KR101666846B1 - Device for Improving Flow Uniformity for Stack - Google Patents

Abstract

The present invention relates to a device for improving flow uniformity for a stack. The device for improving flow uniformity for stack is installed at the front end of a sample sampling shroud nozzle to minimize a recirculation region in the inner flow field of a stack (or a circular duct), and includes a flow mixer of a flow mixing function which does not affect the flow uniformity of fluid in a nozzle installation position. Thereby, uniformity for exhaust gas flow can be secured and improved in the stack (or the circular duct). Reliability for sample sampling can be improved. The leakage of radioactive gas can be prevented. A degree of air pollution can be reduced.

Description

[0001] Device for Improving Flow Uniformity for Stack [

The present invention relates to a device for improving the uniformity of flow of a stack, and more particularly, to an installation position of a shroud nozzle for sampling dust particles or radioactive materials flowing out through a stack or a duct in a nuclear power plant, a radioactive waste facility, The present invention relates to a device for improving the uniformity of flow of a gas to be exhausted and a device for reducing the flow angle by installing the stack in a stack to meet conditions.

Radiation monitoring system (RMS) in nuclear power plants and nuclear fuel handling facilities is installed at the ends of stacks or ducts to monitor and observe the leakage of dust particles and radioactive materials to the atmosphere. This system consists of a shroud nozzle, which is a representative sampling probe, and an analyzer. These dusts or radioactive materials are usually cleaned through an air handling unit (AHU) installed in an exhaust system for air release and then designed to be discharged to the atmosphere through stacks or ducts. However, (HEPA, High Performance Particle Removal Filter) The radioactive monitoring system (RMS) monitors the leakage of radioactive particles when the filter or activated carbon filter is damaged, there is a problem with the installation, or in case of an accident.

Each component of this system is required to meet the standards for the location of sampling nozzles as specified in the technical standards of ANSI N 13.1 (1999), ISO 2888 (2010) and KEPIC NRB 6000 (2010) And examines whether the sample meets the acceptance criteria set out in the Technical Standard. In particular, shroud nozzles are required to verify whether the position of the shroud nozzle is appropriate during the initial installation through verification test, laboratory test or flow analysis, and it is necessary to ensure the reliability of the system through periodic inspection.

The verification items for the shroud nozzle installation position described in the above technical standards are the uniformity of the velocity distribution, the confirmation of the cyclic flow through the flow angle measurement, the particle distribution using the 10 탆 particles and the trace gas And gas distribution.

Table 1 below shows the tolerance criteria for each of these items. Here, COV (Coefficient of Variance) is defined as the standard deviation ratio of the fluid velocity to the mean value of the fluid velocity, that is, COV (%) = standard deviation of velocity / average value of velocity × 100.

Characteristics Methodology Acceptance criteria Measurements to determine if the flow in the stack or duct is a wind blow 40 CFR 60, App. A Method 1 The average flow angle should be within 20˚. Velocity distributions in large ducts (> 0.3 m) and small stacks and ducts (<0.3 m) For the center 2/3 cross-sectional area of the stack or duct 40CFR60, App. A, Method 1 (Figure 1-2). Additional points or areas may be required to adequately cover the sampling area The coefficient of variation (COV) shall not exceed 20% for the central part of the stack containing at least 2/3 of the stack cross-sectional area. Trace gas concentration distribution in small and large stacks and ducts For the center 2/3 cross-sectional area of the stack or duct 40CFR60, App. A, Method 1 (Figure 1-2). Additional points or areas may be required to adequately cover the sampling area. The coefficient of variation (COV) shall not exceed 20% for the central part of the stack containing at least 2/3 of the stack cross-sectional area. Maximum tracer gas concentration in small and large stacks and ducts For the center 2/3 cross-sectional area of the stack or duct 40CFR60, App. A, Method 1 (Figure 1-2). The coefficient of variation (COV) shall not exceed 30% for the central part of the stack containing at least 2/3 of the stack cross-sectional area. Aerosol Particle Concentration Distribution in Small and Large Ducts 40CFR60, App. A, Method 1 (Figure 1-2). Additional points or areas may be required to adequately cover the sampling area. The coefficient of variation (COV) should not exceed 20% for the central part of the stack containing at least 2/3 of the stack cross-sectional area.

