Branch Pipe Research Articles

Determination of heat-transfer coefficients in multi-vortex heat-mass-exchange apparatus

In this work, heat transfer coefficients from the working surfaces of a multi-vortex heat-and-mass exchange apparatus developed by the authors are determined along with dimensionless equations for calculating the heat transfer coefficients from the inner wall of a housing and bottom when generating. Numerical modelling is carried out using the ANSYS Fluent software package. When determining the velocity profile of a fluid in order to calculate the coefficient of heat transfer, the SST k-ω turbulence model is used. This allows for an adequate convergence in near-wall fluid and gas flow areas when simulating flows in similar constructions used, for example, to classify finely dispersed bulk solids. Dimensionless equations are obtained that relate the Nusselt number to the Reynolds and Prandtl numbers. Relationships are obtained for the increase in the heat transfer intensity as a function of the Reynolds number. It is established that the intensity of heat transfer from the inner wall in the multi-vortex apparatus exceeds the heat transfer from the bottom by 12.7–15.8 % depending on the Reynolds number. The values of heat transfer coefficients at the inner wall of the proposed apparatus can reach 14747 W/(m2 ∙ K) at an average fluid flow rate of 1 m/s. The proposed multi-vortex heat-exchange apparatus ensures swirling gas or fluid flow in the annular gap between the branch pipe and unit housing to provide high heat transfer coefficients and, hence, high intensity of heat transfer, especially through the wall of the contact stage. The numerical studies demonstrate the possibility of achieving high values of specific heat flux through the wall of the contact stage, which enables the most efficient use of the apparatus in the processes associated with the additional heat supply or removal from the contact stage through its external.

The Effect of Temperature and Bending Moments on the Strain Accumulation of Carbon Steel Piping Branch

The Effect of Temperature and Bending Moments on the Strain Accumulation of Carbon Steel Piping Branch

다양한 액유체 배관 시스템에서 수격 현상에 따른 유동특성연구

In this paper, the characteristics of changes in pressure head and flow due to water hammer in various piping systems were studied using numerical analysis and experiments. This numerical study on the branch piping system can provide basic data for piping system design. Water hammer was simulated in single piping system and branch piping system using unsteady Reynolds--Averaged Navier-Stocks(URANS) model and user defined function(UDF) for compressible flow. The pressure change of the system was measured at 0.6 m on the upstream of the valve, and the flow rate change of each system was recorded at 30 m, 45 m, and 60 m on the upstream of the valve. As a result of the analysis, both the pressure waves patten of the single piping system and the branch piping system showed small errors compared to the experimental results, and the maximum was 9% in the branch piping system. In the form of the pressure wave, the instantaneous pressure drop was 76% compared to the peak in the branch piping system, unlike the single piping system. The flow rate change of the branch piping system showed a vibration that could not be seen in a single piping system, and the flow rate vibration was up to 28% when the pressure wave decreased.

Solid-body disc valve with a shape memory alloy seat

The relevance of the study is due to the need to increase the technical resource and structural reliability of the disc valve by modernizing its design. Disc valve is the most promising type of shut-off and control valves for oil and gas and chemical industries. Its main problem is a small technical resource and a significant unrealized reliability potential. An increase in the technical resource and the realization of potential reliability will minimize the operating costs due to scheduled repairs, as well as the risks of downtime of production lines due to emergency shutdowns, meet the requirements of industrial safety and environmental legislation, and accelerate the introduction of shut-off and control valves of this class in production. The purpose of this study is to improve the technical life and reliability of a disc valve by modernizing the design with the use of shape memory alloys. To achieve this goal, an analysis of the strength characteristics and resulting deformations of the seat of the developed and existing designs of disc shut-off valves was carried out, the results of studies on the abrasion and cavitation resistance of the Ni – Ti alloy with shape memory effect were described, a seat model made of alloys capable of thermoelastic phase transitions, as well as the deformation behavior of the seat, which ensures installation, was demonstrated. The result of the research was the proposed design of shut-off and control valves, which, in terms of manufacturing complexity, is comparable with existing designs in labor intensity, but at the same time has a large technical resource due to the absence of an additional parting line in it, which is formed in existing designs due to the coupling of the branch pipe and case. Mounting the seat in the case groove is ensured by the peculiarity of materials with a shape memory effect, and increased performance is due to the peculiarity of the properties of alloys with the shape memory effect, in particular, pseudoelasticity, which is manifested during operation in the temperature range Af < T < Md.

