CN101881688B - Standard distribution sample for detecting comprehensive performance of environmental chamber and detection method thereof - Google Patents

Abstract

The invention relates to a standard distribution sample and a detection method thereof for detecting the comprehensive performance of an environmental chamber, and belongs to the field of indoor environmental inspection. A barrier layer placed on the upper end of the cylindrical container and a sealing device for fixing the barrier layer. The method includes: establishing a model: measuring the ventilation volume of the environmental chamber to be tested; placing the sample in the environmental chamber to be detected and placed on an electronic balance, and recording the quality change of the standard distributed sample in real time; in the closed state of the environmental chamber, Let the VOC liquid in the cylindrical container emit, use the model to calculate the emission rate according to the mass change, and then calculate the VOC concentration in the environmental chamber; then collect the VOC concentration at the outlet of the environmental chamber in real time; compare the measured value of the VOC concentration with the calculated value, and evaluate the Comprehensive performance of the environmental chamber. The standard scattered sample and the detection method thereof of the present invention are simple and easy to operate, and have high precision and reliability.

Description

Standard distribution samples for testing the comprehensive performance of environmental chambers and their testing methods

technical field

The invention belongs to the field of indoor environmental inspection, and in particular relates to a liquid-membrane type standard emission sample for calibrating the release rate of organic volatiles and its detection, which are used to detect the airtightness of the cabin body of the indoor environmental cabin, the uniformity of airflow mixing, and the adsorption of the wall surface. method.

Background technique

In recent years, with the improvement of people's living standards, indoor air quality has received more and more attention. Indoor air pollution has a great impact on indoor air quality, thereby affecting people's comfort, health and work efficiency. There are many factors that affect indoor air quality, and the high concentration of indoor volatile organic compounds (VOC) is one of the main reasons for poor indoor air quality and sick building syndrome. Indoors, VOC mainly comes from the emission of various decorative materials. Therefore, it is necessary to monitor the emission of VOC from building materials, furniture, and office appliances. At present, relevant methods have been proposed to detect these properties. Generally, the environmental chamber is used to monitor the VOC emission of the material to be tested. In order to obtain accurate detection results, the comprehensive performance of the environmental chamber (including airtightness, uniformity and wall adsorption For example, a standard emission sample and its detection method for testing the comprehensive performance of the environmental chamber, pour pure VOC liquid into a glass tube to make a standard emission sample, and place the standard emission sample in the environment The chamber is allowed to disperse freely. By comparing the experimental value of the VOC concentration in the environmental chamber directly tested by the environmental chamber test system with the calculated value of the VOC concentration in the environmental chamber calculated by weighing the mass attenuation of the standard emission sample with a balance, it can be evaluated. The comprehensive performance of the environmental chamber. However, this method is greatly affected by convection and diffusion, so the speed of the fan in the environmental chamber must be controlled. When the wind speed at the glass nozzle fluctuates, the accuracy of the standard distribution of samples needs to be improved. Moreover, the model describing the indoor VOC concentration of this method needs to be solved by programming iteratively, which is not convenient for engineering popularization and application.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of existing detection methods to environmental chamber performance evaluation, propose a kind of standard distribution sample and its detection method for detecting the comprehensive performance of environmental chamber, the standard distribution sample and detection method thereof of the present invention are simple and convenient , Easy to operate, with high precision and reliability.

In order to achieve the above object, the present invention proposes a standard emission sample for detecting the comprehensive performance of the environmental chamber, which is characterized in that the sample includes a polytetrafluoroethylene columnar container with an open upper end, an organic volatile VOC liquid placed in the container 1. A barrier layer placed on the upper end surface of the cylindrical container and a sealing device for fixing the barrier layer.

The present invention also proposes a method for detecting the comprehensive performance of the environmental cabin with the above-mentioned standard distribution sample, comprising the steps of:

1) The model for establishing the emission rate of organic volatile compound liquid VOC in the standard emission sample and its influence on the concentration in the environmental chamber is:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; D</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>$

In this model, m is the emission rate, the unit is kg/s; M is the mass of the standard emission sample weighed by the electronic balance, the unit is kg; t is the time, the unit is s; D _e is the diffusion coefficient of VOC, the unit is m ² /s; L is the thickness of the barrier layer, in m; C _s is the saturation concentration of VOC under saturated vapor pressure, in kg/m ³ ; C(t) is the VOC concentration in the environmental chamber, in kg/m m ³ ; A is the cross-sectional area of the equi-cylindrical container, in m ² ; Q is the ventilation volume of the environmental chamber, in m ³ /s; V is the volume of the environmental chamber, in m ³ ;