In general, the shroud nozzle for sampling is installed at the rear end of the air purification unit located at the end of the stack (or duct) of the exhaust system, so that a mistake in installation causes a considerable error in sample sampling.

The sampling nozzle, which is important for sample sampling, is preferably installed in a uniform flow field, but the allowable conditions may not be satisfied depending on the installation conditions of the stack (or duct). A countermeasure to this is to improve the flow uniformity device in the stack (or duct).

For example, as shown in FIG. 1, a branch pipe connected to a stack (or a duct) through an air purification system installed in each exhaust system is connected to one side of a stack (or a duct) If the distance from the branch pipe connection to the outlet of the stack (or duct) is not 10 times the stack hydrodynamic diameter, the fluidity of the exhausted fluid is not uniform and the stack (or duct) It is necessary to provide a flow mixer as a flow uniformizing device inside. The following is a description of a flow mixer shape suitable for this condition.

Patent document 001 Domestic registered patent No. 10-1346634 (Registration notice on December 24, 2013) Patent Document 002 Domestic Registration No. 10-1346633 (Registration Announcement on December 24, 2013)

The present invention for solving the above-mentioned problems is to provide a device for improving flow uniformity of a stack (or a duct) so as to satisfy a permissible standard for a velocity variation coefficient and an average flow angle, Respectively.

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In order to accomplish the above-mentioned object, the present invention provides a flow sampling system, which is installed upstream of a sample sampling shroud nozzle to eliminate a flow-disorder recirculation zone in a stack (or a duct), and to prevent flow uniformity of a fluid at a nozzle- The flow mixer including a ring member fixed along the inner wall of the stack; A blade extending from the inner circumferential surface of the ring member or the inner wall of the stack tube toward the central axis of the tube while being connected at one end thereof, Wherein the flow mixer adjusts the blade length of the flow mixer, the inclination (clockwise or counterclockwise) direction of the flow mixer, and the installation angle of the blades so as to satisfy a tolerance standard for the mounting position of the shroud nozzle installed for sampling the sample The flow uniformity and the flow angle of the fluid are within the allowable reference value, the velocity variation coefficient (COV) of the fluid is within ± 20%, and the flow angle tolerance standard is within ± 20 °; The plurality of blades are shaped to be inclined at an oblique angle of 5 to 25 degrees with respect to the shape of the stack so as to face upward in the central axis length of the stack so as to satisfy the velocity variation coefficient of the fluid and the flow angle tolerance standard, The other side ends of which extend toward the center of the shaft but are not connected to each other up to the center axis of the stack, The flow mixer is installed at a height of 1.5 m at an intersection of a stack of brick ducts inside the stack and the shroud nozzle is installed at a distance of 12.3 m from the bottom of the stack to the height of the outlet, There is an example feature.

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The flow mixer is an example of a stack flow uniformity enhancing device that is divided into segments comprising one or more blades and the ring member, and assembled into one annular shape after fabrication.

The flow mixer is an example of an apparatus for improving the uniformity of flow of a stack formed of one body using at least one of metal, ceramic, resin, and FRP.

As described above, the device for improving the uniformity of the flow of the stack according to the present invention has a coefficient of variation of speed and an average flow angle known in technical standards such as ANSI N 13.1 (1999), ISO 2889 (2007), KEPIC NRB 6000 By installing the equipment in the stack to optimally meet the acceptance criteria, there is an effect of ensuring uniformity of the exhaust gas flow of the stack (or duct).

Further, the apparatus for improving the flow uniformity of the stack according to the present invention can be used not only for sampling of radioactive particles in nuclear power plants or nuclear facilities, but also for environmental exhaust facilities such as incinerators, exhaust facilities for petrochemical complexes and semiconductor waste gas discharge facilities, It is possible to improve the reliability of the sample sampling by improving the fluidity of the inside of the stack (or the duct) to meet the installation requirements of the shroud nozzle used for the representative sampling.

