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The two-stage sleeve control valve has been widely implemented in the high-pressure difference hydraulic system, whose function is to reduce hydrodynamic noise. The sleeve with orifices plays a significant role in reducing the hydrodynamic noise. The ratio of orifices diameter between the outer sleeve and inner sleeve, R i, is investigated in this paper. The coupling effect of R i on the flow field and hydrodynamic noise is analyzed deeply by URANS and FW-H model. Furthermore, the pressure, velocity, turbulent kinetic energy, and sound pressure level of the flow field are monitored. The results indicate that higher R i will restrict the flow velocity in the orifices, and the distributed pressure drop of two sleeves will be even. The velocity of flow in the outer sleeve reduces from 130 m/s to 90 m/s with the increase of R i. In addition, larger R i can reduce the hydrodynamic noise and obtain higher flow capacity. When the R i is 1.2, the sound power level distributes evenly in the gap, and the radiation intensity of the sound source is the smallest. The study can provide a reference for the design of sleeves in high-pressure control valves.

s Feed-water valves (FWVs) are used to regulate the flow rate of water entering steam generators, which are very important devices in nuclear power plants. Due to the working environment of relatively high pressure and temperature, there is strength failure problem of valve body in some cases. Based on the thermo-fluid-solid coupling model, the valve body stress of the feed-water valve in the opening process is investigated. The flow field characteristics inside the valve and temperature change of the valve body with time are studied. The stress analysis of the valve body is carried out considering mechanical stress and thermal stress comprehensively. The results show that the area with relatively high-velocity area moves gradually from the bottom of the cross section to the top of the cross section with the increase of the opening degree. The whole valve body reaches the same temperature of 250 °C at the time of 1894 s. The maximum stress of the valve body meets the design requirements by stress assessment. This work can be referred for the design of FWVs and other similar valves.

Sleeve control valves are one of the most main components of a nuclear piping system, and they are used for superheated steam adjustment, including the flow rate, pressure, temperature, etc. The sleeve, as its core component, plays a critical role in the regulation of flow characteristics in the valve. Therefore, it is very important to study the effect of the sleeve structure of valve core on the flow characteristics in the sleeve control valve. In this paper, the steady numerical model of double-layer sleeve control valve based on the compressible superheated steam was established with full opening, and the effects of sleeve spacing on flow characteristics of double-layer sleeve valve were analyzed based on the standard k-ε turbulence model. The flow characteristics of double-layer sleeve control valve including velocity, turbulence intensity, and Mach number was investigated with four kinds of different sleeve spacing. When the spacing of double-layer becomes larger, it will affect the flow characteristic of double-layer sleeve control valve greatly. This work has a certain reference value for the design of the thickness of the sleeve opening of the sleeve control valve.

As the key device of the secondary circuit system, the main feed water regulating valve plays a significant role in controlling water level, whose reliability directly affects the safety of the nuclear power plant. During the use of the main feed water regulating valve, the movement and stress state of the valve core are affected by the hydraulic force and the hydraulic torque, which is related to the accuracy and stability of the valve. In this paper, a typical throttling window type of main feed water regulating valve was taken as the research object, the shape coefficient of the throttling window was defined, and the effect of the throttling window shape on the force characteristics of the valve core under variable opening was analyzed. The results show that as the valve opening increases, the direction of valve core axial hydraulic force changes. And with the increase of the shape coefficient of the throttling window, the maximum axial hydraulic force and the maximum lateral hydraulic force of valve core first decrease and then increase, and the maximum hydraulic torque increases gradually. This study can provide some references for the optimal design of similar main feed water regulating valves.

