SU1758375A1 - Method for determining coolant steam content - Google Patents

Abstract

Usage: refrigeration equipment, steam flow measurement of the refrigerant. SUMMARY OF THE INVENTION: The refrigerant is throttled, evaporated, heated, the temperature of the vapor-liquid mixture is measured before and after throttling, parts of the refrigerant flow are taken before and after evaporation, and their costs are measured, ensuring equality between them. m, the measurement of the flow rates of the parts — before their output temperatures rise above the input, the excess is determined by simultaneous measurement with the flow rates of the parts before and after heating, and the steam content is determined by the following Drive: x (hi-hfl) (hi-ho) J}, where x - vapor content, mg / kg; qi is the amount of heat supplied to the part of the stream selected after evaporation, kJ / s; Q2 is the amount of heat supplied to the part of the stream selected before evaporation, kJ / s; hi is the enthalpy of the refrigerant at a given boiling temperature and x t, kJ / kg; PD is the enthalpy of the refrigerant before throttling and x O, kJ / kg; ho is the enthalpy of the refrigerant at a given boiling temperature and x, kJ / kg. 1 il. (Ls

Description

The invention relates to refrigeration engineering, in particular to measurements of various parameters in cooling processes.

A known method for determining the steam content includes the processes of heating the refrigerant with an additional heat source, measuring the temperature using a sensor located directly to the heat source or radially at the outlet. The method is based on the determination of the indirect independence of the temperature at the location of the sensor from the heat transfer between the pipe wall and the vapor content of the refrigerant at a constant power of the heat source.

The closest to the present invention is a method for measuring steam content, which includes heating the refrigerant flow after evaporation by a heat source of a pipeline section, along which distances from a source of 2 cm and 10-15 cm measure temperatures, the distribution of which along the length follows an exponential law the deviation of which with respect to the limiting exponents of dry vapor to liquid is indirectly judged to the partial content of production every time the inverse recalculation using the exponent equation.

However, this method also requires calibration every time and the introduction of its result.

SP 00

from h

SP

In addition, the measurement results are influenced by the measurement of refrigerant flow, which are unavoidable during the measurement process, the placement of temperature sensors and their isolation from the ambient temperature, as well as pipeline pollution, which affects the exponential control parameters and temperatures at measurement points. Although the method of measuring at two points of temperature more precisely, the indirect measurement mechanism inherent in it is not accurate enough, since the exponential law of temperature distribution is really affected by all the above parameters. Also, the range of measurement of perosorum is very limited due to the disappearance of the temperature difference during steam content, less than 0.8, for large values of which a liquid film is disrupted from the pipe wall and heat exchange occurs with gas, which worsens it and contributes to an increase in temperature. Finally, this method indirectly determines the steam content without communication with external influences, which would fix the reference dependence in a given measurement range, i.e. with a fixed value of the power of the heat source and, therefore, the claimed reference curve, having the form of the exponent and reflecting only the temperature changes without regular communication with the determining parameter in the measurement range (for example, heat flux) being obtained at a point that is ambiguous. And, it means that different reference curves can correspond to the same value of the lary content, which makes the measurement unreliable, since all range measurements must be tied to at least one of the measured parameters.

A serious disadvantage of this method is the high energy consumption for heating the refrigerant of the entire flow after evaporation, reaching several tens of kilowatts, depending on the power of the evaporation process of the refrigerating machine.

The purpose of the invention is to reduce the energy consumption for heating the refrigerant and to increase the accuracy with the continuous determination of steam content.

The drawing shows a device for implementing a method for measuring the ground content during evaporation.

The device consists of a chiller with a compressor 1, a condenser 2, a tressel 3, an evaporator 4, a sensor 5 of the temperature of the liquid refrigerant after

condensation, the sensor 6 temperature before the evaporator, the microflow 8, taken before the evaporator, and the microflow 10 after the evaporator, the heater 7, the heater 11,

microflow temperature sensor 15 after heating; a temperature sensor 12 after heating the microflow 10; sensor 13 values of micro-flow 10 and 14 of micro-flow 8, computer 16, control valve 9

0 microflow 8,

A method for measuring steam content during evaporation in a chiller is carried out as follows.

