Fluid Transient Responses With Check Valves in Pipe Flow System With Air Entrainment

1997 ◽  
Author(s):  
T. S. Lee ◽  
L. C. Leow
Keyword(s):  
Transient Flow ◽  
Flow System ◽  
Check Valve ◽  
Air Entrainment ◽  
Pipeline System ◽  
Piping System ◽  
Transient Responses ◽  
Fluid System ◽  
Free System ◽  
Fluid Transient

A common flow system arrangement in piping system consists of a lower reservoir, a group of pumps with a check valve in each branch, and a pipeline discharging into a upper reservoir. In earlier studies of check valves performances in transient flow, none considered the effects of air entrainment into a pipeline system and the subsequent effects on the check valve performances in transient flow. Studies on pressure surges during pump tripped in pumping systems showed that by including an air entrainment variable wave speed model, reasonable predictions of fluid transient responses with proper phasing and attenuation of pressure peaks can be obtained. The most severe case where all the pumps in the station fail simultaneously due to power failure was analysed for their maximum and minimum pressure variation along the pipeline. A numerical model is now set up in the present work to investigate the check valve performances in transient flow for a pumping system with air entrainment. The analyses examine a fluid system with a variable air entrainment content (ε) and studied numerically it effects on the flow reversal time and hence determine the appropriate valve selection for a given fluid system to minimize problems of check valve slamming. Present numerical computations show that the air content in a fluid system can adversely affect the check valve transient responses. With the fluid system operating within a critical range of air entrainment values, analysis showed that there is a possibility of “check valve slamming” when the check valves were selected based on the analysis of an air free system. The above phenomena is confirmed through physical field measurements.

Evaluation of Potential to Air Ingestion From RWT Following RAS

2006 ◽  
Author(s):  
Young S. Bang ◽  
Ingoo Kim ◽  
Sweng W. Woo
Keyword(s):  
Water Level ◽  
Power Plants ◽  
Transient Flow ◽  
Cooling System ◽  
Check Valve ◽  
Transient Behavior ◽  
Piping System ◽  
Water Tank ◽  
Two Phase ◽  
Pipe Line

At the Recirculation Actuation Signal (RAS) when the Refueling Water Tank (RWT) water level decreased to a certain value following Loss-of-Coolant Accident (LOCA), the isolation valves of Containment Recirculation Sump (CRS) of the Korean Standard Nuclear Power Plants (KSNP) are open automatically while the RWT isolation valves would be closed manually. It was concerned whether the design has a potential to air ingestion to Emergency Core Cooling System (ECCS) pumps before completion of the manual action to close RWT isolation valves. To support the safety evaluation on this issue including the evaluation of design adequacy, an analysis of the hydraulic transient within the ECCS piping following the RAS in KSNP is performed. RELAP5/MOD3.3 code is used to calculate the transient behavior of the piping network. The code was known to have capability to calculate one-dimensional two-phase transient flow with noncondensible gas in the complex piping. Substantial portion of ECCS are modeled including RWT, CRS, each pipe line from RWT and CRS to connection point with its own isolation valve and check valve, a common pipe line to ECCS header, each pipe line from the header to High Pressure Safety Injection (HPSI) pump, Low Pressure Safety Injection (LPSI) pump, and Containment Spray (CS) pump. Transient hydraulic behavior in the piping system following RAS after LOCA is calculated. It is found that the RWT water level was always higher than the elevation of the check valve at the connecting point by more than 15 ft. It indicates the air intrusion to the check valve can be sufficiently prevented by this amount of water head.

The Numerical and Experimental Investigation Into Hydraulic Characteristics of a No-Load Running Check Valve due to Fluid-Structure Interaction

2018 ◽  
Author(s):  
Xiang-yuan Zhang ◽  
Zhi-jun Shuai ◽  
Chen-xing Jiang ◽  
Wan-you Li ◽  
Jie Jian
Keyword(s):  
Flow Rate ◽  
Ambient Pressure ◽  
Check Valve ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Pipeline System ◽  
Piping System ◽  
Hydraulic Characteristics ◽  
Mass System ◽  
Excited Vibration

Valve is a very important unit in pipeline system. The valve flow fluctuation brings about structural vibration and unpopular noise, and even leads to the safety problems and disasters. In this paper, a special no-load running check valve is investigated. The check valve is structural complex with one inlet and two outlets. It can be simplified as a spring-mass system which manipulates the flow rate by combine action of the ambient pressure of medium and the spring deformation. The three-dimensional model of the valve is established and also the relationship between pressure drops and flow rate of the valve is obtained in various openings and operating conditions. The structure modals were verified by the field tests and thus its fixing boundaries are obtained correctly. The mechanism causing self-excited vibration of a piping system is determined using a dynamic model which couples the hydraulics of internal flow with the structural motion of a three-ports passive check valve. The coupling is obtained by making the fluid flow coefficient at the check valve to be a function of valve plug displacement. The results are compared with the experimental data, which verifies the correctness of the theoretical results. It is shown that the special valve has its own hydraulic characteristics, which greatly influence its flow distribution as it has two outlets. It was also testified that the coupling between fluid and structure changes its natural frequencies and has a non-negligible impact on the pressure fluctuation while working.