The serious aerodynamic noise is caused in the downstream of control valve by high pressure difference. Severe aerodynamic noise will affect worker safety and production safety. Throttling orifice plate located in control valve downstream is one of the most important devices for reducing aerodynamic noise under high pressure difference. Therefore, studying the effect of throttling orifice plate structure parameters on flow characteristics and aerodynamic noise is of great significance. Based on method of computational fluid dynamics, the inclination angle of conical throttling orifice plate is studied as the research variables. The time-average values of the flow field, pressure and velocity are obtained and evaluated through steady-state RANS. Flow rate is evaluated under condition that the throttling area of the plate remains unchanged. Based on the results of steady-state simulation, the aerodynamic acoustic power level in the whole flow field is obtained through the broadband noise source model. Finally, the influence of the plate inclination angle on the aerodynamic noise is comprehensively evaluated. It is concluded that the downward setting orifice plate (45°) is the best among the all orifice plates. The work has a certain reference value for researching the design of throttling orifice plate and improving aerodynamic noise in downstream of high pressure valve.

Hydraulic valve is used as an important hydraulic component, playing a vital role in fluid power transmission and control systems. When the phenomenon of sticking of valve core occurs, it may seriously decrease the accuracy and sensitivity of the hydraulic valve. Micro-deformation is one of the most common faults causing the valve core sticking, which is due to the thermal load. Therefore, studying the mechanism of valve core sticking caused by thermal fluid is of great significance. In this paper, the fluid dynamics in hydraulic valves and the temperature characteristics of valve core are analyzed based on the thermal-fluid-solid coupling method. Results show that the jet angle (θ) will decrease with the increase of opening degree (k), and the maximum velocity and temperature increase with the increase of the opening degree. By loading the temperature field into the thermal analysis as a boundary condition, it shows that the temperature of the U-throttle groove increases with the increase of the opening degree. In addition, with the increase of opening degree, the maximum thermal deformation increases and the contact pressure between valve core and valve body also increases. This work has a certain reference value for researching and improving the phenomenon of valve core stuck in hydraulic valve.

The utilization of V-spirally corrugated tubes has attracted the attention of many researchers recently. As typical enhancement techniques of heat transfer, they combined the merits of roughness, turbulators and enhanced surface. This paper mainly studies the influence of depth ratio (DR = 0.039–0.199), pitch ratio (PR = 2.37–4.77), and various numbers of starts (N = 4,6) on the flow and heat transfer behavior of V-spirally corrugated tubes in the turbulent flow region (10000 ⩽ Re ⩽ 40000). It employs numerical simulation techniques to obtain the heat transfer performance and resistance characteristics. A comparison is made between enhanced tubes and smooth tube considering evaluation parameters, including Nusselt number ratio and fraction factor. On the basis of investigated results, an analysis is made to distinguish the merits and disadvantages of the new-design enhanced tubes on the flow and heat transfer behavior. The computational results reveal that they enhance heat transfer to varying degrees, and the fluid fields differ. Both the six-start V-spirally corrugated tube and four-start V-spirally corrugated tube have larger Nusselt number than smooth tube under the same working condition and the six-start is better. The Nusselt number increases as Reynolds number increases or pitch decreases. Besides, the six-start V-spirally corrugated tube with depth ratio = 0.118 has the largest Nusselt number, which is larger than smooth tube by around 31.3%.

Ambient condition, especially the wind condition, is an important factor to determine the behavior of hydrogen diffusion during hydrogen release. However, only few studies aim at the quantitative study of the hydrogen diffusion in a wind-exist condition. And very little researches aiming at the variable wind condition have been done. In this paper, the hydrogen diffusion in different wind condition which including the constant wind velocity and the variable wind velocity is investigated numerically. When considering the variable wind velocity, the UDF (user defined function) is compiled. Characteristics of the FGC (flammable gas cloud) and the HMF (hydrogen mass fraction) are analyzed in different wind condition and comparisons are made with the no-wind condition. Results indicate that the constant wind velocity and the variable wind velocity have totally different effect for the determination of hydrogen diffusion. Comparisons between the constant wind velocity and the variable wind velocity indicate that the variable wind velocity may cause a more dangerous situation since there has a larger FGC volume. More importantly, the wind condition has a non-negligible effect when considering the HMF along the radial direction. As the wind velocity increases, the distribution of the HMF along the radial direction is not Gaussian anymore when the distance between the release hole and the observation line exceeds to a critical value. This work can be a supplement of the research on the hydrogen release and diffusion and a valuable reference for the researchers.

