvanized steel inlet pipe with jacket for a 50-mm-diameter water pipe, temperature variations and timelapse were recorded and analyzed. The results showed that the frost length on the water pipe surface at either side of the jacket was 1.2–1.8 times of the pipe diameter. The ice length (~45 cm) was longer than the jacket (~34 cm), and the water pressure at the jacket inlet side was 1 kg/cm2 greater than at the exit. Injecting the right amount of liquid nitrogen into the inlet and at a proper speed between 0.7 and 0.8 kg/min will ensure a safe and smooth completion of the ice plug formation process. The design and processes have been used successfully in hospital water supply system fixing works.

An effective leak detection method for in-service gas pipeline systems

Pipeline leakage can lead to production losses and can adversely affect the environment, causing harm to the operator. Monitoring the pressure, volumetric flow rate, and other responses along the pipeline are vital to identifying pipe leaks. In this study, an in-service gas pipeline was modelled using the modified Panhandle equation to estimate the pipeline flow dynamics' properties and establish the baseline for normal operating conditions of the pipeline before the leak scenario. A half-inch leak event was then introduced at various locations along each section of the pipeline transmission system using OLGA software. The baseline pipeline pressure was compared with the pressure responses from the various leak scenario in each pipeline section. The pipeline leakage at proximities close to the downstream outlet area of the pipeline has a lower pressure drop compared to leakages located towards the pipe upstream inlet area. Therefore, for leakages close to the pipe inlet, fluid transportation will be significantly hindered due to drastic pressure reduction from the pipe leakage. A decision-making flowchart for gas pipeline leak detection was proposed to aid the deployment of the emergency leak response by operators. This approach to leak detection does not require significant hardware changes (which are usually expensive to install) to the in-service gas pipeline network.

Numerical study of the separation of two immiscible liquids in helical and straight pipes

This study reports numerical results for the flow of two initially perfectly mixed but immiscible liquids in helical and straight pipes, with a view toward optimal separation. Different flow orientations were considered, horizontal, upward, and downward. Assuming a perfect mixture at the pipe inlet, the main objective is set on investigating the separation behavior, its location, and finding the optimal Reynolds number for the most efficient separation. A laminar flow was considered, covering a wide range of relevant Reynolds numbers (Re = 10 to Re = 2250). The separation was quantified using the average mixing coefficient of the two liquids. It was found that the horizontal helical pipe leads to the maximum separation, while best mixing occurs in the vertical helical pipe with the downward flow. Additionally, the study revealed that an efficient separation can be always obtained in horizontal helical pipes after two turns. This observation is robust since separation is taking place at the same location for a wide range of water Reynolds numbers (28 to 563), with optimal separation at a water Reynolds number of about 225. It is therefore recommended to use these conditions to effectively separate immiscible liquids and extract one liquid out of the mixture.

Identification of inlet pipe blockage level in centrifugal pump over a range of speeds by deep learning algorithm using multi-source data

This paper focusses on the identification of the blockage fault in the inlet pipe of centrifugal pump over a range of speed using data obtained from different types of sensors. Acceleration, pressure and motor line current signatures taken using accelerometer, pressure transducer and current probe, respectively, and are used for identification of the pipe blockage level. Methodology is given for the blockage detection based on the multiclass classification using the deep learning algorithm at different blockage levels and speed of rotation of the pump. Importance of the multi-source data collection is emphasized based on the obtained results. Effect of the motor speed is also discussed when considered as an input feature to the classifier. It is observed that the use of combinations of different types of sensors help to identify the blockage level with better accuracy (close to 100% for many combinations). Blockage level prediction at each speed separately, is also given, which can be used for the fault diagnosis of single speed pumps. Finally, the performance of the classifier is tested using some unknown data (different from the data at training speed) to check the blockage prediction accuracy of the classifier.