CFD Numerical Simulation of Water Hammer in a Vortex Diode

2018 ◽  
Author(s):  
Junrong Wang ◽  
Zhiguo Wei ◽  
Jinlan Gou ◽  
Qi Xiao ◽  
Shaodan Li ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
3D Model ◽  
Transient Flow ◽  
Flow Characteristics ◽  
Check Valve ◽  
Water Hammer ◽  
Nuclear Industry ◽  
Pipeline System ◽  
1D Model ◽  
Inlet Conditions

In the pipeline system of nuclear industry, shock wave pressure in a pipe will be caused by the fast closing check valve after the pumping stops. This phenomenon is known as water hammer, which brings hidden danger to the security and reliability of the pipeline system. Specially, water hammer may cause serious damage on the pipeline system by the valve misoperation, by the valve malfunction, or by other unexpected events. A vortex diode is used as a highly reliable check-valve in nuclear applications, where it mainly benefits from the intrinsic properties of no moving parts and no leakage. In this paper, we proposed a novel method based on a vortex diode to protect water hammer. In the traditional analysis, a simple one-dimensional (1D) model is often used to simulate the water hammer. However, it is difficult to get the transient flow characteristics in a vortex diode using a 1D model. Thus, a three-dimensional (3D) model using computational fluid dynamics (CFD) is proposed to analyze water hammer in a pipeline system with a vortex diode. The 3D model was firstly verified by comparing the numerical results of CFD with experimental results of a water hammer test. Based on the 3D model, the water hammer was simulated at different inlet conditions in a pipeline system with a vertex diode. In order to investigate the vortex diode used as a leaky check-valve, the inlet pressure was decreased by the corresponding value of pump head to simulate the pump stop after the quasi-steady state was achieved in the vortex diode. It is found that the pressure fluctuation of water hammer is comparable to the pump value, which is not varying with initial velocity in the pipeline system. Thus, we have proved that a vortex diode in the pipeline system acts significantly in suppressing pressure fluctuation of water hammer. This study presents a CFD-based numerical method for water hammer and could be useful in protecting water hammer in nuclear industry.

Experimental study of check valves performances in fluid transient

2009 ◽  
Vol 223 (2) ◽  
pp. 61-69
Author(s):  
T S Lee ◽  
H T Low ◽  
D T Nguyen ◽  
W R A Neo
Keyword(s):  
Experimental Study ◽  
Dynamic Behaviour ◽  
Check Valve ◽  
Air Entrainment ◽  
Transient Conditions ◽  
Pressure Transient ◽  
Pumping System ◽  
Fluid Transient ◽  
Different Types ◽  
Set Up

An experimental set-up was introduced to study the dynamic behaviour of different types of check valves under pressure transient conditions. Three types of transient comparison methods were used, with similar results being obtained from all three methods. The experimental results show that the check valves with low inertia, assisted by springs or small travelling distance/angle, gave better performance under pressure transient conditions as compared to check valves without these features. Although different amounts of air entrainment were found to affect the experimental readings, the general characteristics of each check valve remain the same when compared between valves. This study can be applied to help in the choosing of suitable check valves for a particular pumping system.

Effects of Air Entrainment on the Ability of Air Vessels in the Pressure Surge Suppressions

2000 ◽  
Vol 122 (3) ◽  
pp. 499-504 ◽  
Author(s):  
T. S. Lee
Keyword(s):  
Unsteady Flow ◽  
Air Entrainment ◽  
Pipeline System ◽  
Transient Pressure ◽  
Fluid System ◽  
Pressure Peak ◽  
Free Case ◽  
Pressure Surge ◽  
Static Head ◽  
Peak Increase

This paper describes a new and efficient model for the study of air entrainment effects on the responses of a typical horizontal air vessel. The effects of air entrainment on the pressure surges for unsteady flow in a pipeline system were investigated. Studies showed that entrained, entrapped, or released gases in the transient fluid system tend to amplify the first pressure peak, increase surge damping, and produce asymmetric pressure surges with respect to the static head. The pressure surges showed longer periods of down-surge and shorter periods of upsurge. The upsurge was considerably amplified and down-surge was marginally reduced when compared with the gas-free case. With the horizontal air vessel installed, studies showed that the effects of air entrainment on the maximum transient pressure can be considerably reduced with an appropriately configured air vessel. [S0098-2202(00)00203-0]