In addition, the apparatus for improving the flow uniformity according to the present invention can contribute to the flow uniformity that satisfies the sampling requirements of the sample by utilizing the data obtained through the fluid analysis using the computer simulation or the data obtained through the field experiment

FIG. 1 is a schematic diagram illustrating a connection pipe and a flow pattern inside a stack according to the present invention when the branch pipe is vertically connected to one side of the stack and the length of the stack is about 5 times the stack diameter.
FIGS. 2A and 2B are diagrams showing a velocity contour and a velocity vector in a cross section of the stack central axis according to the flow mixer non-installation according to the present invention,
3 is a view showing a speed contour according to a stack height in an XY cross section of a stack according to a flow mixer uninstalled according to the present invention,
FIG. 4 is a view showing speed vectors at respective cross sections of the stack height according to the flow mixer uninstalled according to the present invention,
FIG. 5 is a view showing fluid particle behavior in a stack according to a flow mixer-not-installed according to the present invention,
6 is a view showing a flow mixer installation shape inside a stack according to the present invention,
FIG. 7 is a detailed perspective view of the flow mixer shown in FIG. 6,
Figure 8 is a plan view of the flow mixer shown in Figure 6,
Figure 9 shows a lattice for modeling a flow mixer mounting stack according to the present invention,
FIG. 10 is a flow pattern diagram showing a result of a computer simulation analysis on flow uniformity improvement according to the installation of a flow mixer according to the present invention,
11 is a view showing an internal speed contour of a stack according to the installation of a flow mixer according to the present invention,
FIG. 12 is a view showing a speed contour of a cross-section of a center axis of a stack according to the installation of a flow mixer according to the present invention,
FIG. 13 is a view showing a speed contour in each section of the stack height according to the installation of the flow mixer according to the present invention,
FIG. 14 is a view showing velocity vectors at each cross section of the stack height according to the installation of the flow mixer according to the present invention;
15 is a view showing fluid particle behavior in a stack according to the installation of a flow mixer according to the present invention.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. And it should be interpreted based on the technical ideas throughout the specification taking into consideration that various modifications are made.

In addition, the present invention should not be construed as being limited to the embodiments described below, but should be construed as being within the scope of the scope of the present invention, including the extended scope of interpretation based on the technical content described in the specification.

The flow characteristics and data of the stack according to the uninstalled configuration of the flow mixer in the apparatus for improving the flow uniformity of the stack according to the present invention will be described first and then the flow characteristics and data of the stack according to the installation of the flow mixer will be described .

ANSI N 13.1 (1999), KEPIC NRB 6000 (2010), and ISO 2889 (2007), published from the following description of the present invention, are known technical standards for the design and verification requirements of radioactive material sampling systems The coefficient of variation (COV) disclosed in the description of the present invention can be referred to as a standard deviation / average velocity × 100 (%) with respect to the gas, and is a consideration of the flow angle of the gas.

The present invention relates to a method for monitoring the leakage of particles and radioactive materials in a gas exhausted to the outside of a nuclear power plant, a radioactive waste facility, a nuclear fuel handling building, and a radioactive isotope treatment facility, And a flow mixer as an instrument contributing to the uniformity improvement of the flow of the gas exhausted through the stack together with the wood nozzle.

The apparatus for improving the flow uniformity of a stack according to the present invention will now be described in detail with reference to the accompanying drawings. In FIGS. 1 to 5, the results of analysis for a case where a flow mixer is not installed , And FIGS. 10 to 15 are the results of analysis for a case where a flow mixer is installed.

1 to 5 of a flow mixer non-installation in an apparatus 100 for improving the flow uniformity of a stack according to the present invention will be described below as an embodiment.

As the specification of the stack 110, the height of the stack is 15.45 m, the bottom diameter is 2.8 m, the outlet (O) diameter is 2.5 m, and the position of the breech duct 120 is 3.750 m from the bottom of the stack 110 The fluid used as the medium is air and has a density of 1.21 kg / m &lt; 3 &gt; and a specific heat of static pressure of 1.004 kJ / cm &lt; 3 &gt; to examine the flow analysis and the result of the stack 110 based on the stack 110 specifications. / kg.K, the viscosity is 1.789E-5 kg / ms, the turbulence model is K-ε (2 equation model, standard wall function) and the inlet velocity is 12 m / s (turbulence intensity 5% Is 10% of the inlet diameter), inlet temperature is 298K, wall surface condition is surface temperature is adiabatic condition, outlet condition is ∂P / ∂Xj = 0 and operating condition pressure is 1.013 bar.