Control valves are widely used to regulate fluid flux in nuclear power plants, and there are more than 1500 control valves in the primary circuit of one nuclear power plant. With their help, the flux can be regulated to a specific level of water or steam to guarantee the energy efficiency and safety of the nuclear power plant. The flux characteristics of the control valve mainly depend on the valve core shape. In order to analyze the effects of valve core shapes on flux characteristics of control valves, this paper focuses on the valve core shapes. To begin with, numerical models of different valve core shapes are established, and results are compared with the ideal flux characteristics curve for the purpose of validation. Meanwhile, the flow fields corresponding to different valve core shapes are investigated. Moreover, relationships between the valve core opening and the outlet flux under different valve core shapes are carried out. The flux characteristics curve and equation are proposed to predict the outlet flux under different valve core openings. This work can benefit the further research of the flux control and the optimization of the valve core for control valves in nuclear power plants.

Mechanical heart valves (MHVs) are widely used to replace diseased heart valves, but it may suffer from cavitation due to the rapid closing velocity of the leaflets, resulting in the damage of red blood cells and platelets. The aim of this study is to apply computational fluid dynamics (CFD) method to investigate the cavitation in bileaflets mechanical heart valves (BMHVs) and discuss the effects of the conduit and leaflet geometries on cavitation intensity. Firstly, CFD method together with moving-grid technology were applied and validated by comparing with experimental results obtained from other literature. Then the leaflets movement and the flow rate of BMHVs with different conduit geometries and leaflet geometries are compared. At last, the duration time of the saturated vapor pressure and the closing velocity of leaflets at the instant of valve closure were used to represent the cavitation intensity. Larger closing velocity of leaflets at the instant of valve closure means higher cavitation intensity. For BMHVs with different conduit geometries, the conduit with Valsalva sinuses has the maximum cavitation intensity and the straight conduit has the minimum cavitation intensity, but the leaflets cannot reach the fully opened state in a straight conduit. For BMHVs with different leaflet geometries, in order to minimize the cavitation intensity, the leaflets are better to have a large thickness and a small rotational radius. CFD method is a promising method to deal with cavitation in BMHVs, and the closing velocity of leaflets has the same trend with the cavitation intensity. By using CFD method, the effects of the conduit geometry and the leaflet geometry on cavitaion in BMHVs are found out.

Feed-water valves are widely used in nuclear power plants to regulate the flow rate of the water supplying to steam generators, and thus holding the water level in steam generators at desired values. The flow rate characteristics of feed-water valves have important effects on the management quality of the water level in steam generators and therefore influence the safety and the efficiency of nuclear power plants. In this paper, the effects of throttling window shapes on the flow rate characteristics through feed-water valves are investigated in two aspects, the overall performances and the fluid dynamics. First of all, a dimensionless parameter defining throttling window shapes is proposed for the quantitative assessment. Then, for the analysis of overall performances, the rated flow coefficient, the loss coefficient, and the inherent valve characteristics are investigated. A revised fitting function is obtained to predict the inherent valve characteristics with different throttling window shapes for engineering applications. Finally, for the observation of the fluid dynamics, the velocity characteristics and the pressure characteristics are both discussed. The wear conditions are predicted at different relative travels and throttling window shapes. This paper provides a reference for researchers dealing with the design work of feed-water valves and is beneficial for the improvement of the whole water level control system.

Risk analysis and consequence assessment aimed at the hydrogen refueling station are of great importance for the large-scale commercialization of the hydrogen refueling station. In this paper, the unintended hydrogen release in both momentum-buoyancy dominated regime and momentum dominated regime is investigated numerically. The profile of the flammable gas cloud in release direction, buoyancy/gravity direction and natural convection direction, namely the y direction, z direction and x direction, is plotted quantitatively and comparison between two regimes is presented in detail. Results indicate that in the momentum-buoyancy dominated regime the profile of the flammable gas cloud moves upward during the continuously diffusion process. While in momentum dominated regime, the flammable gas cloud is more likely to be accumulated near the ground. Along the release direction, the marginal profile of the flammable gas cloud is determined by the total volume of the hydrogen in the tank. When the initial pressure increases from 40 MPa to 80 MPa, the marginal profile of the flammable gas cloud is nearly identical at the end of the release. In the natural convection direction, the hydrogen diffusion is driven by the concentration gradient. The hydrogen diffuses symmetrically along the release hole and the profile of the flammable gas cloud is similar in each condition. The results will provide a valuable reference for the later study of the explosion.