Simulation Study on Aircraft Fire Extinguishing Pipeline with Different Filling Conditions and Pipeline Characteristics

The filling conditions and pipeline characteristics of the aircraft fire extinguishing system determine the pressure of the fire extinguishing cylinder outlet, the discharge quality of the extinguishing agent, and the flow distribution during the discharge process. The simulation model of the fire extinguishing system pipeline of an aircraft was established by Amesim. The influence of filling conditions and pipeline characteristics was studied. It was found that the mass curves of the fire extinguishing agent were similar under filling pressures of 4, 5, and 6 MPa with a filling amount of 5.55 kg. The lower the initial temperature is, the pressure at the outlet of the cylinder decreases, but the emptying time is similar to 1.22 s. The lower the roughness is, the faster the discharge is. Under the ideal smooth pipe (ε = 0 mm), the emptying time of the fire extinguishing cylinder is 0.72 s. When the diameter of the short branch pipe is 10 mm, and the diameter of the long branch pipe is 14 mm, the discharge quality of the two pipes is close. The larger the diameter of the main pipe, the higher the discharge rate. The research results have a certain guiding significance for the pipeline design of certain aircraft.

Numerical study to recover low-grade waste heat using pulsating heat pipes and a comparative study on performance of conventional pulsating heat pipe and additional branch pulsating heat pipe

To understand the low-grade waste heat recovery ability of a pulsating heat pipes (PHPs) with water as working fluid. A two-dimensional conventional pulsating heat pipe (C-PHP) and an additional branch pulsating heat pipe (AB-PHP) were simulated using computational fluid dynamics and the volume of fluid method. Results revealed that based on the wall heat flux at condenser walls the waste heat recovery capability of the AB-PHP is 11% more than that of the C-PHP. Current work also presented the outcomes of a numerical simulation that compared the performance of AB-PHP with C-PHP. The comparison is made based on the flow and thermal performance by maintaining constant wall temperature at various filling ratios (FR) and tilt angles (TA). To understand the flow performance of PHP’s mean fluid flow velocity is used. Owing to the additional driving force provided by the additional branch the maximum mean flow velocity of AB-PHP is 1.16 times that of C-PHP. To understand the thermal performance of PHP’s temperature gradient of working fluid is used. In AB-PHP, the minimum fluid temperature gradient is observed at 50% FR and 90° TA. AB-PHP had a 21.6%, 11.5%, 9.3%, and 6% lower temperature gradient than C-PHP at 90°, 60°, 45°, and 30° TA, respectively.

Modeling and analysis of steam-water two-phase flow distribution and wall temperature distribution in parallel heated pipes with different manifold types

In solar tower receiver, boiler water-wall and various heat exchangers, the uneven distribution of two-phase flow often occurs among parallel heated pipes, which seriously reduces the operating efficiency and may further induce heat transfer deterioration and soaring wall temperature. In this paper, a coupling model for the flow distribution and heat transfer process of steam-water two-phase flow in parallel heated pipes was established based on the discrete methods. In the present model, two main improvements were proposed as below. On one hand, the calculated equations for the pressure drop and the phase distribution of two phase fluid in both the combining T-junction and dividing T-junction were established to consider the coupling effects of the inlet manifold and outlet manifold on the flow distribution characteristics. On the other hand, the calculation module for the heat transfer and wall temperature along the branch pipes was also coupled in the present model with considering of different heat transfer regions (saturated nucleate boiling region, liquid deficient region, and superheated steam region) along the pipe. The present model was then verified and used to investigate the effects of system pressure, inlet fluid flow, inlet steam quality and manifold type on the flow distribution characteristics of high temperature and high pressure steam-water in parallel vertical upward pipes, and the effect of the uneven distribution of the gas-liquid two phases on the system safety was analyzed and evaluated. It was found that gas phase preferentially enters the first branch pipe near the inlet of the dividing manifold affected by buoyancy, and this results that the inlet steam quality of the corresponding branch pipe is always obviously higher than that of the subsequent pipes. As the system pressure decreases, the outlet fluid enthalpy distribution and outlet wall temperature distribution among branch pipes become more uneven. Moreover, the outlet fluid enthalpy and outlet wall temperature of the branch pipes closer to the inlet of the dividing manifold increase sharply with the decrease of system pressure. In the U-type parallel pipe system, the branch pipes away from the inlet of the dividing manifold are more prone to wall overheating at the outlet, while the opposite is true for the Z-type parallel pipe system.

