CN113358174A - Space free volume measuring method - Google Patents
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- CN113358174A CN113358174A CN202110539277.1A CN202110539277A CN113358174A CN 113358174 A CN113358174 A CN 113358174A CN 202110539277 A CN202110539277 A CN 202110539277A CN 113358174 A CN113358174 A CN 113358174A
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- 238000000034 method Methods 0.000 title claims abstract description 37
- 239000000700 radioactive tracer Substances 0.000 claims abstract description 133
- 238000002347 injection Methods 0.000 claims abstract description 81
- 239000007924 injection Substances 0.000 claims abstract description 81
- 238000005070 sampling Methods 0.000 claims abstract description 59
- 238000009792 diffusion process Methods 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 9
- 238000004364 calculation method Methods 0.000 claims description 7
- 238000005259 measurement Methods 0.000 abstract description 24
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- 229910018503 SF6 Inorganic materials 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 description 5
- 229960000909 sulfur hexafluoride Drugs 0.000 description 5
- 238000004868 gas analysis Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000009423 ventilation Methods 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- 230000007547 defect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F17/00—Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies
Abstract
The invention relates to the technical field of space free volume measurement, in particular to a space free volume measurement method, which comprises the following steps: step one, enabling a pressure boundary of a space to be measured to be in a sealed state, and measuring the background concentration C of tracer gas in the space to be measured0(ii) a Step two, according to the determined injection concentration C of the tracer gasinInjection flow rate qinAnd injection time tinInjecting tracer gas into the space to be detected; step three, according to the determined sampling interval time tsContinuously sampling for multiple times, analyzing the concentration of the tracer gas in the sample, confirming that the diffusion of the tracer gas in the space to be detected meets the mixing uniformity condition for the first time, and sampling at intervals of time tsContinuously sampling for at least ten times; step four, establishing a trace gas average concentration increase curve according to the trace gas concentrations and the sampling time of all samples and obtaining the trace gas average concentration in the space to be measured
Step five, calculating to-be-detectedFree volume V of spacei：
The method has the advantages of high accuracy, strong operability and good applicability.
Description
Technical Field
The invention relates to the technical field of space free volume measurement, in particular to a space free volume measurement method.
Background
In production and scientific research work, the problem that space free volume measurement is needed exists, for example, in the residence test of a nuclear power station main control room, in order to ensure that working personnel of the main control room are prevented from being damaged by ultra-safe dose radiation and other toxic and harmful substances under the accident condition, the space free volume needs to be accurately measured to calculate the leakage amount.
For the measurement of free volume, there are currently used methods such as geometric measurement, volume comparison, flowmeter measurement, weighing measurement, gas calibration, and the like. The geometric measurement method is to directly measure the actual size by measuring tools such as three-coordinate measuring tools and the like, and calculate the free volume according to the measured size; the volume comparison method is to directly measure other volumes by using a standard volume to determine the free volume of a measured space; the flow meter measuring method is that the measured space is filled with liquid, and the flow meter time of the flow meter is recorded to calculate the volume of the measured space; the weighing measurement method comprises the steps of measuring the weight of a measured object, filling liquid with known density into the measured object, and confirming the increment of mass to calculate the free volume; the gas calibration method is to inject gas into a measured container through a standard container, and to calculate the free volume of a measured space by measuring the pressure and temperature change conditions of the standard container and the measured container.
In the geometric measurement method, for a space with a complex internal structure, practical operation is difficult, and accuracy is greatly influenced. The three methods of volume comparison, flowmeter and weighing are characterized in that the injected medium is liquid, which easily affects the performance of the internal components of the space, and when the internal structure of the object to be measured is complex, the liquid is difficult to fill the whole space, so the three methods have great limitations. The medium of the gas calibration method is gas, but the space measured by the method must be ensured to be completely closed and is limited by a standard container, and the volume of the measured space is relatively small.
