CN117034796A - Method and system for correcting sampling volume in narrow space - Google Patents
Method and system for correcting sampling volume in narrow space Download PDFInfo
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- CN117034796A CN117034796A CN202310856150.1A CN202310856150A CN117034796A CN 117034796 A CN117034796 A CN 117034796A CN 202310856150 A CN202310856150 A CN 202310856150A CN 117034796 A CN117034796 A CN 117034796A
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- 238000000034 method Methods 0.000 title claims abstract description 27
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- 238000012937 correction Methods 0.000 claims abstract description 27
- 238000012216 screening Methods 0.000 claims abstract description 10
- 238000004364 calculation method Methods 0.000 claims description 15
- 238000009423 ventilation Methods 0.000 claims description 3
- 238000012795 verification Methods 0.000 abstract description 3
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Abstract
The invention relates to a method for correcting a sampling volume in a narrow space, which comprises the following steps: establishing a standard cube model, and performing flow field and concentration simulation; basic information of a place to be simulated is collected, and a standard sampling volume is calculated; establishing a physical model based on an actual place, respectively simulating flow field characteristics in the actual place by adopting different CFD modes, and screening; performing concentration simulation based on actual places by using the screened CFD mode; recommending a sampling position according to a concentration simulation result, adding a sampling device in an original simulation place, and performing numerical simulation on the sampling device; the invention also relates to a small space sampling volume correction system, which adopts a small space sampling volume correction method and system, and comprises multi-angle verification in the implementation process to ensure the effectiveness of the correction coefficient.
Description
Technical Field
The invention belongs to the technical field of environmental monitoring under nuclear accident emergency conditions, and particularly relates to a method and a system for correcting a sampling volume of a narrow space.
Background
Nuclear facility workplaces belong to relatively narrow semi-enclosed spaces, and in order to ensure personnel health and environmental safety, on-site radionuclides need to be periodically sampled and monitored, and the radioactivity level in the place is analyzed. The sampling time length determines the sampling efficiency and the effectiveness thereof, if the sampling time length is too short, the gas in the place cannot be fully collected, and the continuous unlimited sampling can cause repeated collection of the air sample, so that the overestimation of the sample volume is caused, the accuracy of the monitoring result is affected, and therefore, the research on the nuclide sampling volume in a narrow space is necessary to be carried out, and the accuracy and the reliability of the analysis result are ensured.
Therefore, it is necessary to perform a preliminary simulation of the sampling of the radionuclides at the workplace by means of numerical simulation and to establish a set of sampling volume correction methods for providing an effective sampling volume to improve the sampling efficiency and the sampling accuracy. The method provides basis for the related research work of radiation protection, and particularly for solving the monitoring and evaluation work of the radionuclide intake of the current professionals.
In actual sampling, the time required for collecting all gases in a place can be calculated according to the sampling flow and the place volume, but the sampling of an air stagnation area in the place is insufficient due to the influence of the difference of place characteristics and aerodynamic conditions.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a small space sampling volume correction method and a system, which ensure the effectiveness of correction coefficients by including multi-angle verification in the implementation process so as to improve the sampling efficiency and the sampling accuracy.
In order to achieve the above purpose, the invention adopts the technical scheme that: a method for correcting the sampling volume of a narrow space comprises the following steps: establishing a standard cube model, performing flow field and concentration simulation, and comparing a numerical calculation result with corresponding experimental data; basic information of a place to be simulated is collected, and a standard sampling volume is calculated according to the basic information; establishing a physical model based on an actual place, adopting different CFD modes to simulate flow field characteristics in the actual place, and screening the CFD modes; setting initial boundary conditions according to site characteristic parameters by using the screened CFD mode, and then performing concentration simulation based on actual sites; recommending a sampling position according to a concentration simulation result, adding a sampling device in an original simulation place according to the sampling position, and performing numerical simulation on the sampling device; and calculating the actual sampling volume according to the change rule of the concentration at the inlet of the sampling device in the numerical simulation so as to calculate the correction coefficient of the sampling volume by using the actual sampling volume and the standard sampling volume.
Further, the basic information includes model features and their geometry, ambient temperature, ambient pressure, site boundary features, ventilation, leak location and release, average flow of the sampler, sampling temperature, and sampling air pressure.