Study on Measurement of Penstock Head Loss for Hydropower Station with Multiple Units Per Penstock

For a hydropower station with multiple units per penstock, how to get the head loss of penstock has usually been a difficult problem, which the core issue is that it is hard to obtain the flow of each branch pipe. For power stations that have installed flow measurement devices for all units, or have undergone absolute turbine efficiency tests, the head measurement is relatively simple, but if the flow measuring device is not installed for each unit in advance, the head loss measurement will be difficult. This paper proposes an optimized measurement method performed in a hydropower station in Pakistan, which is to arrange an ultrasonic flowmeter on the main penstock, and then use the Winter-Kennedy method and flow rate measured by Ultrasonic flow meter to calibrate the Winter-Kennedy coefficients of unit one by one. Finally, by running three units at the same time and adjusting them with the same flow rate, the total loss of the penstock is calculated. At the same time, the flow rate measured by the Winter-Kennedy coefficient and that measured by the ultrasonic method has been checked and compared. The result proves that the accuracy of the result is high, and the result has a good consistency, which can fully meet the requirements of penstock head loss calculation and evaluation. The method has a certain practical value and can be referred to by other power station which has similar measurement.

Analysis of drainage efficiency under extreme precipitation events based on numerical simulation

AbstractThe recent increase in extreme climatic phenomena has gradually attracted the attention of researchers regarding urban flooding. This paper used a hydrological model combined with the Computational Fluid Dynamics software to assess the drainage efficiency, predict the hydrological processes under different precipitation intensities and establish the relationship between rainfall intensity and inundation depth under extreme rainstorm events. The study proposed several thresholds such as specific rainfall intensities (that is, RI95% and RI50%), drainage efficiency, and the limited flow rate of pipes. Based on 2021 July 20, 0:00 to 24:00 precipitation monitoring data from the “7.20 Zhengzhou Rainstorm Extreme Event,” the relationship between rainfall intensity and road‐pipe overflow patterns was determined by analysing these thresholds for different drainpipe diameters and spacings of catchment wells. The results demonstrated the evaluation parameters varied with rainfall intensities and pipe characteristics and revealed the main limitation of drainage efficiency and flow rate of drainpipes. The simulation helped the drainage systems design for different precipitations and proposed several relative suggestions for drainage‐system improvements, wherein the diameter of the branch pipes plays a dominant role in coping with extreme rainstorm events.

Dynamic calculation and optimization design of arbitrary planar branch piping system

The absorbing transfer matrix method (ATMM) is applied to dynamics calculation and optimization design of planar branch piping systems combined with the response surface model or method (RSM) and a new proposed hybrid RSM (HRSM). A main path is chosen to absorb the influences of sub-branches, and the branch point transfer matrix in the main transfer path is established and proved by the ANSYS simulation and experimental results. It shows that the errors between the ATMM and the finite element method are less than 0.36% in the calculation of the natural frequencies of the two-branch piping system, and the ATMM also agrees well with the dynamics response experimental results of the cross-branch piping system. Then, based on the initial design model of a double-branch piping system, first order natural frequency analysis samples are selected for the branch point positions optimization using the uniform design method (UD) and calculated by the ATMM; the minimum value of the RSM, obtained by fitting the samples with a second-order polynomial (SOP) function, is solved as the best design scheme using the genetic algorithm (GA). Finally, for the problem of supporting positions optimization of a T-branch piping system, a HRSM using the SOP function to fit the variation law with different supporting positions in the samples of the dynamics response optimization target, which is the total x-directional vibration acceleration level (TAC) of three supporting points in the frequency 1–300 Hz and the Fourier basis function to fit the relationship of SOP function error with independent variables is proposed combining the Minimize Prediction (MP) adding point criterion to gradually update the samples, until the HRSM reaches stability and obtains the wanted design solution.