Disclosure of Invention
The invention aims to provide a space free volume measuring method with high accuracy, strong operability and good applicability, so as to overcome the defects in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme: a method for measuring free volume in space sequentially comprises the following steps: step one, enabling a pressure boundary of a space to be measured to be in a sealed state, and measuring the background concentration C of tracer gas in the space to be measured0(ii) a Step two, according to the determined injection concentration C of the tracer gasinInjection flow rate qinAnd injection time tinInjecting tracer gas into the space to be detected; step three, setting a plurality of sampling points in the space to be measured according to the determined sampling interval time tsContinuously sampling for multiple times, analyzing the concentration of the tracer gas of the obtained sample, and after confirming that the diffusion of the tracer gas in the space to be measured meets the mixing uniformity condition for the first time in the sampling process, sampling at an interval time tsContinuously sampling for at least ten times; step four, establishing a trace gas average concentration increase curve according to the trace gas concentrations and the sampling time of all samples and obtaining the trace gas average concentration in the space to be measured
Step five, calculating the free volume V of the space to be measurediThe calculation formula is as follows:
preferably, in step one, the air exchange rate of the space to be measured is estimated as AmDetermining the phase time control reference as TmAnd satisfies the following conditions: t ism<0.1/Am。
Preferably, in step two, the tracer gas injection time is determined to be tinAnd satisfies the following conditions: t is tin<0.1Tm(ii) a Determination of tracer gas injection concentration CinA trace gas concentration provided for a selected trace gas source; determining the injection flow rate q of the tracer gasinAnd satisfies the following conditions: q. q.sin×Cin×tin＝＝Ct×VmIn the formula, CtFor the target concentration, V, of the tracer gas in the space to be measuredmIs the estimated value of the free volume of the space to be measured.
Preferably, in the second step, when the tracer gas is injected into the space to be measured, the tracer gas is mixed in the space to be measured for a determined mixing time t by a mixing device arranged in the space to be measuredmixThe diffusion is uniform.
Preferably, the mixing time tmixSatisfies the following conditions: t is tmix<0.2Tm。
Preferably, in step three, the sampling interval time tsSatisfies the following conditions: t is ts<0.2Tm。
Preferably, in step three, the mixing uniformity condition is that the sample tracer gas concentration at each set sampling point does not deviate more than 5% from the average value of the sample tracer gas concentrations at all set sampling points.
Preferably, in the second step, a return air duct communicated with the space to be measured is arranged outside the space to be measured, and the outlet of the trace gas source is connected to the return air duct through a single injection duct.
Preferably, in the second step, a plurality of injection points are arranged in the space to be measured, and the outlet of the tracer gas source is connected to the plurality of injection points through a plurality of injection pipelines.
Compared with the prior art, the invention has the remarkable progress that:
the space free volume measuring method provided by the invention has the advantages that the free volume of the space to be measured can be obtained by injecting quantitative tracer gas into the space to be measured and then analyzing the average concentration of the tracer gas after diffusion and mixing in the space to be measured through sampling according to the concentration, flow and time of the tracer gas injection, the background concentration of the tracer gas in the space to be measured and the average concentration of the tracer gas in the space to be measured after the tracer gas injection, the problems of large difficulty in free volume measurement and poor precision caused by complex structure and more contents of the space to be measured can be solved, and the space free volume measuring method has the advantages of high accuracy, strong operability and good applicability.
Drawings
FIG. 1 is a schematic diagram of an embodiment of a free-space volume measurement method according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of another embodiment of a free-space volume measurement method according to an embodiment of the present invention.
Wherein the reference numerals are as follows:
1 space to be measured
2 tracer gas source
3 mixing device
4 return air pipeline
5 air return fan
6. 61, 62 injection line
7 pressure reducing valve
8. 80, 81, 82 stop valve
9. 91, 92 flow controller
10 flow distributor
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and are not intended to limit the present invention.
In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
As shown in fig. 1 and 2, one embodiment of the spatial free volume measurement method of the present invention. The space free volume measuring method of the embodiment is used for measuring the free volume of the space to be measured 1, and the space to be measured 1 can be any space which needs to be subjected to free volume measurement, such as a large building, a closed container and the like. Specifically, the spatial free volume measurement method of the present embodiment includes the following steps in order.
