The way of measuring the humidity of gases

 

(57) Abstract:

Usage: in the instrument. The inventive analyzed gas are separated in the vortex tube on the cold and hot streams, which are then divided respectively in the second and third vortex tube, is obtained by means of thermocouples first thermo-EMF proportional to the temperature difference between hot and cold streams of the second vortex tube, and a second thermo-EMF proportional to the temperature difference between the hot streams of the second and third vortex tubes. Change at least one of these thermo-EMF to minimize the effect of the temperature of the source of the sample gas on the difference between thermo-EMF, measure at least one of the parameters of the electric circuit, including the difference between thermo-EMF, the largest of which is judged on the moisture content of the sample gas. The technical result is to increase the reliability and accuracy of measurements. 5 Il.

The invention relates to the instrument and can be used when the humidity of compressed gases.

The known method of measuring the dew point of the compressed gas temperature readings of dry and wet thermometers measured after throttling gas by peresilaet to consider the effect of loss of moisture after throttling and influence of the phase transition temperatures of dry and wet thermometers. Method [1] allows to determine the humidity of gases in a wide range of measurements of pressure, temperature and moisture content of gases, however, requires complex computing devices and Bolotnikova devices for slow throttling gas.

The main drawback of this method is the dependence of the accuracy of determining the moisture content of the compressed gas from the accuracy of the approximation of the empirical formula, which can be different in different ranges of change in input parameters gas.

The disadvantages of this method include the difficulty of implementation in the technical device and the greater cost of the device for its implementation.

There is also known a method of measuring the humidity of gases, which consists in the separation of the sample gas in the vortex tube on the hot and cold streams [2]. By monotonic changes in the gas pressure or the change of the cross section of the cold stream in this way change the temperature of the hot and cold streams. When the condensation in a cold stream heat of the phase transition, the rate of change of the temperature difference between the hot and cold streams is markedly reduced, and this serves as a signal for measuring the temperature of the cold stream, which is agostiniana cold stream below the initial moisture content of the sample gas. The effects of reducing the moisture content of the cold flow, and improve the moisture content of the hot gas stream after the vortex tube depend on the design of the vortex tube, the temperature and moisture content of the source gas. In addition, the ingress of condensate at the temperature sensor may reduce the accuracy of measurements.

For the prototype accepted method [2] as the closest to the offer.

The aim of the invention is to increase the reliability and accuracy of measurement, the ease and convenience of the measurement process.

This goal is achieved in that the cold and hot flows after the vortex tube share respectively in the second and third vortex tubes, get the first thermo-EMF proportional to the temperature difference between hot and cold streams of the second vortex tube, and a second thermo-EMF proportional to the temperature difference between the hot streams of the second and third vortex tubes, and changing at least one of these thermo-EMF to minimize the effect of the temperature of the source of the sample gas on the difference between thermo-EMF, measure at least one of the parameters of the electric circuit, including the difference between thermo-EMF, largest of which is judged on vlagosoderzhaniya separation in the first vortex tube on the cold and hot streams are then divided respectively in the second and third vortex tubes.

Since according to [3] the moisture content of the cold gas stream after the vortex tube can be 3-4 times lower than the initial moisture content of the sample gas, then the input to the second vortex tube will flow sufficiently dry gas. Therefore, after the second vortex tube the temperature difference between the hot and cold flows is proportional to the temperature of the cold gas after the first vortex tube and, consequently, the temperature of the source of the sample gas. In addition, a significant reduction in the moisture content of the cold gas stream after the second vortex tube as compared with the moisture content of the initial gas ensures penetration of condensate on the sensitive element of the sensor that is installed in a cold stream.

Another distinctive feature of the proposed method from the prototype is that it is proportional to the temperature difference between hot and cold streams of the second vortex tube to receive the first thermo-EMF and is proportional to the temperature difference between the hot streams of the second and third vortex tubes to get the second thermo-EMF of at least one of these thermo-EMF change to minimize the effect of the temperature of the source of the sample gas on the difference between thermo-EMF and measure kailasodharanam the sample gas. The first of these thermo-EMF is proportional to the temperature of the sample gas and weakly depends on its moisture content. The second thermo-EMF is also proportional to the temperature of the sample gas and to a large extent depends on the moisture content of the sample gas. The difference between thermo-EMF is not influenced by the temperature of the source gas and proportional only to the original moisture content of the gas. If you measure any parameter of an electric circuit in which is included oppositely directed thermo-EMF, the value of this parameter is proportional to their difference and, therefore, the initial moisture content of the gas. The absence of an electric circuit of the other current sources, in addition to thermo-EMF, simplifies and reduces the cost of the measurement process humidity, and it also simplifies the process of presentation of measurement results, since the measurement result is immediate moisture, not temperature dew point, as in the prototype.

Thus, the proposed method new actions over the analyzed gas provides new opportunities for moisture measurement, namely to prevent condensation on the sensing element of the temperature sensor installed in Kholodnov the sample gas, which increases the reliability of the results, and to provide simplicity and convenience of the measurement process. This proves that the proposed method criteria of "novelty" and "inventive step".

Signs in the aggregate have not been identified in other technical solutions in this field of technology, they are necessary and sufficient to reduce the achievement of the goal, i.e. increasing the reliability and accuracy of measurement, ease of convenience of the measurement process.

In Fig. 1 shows a device, which is one example of specific performance of the proposed method, Fig. 2 is an electric circuit providing an indication device values, proportional to the moisture content of the gas; Fig. 3, 4, 5 - graphs of the experimental dependences of the parameters of the device.