Study on the Uniformity of Secondary Air of a 660 MW Ultra-Supercritical CFB Boiler

Based on the field test of a 600 MW supercritical circulating-fluidized bed boiler, this paper optimizes the secondary air pipe layout scheme of a 660 MW ultra-supercritical circulating fluidized bed boiler with a similar furnace structure and carried out a numerical simulation on its air distribution uniformity. The secondary air box of the 660 MW ultra-supercritical circulating-fluidized bed boiler adopts a variable section design, and the secondary air branch pipe adopts a separate air inlet mode. The experimental results showed that the oxygen concentration was uniform near the rear wall, but all exhibited a “decrease–increase–decrease” profile along the horizontal line, which indicated that the trajectory of the secondary air jet was first in the shape of bending downward and then upward. To achieve a more uniform secondary air distribution for supercritical CFB boilers, further optimization of the layout of the bellows and branch pipes should be considered. Numerical results showed that the deviation rate of the internal and lower secondary air reached 17%, and there was optimization space for the secondary air branch pipe layout of the boiler. Its uniformity can be increased by adding valves and other measures. The velocity deviation of the secondary air of the 660 MW ultra-supercritical circulating-fluidized bed boiler can be within 3% by means of separate air supply and pipe diameter change, and better uniform air supply can be achieved to reduce the speed deviation by adding valves and adjusting the combustion.

Intake Manifold Flow Study using Numerical Method with all Runners Opened

Intake manifolds have to be designed to improve engine performance by avoiding the phenomena like inter-cylinder robbery of charge, inertia of the flow in the individual branch pipes, resonance of the air masses in the pipes and the Helmholtz effect. The objective of work is to predict and analyze the flow through intake manifold of four cylinder spark ignition engine. One of the important factors is air flow inside the intake manifold; the ideal intake manifold distributes flow evenly to the piston valves. The structural analysis has been conducted to decide the thickness and material that is suitable for intake manifold to withstand bursting pressure. Three-dimensional inlet manifold was modeled in ANSYS workbench and numerically analyzed by using the commercially available FLUENT software to study the pressure, velocity and flow characteristics inside the runner. The steady state analysis has been carried out for three for All runners open, The predicted results of total pressure loss and total outlet mass flow were discussed. Inlet pipe and plenum connection creates a back step geometry which causes more total pressure loss due to flow recirculation in conventional model. Tapering the geometry is causing more inlet mass flow due to reduction in total pressure loss in the plenum chamber.

Manual Hydraulic Calculation Method of the Fire Sprinkler System Design Considering Velocity Pressure

Theoretical calculation methods for hydraulic calculation of fire sprinkler systems considering the velocity pressure have been proposed; however, there has been no specific application method to the design. Understanding the design considering the velocity pressure is important because it is the actual situation that occurs in the pipe when calculating the friction loss. Therefore, the procedure for the design considering the velocity pressure is explained in detail from beginning to end of the design. Two simple points can be summarized for the hydraulic calculation procedure considering the velocity pressure. 1) the sprinklers discharge flow rate on the branch is calculated by the discharge flow rate equation due to normal pressure. 2) Flow is adjusted at the intersection point of the pipe where the branch pipe is connected and two different pressures are present. The calculated value according to the manual hydraulic calculation procedure considering the velocity pressure presented in this paper is 12.9642 bar for pump demand pressure, and it is consistent with the value (12.96 bar) calculated under the same condition by the PIPENET computer program. As for the required flow rate of the pump, the value directly calculated in this study is 3137 lpm, which is 99.81% of the value (3143 lpm) calculated by PIPENET computer program, indicating that the calculation procedure is accurate.