Further, the calculation formula of the standard sampling volume is as follows:
wherein V is 0 The air sampling volume under the standard condition is F is the air sampling instantaneous flow, T is the sampling time length and T is 0 Is the temperature under standard conditions, P 0 Is the air pressure under the standard condition,for instantaneous sampling temperature, +.>For instantaneous sampling of the air pressure.
Further, the physical model and the boundary condition in the CFD mode are set to be the same, and the grid precision is similar.
Further, the CFD pattern is screened as follows: and comparing flow field results of the same example obtained by simulating different modes, and selecting a mode with a simulation result more conforming to actual characteristics.
Further, the sampling device inlet is provided with a focus point, and the change rule of the concentration at the sampling device inlet along with time is reflected through the change rule of the concentration at the focus point along with time.
Further, the correlation of the concentration with time in the law of variation of the concentration with time is analyzed by using variance.
Further, the variance calculation method of the concentration and time is as follows:
wherein t is the sampling duration, X i The sampling concentration at time i.
Further, after recommending the sampling position, the method further comprises: and analyzing the concentration ratio of the attention points of different concentration areas, comparing the concentration ratio with the concentration ratio obtained by actual sampling, and verifying the effectiveness of the simulation of the flow field and the concentration distribution characteristics of the place.
The invention also provides a system for correcting the sampling volume of a narrow space, which comprises: the standard building unit is used for building a standard cube model, simulating a flow field and concentration, and comparing a numerical value calculation result with corresponding experimental data; the collecting unit is used for collecting basic information of a place to be simulated and calculating a standard sampling volume according to the basic information; the screening unit is used for establishing a physical model based on an actual place, adopting different CFD modes to simulate flow field characteristics in the actual place and screening the CFD modes; the concentration simulation unit is used for performing concentration simulation based on an actual place after setting initial boundary conditions according to place characteristic parameters by using the screened CFD mode; the recommending unit is used for recommending a sampling position according to the concentration simulation result, adding a sampling device in the original simulation place according to the sampling position and carrying out numerical simulation on the sampling device; and the correction unit is used for calculating the actual sampling volume according to the change rule of the concentration at the inlet of the sampling device in the numerical simulation along with time so as to calculate the correction coefficient of the sampling volume by utilizing the actual sampling volume and the standard sampling volume.
The invention has the following effects: in the implementation process, multi-angle verification is included to ensure the effectiveness of correction coefficients, specifically, a standard cube model is established, flow field and concentration simulation are carried out, and the flow field and concentration simulation is compared with experimental results to verify the effectiveness of numerical simulation means, different CFD modes are adopted to carry out flow field simulation aiming at the same physical model, boundary conditions and similar grid precision, a mode that simulation results more accord with actual characteristics is selected to carry out further simulation, concentration ratios of concentration points in different concentration areas are examined, and the concentration ratios obtained by actual sampling are compared to verify the effectiveness of flow field and concentration distribution characteristic simulation in an actual place.
Drawings
FIG. 1 is a flow chart of steps of a method for correcting a sampling volume in a small space according to the present invention.
Detailed Description
The invention is further described below with reference to the drawings and detailed description.
As shown in fig. 1, the invention provides a method for correcting a sampling volume of a narrow space, which comprises the following steps:
s1, a standard cube model is established, flow field and concentration simulation is carried out, and a numerical calculation result is compared with corresponding experimental data;
specifically, a standard cube model is established, flow field and concentration simulation is carried out by using a CFD (computational fluid dynamics) means, a numerical calculation result is compared with corresponding experimental data, and the effectiveness and feasibility of the numerical simulation means are verified.
S2, basic information of a place to be simulated is collected, and a standard sampling volume is calculated according to the basic information;
specifically, basic information of a place to be simulated is collected, including model features and geometric dimensions thereof, ambient temperature, ambient pressure, place boundary features such as doors, ventilation devices and the like, leakage positions and release amounts, average flow rate, sampling temperature, sampling air pressure and the like of a sampler, and initial boundary conditions are determined.
Calculating the sampling volume under the standard condition according to the acquired flow, sampling temperature and sampling air pressure of the sampler, and calculating a standard sampling volume calculation formula:
wherein V is 0 The air sampling volume under the standard condition is F is the air sampling instantaneous flow, T is the sampling time length and T is 0 Is the temperature under standard conditions, P 0 Is the air pressure under the standard condition,for instantaneous sampling temperature, +.>For instantaneous sampling of the air pressure.