Air Entrainment Effects on the Pressure Transients of Pumping Systems With Weir Discharge Chamber

2002 ◽  
Vol 124 (4) ◽  
pp. 1034-1043 ◽  
Author(s):  
T. S. Lee ◽  
K. L. Ngoh
Keyword(s):  
Discharge Chamber ◽  
Field Measurements ◽  
Air Entrainment ◽  
Pipeline System ◽  
Extreme Pressure ◽  
Fluid System ◽  
Pressure Transients ◽  
Proposed Model ◽  
Design Characteristics ◽  
Surface Vortex

This paper presents a new model for the study of air entrainment on the extreme pressure surges in pumping systems. For the present fluid system considered with a weir discharge chamber, numerical investigations showed that, with the proposed model of the air entrainment, reasonable predictions of transient pressures with proper phasing and attenuation of pressure peaks can be obtained. The results obtained are consistent with observations from field measurements made when the pumps were operating at low pump cutout levels where air entrainment due to attached surface vortex and falling jets from the inflow near the pump intake were present. Further studies were also made on the design characteristics of the weir discharge chamber on the extreme pressure transients for the unsteady flow in the pipeline system with various degrees of air entrainment.

Transient Kinetic and Thermodynamic Behaviour of Langmuir Adsorption in a Flow System

1999 ◽  
Vol 64 (4) ◽  
pp. 726-734 ◽  
Author(s):  
Miloslav Pekař ◽  
Josef Koubek
Keyword(s):  
Adsorption Equilibrium ◽  
Flow System ◽  
Adsorption Rate ◽  
Adsorption Behaviour ◽  
Transient Responses ◽  
Simple Reaction ◽  
Langmuir Adsorption ◽  
Thermodynamic Behaviour

Various kinetic pathways to the adsorption equilibrium in an isothermal differential bed of adsorbent are illustrated on several examples. Discussion is based on the computed transient responses of adsorption rate and distance from adsorption equilibrium to the start of adsorptive feed. It is shown that adsorption behaviour in flow system may not be smooth and very steep changes on the rate responses may appear. Even the simple reaction need not approach equilibrium smoothly but at a jump. The approach assuming "closeness to the equilibrium" should be used very carefully, in this case.

Transient flow behaviors of the check valve with different spool-head angle in high-pressure hydrogen storage systems

2022 ◽  
Vol 46 ◽  
pp. 103761
Author(s):  
Jianjun Ye ◽  
Zhenhua Zhao ◽  
Junxu Cui ◽  
Zhengli Hua ◽  
Wenzhu Peng ◽  
...  
Keyword(s):  
High Pressure ◽  
Hydrogen Storage ◽  
Transient Flow ◽  
Storage Systems ◽  
Check Valve ◽  
Pressure Hydrogen

Effects of Valve Disc on Flow Characteristics Inside a Swing Check Valve During Opening and Closing Processes

2021 ◽  
Author(s):  
Yi-xiang Xu ◽  
Qiang Ru ◽  
Huai-yu Yao ◽  
Zhi-jiang Jin ◽  
Jin-yuan Qian
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Power Plants ◽  
Flow Characteristics ◽  
Check Valve ◽  
Opening Angle ◽  
Piping System ◽  
Total Moment ◽  
Valve Disc ◽  
Opening And Closing

Abstract The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.

Dynamic Simulation of Piping System Around Safety Valve for Closed Discharge System

2011 ◽  
Author(s):  
Yoshiaki Sakamoto ◽  
Hisao Izuchi ◽  
Naoko Suzuki
Keyword(s):  
Dynamic Simulation ◽  
Safety Valve ◽  
Flow Direction ◽  
Reaction Force ◽  
Time History ◽  
Piping System ◽  
Discharge System ◽  
Fluid Transient ◽  
Short Period ◽  
Reaction Forces

Reaction force of safety valves acting to the piping system is one of key factors for the piping system design around the safety valves. In case of open discharge system, it is well known that a large reaction force acts to the piping corresponding to the fluid momentum force at the atmospheric discharge. On the other hand, reaction forces for closed discharge system may be relatively small since the forces acting to the adjacent two points with flow direction change such as elbows and tees are balanced within very short period. However, large reaction forces may act as a result of unsteady flow just after the initial activation of the safety valve. API RP520 mentioned that a complex time history analysis of the piping system around the safety valves may be required to obtain the transient forces. This paper explains a method of a comprehensive dynamic simulation of piping system around safety valves taking interaction among the valve disc motion, the fluid transient for compressible flow and the piping structural dynamics into account. The simulation results have good agreement with the experimental data. The effectiveness of this method is confirmed throughout an application to actual piping system around safety valves.

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