Based on the above-described conditions, the flow analysis is performed to examine the velocity distribution characteristics in the stack 110, and to determine the nozzle installation position, and the basis for judging this is provided.

In reviewing the velocity distribution characteristics in the stack based on FIGS. 1 to 5 and selecting the nozzle mounting position, the velocity distribution in the XZ cross section in the stack 110 shows that the majority of the fluid flows from the opposite side of the inlet I It can be seen that there is a recirculation flow from above the connecting portion of the brick duct 120. In this case,

Referring to Tables 2 and 3 and FIGS. 1 to 5, which summarize the results of the flow analysis for each stack 110 position obtained using the above results, the length of the stack 110 (COV) value exceeds the allowable reference value due to a recirculating flow which is large enough to correspond to the flow field inside the stack 110 due to the fact that the COV is not sufficiently long, Apply a flow mixer as a solution.

The mean velocity and coefficient of variation (COV) of the stack cross section according to the position of the stack Location (m) * Average speed (m / sec) Standard Deviation COV (%) 7 12.16 6.71 55.18 8 12.17 6.59 54.14 9 11.35 5.885 51.85 10 11.33 4.13 36.45 11 11.31 3.01 27.31 12 11.68 3.31 29.08 13 11.87 3.42 28.8 14 11.83 3.09 26.1 Review comments Not suitable for ANSI N13.1 Technical Standard (COV ≤ 20%)

*: The reference position is set to the position Zero (0) at the bottom of the stack.

Location (m) * Average speed (m / sec) Standard Deviation COV (%) 11.1 11.37 2.95 25.94 11.2 11.36 2.96 26.05 11.3 11.48 2.98 25.95 11.4 11.51 2.99 25.97 11.5 11.51 3.09 26.84 11.6 11.48 3.13 27.26 11.7 11.60 3.17 28.66 11.8 11.65 3.21 27.63 11.9 11.69 3.26 27.88 Review comments Not suitable for ANSI N13.1 Technical Standard (COV ≤ 20%)

*: The reference position is set to the position Zero (0) at the bottom of the stack.

6 to 15 for the installation of the flow mixer 140 in the stack 110 according to the present invention will be described below with reference to an embodiment.

In the fluid flow characteristics in the state where the flow mixer 140 in the stack 110 is installed, the same computational fluid analysis technique as that described above is applied, and the analysis results for the installation of the flow mixer 140 are as follows.

The specifications of the applicable flow mixer 140 can be found in Table 4 below. That is, the flow mixer 140 may be installed at a height of 1.5 m at the floor height of the flow mixer 140 at the inlet center (3.75 m) of the stack 110. 10 and 15, it is preferable that the flow mixer 140 is installed at a height of 5.25 m from the bottom surface of the stack 110 to the outlet O direction.

The blade 142, which will be described later in the flow mixer 140, can be defined as 750 mm wide and 700 mm high in the direction of the center O of the outlet 110 of the stack 110, 110 may have a slightly convex shape in the direction of the exit (O) of the substrate 110, and the thickness may be 5 mm.

Height 700 mm Inside diameter of flow surface 1,000 mm Outer diameter 2,500 mm Inner Blade Thickness 5 mm Radial length of inner blade 750 mm Internal blade tilt angle 25 degree In-stack flow mixer installation location Installed so that the floor of the flow mixer is fixed at a height of 1.5m at the intersection where the breach circular duct meets the stack.

The analysis result obtained when the flow mixer 140 of the drawing is installed at a height of 1.5 m at the intersection point (ie, 5.25 m height at the bottom of the stack) where the internal bleed duct 120 of the stack 110 and the stack 110 meet, From the results of the following drawings, the stack 110 having the flow mixer 140 satisfies the acceptance criterion of ANSI N13.1 which describes the technical requirements, and based on the analysis result, the flow mixer installation Was determined.

Here, the results of the coefficient of variation (COV) after deducing the average speed and the standard deviation of each cross section according to the height of the stack 110 can be referred to Tables 5 and 6 below.