S3, establishing a physical model based on an actual place, adopting different CFD modes to simulate flow field characteristics in the actual place, and screening the CFD modes;
specifically, a physical model based on an actual place is established, different CFD modes are adopted to simulate flow field characteristics in the actual place, and flow field simulation results are compared. Wherein, the physical models and boundary condition settings in different CFD modes are the same, and the grid precision is similar. And comparing flow field results of the same example obtained by simulating different modes, and selecting a mode with a simulation result more in line with actual characteristics to perform further simulation.
S4, setting initial boundary conditions according to the site characteristic parameters by using the screened CFD mode, and then performing concentration simulation based on actual sites;
specifically, an initial boundary condition is set according to the characteristic parameters of the places by using the screened CFD mode, the leakage position and the release amount are considered, the concentration simulation based on the actual places is further developed, and the flow field characteristics and the nuclide diffusion rules of the CFD mode are researched.
S5, recommending a sampling position according to a concentration simulation result, adding a sampling device in an original simulation place according to the sampling position, and performing numerical simulation on the sampling device;
specifically, according to the flow field and the concentration simulation result in the actual scene, the nuclide distribution characteristics and the different concentration areas of the distribution are analyzed, the sampling positions are recommended, and sampling points are respectively established in the high, medium and low different concentration areas.
And adding a sampling device on the basis of the original place model according to the recommended sampling point positions, and further carrying out numerical simulation aiming at the sampling device. And respectively establishing sampling device models in the high, medium and low concentration areas, combining the site boundary conditions and the initial conditions of the sampling devices, and performing transient calculation to simulate the flow field and concentration distribution characteristics under the sampling devices.
S6, calculating the actual sampling volume according to the change rule of the concentration at the inlet of the sampling device in numerical simulation along with time so as to calculate the correction coefficient of the sampling volume by utilizing the actual sampling volume and the standard sampling volume;
specifically, a focus point is set at each sampling device inlet, and the time-dependent change rule of the concentration at the sampling port is focused, namely, the time-dependent change rule of the concentration at the sampling device inlet is reflected through the time-dependent change rule of the concentration at the focus point. Using the correlation of the analysis of variance concentration with time, when t i When the variance results in 0 or approximately 0, then t is considered to be i The sampling concentration after the moment has correlation with the sampling time, and the sampling time length is determined as t i 。
The variance calculation method of time and concentration is as follows:
wherein t is the sampling duration, X i The sampling concentration at time i.
According to the sampling time t i And calculating the actual sampling volume V by the instantaneous flow F of the sampler, and further taking the ratio of the sampling volume V_0 under the standard condition to the sampling volume V obtained by analog calculation as a correction coefficient of the sampling volume.
Further, after recommending the sampling position in step S5, the method further includes the steps of:
s51, analyzing concentration ratios of the attention points of different concentration areas, comparing the concentration ratios with the concentration ratios obtained by actual sampling, and verifying the effectiveness of the simulation of the flow field and the concentration distribution characteristics of the place.
The invention also provides a system for correcting the sampling volume of a narrow space, which comprises:
the standard building unit is used for building a standard cube model, simulating a flow field and concentration, and comparing a numerical value calculation result with corresponding experimental data;
the collecting unit is used for collecting basic information of a place to be simulated and calculating a standard sampling volume according to the basic information;
the screening unit is used for establishing a physical model based on an actual place, adopting different CFD modes to simulate flow field characteristics in the actual place and screening the CFD modes;
the concentration simulation unit is used for performing concentration simulation based on an actual place after setting initial boundary conditions according to place characteristic parameters by using the screened CFD mode;
the recommending unit is used for recommending a sampling position according to the concentration simulation result, adding a sampling device in the original simulation place according to the sampling position and carrying out numerical simulation on the sampling device;
and the correction unit is used for calculating the actual sampling volume according to the change rule of the concentration at the inlet of the sampling device in the numerical simulation along with time so as to calculate the correction coefficient of the sampling volume by utilizing the actual sampling volume and the standard sampling volume.
According to the embodiment, the method comprises the steps of verifying at multiple angles in the implementation process to ensure the effectiveness of correction coefficients, specifically, establishing a standard cube model, developing flow field and concentration simulation, comparing the flow field and concentration simulation with experimental results to verify the effectiveness of numerical simulation means, adopting different CFD modes, developing flow field simulation aiming at the same physical model, boundary conditions and similar grid precision, developing further simulation by selecting a mode with simulation results more conforming to actual characteristics, examining concentration ratios of points of interest in different concentration areas, and comparing the concentration ratios obtained by actual sampling to verify the effectiveness of flow field and concentration distribution characteristic simulation of an actual place.