2) Measuring the ventilation rate Q of the environmental chamber to be tested;

3) Place the liquid-membrane type organic volatiles release standard emission sample in the environmental chamber to be tested, and place it on the electronic balance. The electronic balance is connected to the computer through the data line, which can record the quality change of the standard emission sample in real time; In the closed state of the cabin, let the VOC liquid in the cylindrical container dissipate freely, and the experiment time is not less than 24 hours;

4) Use the model described in step 1) to calculate the emission rate according to the balance mass change, and then calculate the VOC concentration C (t) in the environmental chamber; collect and measure the VOC concentration at the outlet of the environmental chamber in real time with a gas chromatograph;

5) Compare the measured value with the VOC concentration calculated by the model in real time, and evaluate the comprehensive performance of the environmental chamber by comparing the relative error between the calculated value and the measured value.

Features and effects of the present invention:

The standard emission sample and detection method thereof of the present invention adopts the emission source of the constant rate of the combined construction of pure VOC liquid plus barrier layer, by studying the emission law of this emission source and the transmission law of VOC in the environmental chamber, and by calculating the value and The comparison of the measured values reflects the comprehensive performance of the environmental chamber, which avoids the shortcomings of the previous independent detection of various performances of the environmental chamber, and can overcome the influence of wind speed and complex iterative calculations in previous patents. This method is simple, easy to operate, and has a high accuracy and reliability.

Description of drawings

Fig. 1 is that liquid-membrane type organic volatiles of the present invention releases the standard distribution sample structure diagram

Figure 2 shows the pretreatment process of the barrier layer.

Fig. 3 is an overall schematic diagram of the detection of the liquid-membrane standard emission sample in the environmental chamber of the present invention.

Figure 4 is the mass linear attenuation measured when the liquid-membrane standard distribution sample of the present invention is used

Detailed ways

The standard distribution sample and its detection method for detecting the comprehensive performance of the environmental chamber proposed by the present invention are described in detail as follows in conjunction with the accompanying drawings and embodiments:

The standard distribution sample of the present invention is a liquid-membrane type organic volatile release standard distribution sample, and its structure is as shown in Figure 1,

The sample includes a polytetrafluoroethylene cylindrical container 11 with an open upper end, an organic volatile VOC liquid 12 placed in the container, a barrier layer 13 placed on the upper end of the cylindrical container and a sealing device for fixing the barrier layer.

The sealing device is composed of two PTFE gaskets 141 placed on the upper and lower sides of the barrier layer, which are sleeved outside the two PTFE gaskets, and are formed by a PTFE top hollow bottle cap 142 threaded with the cylindrical container , the bottle cap compresses the two polytetrafluoroethylene gaskets on the upper end surface of the polytetrafluoroethylene cylindrical container.

The standard distributing sample of the present embodiment adopts the size of the cylindrical container 11 to be Φ42mm (outer diameter) * 46mm (high), the thickness of the polytetrafluoroethylene gasket 141 is 1mm, and the thickness of the barrier layer 13 is 1.5mm. Toluene (C ₇ H ₈ ) was used as the VOC liquid 12, and the initial charging volume of toluene was 40 ml.

The barrier layer 13 of the present invention adopts a building material film or an engineering plastic film, and the VOC contained therein has been removed from the film after a long-time blowing and heating treatment in advance.

The specific process is shown in Figure 2. Put the barrier layer 13 in the glass container 21, and heat it through the annular heating jacket 22. One side of the glass container 21 is connected to the high-pressure gas cylinder 24 through the flow regulating valve 23, and the other side is connected to the vacuum pump 25. Due to the pressure difference, no The pure gas containing VOC flows through the glass container to take away the VOC released by thermal decomposition of the barrier layer. The whole process generally takes 72 hours.

The detection method of the present invention is as shown in Figure 3, and stirring fan 32 is installed in the environment chamber 31 to be detected, and cabin body is provided with inlet 331, outlet 332, is provided with gas chromatograph (GC) 34 outside the cabin and communicates with outlet 332 , and a temperature sampler 351 and a pressure sampler 352 are provided. A microbalance 36 is placed in the cabin, and the liquid-membrane type organic volatile emission standard distribution sample 37 is placed on the microbalance 36.