Studies focused on the behavior of the hydrogen leakage and diffusion are of great importance for facilitating the large scale application of the hydrogen energy. In this paper, the hydrogen leakage and diffusion in six scenarios which including comparison of different leakage position and different wind effect are analyzed numerically. The studied geometry is derived from the hydrogen refueling station in China. Due to the high pressure in hydrogen storage take, the hydrogen leakage is momentum dominated. The hydrogen volume concentration with the variation of the leakage time in different scenarios is plotted. More importantly, profiles of the flammable gas cloud at the end of the leakage are quantitatively studied. Results indicate that a more narrow space between the leakage hole and the obstacle and a smaller contact area with the obstacle make the profile of the flammable gas cloud more irregular and unpredictable. In addition, results highlight the wind effect on the hydrogen leakage and diffusion. Comparing with scenario which the wind direction consistent with the leakage direction, the opposite wind direction may result in a larger profile of the flammable gas cloud. With wind velocity increasing, the profile of the flammable gas cloud is confined in a smaller range. However, the presence of the wind facilitates the form of the recirculation zone near the obstacle. With an increase of the wind velocity, the recirculation zone moves downward along the obstacle. Thus, the hydrogen accumulation is more prominent near the obstacle.

Steam is a common medium in thermal engineering. When it flows through a throttling element, the aerodynamic noise may occur due to the disturbance. In this investigation, superheated steam flowing...

Cavitation occurring in a sleeve regulating valve not only increases the energy waste of the whole piping system but also causes severe and costly damage to the valve body and the piping system. In this paper, in order to reduce the cavitation inside the sleeve regulating valve, the effects of different valve core shapes, including flat bottom, ellipsoid, circular truncated cone, and cylinder, on cavitation are investigated by using a cavitation model. The pressure, velocity, and vapor volume fraction distribution in the regulating valve are obtained and compared for different valve core shapes and valve core displacements. The total vapor volumes are also predicted and compared. The results show that vapor primarily appears in the gap between the sleeve and the valve core surface. The cavitation intensities for the ellipsoid and cylinder valve cores are greater than those for the other two valve cores. With the increase of the valve core displacement, the total vapor volumes for all four valve core shapes first increase and then decrease. This work is of significance for the optimization and design of sleeve regulating valves.

The steam trap valve is used in thermal power systems to pour out condensate water and keep steam inside. While flowing through steam trap valves, the condensate water can easily reach cavitation, which may cause serious damage to the piping system. In this paper, in order to control cavitation inside steam trap valves, effects of sleeve parameters, including orifice diameter, installation angle and thickness, are investigated using a cavitation model. The pressure, velocity, and vapor distribution inside valves are analyzed and compared for different sleeve geometrical parameters. The total vapor volumes are also predicted and compared. The results show that the sleeve parameters have a significant influence on the cavitation intensity and cavitation vapor distributions. Specifically, the orifice diameter of the sleeve has much larger effect on each aspect than that of other two geometrical parameters of the sleeve. The improved geometrical parameters of the sleeve are determined to suppress the cavitation inside the valve. The sleeve with smaller diameter orifices, higher installation angle (maximum 80 deg), and higher thickness is recommended in practice for better anticavitation performance. The work is of significance for cavitation control and the optimization design of steam trap valves.