Step one, enabling a pressure boundary of a space to be measured 1 to be in a sealed state, and measuring the background concentration C of tracer gas in the space to be measured 10. Background concentration C of tracer gas in space 1 to be measured0(unit is m)3/m3) The method can be used for measuring the background concentration of the tracer gas by the conventional tracer gas background concentration measuring instrument after sampling in the space 1 to be measured.
Before the free volume measurement test of the space to be measured 1 is carried out, the tightness of the pressure boundary of the space to be measured 1 needs to be checked, and the pressure boundary of the space to be measured 1 is ensured to be in a sealed state. The pressure boundary of the space refers to the connection boundary of structures such as a boundary door, a boundary penetrating piece, an inlet and an outlet of a ventilating duct and the like. If the pressure boundary of the space to be tested 1 is provided with the opening, the opening needs to be plugged so that the pressure boundary of the space to be tested 1 is in a sealed state, the trace gas injected into the space to be tested 1 in the subsequent test process is prevented from being polluted and diluted, and the accuracy of the test result is ensured.
In this embodiment, the sealing state is not a hundred-percent strict sealing without one-wire leakage, and because in actual operation, the space 1 to be measured may not be guaranteed to be completely sealed because of the reasons of complex space structure, more contents, more pressure boundaries, and the like, preferably, after the pressure boundary of the space 1 to be measured is subjected to sealing inspection and plugging measures, the possible ventilation rate of the space 1 to be measured due to poor sealing can be estimated according to the actual sealing state of the space 1 to be measured, and the estimated ventilation rate of the space 1 to be measured is obtained as am(unit is 1/min) and based on this estimate the measured spatial air exchange rate AmDetermining a phase time control reference as Tm(in min), TmSatisfies the following conditions: t ism<0.1/AmThe phase time controls the reference TmCan provide a determination reference for the time control of each stage when the free volume measurement test of the space 1 to be measured is carried out subsequently.
Step two, according to the determined injection concentration C of the tracer gasinInjection flow rate qinAnd injection time tinAnd injecting tracer gas into the space 1 to be detected.
The tracer gas is provided by a tracer gas source 2, preferably a pressurized gas cylinder being used as tracer gas source 2. The type of the trace gas is not limited, and preferably, the trace gas may be sulfur hexafluoride, and the trace gas source 2 is a sulfur hexafluoride gas source. The concentration of the sulfur hexafluoride tracer gas in the air is extremely low, meanwhile, the sulfur hexafluoride tracer gas is stable in property and is not easy to react with other substances, the influence of error signals on measurement results can be effectively avoided, the measurement precision is high, the average concentration of the tracer gas in the space 1 to be measured is in ppb level, the measurement test can be completed only by a small amount of tracer gas, and the influence on the environment and the safety is small.
Injecting a tracer into the space 1 to be testedThe duration of the gas should not be too long, and preferably the reference T can be controlled according to the phase timemTo determine the trace gas injection time, tin(in min), tinSatisfies the following conditions: t is tin<0.1Tm。
The concentration of the tracer gas injected into the space 1 to be measured is the concentration of the tracer gas provided by the selected tracer gas source 2, namely: determination of tracer gas injection concentration Cin(unit is m)3/m3) The concentration of the tracer gas provided for the selected tracer gas source 2. The concentration of the trace gas provided by the trace gas source 2 can be selected according to actual conditions, and preferably sulfur hexafluoride with the concentration of 1ppm-1000ppm can be mixed in nitrogen.
The flow rate of the tracer gas injected into the space 1 to be measured can be determined according to the principle of conservation of mass of the tracer gas, and the injection flow rate of the tracer gas is determined to be qin(unit is m)3/min)，qinSatisfies the following conditions:
qin×Cin×tin＝＝Ct×Vm
the formula is a mass conservation formula, wherein CtIs the target concentration of the tracer gas in the space 1 to be measured, and the unit is m3/m3Target concentration C of the trace gastCan be determined according to the type of tracer gas analyzer used, preferably the target concentration C of the tracer gastFrom 20ppb to 50 ppb; vmIs an estimate of the free volume of the space 1 to be measured, in m3An estimated value V of the free volume of the space 1 to be measuredmCan be obtained by field drawing or estimation according to the drawing of the space 1 to be measured.