The embodiments of the present invention are not limited to the embodiments described in the specific embodiments, and those skilled in the art may obtain other embodiments according to the technical solutions of the present invention, which also belong to the technical innovation scope of the present invention.
Claims (10)
1. A method for correcting a sampling volume in a small space, comprising:
establishing a standard cube model, performing flow field and concentration simulation, and comparing a numerical calculation result with corresponding experimental data;
basic information of a place to be simulated is collected, and a standard sampling volume is calculated according to the basic information;
establishing a physical model based on an actual place, adopting different CFD modes to simulate flow field characteristics in the actual place, and screening the CFD modes;
setting initial boundary conditions according to site characteristic parameters by using the screened CFD mode, and then performing concentration simulation based on actual sites;
recommending a sampling position according to a concentration simulation result, adding a sampling device in an original simulation place according to the sampling position, and performing numerical simulation on the sampling device;
and calculating the actual sampling volume according to the change rule of the concentration at the inlet of the sampling device in the numerical simulation so as to calculate the correction coefficient of the sampling volume by using the actual sampling volume and the standard sampling volume.
2. The small space sampling volume correction method as claimed in claim 1, wherein:
the basic information comprises model characteristics and geometric dimensions thereof, ambient temperature, ambient pressure, site boundary characteristics, ventilation devices, leakage positions and release amounts, average flow of a sampler, sampling temperature and sampling air pressure.
3. The small space sampling volume correction method as claimed in claim 2, wherein:
the calculation formula of the standard sampling volume is as follows:
wherein V is 0 The air sampling volume under the standard condition is F is the air sampling instantaneous flow, T is the sampling time length and T is 0 Is the temperature under standard conditions, P 0 Is the air pressure under the standard condition,for instantaneous sampling temperature, +.>For instantaneous sampling of the air pressure.
4. The small space sampling volume correction method as claimed in claim 1, wherein:
the physical model and boundary condition settings in the CFD mode are the same, and the grid precision is similar.
5. The small space sampling volume correction method as claimed in claim 1, wherein:
the CFD pattern is screened as follows: and comparing flow field results of the same example obtained by simulating different modes, and selecting a mode with a simulation result more conforming to actual characteristics.
6. The small space sampling volume correction method as claimed in claim 1, wherein:
and the sampling device inlet is provided with a focus point, and the change rule of the concentration at the sampling device inlet along with time is reflected by the change rule of the concentration at the focus point along with time.
7. The small space sampling volume correction method as claimed in claim 6, wherein:
and analyzing the correlation of the concentration and time in the change rule of the concentration with time by using variance.
8. The small space sampling volume correction method as claimed in claim 7, wherein:
the variance calculation method of the concentration and the time comprises the following steps:
wherein t is the sampling duration, X i Time iIs a sampling concentration of (a).
9. The small space sampling volume correction method as claimed in claim 1, further comprising, after said recommending the sampling position:
and analyzing the concentration ratio of the attention points of different concentration areas, comparing the concentration ratio with the concentration ratio obtained by actual sampling, and verifying the effectiveness of the simulation of the flow field and the concentration distribution characteristics of the place.
10. A small space sampling volume correction system, comprising:
the standard building unit is used for building a standard cube model, simulating a flow field and concentration, and comparing a numerical value calculation result with corresponding experimental data;
the collecting unit is used for collecting basic information of a place to be simulated and calculating a standard sampling volume according to the basic information;
the screening unit is used for establishing a physical model based on an actual place, adopting different CFD modes to simulate flow field characteristics in the actual place and screening the CFD modes;
the concentration simulation unit is used for performing concentration simulation based on an actual place after setting initial boundary conditions according to place characteristic parameters by using the screened CFD mode;
the recommending unit is used for recommending a sampling position according to the concentration simulation result, adding a sampling device in the original simulation place according to the sampling position and carrying out numerical simulation on the sampling device;
and the correction unit is used for calculating the actual sampling volume according to the change rule of the concentration at the inlet of the sampling device in the numerical simulation along with time so as to calculate the correction coefficient of the sampling volume by utilizing the actual sampling volume and the standard sampling volume.
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