LNG (liquefied natural gas) cryogenic ball valve (CBV) is an important flow control device in LNG receiving stations. Its reliability directly affects the stability of the pipeline system, especially its damage or leak in the seat seal will seriously threaten the normal operation and the safety of LNG receiving stations. When LNG flows through the CBV, due to the interaction between fluid pressure and the valve structure, the hard sealing at the valve seat is not only subjected to the pre-tightening force of saucer spring, but also affected by the fluid pressure of the complex flow. Therefore, it is necessary to study the flow characteristics in the CBV and the hard sealing performance affected by the LNG. In this paper, the fluid dynamics and the contact stress on hard sealing performance in the CBV are analyzed. The pressure drop, pressure, and velocity distributions were analyzed, respectively. The contact stress on the hard sealing surfaces of the CBV with fluid pressure was analyzed by the fluid-structure coupling method. This work has a certain reference value for researching and mastering the hard sealing performance of cryogenic ball valves.

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.

Due to the merits of higher heat transfer efficiency, spirally corrugated tubes are widely used in a range of applications for heat transfer enhancement, especially in coaxial heat exchangers. This...

Fouling on heat exchanger surfaces can weaken the heat-transfer capability, increase the energy consumption, and even cause the failure of the whole system. In coaxial heat exchangers, spirally cor...

Superheated steam is the main medium in the piping system of steam power plants. In these pipelines, perforated plates are widely used to regulate the flow rate, pressure, and also reduce aerodynamics noise of steam. For the superheated steam flow, the flow resistance and aerodynamic noise are two key parameters of the perforated plates. In order to investigate the flow resistance and steam aerodynamic characteristics, this paper presents a systematic study of superheated steam and water through multi-stage perforated plates under a wide range of operating conditions with both experimental and numerical methods. The experiments are conducted out to validate the applicability of the adopted numerical models. Then numerical methods are used to investigate the water flow resistance and the Mach number distributions of the steam flow with different structural parameters. The results show that with the increase of the holes diameter, the pressure drop decreases and the Mach number increases. Mach number drops significantly when the position of side holes moves towards the edge of the perforated plate. A critical stage distance is found, at which the pressure drop has the maximum value. Besides, the occurrence probability of supersonic steam flow increases as the decrease of stage distance under a restricted space, and the disturbed length of supersonic steam flow is longer when the stage distance is smaller. This work can be referred by someone who deals with perforated plate design in steam piping systems or related research topics.

Purpose The purpose of this paper is to study the effects of dimple geometries and arrangements on the heat transfer enhancement in a dimple jacketed heat exchanger. Design/methodology/approach For the purpose of this paper, with the experimental validated numerical model, this paper carries out numerical simulations of both single dimples with different geometries and the whole dimple jacketed heat exchanger with different dimple arrangements. For a single dimple, its secondary vortex flow, temperature differences and the pressure drop performance for different geometries are analyzed. For the whole dimple jacketed heat exchanger, the heat transfer and pressure drop performances are investigated by comparing the no dimple, triangular and rectangular dimple arrangements. Findings Results show that dimples can improve the heat transfer efficiency compared with conventional jacketed heat exchanger, and specific geometries and arrangement of dimples for better heat transfer performance are figured out. Originality/value This paper considers both dimple geometries and arrangements, which can be useful for further applications in specific integrated devices or similar applications.

Multi-stage Tesla valves in the reversed flow state can be applied during the hydrogen decompression process between the high pressure hydrogen storage vessel and the fuel cell. Under high-pressure turbulent hydrogen flow, severe aerodynamic noise may be caused and large energy loss inside Tesla valves may be generated, which can cause uncomfortable noise in vehicles. In this paper, the valve stage number and the pressure ratio between the inlet and the outlet are analyzed to investigate the possibility of the occurrence of aerodynamic noise and energy loss inside Tesla valves, and Mach number, turbulent dissipation rate, and exergy loss are used and evaluated as the criterion. The results show that both Mach number and exergy loss increase with the increasing of pressure ratio, but with the decrease of valve stage number, Mach number increases and exergy loss decreases. In addition, large turbulent dissipation rate at each valve stage appears near the bifurcation and the confluence between the straight channel and the bend channel of multi-stage Tesla valves. The correlation between the valve stage number, the pressure ratio, and the maximum Mach number is fitted, which can be used to estimate the possibility of the occurrence of aerodynamic noise.