Therefore, before the free volume measurement test of the space 1 to be measured is carried out, the injection concentration C of the tracer gas can be determined according to the actual situationinInjection flow rate qinAnd injection time tinSo that the trace gas injection concentration C can be determined while the test is in progressinInjection flow rate qinAnd injection time tinA quantitative amount of trace gas is injected into the space 1 to be measured.
If the tracer gas can not be fully and uniformly diffused in the space to be measured 1 after being injected into the space to be measured 1, the measurement test result has errors, and therefore when the tracer gas is injected into the space to be measured 1, the tracer gas is preferably enabled to be mixed in the space to be measured 1 according to the determined mixing time t through the mixing device 3 arranged in the space to be measured 1mixThe diffusion is uniform. Mixing arrangement 3 can adopt current air mixing equipment, dispose mixing arrangement 3 in space 1 that awaits measuring, open mixing arrangement 3 when injecting tracer gas into space 1 that awaits measuring, tracer gas's diffusion in space 1 that awaits measuring can be accelerated, reduce the even required time of tracer gas concentration diffusion in space 1 that awaits measuring, reach the purpose of the even mixing time control of sufficient diffusion of tracer gas in space 1 that awaits measuring in short time, it is whole consuming time to shorten the measurement test, and effective control measuring error. For example, for a larger space 1 to be measured (such as an internal space of a large building), if the tracer gas injected into the space is mixed only by an air supply system provided in the space, the sufficient mixing may take 15 minutes to 1 hour, and the time required for the sufficient mixing may be controlled to 5 minutes to 10 minutes by adding the mixing device 3 to enhance the mixing. Preferably, the reference T can be controlled according to the phase timemTo control the mixing time, mixing time tmix(in min) satisfies: t is tmix<0.2Tm。
In addition, in order to ensure uniform diffusion of trace gas in the space 1 to be measured, all doors inside the space 1 to be measured need to be opened, and if a ceiling, a floor or other structures for separating the space exist in the space 1 to be measured, some of the ceiling and the floor need to be opened, so that all the interiors of the space 1 to be measured (within a pressure boundary) are communicated.
Step three, setting a plurality of sampling points in the space 1 to be measured according to the determined sampling interval time tsContinuously sampling for multiple times, analyzing the concentration of the tracer gas of the obtained sample, and after confirming that the diffusion of the tracer gas in the space 1 to be measured meets the mixing uniformity condition for the first time in the sampling process, sampling at intervals of time tsAt least ten sampling runs were continued.
A plurality of set sampling points in the space 1 to be measured can be determined according to the internal structure of the space 1 to be measured, the distribution of the set sampling points is such that a representative sample is obtained by sampling the internal area of the whole space 1 to be measured, for the space 1 to be measured with a structure separating the space such as a ceiling, a floor and the like, the plurality of set sampling points comprise the upper part of the ceiling, the lower part of the floor, the middle part between the ceiling and the floor and the independent sampling points in each independent space, and the number of the set sampling points in the internal area of the whole space 1 to be measured is not less than three. The sampling can be carried out by adopting syringes numbered in advance, the number of each syringe has uniqueness and identifiability, and the information of the sample can be identified according to the number, including the corresponding set sampling point and sampling time. The syringe volume should be at least three times the minimum sample volume of the trace gas analyzer and have good sealing properties to ensure that the sample is not diluted or contaminated. The sampling can be carried out manually by adopting an injector or automatically by adopting a sampling device.
The intervals of the multiple samplings are equal and determined, and the reference T can be controlled according to the phase timemTo determine a sampling interval time, ts(in min) satisfies: t is ts<0.2Tm。
The sample of acquireing passes through the tracer gas analysis appearance and carries out the analysis to sample tracer gas concentration, preferably, before analysis sample tracer gas concentration, debug the tracer gas analysis appearance and make it possess the test condition, can adopt the tracer gas standard gas of at least three kinds of different concentrations to carry out calibration once to the tracer gas analysis appearance, and, in the use, can regularly use tracer gas standard gas to carry out the inspection to tracer gas analysis appearance indicating value drift, if the indicating value drift exceeds 5%, then should revise test sample analysis result according to twice tracer gas standard gas's analysis indicating value around, in order to guarantee to obtain accurate sample tracer gas concentration.