Calculation of Hydrodynamic Parameters of the Apparatus of Shock-and-Vortex Action with a Regular Tubular Packing

An analysis of the operation of gas cleaning equipment for gas purification technological schemes, including apparatuses for carrying out a single process, combined apparatuses combining several zones for carrying out various processes, and an apparatus with autonomous irrigation circuits, has allowed developing the design of a two-stage apparatus of shock-vortex action with a regular tubular packing. As a result of the studies carried out for the apparatus’ packed zone, graphical dependences of the hydraulic resistance, the retained liquid amount and the layer’s gas content on the gas velocity and irrigation density, as well as the hydraulic resistance of the tubular bundle during the coolant movement inside the pipes, on the Reynolds number are obtained. In addition, the results of the studies of the hydraulic resistance of the gas-liquid impact zone, the inclined baffle, and the total hydraulic resistance depending on the gas velocity in the inlet branch pipe and the initial liquid level are obtained. Based on the research, a method for calculating hydrodynamic parameters is proposed, including equations for calculating the hydraulic resistance of the ejection zone, the gas flow exit zone from the central pipe, the packed zone and the apparatus as a whole, the retained liquid amount and the layer’s gas content. For this design of a tubular packing, when the coolant moves inside the pipes, equations are obtained for calculating the total hydraulic resistance of the tubular bundle, resistance due to friction, and local resistances.

Design and Experimental Investigation of a Novel Piezoelectric Energy Harvester in Pneumatic System

Herein, a novel piezoelectric energy harvester (PEH) with good sealing and insulation performance is proposed, which can be connected with the branch pipe to capture the air pressure impact energy in the pneumatic system. The transient energy harvesting process and effect of parameters on the performance of the PEH are experimentally investigated. The results show that the harvested transient voltage has alternating characteristics. The voltage, peak power, and electric work are improved with the decreasing minimum pressure and increasing maximum pressure. The pressure has an effect on the harvested voltage even under the same pressure difference. When the pressure is raised, the rising time and voltage slightly decrease. Specially, the minimum pressure of the PEH should be close to zero for high harvested peak power. In addition, the peak voltage and electric work increases with the increasing resistance. The peak power increases to the maximum value first and then decreases with the increase in resistance. When the pressure varies from 0 to 0.5 MPa, the maximum peak power can reach up to 140 μW at 1500 KΩ, and the power density is 1.43 mW cm−3.

Failure analysis of M400 alloy distributor of top gas scrubber in alkane dehydrogenation unit

M400 alloy distributor used to disperse acid gas containing HCl and H2S in the stabilizer top gas scrubber suffers from severe corrosion attack at the connection between distribution pipe, branch pipe and distribution hole during service. The failure analysis is carried out through experimental and numerical simulation methods. The results show that the acidic gas has scouring effect, and the corrosion products in the front gas transmission pipeline are brought into distributor by high-speed airflow and promote its corrosion. In addition, dew-point corrosion on the scrubber wall and the entrance of oxidized Fe3+ into the distributor, further aggravate its erosion corrosion. The erosion corrosion of the distributor and the dew-point corrosion of the scrubber wall build a vicious cycle in common, which eventually leads to the failure of the distributor. A series of protection suggestions are put forward to mitigate and avoid similar incidents.

Modeling the process of mixing the coolant in the lower section and pressure mixing chamber of VVER-1200 (V-491)

The most representative accident scenario is determined and a physical and mathematical model is developed for studying the mixing of non-isothermal coolant flows in the structural elements of the V-491 reactor facility (VVER-1200), in which the motion of the medium is described in a three-dimensional non-stationary formulation. Based on the analytical estimates of the list of initiating events, a scenario was chosen with the connection of an idle loop of the main circulation pipeline to three operating ones without a preliminary power reduction. A computational algorithm and a numerical method have been developed for the computational analysis of the selected accident scenario and the justification of the safety of operation of the V-491 reactor facility (VVER-1200). During the numerical simulation, the RANS method was used, which consists in solving the Reynolds-averaged Navier–Stokes equations, the continuity equation and the energy equation. The SST k–ω model of turbulence by Florian Menter is used to close the equations. The verification of the developed physical and mathematical model and calculation procedure was carried out by modeling thermohydraulic processes in models with both a relatively simple geometric design (tee connection) and in a scale model of the reactor vessel (ROCOM experiment), including a lowering section and a pressure mixing chamber. The qualitative agreement of the numerical simulation results with the available data of physical experiments is shown. The results of numerical simulation of the mixing process of non-isothermal coolant flows in the section from the branch pipe of the “cold” thread of the main circulation pipeline to the lower boundary of the fuel of the VVER-1200 core (V-491) are presented. It is shown that the heterogeneity in the temperature distribution at the entrance to the core manifests itself up to 15.5 s of the calculated accident scenario. For calculations the following code coupling were used: Ansys Fluent/Rainbow-TPP.