The method is implemented in the device as follows.

The device comprises a vortex tube 1, dividing the analyzed gas flowing through the reduction gear 2, 3 cold and hot 4 threads, the separator 5, separating the condensate from the cold stream 3, the second vortex tube 6, separating the cold gas stream 3 cold flow 7 and the hot stream 8, the third -- thermocouple of the same type 13 and 14. thermocouple 13 and the cold junction is placed in a cold stream 7, the hot junction is in the hot stream 8; thermocouple 14 cold junction is placed in a hot stream 8, and the hot junction is in the hot stream 12. The outputs of thermocouples 13 and 14 are connected in series in an electrical circuit with the indicating device 15 type milliammeter and the first resistor 16 and in parallel with the second resistor 17, one output of which is connected with the findings showing the device 15 and the first resistor 16, and the other output is connected to the outputs of thermocouples 13 and 14. The direction of thermo-EMF in a thermocouple 13 and 14 in opposite direction, and the resistance of the resistors 16 and 17 correspond as 4:1.

One possible design implementations of the proposed method lies in the fact that the relationship of the values of the pressure at the inlet of the vortex tube to the pressure of cold streams in all three vortex tubes of the circuit of Fig. 1 the same and equal to 2. This is achieved by installing at the inlet of the vortex tube 1 gear 2, selection of hydraulic resistance 10 and the ratio of the areas of nozzle inlets of the first, second and third vortex tubes, equal to 1: 1,56:1,14.

The device for the proposed method works as follows.

The gas is fed through the gear 2 in the vortex is less than the moisture content of the source gas, and the moisture contained in the liquid and solid (as frost). The moisture from the cold stream 3 is separated in the separator 5, and then the cold stream is fed into the second vortex tube, where again is divided into hot and cold streams. The second vortex tube works on almost dry air, so the temperature difference between its hot and cold streams depends only on the temperature of the source gas and does not depend on the initial moisture content of the gas. The form of the dependence of the temperature difference between hot and cold gas streams after the second vortex tube the temperature of the source gas is shown in Fig. 3.

Hot stream 4 is fed through the orifice 10 in the third vortex tube 9, which again is divided into hot and cold streams. The moisture content of the hot stream 4 is higher than the moisture content of the source gas, so the effect of the moisture content of the gas to the temperature difference between the cold 11 and 12 hot flows are more pronounced. The temperature of the cold stream 11 is closest in value to the value of the temperature of the hot stream 8, since the degree of expansion of the gas at all vortex tubes are the same (equal to 2), and all pipes are configured, the relative share of cold flow, equal to 0.6. Therefore, the t different values of the temperature of the source gas is shown in Fig. 4.

The premise of the cold junction of thermocouple 14 into the hot stream 8, and not in a cold stream 11 has the advantage that in the output streams of the second vortex tube 6 is not allocated condensate, therefore, the reliability of temperature measurements above. The temperature difference between the hot threads 12 and 8 at constant initial moisture content of the sample gas increases with the temperature of the source gas, the form of the dependence shown in Fig. 5.

As can be seen from comparison of Fig. 3 and 5, the gradient of the temperature difference between hot and cold streams of the second vortex tube the temperature of the source air is 5 times less than the gradient of the temperature difference between the hot streams of the third and second vortex tubes.

Connection of thermocouples in the electrical circuit shown in Fig. 2, causes the flow of electric current through the indicating device power.

< / BR>
where E1E2- thermo-EMF, respectively 13 and 14 of thermocouple;

R1, R2the resistance of the resistors 16 and 17;

Rp- resistance of the device showing.

As thermo-EMF is proportional to the temperature difference between hot and cold junctions of thermocouples, the first thermo-EMF is proportionally temperature difference between the flows of the second and third vortex tubes. Then, the relationship of resistance1: R2= 4 : 1 leads, according to the formula (1), to the fact that the current Ipnot affected by changes in the temperature of the source gas, and depends on its moisture content.

Thus, a scale showing the device can be calibrated in terms of moisture content of the source gas.

An example of embodiment of the proposed method for measuring the humidity of gases provides the indication device of the magnitude of the moisture content of the sample gas in the range of 2 to 10 g/kg at the temperature of the source gas from 283 to 323 K, and the additional current sources are not required. The pressure of the sample gas should be the example not lower than 0.4 MPa.

Sources of information

1. Golikov Century A. method of measurement of the dew point temperature of the compressed air-gas environment. - RF patent N 2082157, G 01 N 25/66, 1997, bull. 17.

2. Paklin C. A., Bahtinov N. A. The way of measuring the humidity of gases. - Ed. mon. USSR N 1350582, G 01 N 25/66, 1987, bull. 41.

3. Vortex devices / A. D. Suslov, P. C. Ivanov, A. C. Murashkin, Y. C. Chizhikov. - Engineering, 1985. - S. 69.

The way of measuring the humidity of gases, which consists in the separation of the sample gas through the vortex tube hot and x is on the second and third vortex tubes, get the first thermo-emf. proportional to the temperature difference between hot and cold streams of the second vortex tube, and a second thermo-emf. proportional to the temperature difference between the hot streams of the second and third vortex tubes, and changing at least one of these thermo-emf. to minimize the effect of the temperature of the source of the sample gas on the difference between thermo-emf. to measure at least one of the parameters of the electric circuit, including a differential thermo-emf. , the largest of which is judged on the moisture content of the sample gas.

 

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