In the sampling process, the diffusion condition of the tracer gas in the space to be measured 1 can be judged according to the concentration of the tracer gas of the sample of each set sampling point measured by analysis, and the concentration is used for formally calculating the space to be measured1 the sample data of the free volume should be the data of the sample satisfying the condition of the mixing uniformity of the tracer gas in the space 1 to be measured, therefore, in the sampling process, after the diffusion of the tracer gas in the space 1 to be measured is firstly confirmed to satisfy the condition of the mixing uniformity, the sampling interval time t is requiredsAnd continuously sampling for at least ten times for formally calculating the free volume of the space 1 to be measured. Preferably, the mixing uniformity condition of the tracer gas diffusing in the space 1 to be measured is as follows: the deviation of the sample tracer gas concentration of each set sampling point relative to the sample tracer gas concentration average value of all set sampling points does not exceed 5%, namely, when the deviation of the sample tracer gas concentration of each set sampling point relative to the sample tracer gas concentration average value of all set sampling points is within 5%, the tracer gas is considered to be fully and uniformly diffused in the space to be measured 1, the measurement data of the sample obtained later can be used for formally calculating the free volume of the space to be measured 1, and the error of the calculation result of the free volume of the space to be measured 1 caused by the non-uniform mixing of the tracer gas in the space to be measured 1 is avoided.
Step four, establishing a tracer gas average concentration increase curve according to the tracer gas concentrations and sampling time of all samples and obtaining the tracer gas average concentration in the space 1 to be measured
The average concentration of tracer gas increases in a short time at the beginning, and then enters an equilibrium stage, wherein the time of the increasing stage before entering the equilibrium stage is about the mixing time tmixThree times that of the original. Preferably, when the free volume of the space 1 to be measured is calculated by using the trace gas average concentration increase curve data, the data before the equilibrium stage is reached in the trace gas average concentration increase curve should be excluded to ensure the accuracy of the calculation result. Average concentration of trace gas in space 1 to be measured
(unit is m)3/m3) May be obtained from data from the equilibrium phase in the trace gas mean concentration increase curve.
Step five, calculating the free volume V of the space 1 to be measurediThe calculation formula is as follows:
in the formula, the injection concentration of trace gas CinInjection flow rate qinAnd injection time tinAverage concentration of trace gas in space 1 to be measured
And the background concentration C of the tracer gas in the space 1 to be measured0The free volume V of the space 1 to be measured, which has been determined and measured by the above-mentioned steps, is calculatediHas the unit of m3。
Further, after the measurement calculation, the uncertainty analysis evaluation can be performed according to the method specified in the standard JJF 1059.1 "measurement uncertainty evaluation and representation". If the measurement calculation is accurately and effectively performed according to the above steps of the space free volume measurement method of the present embodiment, the finally obtained free volume V of the space 1 to be measurediCan be controlled within 10%.
Therefore, the space free volume measuring method of the embodiment injects a quantitative tracer gas into the space to be measured 1, and then analyzes the average concentration of the tracer gas after diffusion and mixing in the space to be measured 1 by sampling, so that the free volume of the space to be measured 1 can be obtained by calculating the background concentration of the tracer gas in the space to be measured 1 and the average concentration of the tracer gas in the space to be measured 1 after injecting the tracer gas, and the problems of large difficulty and poor precision in free volume measurement caused by complicated structure and more content of the space to be measured 1 can be solved, especially the accurate measurement of the free volume of the space to be measured 1 with a complicated ventilation pipeline, which has the advantages of high accuracy, strong operability and good applicability.
In this embodiment, in the second step, the modes of injecting the trace gas into the space 1 to be measured include two modes, namely single-point injection of the return air pipeline and multi-point injection of the network pipeline. As shown in fig. 1 and fig. 2, the mixing device 3 is disposed inside the space to be measured 1, the return air duct 4 communicated with the space to be measured 1 is disposed outside the space to be measured 1, the return air fan 5 is disposed on the return air duct 4, and when the return air fan 5 is turned on, the gas inside the space to be measured 1 can circularly flow through the return air duct 4, so that mixing can be accelerated.