Design of Smart Home Alarm System Based on Internet of Things Technology

The intelligent home alarm system based on the Internet of Things technology belongs to the field of alarm devices. The intelligent home alarm system based on the Internet of Things technology includes a HVAC household boiler and an alarm radiator matched with the HVAC household boiler. The upper and lower ends of the alarm radiator are fixedly connected with radiator branch pipes. The left and right ends of the radiator branch pipe are internally provided with pressure alarm cavities, which can send out sound alarms to family members located in the living quarters through the cooperation of the air drum breathing balls, electromagnetic action alarm components and self-induction alarm systems, effectively improve the transmission effectiveness of safety alarms of HVAC domestic boilers, and reduce the gas consumption risk of HVAC equipment in families. In addition, through the cooperation of the alarm radiator and the smart home controller, not only can sound alarm be given to all parts of the home, but also the home ventilation can be independently controlled by electrical signals, thus improving the dispersion effect of natural gas.

Water hammer response characteristics of wellbore-fracture system: Multi-dimensional analysis in time, frequency and quefrency domain

Water hammer fracture diagnostics is a promising fracture diagnostic method, which is nonintrusive, economical, timely performed and easily operated. In present studies, the propagation behavior of the water hammer in the wellbore-fracture system remains unclear, which brings uncertainty to locating the hydraulic-stimulated fractures. In this paper, the transient flow model was used to describe the water hammer pressure fluctuation, which was generated after the pump shut down during the hydraulic fracturing treatment, and the wellbore-fracture system was built by introducing the branch pipe to the wellbore as the fracture. The method of characteristics (MOC) was used to solve this model, then was validated by the computational fluid dynamics software FLUENT. Combining water hammer signal analysis in time, frequency, and quefrency domain, the fracture effect on the water hammer response characteristics in the wellbore-fracture system was investigated in multiple dimensions. We then built eight cases to simulate the water hammer pressure fluctuation in different wellbore-fracture systems, including the existence, the varied location and the varied length of the fracture and conducted the multi-dimensional analysis. After that, results were discussed and the response characteristics of the water hammer in the wellbore-fracture system were summarized. From this work, a multi-dimensional analysis method in time, frequency and quefrency domain is proposed. Meanwhile, the water hammer response characteristics of the wellbore-fracture system are sufficiently presented for the first time to accurately investigate the water hammer pressure propagation in the wellbore-fracture system and provide useful insights for water hammer diagnostics in field application.

Numerical Simulation on the Structural Design of a Multi-Pore Water Diffuser during the External Ice Melting Process of an Ice Storage System

A water diffuser is a critical auxiliary equipment for an ice storage system during the external ice melting process. This paper proposes a linear multi-pore water diffuser for an ice storage system with 500 t of refrigeration capacity to enhance the performance of external ice melting. By establishing a three-dimensional two-phase volume of fluid (VOF) model, different structural designs of water diffusers for the ice storage device are numerically examined regarding the degree of turbulence, flow velocity, and pressure drop. The results show that the optimal water diffuser with five rows of trunk pipe and six perforated pores arranged in per row of branch pipe with a 4 mm diameter of perforated pores exhibiting a relatively lower degree of turbulence with a lower pressure drop compared with the other designs in this study. Meanwhile, the influence of the flow velocity on the ice melting process is also investigated by a numerical model of ice melting. It is found that the fed flow velocity from the main pipe inlet exhibits a great impact on the external ice melting process. Compared with the external ice melting process without the water diffuser, the external ice melting process with optimal water diffuser design under flow velocity of 1.0 m s−1 could shorten the overall ice-melting time by 16 h. Additionally, through adjusting the water flow velocity, different output cooling can be realized to provide a fast response speed to the cooling variations in demand of the terminal users with a reduced cost.