Outlet Pipe Research Articles

Numerical study of turbulent flow in USBR VI stilling basin

The USBR VI stilling basin is one of the oldest basins designed to dissipate the energy at the outlet of pipes. In this study, the effect of two parameters including the Froude number (Fr) of inlet flow to the basin and the ratio of basin width to equivalent depth of the inlet flow (W/D) on the characteristics of mean and turbulent flow inside the USBR VI stilling basin were investigated, numerically. Reynolds Averaged Navier–Stokes (RANS) equations were solved with Re-Normalization Group (RNG) k-ε turbulence model. Results showed that by increasing W⁄D, from 3.50 to 9.23, decreasing rate of the average velocity at the end of the basin to the average velocity of the inflow increases from 80 to 97% and decreasing rate of the maximum velocity at the end of the basin to the average velocity of the inflow increases from 40 to 87%. Also, by increasing W⁄D, from 3.50 to 9.23, the average turbulent dissipation rate in the whole basin increases to 4.5 times, moderately. Moreover, by increasing W⁄D, from 3.50 to 9.23, the dissipation of turbulent flow energy in the basin becomes four times. Therefore, to design a USBR VI stilling basin based on the existing conditions, W⁄D recommended to increase as much as possible until nearly 10.

Numerical study of the effect of axial cyclone inlet velocity and geometrical parameters on separation efficiency and pressure drop

The effects of cyclone separation length lm, outlet pipe inner diameter dw and swirl guide angle β were numerically studied for different inlet velocities: 2.5 m/s, 5 m/s, 7.5 m/s, 10 m/s in four cyclone models, using Ansys Fluent software. The fractional composition of the test dust was considered using the Rosin- Rammler model. Four cyclone models were tested for velocities in the range of 2.5–10 m/s and five particle size ranges. The mass proportion of particles in the cyclone and the filtration efficiency were determined, which is a novel method for evaluating cyclones. The lowest filtration efficiency, regardless of the cyclone model, was found, for particles in the 0–5 μm range, and the highest in the 20–40 μm range. Better results were obtained for higher values of lm smaller dw and β = 90o. Optimal performance and the highest value of the filtration quality factor is obtained by cyclone model B for υ0 = 5–10 m/s.

Improving mixing and renewal in drinking water storage tanks: lessons learnt and practical measures

ABSTRACT This paper investigates the effect of different types of structural and operational measures on water mixing and renewal time in circular and rectangular cross-section water storage tanks, aiming at a better understanding of the flow dynamics to find practicable solutions to improve their design, rehabilitation and operation. An experimental programme, including traditional tracer and dye tracer tests, was carried out in small-scale tanks for different configurations and operating conditions. Two tanks were tested with and without interior structures, with the inlet/outlet pipes at different locations and for constant and variable water level. The main findings are that: i) the most effective measure is operating with fill-and-draw cycles, however, for tanks operated nearly full structural measures are recommendable; ii) reducing the inlet pipe diameter and installing nozzles near the tank bottom improve the mixing conditions; iii) the use of baffles is recommendable when the inlet and outlet pipes are very close.

Recent gully erosion intensity in an agricultural landscape underlain by fluvioglacial sediments (NE Czechia)

AbstractInappropriate agricultural management practices combined with intense rainfall often lead to gully erosion. Knowledge of the causes and consequences of past erosion pulses is essential not only for farmers to improve land management, but also for municipalities to define infrastructure threats associated with material transport. This study comprehensively evaluates accelerated gully erosion and estimates gully transport capacity in fluvioglacial sediments left by a Pleistocene ice sheet in northeastern Czechia. Geomorphic mapping of an area of approximately 2 km2 revealed gullies up to 3.5 m wide and deep, with their heads starting at the boundaries of fields and pastures. The ground‐penetrating radar survey confirmed the presence of soil pipes contributing to gully formation due to unmaintained field drainage combined with the natural occurrence of soil pipes. Microscopic analysis and dendrogeomorphic dating of 102 cross‐sections from 28 exposed tree roots revealed 18 years of gully incision since 1985, with increased activity from 2007 to 2014. The mean incision rates ranged between 1–20 cm/year, but could reach 1 m during individual events. More intensive incisions were typical for soils with higher smectite content. The last severe erosion event in 2014 caused clogging of culverts and damage to infrastructure by transporting boulders up to 34 cm in diameter at critical flow velocities of 2.4–2.8 ms−1. Considering the predominance of human‐induced factors (e.g., current soil compaction due to grazing and failure to maintain the drainage pipe outlets), ongoing gully erosion can be expected during intense rainfall events unless appropriate agricultural or stabilization measures are addressed.