Referring to fig. 1, in one embodiment, the trace gas may be injected into the space 1 to be measured by using a single-point injection manner of a return air duct. The return duct single point injection mode is to connect the outlet of the tracer gas source 2 to the return duct 4 through a single injection duct 6. At this moment, tracer gas single-point is injected into return air duct 4, and return air machine 5 opens, sends into the space 1 that awaits measuring tracer gas through air current distribution, the air return of return air duct 4 stirs to under mixing arrangement 3's combined action in the space 1 that awaits measuring rapid mixing is even. Preferably, the outlet of the tracer gas source 2 may be connected to the inlet of an injection pipe 6 through a pressure reducing valve 7, the outlet of the injection pipe 6 is connected to the return air pipe 4, and a stop valve 8 and a flow controller 9 are sequentially arranged on the injection pipe 6. And (3) opening the tracer gas source 2, the pressure reducing valve 7 and the stop valve 8, and injecting tracer gas into the space to be detected 1. The pressure of the tracer gas fed into the injection line 6 can be adjusted to meet the inlet pressure of the flow controller 9 by means of the pressure reducing valve 7. The flow controller 9 can control the flow of the tracer gas fed into the space 1 to be measured at a determined tracer gas injection flow qin. During the test, can open back fan 5 earlier, start mixing arrangement 3, then open tracer gas source 2, adjust relief pressure valve 7 in order to satisfy 9 inlet pressure of flow controller, open stop valve 8 at last, by the flow controller 9 control flow, with tracer gas with definite injection flow qinInjecting the mixture into a space 1 to be measured; after the injection of the trace gas is completed, closing the stop valve 8, the pressure reducing valve 7 and the trace gas source 2 in sequence; during the process, the time at which the tracer gas starts and ends injection is recorded. Sampling can then begin.
Referring to fig. 2, in another embodiment, a network pipeline multi-point injection mode may be adopted to inject tracers into the space 1 to be measuredA gas. The multi-point injection mode of the network pipeline is to arrange a plurality of injection points in the space 1 to be measured and connect the outlet of the tracer gas source 2 to the plurality of injection points through a plurality of injection pipelines 61 and 62. The plurality of injection points are distributed at different positions in the space 1 to be measured, so that the injected tracer gas can be directly distributed to different positions in the space 1 to be measured through the plurality of injection pipelines 61 and 62, and can be quickly and uniformly mixed in the space 1 to be measured under the combined action of the mixing device 3. At this time, the trace gas is injected in a multi-point dispersion manner to be well diffused, so that the air return fan 5 does not need to be started, but the air return fan 5 can be started if the condition of the actual space to be measured 1 needs to further enhance the diffusion of the trace gas. Preferably, the outlet of the tracer gas source 2 can be connected with the inlets of the plurality of injection pipes 61 and 62 through the pressure reducing valve 7, the stop valve 80 and the flow distributor 10 which are sequentially arranged, the plurality of injection pipes 61 and 62 are connected in parallel, the outlets of the plurality of injection pipes 61 and 62 are respectively connected to the plurality of injection points in the space 1 to be measured, and the plurality of injection pipes 61 and 62 are sequentially provided with the stop valves 81 and 82 and the flow controllers 91 and 92. The tracer gas source 2, the pressure reducing valve 7 and the stop valves 80, 81 and 82 are opened, and tracer gas can be injected into the space to be tested 1. The pressure of the tracer gas fed into the injection lines 61, 62 can be adjusted to meet the inlet pressure of the flow controllers 91, 92 by the pressure reducing valve 7. The total flow rate of the tracer gas fed into the space 1 to be measured from the plurality of injection pipes 61, 62 can be controlled by the flow controllers 91, 92 at a certain tracer gas injection flow rate qin. The gas flow in the respective injection lines 61, 62 can be controlled by means of shut-off valves 81, 82, with the aim of distributing tracer gas according to the tracer gas demand at each injection point. During the experiment, can start mixing arrangement 3 earlier to whether open return air machine 5 according to actual conditions selection, then open tracer gas source 2, adjust relief pressure valve 7 in order to satisfy flow controller 91, 92 inlet pressure, then open stop valve 81, 82, open stop valve 80 at last, by flow controller 91, 92 control flow, with tracer gas with definite injection flow qinInjecting the mixture into the space 1 to be measured at multiple points through injection pipelines 61 and 62; after the injection of the tracer gas in the single injection pipeline is finished, closing a stop valve on the injection pipeline; after the trace gas is completely injectedSequentially closing the stop valve 80, the pressure reducing valve 7 and the trace gas source 2; in the process, the time for starting the injection of the tracer gas and the time for finishing the injection of each injection pipeline are recorded. Sampling can then begin.