The detection method of the present embodiment comprises the following steps:

1) Establish the model of the emission rate of organic volatile liquid VOC in the standard emission sample and the influence on the concentration in the environmental chamber: VOC is emitted to the environmental chamber through the barrier layer in the cylindrical container, and this process is a diffusion mass transfer process. It can be described by the following model:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; D</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The numerator of (1) should be C _s -C(t), because C(t)<<C _s , so the influence of C(t) can be ignored when calculating the emission rate. In this model, m is the emission rate, the unit is kg/(m ² s); M is the mass of the sealing device weighed by the electronic balance, the unit is kg; t is the time, the unit is s, and the emission rate is constant when it is stable, M should be linear attenuation as shown in Figure 4; D _e is the diffusion coefficient of VOC in the barrier layer, the unit is m ² /s; C(t) is the VOC concentration in the environmental chamber, the unit is kg/m ³ ; C _s VOC concentration in equal-diameter tubes, which can be considered as the corresponding concentration under saturated vapor pressure; L is the thickness of the barrier layer, in m; Q is the ventilation rate, in m ³ /s; V is the volume of the environmental chamber, in is m ³ . Equation (1) shows that the emission rate is constant.

2) Measuring the ventilation rate Q of the environmental chamber to be tested;

3) Turn on the air-conditioning system and stirring fan of the ^30m3 environmental chamber, place the liquid-film type organic volatiles release standard emission sample in the environmental chamber to be tested, and place it on the electronic balance, which is connected to the computer through the data line, The quality change of the standard emission sample can be recorded in real time; the door of the environmental chamber is closed to allow the standard emission sample to diffuse freely in the environmental chamber; in the closed state of the environmental chamber, the VOC liquid in the standard emission sample is freely emitted, and the experiment not less than 24 hours;

4) Use the model described in step 1) to first calculate the emission rate according to the balance mass change, and then calculate the VOC concentration C (t) in the environmental cabin; collect and measure the VOC concentration at the outlet of the environmental cabin in real time with a gas chromatograph (GC);

5) Compare the measured value with the calculation result of the model to evaluate the comprehensive performance of the environmental chamber. If the average value of the relative error between the concentration measurement value and the model calculation value at each time point is within 15%, it means that the overall performance of the environmental chamber is up to standard. Principle of the present invention: solving the equation (1) and (2) in the model can obtain the VOC concentration at the outlet of the environmental cabin, which is that the comprehensive performances such as airtightness, uniformity and wall surface adsorption of the environmental cabin are good and under ideal conditions At the same time, use a gas chromatograph (GC) to measure the outlet concentration of the environmental chamber in real time, which is the outlet concentration of the environmental chamber when the airtightness, uniformity and wall adsorption are in the actual situation. If the concentration measurements at each time point If the average value of the relative error with the calculated value of the model is within 15%, it indicates that the comprehensive performance of the environmental chamber is up to the standard.

Claims (1)

1. a method that adopts standard distribution sample test atmosphere cabin combination property is characterized in that,

This sample comprises the unlimited teflon cylindrical container in upper end, places the organic volatile VOC liquid of container, places the barrier layer of this cylindrical container upper surface to reach the fixedly packoff of barrier layer;

Comprise the steps:

1) set up the influence model of the organic volatile liquid VOC emission rate of standard distribution sample to concentration in the environmental chamber:

$m=D_e\frac{C_s}{L}=-\frac{\mathrm{dM}}{\mathrm{dt}}$

$C\left(t\right)=\frac{A}{Q}m(1-e^{-\frac{Q}{V}t})$

In this model, m is an emission rate, and unit is kg/s; M be electronic balance claim the quality of standard distribution sample, unit is kg; T is the time, and unit is s; D _eBe the coefficient of diffusion of VOC, unit is m ²/ s; L is the thickness of barrier layer, and unit is m; C _sDepress the saturation concentration of VOC for saturated vapour, unit is kg/m ³C (t) is a VOC concentration in the environmental chamber, and unit is kg/m ³A is the sectional area of cylindrical container, and unit is m ²Q is the ventilation of environmental chamber, and unit is m ³/ s; V is the environmental chamber volume, and unit is m ³

2) measure environmental chamber ventilation Q to be detected;

3) standard distribution sample is placed environmental chamber to be detected, and be positioned on the electronic balance, electronic balance connects computer by data line, the mass change of real time record standard distribution sample; Under the state of environmental chamber sealing, allow VOC liquid freely distributes in the cylindrical container, experimental period is no less than 24 hours;

4) with the described model of step 1) earlier according to electronic balance claim mass change calculate emission rate, calculate VOC concentration C (t) in the environmental chamber then; Gather the VOC concentration in environmental chamber exit in real time with gas chromatograph;

5) the VOC concentration measurement in above-mentioned environmental chamber exit and the VOC concentration value of Model Calculation are contrasted,, estimate out the combination property of environmental chamber by comparing the relative error of calculated value and measured value.

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