The average flow velocity and standard deviation of the stack cross-section according to the position interval of the stack Location (m) Average speed (m / sec) Standard Deviation COV (%) 8 12.79 4.11 32.1 9 12.58 3.39 26.9 10 12.23 2.73 22.3 11 11.95 2.42 20.2 12 12.78 2.34 18.3 13 12.59 2.30 18.3 14 12.46 2.20 17.8 15 12.33 2.10 17.0

It is preferable that the position of the shroud nozzle 130 is located at 12 to 13 m from the bottom portion in the direction of the inlet I of the stack 110 to the height in the direction of the outlet O in the computerized analysis.

Location (m) Average speed (m / sec) Standard Deviation COV (%) 12.1 12.78 2.34 18.3 12.2 12.78 2.34 18.3 12.3 12.74 2.33 18.3 12.4 12.73 2.32 18.2 12.5 12.69 2.32 18.3 12.6 12.69 2.32 18.3 12.7 12.69 2.32 18.3 12.8 12.63 2.31 18.3 12.9 12.59 2.30 18.3

As a result, the installation position of the shroud nozzle 130 can be set to 12.3 m from the bottom surface of the stack 110 to the height in the direction of the exit (O).

This value indicates that the coefficient of variation (COV) of the velocity distribution satisfies 20% or less of the reference value. If the flow mixer 140 determines that the coefficient of variation (COV) of the installation position and velocity distribution of the shroud nozzle 130 is 20 % Of the total amount of the product.

As a result of studying the flow angle inside the stack 110 as a flow angle problem, it is found that the axial velocity component of the stack 110 is higher than the radial velocity component or the center velocity component of the circle (C) 130) at the installation site of 12.3m, the value of the flow angle was examined and the value satisfied the allowance criterion

The flow angle (average value) of the cross section of each stack height, X-Z Plane Location (m) * Vz (m / sec), avg Flow angle (degree, °) 12.3 12.7 14.9 Review comments Suitable for ANSI N13.1 technical standards (flow angle ≤ 20 °)

*: The reference position is set to the position Zero (0) at the bottom of the stack.

The flow angle (average value) of the cross section according to the stack height, the Y-Z plane Location (m) * Vz (m / sec), avg Flow angle (degree, °) 12.3 12.7 14.9 Review comments Suitable for ANSI N13.1 technical standards (flow angle ≤ 20 °)

*: The reference position is set to the position Zero (0) at the bottom of the stack.

Based on the above results, it is preferable to determine the shape of the flow mixer 140 having the inlet I at one side of the stack 110 and satisfying the design requirements of the stack 110 vertically connected to the stack 110.

6 to 8, the flow mixer 140 includes a ring member 141 coupled to an inner wall of a pipe of the stack 110 when installed in the stack 110, The blade 142 includes a plurality of blades 142 that are formed while maintaining a constant gap between the inner wall and the inner wall of the inner wall 142. The slope 142a, which is the boundary of the blade 142 formed from the ring member 141, And has a convex shape in the direction of the exit (O) of the stack 110 by being inclined at an angle of at most 25 degrees.

Also, the flow mixer may be made of a single body using at least one of metal, ceramic, resin and FRP as a material thereof.

In addition, as a shroud nozzle 130 installation requirement, the axis of the stack 110, as verified in the mid-2/3 section A1 based on the inner cross-sectional area A of the stack or circular duct within 30 cm of the nozzle inlet, A plurality of blades 142 are preferably inclined at an inclination angle of 5 to 25 degrees in the direction of the stack 110 and extend in the radial direction of the stack 110 toward a center point C of the axis, They are not connected to the center point C, so that they have independent shapes without being constrained to each other.

If the flow uniformity and the flow angle of the fluid in the stack 110 (or duct) through which the gas exhausted to the outside of the nuclear facility passes do not meet the acceptance criterion, then through Figures 10-15 and Tables 7 through 8 As can be seen, a plurality of blades 142 installed at a specific position of the stack (or circular duct) 110 in the radial direction of the stack 110 toward the center of the axis have a curvature The exhaust gas passing through the inside of the stack 110 passes through the flow mixer 140 so that both the velocity distribution coefficient of variation (COV) and the flow angle proposed in the technical standard described above satisfy both of the allowable reference values .