Performance analysis of a gas cyclone with a converging-diverging vortex finder

In this study, the influence of a novel converging-diverging (CD) vortex finder on the performance of a gas cyclone was studied using the computational fluid dynamics (CFD) method. In addition, the influence of the CD outlet pipe on the erosion rate of the cyclone was investigated. The cutoff diameter, pressure drop, and erosion rates of the new vortex finder design were compared with those of the conventional straight outlet pipe cyclone. The throat of the CD pipe was at the same level as the cyclone's roof. The simulation showed that the CD outlet pipe significantly reduced the cyclone pressure drop. The height and diameter of the converging part of the vortex finder affected the cyclone pressure drop and separation efficiency. Increasing the converging part's inlet diameter reduced the outer vortex tangential velocity and the cyclone separation efficiency. Increasing the converging part inlet diameter reduced turbulent intensity at different cyclone levels. The CD vortex finder with the shortest height and inlet diameter of the converging part (model C1) reduced the cutoff diameter from 6.2 µm to 5.9 µm. The CD outlet pipe with the largest height and inlet diameter of the converging part (model C6) reduced the pressure drop by 42.2% compared to the conventional cylindrical vortex finder. The erosion rate also decreased significantly with an increase in the converging part inlet diameter. However, the converging part height only slightly affected cyclone performance.

Mixed Seeds of Oat and Vetch Based on DEM-Fluent Coupling Motion Simulation in a Venturi Tube

The gas–solid flow of mixed seeds of oat and vetch in the air-blowing venturi tube was simulated numerically by means of a coupling approach of the discrete element method (DEM) and computational fluid dynamics (CFD). In the gas–solid coupling model, EDEM software was used to depict the discrete particle phase, and ANSYS Fluent software was used to describe the continuous gas phase. The effects of the seed entry angle and inlet air velocity on the uniformity of mixed seed supply were studied and analyzed from the angle of airflow field variation and mixed seeds movement characteristics. The simulation results showed that the seeding angle has a great influence on the seed movement in the tube and affects the pressure and velocity gradient of the airflow field. If the seed insertion angle is too large, the number of collisions between the seed and the tube wall will increase, and the phenomenon of seeds retention and disordered jumping will occur. The inlet air velocity mainly affects the outlet air velocity and seed velocity and has little effect on the change in airfield. With the increase in inlet air velocity, the greater the velocity and force of the seeds, the closer the mixed seeds collide with the wall to the outlet pipe. At high inlet airflow velocity, there is a great disparity in the movement speed between the seeds, resulting in uneven spacing between the seeds. The results showed that under the conditions of 60° seed entry angle and 35~40 m/s inlet air velocity, the airflow field distribution in the tube was uniform and the seed movement was continuous and uniform.

Experimental test analysis of hydram pump flow rate using L9 Taguchi at fish pond aquaculture

Good water quality in fish nursery cultivation greatly influences the harvest quality. Temperature and Ph can be maintained properly with proper air circulation. The main problem is that the best flow rate quality in fish ponds of 0.123m3/second is only achieved through the flow from the dam. In this study, the installation of hydram pumps in fish ponds was carried out with the angle of assessing the inflow and discharge to adjust to variations in the diameter of the inlet and outlet pipes, the height of the inlet pipe, and the height of the tank. The experimental design used L9 orthogonal array Taguchi with four replicas. The result of this study was that the maximum value of the input flow rate was 305.73 cm3/second, and the discharge flow rate was 40.35 cm3/second. The maximum value was in the 8th composition; namely, the variation of the inlet pipe height was 200 in, the outlet pipe height was 350 cm, the inlet pipe diameter was 1 in, and the outlet pipe diameter was ½ in.