Set the condensation temperature tK

5 40 ° C and evaporation tn 20 ° C, then during operation of the refrigeration machine after condensation in the condenser 2 and throttling in the throttle 3 of the refrigerant flow, the temperature is measured by sensor 5 equal to

0 40 ° C. After measuring the temperature by sensor 5 equal to 30 ° C before and after evaporation of the refrigerant in the evaporator 4, equal microflows 8 and 10 of the refrigerant are taken of the value of 0.002 kg / s, which are then heated

5, respectively, in heaters 7 and 11 by increasing the thermal flows q2, qi conducted to microflows 8 and 10, and simultaneously measuring the temperature of the refrigerant flow before sampling of microflows by sensor 5, equal to and after heaters 7 and 11 by sensors 15 and 12. Heat fluxes Q2 of 0.1796 kJ / s and q 1 of 0.0186 kJ / s are measured as soon as the measurement temperatures of the sensors 15 and 12 after heaters 7 and 11 have reached 5 values of 20.1 ° C, i.e. will exceed the temperature measured by sensor 5 at the inlet of the evaporator and 0.1 ° C. A microcurrent 10 equal to about 0.001 kg / s is set in the place of a capillary tube.

0 is taken and measured by sensor 13. The magnitude of microcurrent 8 is measured by sensor 14 and set equal to the magnitude of microcurrent 10 by measuring the flow area of control valve 9. According to the measured temperature, sensor 5 of liquid after condenser 2 equals 40 ° C and at zero steam content the tables or diagrams determine the corresponding enthalpy Id 131 kJ / kg (the diagrams of the Odessa Institute of Marine Engineers are used here), and from the measured boiling point 1K - 20 ° С (sensor 5} at zero content) w ho

5 125 kJ / kg and enthalpy hi - 131 kJ / kg, with a single steam content of the same temperature hi 311 XJ / kg Then use the obtained values of heat fluxes and enthalpy h to calculate the steam content:

X - 1 Ql (hl-pd) - -j q2 (hi -h0)

- 0.0186 (311-131) s

0.1796 (311-128) and OU mPri of the power of the refrigerating machine of the order of 125 kJ / s. The power consumed for heating the refrigerant and during the measurement process was 0.1796 + 0.0186 - 0.1982 kJ / s and in the limit at zero steam concentration would be about 0.32 kJ / kg, while in the known device it would be 13 kJ / s and 102 kJ / s, respectively, which has more advantages in energy saving. In addition, the accuracy of continuous measurement of steam content is also very high, as it depends only on the accuracy of temperature measurement and reading from tables, which are simple, accurate and well worked out, while in the known device the accuracy depends on the conditions in which the calibration curves were taken and which must be maintained in the measurement process. In addition, the measurement process is interrupted and limited, i.e. it is impossible to measure in the full range of 0-1 (steam content), whereas in the proposed method this full range is not limited, and the energy consumption is thousands and more times less.

Claims (1)

Comparing the proposed method for determining the steam content with the table values, which are equal to 0.9, we see that the accuracy of the determination of steam content is very high, is about 0.02% and is determined solely by the metrological characteristics of the embedded technical means. The invention The method of determining the steam content refrigerant by throttling it, evaporating, heating and measuring the temperature of the resulting vapor-liquid mixture, characterized by that. that, in order to reduce energy consumption and improve accuracy with continuous steam content determination, additional refrigerant temperatures are measured before and after throttling, portions of the refrigerant stream are taken before and after evaporation, and measured the costs are equal, they are heated by supplying heat to these parts, the parts are measured before their output temperatures exceed the input temperatures, the excess is determined by simultaneous measurement with the parts of their temperatures before and after heating, and the steam content is determined by following dependency: 25 X 1 qi (ht-pd) q2 (hi-h0) 1 where x is the steam content, kg / kg; qi is the amount of heat supplied to the part of the stream selected after evaporation, kJ / s; Q2 is the amount of heat supplied to the part of the stream selected before evaporation, kJ / s; hi-enthalpy of the refrigerant at a given boiling point and X 1, kJ / kg; hA is the enthalpy of the refrigerant prior to throttling and X 0, kJ / kg; ho-enthalpy of the refrigerant at a given boiling point and X 0, kJ / kg. 4 s five ff -to YU YU eight x t