When the flow mixer 140 is installed in the stack 110 as described above, the flow mixer 140 is installed at the front end of the sample collection and extends from the inner wall surface of the stack 110 toward the center point C, Due to the shape of the plurality of blades 142 having the shape, the fluid of the exhaust gas passing through the flow mixer 140 is prevented from developing the recirculating flow and naturally the flow path is changed, so that the shroud nozzle 30 cm in front Sectional area A 1 of the inner wall of the stack 110, the effect of reducing the uniformity of the velocity distribution of the fluid and the flow angle at the center 2/3 cross-sectional area A 1 can be provided.

The flow mixer 140 is configured to mix the recirculation flow generated at a specific portion of the stack (or the circular duct) with the fluid flowing between the blades 142 installed at an angle of 5 to 25 degrees As a result, the coefficient of variation (COV) and the flow angle of the fluid velocity are within ± 20% of the allowable value of the technical standard and within ± 20 ° of the flow angle, respectively. The condition can be satisfied.

Also, the flow mixer 140 may be adjusted so as to satisfy the mounting position tolerance standard of the shroud nozzle 130 used for sampling the representative sample of the discharged air as shown in the figure. For this purpose, the length, direction, installation angle and position of the inlet (I) of the blade 142 of the flow mixer 140 can be considered.

As described above, according to the present invention, by utilizing the data obtained through the fluid analysis using computer simulation or the data obtained through the field experiment, the information such as the speed distribution COV and the flow angle of the fluid in the stack or the circular duct can be utilized, A flow mixer may be installed at a front end of the nozzle together with a shroud nozzle provided for sampling the sample in the flow pattern to satisfy a sampling requirement of the sample.

In addition, the present invention is a device installed at the front end of the shroud and having a constant angle in the axial direction. As the fluid passes through the blade (blade) of the device, the velocity distribution and flow And the angle was improved. In other words, the COV and the flow angle of the fluid velocity at the center 2/3 of the stack (or circular duct) can satisfy the conditions within ± 20% and ± 20%, respectively.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of example, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

110: Stack 120: Breech duct
130: shroud nozzle
140: Flow mixer
141: ring member 142: blade
142a:
A: Stack bore cross sectional area A1: Stack center 2/3 Cross sectional area
C: Axis center point O: Exit, I: Entrance

Claims (6)

delete delete delete A flow mixer disposed upstream of the sample sampling shroud nozzle and having a flow mixing function so as to eliminate the flow failure recirculation zone within the stack (or duct) while not affecting flow uniformity at the nozzle installation location, The mixer includes a ring member fixed along the inner wall of the stack; A blade extending from the inner circumferential surface of the ring member or the inner wall of the stack tube toward the central axis of the tube while being connected at one end thereof, Wherein the flow mixer adjusts the blade length of the flow mixer, the inclination (clockwise or counterclockwise) direction of the flow mixer, and the installation angle of the blades so as to satisfy a tolerance standard for the mounting position of the shroud nozzle installed for sampling the sample The flow uniformity and the flow angle of the fluid are within the allowable reference value, the velocity variation coefficient (COV) of the fluid is within ± 20%, and the flow angle tolerance standard is within ± 20 °; The plurality of blades are shaped to be inclined at an oblique angle of 5 to 25 degrees with respect to the shape of the stack so as to face upward in the central axis length of the stack so as to satisfy the velocity variation coefficient of the fluid and the flow angle tolerance standard, The other side ends of which extend toward the center of the shaft but are not connected to each other up to the central axis of the stack,
Characterized in that the flow mixer is installed at a height of 1.5 m at the intersection of the stack of brecc ducts within the stack and the shroud nozzle is located at a distance of 12.3 m from the bottom of the stack to the height in the direction of the outlet. Gender improvement device. 5. The method of claim 4,
Wherein the flow mixer is divided into at least one blade and a segment comprising the ring member, wherein the flow mixer is assembled into one annular shape after fabrication. 5. The method of claim 4,
Wherein the material of the flow mixer is one body made of at least one of metal, ceramic, resin, and FRP.

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