The method of measuring the dew point temperature and device for its implementation

 

(57) Abstract:

Usage: in measurement technology, in particular for measuring the humidity of gases by the method of dew point. The inventive method for measuring the dew point is in the cooling section of optically transparent body, through which pass the light flux, and register the change in intensity of the light flux. The gas flow rate to the cooled area limit to the level determined by the diffusion of gas molecules. Measuring the dew point contains an optically transparent body 1, is connected to the emitter 5 and the Converter of the light flux 7, the cooler 9, the temperature sensor 8 and the sampling tube 10 mounted on the housing of the cooled area and set in the direction of the action of gravitational forces. The ratio of the area of the inner cross section of the tube S to the area of cooled surface area greater than 5, and l2/S > 25, where l is the length of the sampling tube. The tube end is made with a bevel. 2C. and 1 C.p. f-crystals, 1 Il.

The invention relates to the field of measurement technology, in particular to measuring the humidity of gases by the method of dew point and can be used in the condensation specialists and indicators corrosion condense plot optically transparent body, through which pass the light flux, register the change of intensity of the light flux, which is judged on the occurrence of the dew point (ed. St. USSR N 593127, CL G 01 N 25/66, 1975).

However, when using this method in the condensation hygrometers due to contamination of the cooled mirror is greatly reduced and the reliability.

A device for measuring the dew point, contains two fiber with a pure heart, in the gap between the ends which has a condensing mirror, a condensing surface which is covered namachivayam film, the cooling unit and the Registrar dew point, and the bottom ends of the optical fibers are located in the plane of the condensing surface (patent USSR N 1806361, CL G 01 N 25/66, 15.01.90).

However, when using this device possible contamination by impurities mirror, which reduces the measurement accuracy.

The technical nature closest to the proposed technical solution is the method of measuring the dew point, which consists in the supply of the test gas in the cooled area of the optically transparent body, through which pass the light flux, and registration of the change and the sobe measuring the dew point, containing a cooled section of optically transparent body, enclosed in the housing and connected through the optical fibers with emitters and with the Converter of the light flux that is connected to the logger, cooler and temperature sensor (ed. St. USSR N 1744618, CL G 01 N 25/66, 06.06.89).

A disadvantage of the known technical solutions is a low reliability due to possible contamination with impurities of the test gas is optically transparent body, may result in Vozniknovenie unnecessary layer, which can lead to inaccurate measurements and loss of efficiency.

The technical result is to reduce possible contamination of the optically transparent body.

For this purpose, the method of measuring the dew point, which consists in the supply of the test gas in the cooled area of the optically transparent body, through which pass the light flux, and registration of the change of the intensity of the light flux, which is judged on the occurrence of the dew point, the feed rate of the test gas in the cooled area of the optically transparent body limit to zero while maintaining the diffusion of molecules to the cooled section of the optically transparent body, and measuring the dew point, provided the switch and the Converter of the light flux, connected to the logger, a cooler and a temperature sensor, equipped with a sampling tube, one end of which is mounted on the housing around the cooled area of the optically transparent body, and the other set in the direction of the action of gravitational forces, moreover, the ratio of square internal cross-section of the tube to the surface area of the cooled area of the optically transparent body exceeds 5, and l2/S > 25, where l is the length of the sampling tube, S the area of its inner section. The sample tube is made with a bevel at the other end and set the bevel is opposite to the flow of the test gas.

The essence of the invention lies in the fact that the creation of near-cooled section of optically transparent body of stagnant zones of the test gas before passing the light flux due to the introduction in measuring the dew point of the sample tube, restricting the gas flow rate to zero, and the implementation of registration of the change of the intensity of the light flux due to diffusion of the test gas to the cooled section of the optically transparent body can significantly reduce the pollution of the cooled area of the optically transparent body.

Comparison predlagaemoj the significant features allows you to judge the fulfillment of the criterion of "inventive step", and the results of the model tests indicate the possibility of industrial use.

The drawing shows the design of the proposed meter dew point.

The method of measuring the dew point includes the supply of the test gas in the cooled area of the optically transparent body, through which pass the light flux, and the registration of changes in the intensity of the light flux, which is judged on the occurrence of the dew point. A special feature of this method is that before passing the light flux through a cooled section of optically transparent body form near him stagnant zone of the test gas by limiting the rate of gas supply to zero, and keep the diffusion of the molecules of the test gas to the cooled section of the optically transparent body.

Create stagnant zones allows different impurities in the gas to be deposited on the surface of the cooled area of the optically transparent body, as well as gravitational forces act in the opposite direction, it contributes to maintaining the accuracy of the measurement of the dew point and hence increased reliability.

The device has cooled section 1 optical Pro is OBRAZOVATEL 6 of the light flux, the output of which is connected to the recorder 7. In the housing 2 is installed the temperature sensor 8 and the cooler 9. The device is equipped with a sampling tube 10, one end of which is fixed on the housing 2 around the cooled section 1 optically transparent body and the other end is made with a bevel and installed in the direction of the action of gravitational forces. The sample tube 10 is installed slant opposite to the flow of the test gas and has three zones 11 13 transfer of molecules of the test gas to the cooling section 1.

The device fits in the hole of the pipe 14 having a flange 15, is bonded with the pipe 14 by a locking connection 16.