Design and Performnce Study of Domestic Hydro Power Plant

Hydropower generated systems are one of the common source to generate energy. The renewable energy generation system is designed to use the water flow from an overhead tank during normal consumption of water for domestic use. The system produces electricity from the potential energy of water flow through water pipelines by changing the kinetic energy of water into electricity. The electrical energy is stored in batteries for domestic purposes like lighting and other electrical applications. The system has two turbines coupled with generator, placed at the inlet and outlet pipe of the water tank. The status of water level is detected with the help of float sensor. The motor performs automatically according to the level of water. The generated power is informed to the user and then stored in a battery storage unit. When the energy saved within the battery is sufficient an inverter is switched ON for domestic use. During the normal time of working load receives power from the ordinary commercial line. The system is simulated with Proteus software and analysed.

Hydrogen removal in circulating vacuum degasser under conditions of PJSC “NLMK”

For high­quality steel smelting, stage­by­stage production is required, which has a complex of metallurgical units capable for producing products with high performance properties and low content of harmful impurities. One of the harmful impurities is hydrogen, so it is important to limit its content in the metal. To ensure the specifed hydrogen content, the metal in the steel out­of­furnace treatment at Converter Shop No. 2 (CS­2) of PJSC “Novolipetsk Metallurgical Plant” (“NLMK”) is subjected to vacuum treatment in a circulating vacuum degasser. Despite the prevalence of circulating vacuum derassers, theoretically, mechanism of hydrogen removal in these metallurgical units has been insufciently studied. To increase efciency of hydrogen removal, theoretical calculations were performed to remove it from the metal. There are several mechanisms for hydrogen removing: direct transfer of hydrogen from metal to the surrounding space; formation of gas bubbles in metal and their direct ascent; nucleation of hydrogen bubbles at the border of refractory wall and metal; removal of hydrogen by metal blowing with neutral gas (argon). It is shown that the main ways of hydrogen removal in a circulating vacuum degasser are direct transfer of hydrogen from metal to the surrounding space and blowing of melt with transporting gas. In the CS­2 of PJSC “NLMK”, both ways are implemented at a circulating vacuum degasser. Vacuum pumps provide pressure in a vacuum chamber of less than 101.3 Pa (0.001 atm.). It promotes intensive removal of hydrogen from the metal surface. To ensure circulation of metal, transporting gas argon is supplied to the inlet pipe of the RH degasser, which also takes part in removal of dissolved gases by transferring hydrogen to neutral gas bubbles. Additionally, performed calculations have shown that the main way of degassing in conditions of CS­2 of PJSC “NLMK” is removal of hydrogen into the bubbles of carrier gas.

Modification and Performance Evaluation of a Floating Drum Biogas Digester

Biogas is a renewable source of energy that is obtained from the anaerobic digestion of agricultural residues, animal dung, energy crops, domestic wastes and industrial wastes. These categories of waste that produce biogas are promising sources of energy and the biotechnology process of biofuel is environmentally friendly. This study aimed at modifying, fabricating and evaluating a floating drum digester. The modified floating drum digester consists of the digester tank, gas holder tank, feeding inlet pipe, gas collector outlet, slurry outlet, thermometer and hose. The gas holder tank was inserted into the digester tank while the biogas is generated in the digester tank by pressure. The biogas was produced from the mixture of cattle dung 30 % and 50 % plant wastes. Hence, the organic waste mixed with water in the ratio of 1: 2 for the digestion process. The digestion temperature was recorded daily for a period of 21 days at constant pressure of 1.32 KN/m2 throughout the experiment. The result revealed that the minimum and maximum average temperatures are 25 to 33 oC. This shows that the ambient temperature affects the temperature in the digester and the amount of gas produced is a function of the accumulated temperature in the digester. It was observed that the biogas generated increase as temperature rise. The modified floating drum digester is affordable and it is recommended for small- and large-scale production.

Design of Autonomous Mobile Robot for Cleaning in the Environment with Obstacles

This paper describes the design and development of a cleaning robot, using adaptive manufacturing technology and its use with a control algorithm for which there is a stability proof. The authors’ goal was to fill the gap between theory and practical implementation based on available low-cost components. Adaptive manufacturing was chosen to cut down the cost of manufacturing the robot. Practical verification of the effectiveness of the control algorithm was achieved with the experiments. The robot comprises mainly three assemblies, a four-wheel-drive platform, a four-degrees-of-freedom robotic arm, and a vacuum system. The inlet pipe of the vacuum system was attached to the end effector of the robotic arm, which makes the robot more flexible to clean uneven areas, such as skirting on floors. The robot was equipped with a LIDAR sensor and web camera, giving the opportunity to develop more complex methods. A low-level proportional–integral–derivative (PID) speed controller was implemented, and a high-level controller that uses artificial potential functions to generate repulsive components, which avoids collision with obstacles. Robot operating system (ROS) was installed in the robot’s on-board system. With the help of the ROS node, the high-level controller generates control signals for the low-level controller.