A data-based reduced-order model for dynamic simulation and control of district-heating networks

This study concerns the development of a data-based compact model for the prediction of the fluid temperature evolution in district heating (DH) pipeline networks. This so-called “reduced-order model” (ROM) is obtained from reduction of the conservation law for energy for each pipe segment to a semi-analytical input–output relation between the pipe outlet temperature and the pipe inlet and ground temperatures that can be identified from training data. The ROM basically is valid for generic pipe configurations involving 3D unsteady heat transfer and 3D steady flow as long as heat-transfer mechanisms are linearly dependent on the temperature field. Moreover, the training data can be generated by physics-based computational “full-order” models (FOMs) yet also by (calibration) experiments or field measurements. Performance tests using computational training data for a single-pipe configuration demonstrate that the ROM (i) can be successfully identified and (ii) can accurately describe the response of the outlet temperature to arbitrary input profiles for inlet and ground temperatures. Application of the ROM to two case studies, i.e. fast simulation of a small DH network and design of a controller for user-defined temperature regulation of a DH system, demonstrate its predictive ability and efficiency also for realistic systems. Dedicated cost analyses further reveal that the ROM may significantly reduce the computational costs compared to FOMs by (up to) orders of magnitude for higher-dimensional pipe configurations. These findings advance the proposed ROM as a robust and efficient simulation tool for practical DH systems with a far greater predictive ability than existing compact models.

Research on the performance characteristics of an oil-free scroll expander that is applied to a micro-scale compressed air energy storage system

The oil-free scroll expander, which is the power component of the micro-scale compressed air energy storage (CAES) system, exhibits a satisfactory application prospect. The expander's performance directly influences the efficiency of the expansion power generation system. To enhance the work efficiency of the power generation system, we built a thermodynamic model that facilitates the oil-free scroll expansion mechanism by considering heat transfer and leakage; furthermore, for the micro-scale CAES, we constructed an experiment bench that utilizes air as the working fluid. Based on computational fluid dynamics (CFD), we conducted a three-dimensional unsteady numerical simulation of the fluid flow that occurs in the working chamber of the scroll expander. We observed that the suction pressure loss that occurs during the suction process, which is initiated by the scroll expander, leads to inlet pressure drop, and we noted that the suction pressure directly influences the work efficiency of the power generation system. When the setup is subjected to rotational speeds of 1200–3200 r/min, the difference between the theoretical and measured values of volumetric flow decreases from 0.0226 to 0.000527 m3/min. The pressure, velocity, and temperature distribution of the fluid that exists in the working chamber of the expander are not uniform, and the mass exchange that occurs between adjacent working chambers considerably impacts the distribution of velocity and temperature. As gas flows from the back-pressure chamber to the outlet pipe, most of it flows through the non-deforming domain before flowing into the outlet pipe. The fluid flow in the deforming domain is highly complicated, and even secondary flow can occur.

Experimental study on transient flow characteristics in an equal-height-difference passive heat removal system for ocean nuclear power plants

The equal-height-difference passive heat removal system (EHDPHRS) utilizes the ocean as the heat sink for infinite heat dissipation and has broad application prospects in ocean nuclear power plants. However, the equal height difference between the heat source and heat sink is susceptible to severe flow instability. In this study, a fully visualized experimental facility was constructed to analyze the transient flow characteristics in the EHDPHRS. The experimental results revealed three typical two-phase natural circulation flow modes in the EHDPHRS. The formation mechanism of each flow mode was analyzed using thermal–hydraulic parameters. The results revealed that the flow mode is determined by the steam–water direct contact condensation and reverse flow of subcooled water, and both factors promote each other. Moreover, condensation-induced water hammer (CIWH) was found to be the most severe flow instability in the EHDPHRS. CIWH events can lead to violent pressure peaks and reduce the natural circulation capacity. In addition, when the occurrence position of CIWH events is concentrated at the pipe outlet, the influence of CIWH events on the two-phase natural circulation flow capacity gradually decreases. These research results aid in the optimal design of the EHDPHRS and prevention and control of CIWH events.