The sample tube 10 is installed slant opposite to the flow of the test gas, and the ratio of the area S of the internal cross section of the sample tube 10 to the area of Skthe surface of the cooled section 1 optically transparent body exceeds 5, and l2/S > 25, where l is the length of the sampling tube 10, S the area of its inner section.

As the cooled section 1 optically transparent body can be used curved optical fiber, and the emitter 5 led type AL-B.

And the Aza or mixture of gases the last act on the condensation surface of the cooled section 1 optically transparent body, in the absence of moisture condensation on the surface of the condensate is not allocated, and the flow of light from the emitter 5 to the optical fiber 3 passes through the cooling section 1 and the light guide 4, goes to the input of the Converter 6, but output it to the Registrar 7 nothing is supplied, indicating the absence of the condensate, and it does not register the temperature of the dew point.

In the presence of moisture in the analyzed gas cooled section 1 optically transparent body at a certain temperature it forms a layer of condensate from melkodisperstnoy drops of spherical shape having a diameter commensurate with the diameter of the core of the applicable light guide 3. Due to the dispersion of the luminous flux surfaces of fine droplets of condensate intensity sharply decreases until complete dispersion and misses in the light guide 4. With the loss of luminous flux in the dispersion in the refrigerated section 1 optically transparent body Converter 6 outputs a signal to the controller 7, which records the occurrence of the dew point. The temperature of the cooler 9 is determined by the temperature sensor 8, the role of which can play a thermocouple connected to the galvanometer. The measured temperature and process automation, which yields this gas mixture.

The leakage test gas in the sample tube 10 is on the opposite side of the bevel, thus protected from direct splashes, droplets and particles in the zone of the sensor. In the sampling tube 10 there are three zones 11 13 transmission of the test gas molecules to plot 1. Direct air cooling of the sample tube 10 by the gas flow causes turbulence inside her in the zone 11, which carry the molecules of the test gas, possible impurities, aerosols and solid particles in zone 12. The energy of the vortices is lost and in zone 12, the movement of the gases is laminar in nature, and bringing the gas into the zone 13 diffusive exchange of molecules, the presence of which leads to filtration of aerosols and trace contaminants present in the analyzed gas and aerosols and solids reach only zone 12 laminar flows, not penetrating into the diffusion zone 13 due to the impact of gravitational forces on them.

If the length of the sample tube 10 is shorter than or equal to the sum of the lengths of the zones 11, 12, turbulent, and then laminar flow will bring aerosols and trace amounts of condensation on the surface of the sensor and cause contamination. Dvorni tube 10. If the sample tube 10 is cylindrical, then the sum of the lengths of the zones 11 and 12 does not exceed five diameters, i.e., if the length of the tube 10 to be shorter than five diameters, particles and aerosols from contaminating the mirror and cause a malfunction.

If the sample tube has a cross section is not circular, then there is a limit of l2/S > 25, where l is the length of the sampling tube 10, S - the area of its inner section.

For fixing the dew point without over-cooling the condensing surface is necessary in areas adjacent to the surface boundary layer of the sample gas to have the necessary number of layers of water molecules.

Intensive dissipation of light energy gives this layer of water molecules, which is three times the wavelength of the light flux. Given that the number of water molecules in solid monolayer of 1 cm condensing surface 0,87 1015cm-2the diameter of molecules of H2O equal 0,348 nm, and the wavelength of the light energy introduced into the optically transparent body, is 900 nm, it is not difficult to determine that the required number of layers of water molecules for stable fixation of the condensing temperature is approximately equal to 3000, and the number of water molecules, which must be adjacent sensational surface Sk1 cm2the cooled section 1 optically transparent body).

Condensation of water molecules in the diffusion zone leads to diffusion from the zone of laminar flow the same amount of molecules that condense.

Therefore, at time t on the condensation surface is formed from the required number of layers of water molecules for stable fixation of the condensation temperature due to diffusion.

The amount of mass of moisture transferred over time t due to the diffusion

< / BR>
where m is the mass of moisture;

D is the diffusion coefficient;

S surface area, which passes through the diffusion, i.e., the inner section of the sampling tube;

t the time of the transfer;

the gradient of the density (concentration).

Hence, the ratio should be greater than 5. When the ratio is less than 5 errors of measurement occur.

Thus, in the proposed method and the device provided with high reliability and measurement accuracy by eliminating pollution.

1. The method of measuring the dew point temperature, which consists in the supply of the test gas in the cooled area of the optically transparent body, through which pass the light flux, and the registration of the action scene, the feed rate of the test gas in the cooled area optical prozrachnogo body limit to the level determined by the diffusion of molecules.

2. Measuring the dew point temperature, containing a cooled section of optically transparent body, enclosed in the housing and connected through the optical fibers with the emitter and transducer of the light flux that is connected to the recorder, a cooler and a temperature sensor, characterized in that it is equipped with a sampling tube, one end of which is mounted on the housing of the cooled area of the optically transparent body and the other end installed in the direction of the action of gravitational forces, and the ratio of the area of the inner cross section of the sampling tube to the surface area of the cooled area of the optically transparent body exceeds 5, and l2/ S > 25, where l is the length of the sampling tube, S the area of its inner section.

3. The device according to p. 2, wherein the sample tube is made with a bevel at the other end and set the bevel is opposite to the flow of the test gas.

 

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