Dynamics of circular and rectangular jets in crossflow

In this work, jets in crossflow (JICFs) were studied numerically through large-eddy simulation using a velocity ratio of 5.7 and a jet Reynolds number of 5000. A parabolic profile was used for the jet inlet and four specific cases were compared: one with a circular inlet and three with rectangular pipe inlets (aspect ratios: 2:1, 0.5:1, and 3:1) having the same mass flow rate of the jet. The results indicated that the rectangular JICFs penetrated the domain more deeply than the circular JICF and delayed the vortex and turbulence breakdown. The effect of the crossflow on the jet orientation was also studied and quantified, and modal analysis was conducted on the cases with dynamic mode decomposition. The significant modes were found to be consistent with spectral analysis of convectively unstable JICFs in the literature. The rectangular JICFs showed increased dominant modes frequencies compared to the circular JICF.

Research on Characteristics of U-tube Backflow in Natural Circulation Steam Generator under Ocean Conditions

When the pressurized water reactor is in natural circulation, reverse flow may occur in the U-tube of the steam generator, which will increase the flow resistance of the primary circuit and decrease the flow of natural circulation, which will adversely affect the safe operation of the reactor. Based on the RELAP5 program, the additional force model under ocean conditions and the spatial coordinate solution model of the control body are established, all U-tubes of the steam generator are modeled and node division are conducted, and the steam generator under ocean conditions (inclination, undulation, swing) is calculated. The critical mass flow rate of the reverse flow and the pressure difference between the inlet and outlet of the inner U-shaped pipe are analyzed. Finally, the influence of three ocean conditions on the reverse flow of the fluid in the U-shaped pipe is analyzed. The results show that the backflow phenomenon may be changed under inclined conditions; the undulating conditions that may be encountered during navigation cannot change the backflow phenomenon; the backflow phenomenon may be changed when the sway conditions are severe.

Hydrogen Removal in Circulating Vacuum Degasser under Conditions of PJSC “NLMK”

For high-quality steel smelting, stagebystage production is required, which has a complex of metallurgical units capable for producing products with high performance properties and low content of harmful impurities. One of the harmful impurities is hydrogen, so it is important to limit its content in the metal. To ensure the specified hydrogen content, the metal in the steel outoffurnace treatment at Converter Shop No. 2 (CS2) of PJSC “Novolipetsk Metallurgical Plant” (“NLMK”) is subjected to vacuum treatment in a circulating vacuum degasser. Despite the prevalence of circulating vacuum degassers, theoretically, mechanism of hydrogen removal in these metallurgical units has been insufficiently studied. To increase efficiency of hydrogen removal, theoretical calculations were performed to remove it from the metal. There are several mechanisms for hydrogen removing: direct transfer of hydrogen from metal to the surrounding space; formation of gas bubbles in metal and their direct ascent; nucleation of hydrogen bubbles at the border of refractory wall and metal; and removal of hydrogen by metal blowing with neutral gas (argon). It is shown that the main ways of hydrogen removal in a circulating vacuum degasser are direct transfer of hydrogen from metal to the surrounding space and blowing of melt with transporting gas. In the CS2 of PJSC “NLMK”, both ways are implemented at a circulating vacuum degasser. Vacuum pumps provide pressure in a vacuum chamber of less than 101.3 Pa (0.001 atm). It promotes intensive removal of hydrogen from the metal surface. To ensure circulation of metal, transporting gas argon is supplied to the inlet pipe of the RH degasser, which also takes part in removal of dissolved gases by transferring hydrogen to neutral gas bubbles. Additionally, performed calculations have shown that the main way of degassing in conditions of CS2 of PJSC “NLMK” is removal of hydrogen into the bubbles of carrier gas.