Numerical studies on internal flow in pipelines of an aquaculture vessel and flow control using a special branch pipe

IntroductionRegarded as the world’s largest smart-aquaculture vessel so far, Guoxin No. 1, has achieved remarkable success in aim to develop large-scale cruising aquaculture platforms. Guoxin No. 1 is 816 feet long with 15 fish farming tanks, which has a tank capacity of up to 900,000 square feet. It is of great practical interest to study the pipe flow rate distribution involving oxygen and novel flow control schemes for internal flows of aquacultural facilities connecting fish farming tanks.MethodsIn this paper, three-dimensional numerical investigations on internal flow in a T-type pipeline and its flow control are carried out. A single pump is designed to convert water to two separate farming tanks through a pipeline system, which is composed of one main inlet pipe and two outlet pipes with the same diameter as that of the inlet pipe. A horizontal arrangement of the pipes, in which the flow rate of an outlet pipe must be half of the inflow rate, is firstly studied for validation. To guarantee a balanced oxygen supply, equilibrium outflow rates can be achieved as a consequence of using a branch with a smaller diameter installed on the main inlet pipe. 3-D unsteady RANS solvers were employed to simulate the incompressible viscous flow and the pipe walls were assumed as rigid bodies.ResultsA couple of flow rates and three pipe angles were then investigated to assess the change of the outflow rates. Based on the simulations, a flow control scheme was proposed including to optimize the central included angle between the main inlet pipe and the small branch pipe, and the inflow rate of the branch pipe in order to balance the outflow rates. The results show that the central included angle has a significant influence on the flow field and flow rate of the two outlet pipes.DiscussionIf the angle was fixed, it can be indicated that adjusting the flow rate of the branch inlet can be an efficient method to unify the flow rate of the outlet pipes and improve the water exchange among fish farming tanks.

Design optimization of a rotating packed bed based on dry hydraulic performance

The current study focuses on enhancing the fidelity of the hydraulic performance of Rotating Packed Beds (RPB) by modifying the conventional geometrical construction of the inner cavity, outlet pipe, and its packing. RPB technology has been playing an increasing role in intensifying different petrochemical processes, such as CO2 capture, due to the potential of a several-order-of-magnitude mass transfer enhancement induced by the HiGee field. In this context, four novel geometries of the RPB are proposed and analyzed using a validated CFD model that utilizes the porous media approach to model the pressure losses in the RPB packing. The impact of liquid distributor was also investigated and compared to the original design. Results of the modified geometries conclude that optimizing the flow pattern at the exit of the packing by modifying the inner cavity's shape reduces the total pressure drops by up to 22%. At the same time, it is found that a further decrease of 13% in the pressure drop can be achieved by attaching a nozzle at the entry of the outlet pipe. On the other hand, the modified packing that imposes a constant radial flow velocity increases the packing's pressure drop by 10%. Furthermore, the data analysis show that a lower pressure drop within the inner cavity could be achieved, in principle, by regulating the exit packing velocity or raising the free vortex pressure. Finally, it is noted that the gross pressure drop reduction, which is be obtained from combining the two former modifications, can reach up to 33% at the high gas volume flow rates. This reduction accounts for 60% of the inner cavity pressure drop, which can help avoid costly and complicated engineering designs.