In this embodiment, the high-precision flow controllers 9, 91, and 92 are used to quantitatively inject the trace gas from the trace gas source 2 into the space 1 to be measured, the precision of the flow controllers 9, 91, and 92 should be within ± 2%, and the determined trace gas injection flow q is determinedinThe error from the actual injection flow should not exceed 2%. The timing of each stage in the test process adopts uniform timing equipment, and the timing measurement error is controlled within +/-1%.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.
Claims (9)
1. A method for measuring the free volume in space is characterized by sequentially comprising the following steps:
step one, enabling a pressure boundary of a space to be measured to be in a sealed state, and measuring the background concentration C of tracer gas in the space to be measured0；
Step two, according to the determined injection concentration C of the tracer gasinInjection flow rate qinAnd injection time tinInjecting tracer gas into the space to be detected;
step three, setting a plurality of sampling points in the space to be measured according to the determined sampling interval time tsContinuously sampling for multiple times, analyzing the concentration of the tracer gas of the obtained sample, and after confirming that the diffusion of the tracer gas in the space to be detected meets the condition of mixing uniformity for the first time in the sampling process, according to the sampling interval time tsContinuously sampling for at least ten times;
step four, establishing a trace gas average concentration increase curve according to the trace gas concentrations and the sampling time of all samples and obtaining the trace gas average concentration in the space to be detectedAverage concentration
Step five, calculating the free volume V of the space to be measurediThe calculation formula is as follows:
2. the method according to claim 1, wherein in step one, the air exchange rate of the space to be measured is estimated as AmDetermining the phase time control reference as TmAnd satisfies the following conditions: t ism<0.1/Am。
3. The method according to claim 2, wherein in step two, the tracer gas injection time is determined to be tinAnd satisfies the following conditions: t is tin<0.1Tm(ii) a Determination of tracer gas injection concentration CinA trace gas concentration provided for a selected trace gas source; determining the injection flow rate q of the tracer gasinAnd satisfies the following conditions: q. q.sin×Cin×tin＝＝Ct×VmIn the formula, CtIs the target concentration, V, of the tracer gas in the space to be measuredmAnd the estimated value of the free volume of the space to be measured is obtained.
4. The method according to claim 2, wherein in the second step, when the tracer gas is injected into the space to be measured, the tracer gas is mixed in the space to be measured for a predetermined mixing time t by a mixing device provided in the space to be measuredmixThe diffusion is uniform.
5. Method according to claim 4, characterized in that said mixing time tmixSatisfies the following conditions: t is tmix<0.2Tm。
6. The method according to claim 2, wherein in step three, the sampling interval time tsSatisfies the following conditions: t is ts<0.2Tm。
7. The method according to claim 1, wherein in step three, the mixing uniformity condition is that the sample trace gas concentration at each set sampling point does not deviate more than 5% from the average value of the sample trace gas concentrations at all set sampling points.
8. The method according to any one of claims 1 to 7, wherein in the second step, a return duct communicating with the space to be measured is provided outside the space to be measured, and an outlet of the tracer gas source is connected to the return duct through a single injection duct.
9. The method according to any one of claims 1 to 7, wherein in the second step, a plurality of injection points are provided in the space to be measured, and the outlet of the tracer gas source is connected to the plurality of injection points through a plurality of injection pipes.
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