Influence of inlet placement on the hydrodynamics of the dual-drain arc angle tank for fish growth

The aquaculture tank is an infrastructure for aquaculture, and the choice of its geometry, structural design of the inlet and outlet pipes and the placement position and other parameters are crucial to the influence of the hydrodynamic performance of the tank. In this paper, a numerical computational model of the hydrodynamics of a dual-channel rectangular circular-angle culture tank is established using the RNG k-ε turbulence model based on the Reynolds-averaged N-S equation (RANS) averaged over time. The three-dimensional simulation of the internal flow field of the breeding tank under the hydraulic drive mode of the dual inlet pipe structure was verified by comparing with the experimental results of the physical model, and the accuracy of the numerical model in simulating the flow characteristics in the rectangular circular-angle breeding tank was demonstrated. The model was further applied to study the effect of the relative inflow distance on the hydrodynamic characteristics inside the culture tank, and the energy effective utilization coefficient was proposed to measure the effective utilization of energy inside the culture tank system.The present study has shown that the relative inflow distance was an important parameter in the construction of the system flow field, the average velocity of aquaculture system (a = 0.05, P < 0.0001), the velocity distribution uniformity at the bottom of the tank as well as the kinetic energy gradient of flow field sublayer are significantly affected by which adjusting the relative inflow distance. The ratio parameter C/B in the range of 0.02–0.04 could effectively improve flow field characteristics of the system so as to get better hydrodynamic conditions for circulating aquaculture.

Analisa Prestasi Pompa Hidram Dengan Variasi Katub Beban Dan Kondisi Inlet

Water transfer in inland areas is still done manually, so we need a water pump with efficiency, technology, economy without the use of electricity and fuel, namely a hydram pump. A hydram pump is a water pump that relies on the momentum of water to raise water. The purpose of this study was to determine the effect of inlet pipe size on pump efficiency, outlet pipe flow rate and the effect of pipe joints on major and minor losses. This research was made with a water source height of 1 m, varying inlet pipes measuring ¾ inch, 1 inch, and 1,5 inch with a length of 5 m, a hydram pump body with a diameter of 1 inch, an air tube with a diameter of 3 inch with a length of 40 cm and an outlet pipe measuring ½ inch. The largest hydram pump efficiency is found in the ¾ inch inlet pipe with 1.94% with an outlet pipe flow rate of 1.79 l/min and the lowest efficiency is in a 1 inch inlet pipe with 1.49% with an outlet pipe flow rate is 1.55 l/min while the major value and the biggest loss value are in the ¾ inch inlet pipe with values of 0.00754 m and 0.678 m and the lowest values are in the 1.5 inch inlet pipe with values of 0.000410 m and 0.019 m so that it can be concluded that the cross-sectional area and the number of connections in the hydram pump installation are very influential on the value of major and minor losses.Keywords: Diameter, Waste Valve, Pipe, Pump

Damage analysis of 800 series materials from reformer tube outlet components

To investigate the failure of 800 series materials from the furnace tube outlet components of the reformers, the test devices such as metallographic microscope, scanning electron microscope, carburizing detector and high temperature endurance testing machine were adopted. The failure mode and failure mechanism of 800 series materials for outlet components of reformer such as pig tail pipe, outlet pipe, stiffenerjoint and collection tube, which had been in service for 1–11 years from 7 petrochemical and chemical fertilizer enterprises were analyzed. The results suggest that the damage of 800 series materials from reformer outlet components in 7 petrochemical and chemical fertilizer enterprises mainly occurred on the base metal. The failure modes included bulging, cracking and fracture, and the principal failure mechanisms were creep and carburizing, respectively. The main factors affecting the failure of 800 series materials in the tube outlet components of reformer were discussed with respect to grain size, metal temperature and stress concentration. Consequently, multiple suggestions were given to avoid premature damage and failure of such components.

유동 가시화를 이용한 PCHE의 유동분배에 관한 실험적 연구

PCHE, Printed Circuit Heat Exchanger, is widely used for industrial applications with increasing demand in extreme environments. As interest in hydrogen for future fuel is increased, the interest in PCHE is also increased. In this study, we focused on the flow distribution in channels of PCHE. Although flow distribution has been employed a lot of times for decades, there are few reliable studies based on experimental results that can be directly applied in actual industrial fields. Here, we introduce experimental results about flow distribution by flow visualization. Effects of flow rates and the verticality are addressed to clarify the difference in distribution. When the flow rate is low, the flow speed difference between channels is not significantly large. If it becomes larger, the difference becomes large. Moreover, when inlet and outlet pipes are installed at a slight angle, back flow is observed. The speed profile of the tilted case in high flow rate is not easily predicted. Although the tilting angle looks very small, the measured speed profile can be completely different.

Parametric Study of the Ground-Air Heat Exchanger (GAHE): Effect of Burial Depth and Insulation Length

A parametric study of a ground-to-air heat exchanger (GAHE) using numerical models based on computational fluid dynamics with the finite volume method to evaluate the thermal potential of GAHE is presented. After the validation of the numerical code developed with published experimental data, it is proceeded to the study of the geometric parameters to define those that have the greatest impact on the application potential of GAHE. Climatological variables such as relative humidity, air flow velocity, and inlet air temperature are analyzed, as well as the increase in the thermal conductivity of the soil due to its humidity content. In addition, a study of the optimal installation depth as well as the length of the thermal insulation in the outlet pipe of the GAHE is presented. The results reveal that there is a higher heat exchange potential in the GAHE for an optimal burial depth of 4 m and a length of pipe of 15 m, 30% soil moisture content for heating and 32% for cooling, and a pipe diameter of 0.15 m. The use of thermal insulating is recommended only for the last 2 m of length in the outlet pipe of the GAHE.

Split Second Analysis Covering High Pressure Gas Flow Dynamics At Pipe Outlet – Mathematical / CFD Investigation

Split Second Analysis Covering High Pressure Gas Flow Dynamics At Pipe Outlet – Mathematical / CFD Investigation

Numerical investigation of clocking effect on irreversible energy loss in volute for centrifugal pump with vaned diffuser based on entropy generation method

In order to study temporal and spatial variation of energy loss and reveal influence rule of clocking effect on energy loss and flow field in centrifugal pump with vaned diffuser, numerical simulations were carried out. Numerical simulations were validated by experiments. Local equilibrium of turbulence generation and dissipation was verified to state feasibility of energy loss methods. Hydraulic loss in each component was assessed, which shows that variation of hydraulic loss in volute is more significant due to clocking effect than that in other components. Vortical structure in volute varies greater under different guide vane positions than it in other components. The results show that positive and negative flow angle appears interlaced in tongue region with high velocity gradient, especially when diffuser is mounted at θd1. Since a clearance presents between tongue and vane trailing edge at θd1, a small vortex forms. Which promotes the blocking effect of the large-scale vortex at volute outlet pipe. Therefore, high velocity gradient appears at small vortex region and volute outlet pipe region. The shear strain rate at the tongue and volute outlet pipe is more significant than that at other diffuser mounted positions. Energy loss at these regions increases. This situation can be improved by a more suitable diffuser mounted position θd4, where the clearance and small vortex vanishes, the shear strain rate, velocity gradient, and energy loss decrease.

Fully 3D Modeling of Electrochemical Deionization.

Electrochemical deionization devices are crucial for meeting global freshwater demands. One such is capacitive deionization (CDI), which is an emerging technology especially suited for brackish water desalination. In this work, we extend an electrolytic capacitor (ELC) model that exploits the similarities between CDI systems and supercapacitor/battery systems. Compared to the previous work, we introduce new implementational strategies for enhanced stability, a more detailed method of describing charge efficiency, layered integration of leakage reactions, and theory extensions to new material and operational conditions. Thanks to the stability and flexibility the approach brings, the current work can present the first fully coupled and spatiotemporal three-dimensional (3D) CDI model. We hope that this can pave the way toward generalized and full-scale modeling of CDI units under varying conditions. A 3D model can be beneficial for investigating asymmetric CDI device structures, and the work investigates a flow-through device structure with inlet and outlet pipes at the center and corners, respectively. The results show that dead (low-flow) areas can reduce desalination rates while also raising the total leakage. However, the ionic flux in this device is still enough under normal operating conditions to ensure reasonable performance. In conclusion, researchers will now have some flexibility in designing device structures that are not perfectly symmetric (real-life case), and hence we share the model files to facilitate future research with 3D modeling of these electrochemical deionization devices.