A device and method for online measurement of non-condensable gas concentration in a gas-liquid two-phase system

Abstract

The present invention proposes an online device and method for measuring the concentration of non-condensable gas in a gas-liquid two-phase system, which belongs to the field of thermal measurement technology. The device and method include an absolute pressure sensor and a temperature sensor. Both the absolute pressure sensor and the temperature sensor are inserted into a pipeline perpendicular to the pipeline wall, and the insertion depth of the two is equal to the radius length of the pipeline. The absolute pressure sensor measures the total absolute pressure of the pipeline, and the temperature sensor measures the saturated steam temperature in the pipeline. Both the absolute pressure sensor and the temperature sensor are connected to a microprocessor. The microprocessor calculates the saturated steam pressure according to the saturated steam temperature, and then calculates the non-condensable gas partial pressure and the non-condensable gas concentration in the pipeline according to the total absolute pressure of the pipeline.

Description

Technical Field

[0001] The invention relates to the field of thermal measurement technology, and in particular to a device and method for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The gas-liquid two-phase system refers to a system with two parts of liquid and gas. When the parameters of the system change, the substance will undergo a phase change. The phase change of the substance can absorb or release heat without changing the temperature of the system. Phase change heat transfer has the advantage of high surface heat transfer coefficient and is widely used in heat exchangers, such as loop heat pipes.

[0004] The loop heat pipe is a heat exchanger composed of an evaporator, a condenser, and a steam-liquid pipeline. In the evaporator, the liquid working medium is heated by the heat source and evaporated into steam, which passes through the ascending pipeline to the condenser; in the condenser, the cold source condenses the working medium vapor into liquid, which passes through the descending pipeline and returns to the evaporator, forming a complete circulation loop. The loop heat pipe performs efficient heat exchange through the phase change of the working medium. The driving force for the flow of the working medium is provided by gravity. As long as the temperature difference between the cold and hot sources can be maintained, it can work without external input of energy.

[0005] There will be a small amount of non-condensable gas (air) entering from the outside in the loop heat pipe. The non-condensable gas will not change phase with the working fluid. Therefore, in the condenser, the non-condensable gas will form additional thermal resistance on the inner wall of the pipe, reducing the heat exchange efficiency of the condenser, and then reducing the overall heat exchange efficiency of the loop heat pipe, making it unable to meet working requirements. In some applications, it may cause major safety hazards. Therefore, it is necessary to measure the content of non-condensable gas in the gas in the loop heat pipe.

[0006] The inventors found that the concentration of non-condensable gas in a gas-liquid two-phase flow system is currently measured using a steam quality detector. The principle of the steam quality detector for measuring non-condensable gas is to introduce steam into a container through a branch pipe, condense the steam in the container, measure the volume of the condensed liquid and the volume of the gas, and then obtain the concentration of the non-condensable gas in the steam.

[0007] The steam quality detector is mainly suitable for systems above normal pressure. The loop heat pipe system is a closed system. When the working fluid is added, the system needs to be evacuated. When the loop heat pipe is not put into use, the system is under negative pressure and the steam quality detector cannot be used. The steam quality detector needs to partially extract the working fluid in the system, which affects the gas-liquid interface of the loop heat pipe and thus affects the heat exchange performance. Moreover, the steam quality detector cannot measure the concentration of non-condensable gases in real time, which is not convenient to use.

[0008] In air conditioning refrigeration systems, it is usually necessary to shut down the system and measure the condenser outlet temperature to detect whether non-condensable gases have been mixed in. When the temperature is close to the ambient temperature, the internal pressure of the condenser is recorded and compared with the saturated pressure at the ambient temperature. If the pressure in the condenser is higher, there is non-condensable gas in the system. This method is relatively rough in terms of measurement and can only obtain qualitative results. It also cannot be measured online. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a device and method for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system, wherein the saturated vapor temperature is measured by a temperature sensor, the saturated vapor pressure is calculated by a microprocessor based on the saturated vapor temperature, and the total absolute pressure value of the gas-liquid two-phase system is measured by an absolute pressure sensor. The microprocessor can calculate the partial pressure of the non-condensable gas based on the total absolute pressure value and the saturated vapor pressure, and the concentration of the non-condensable gas is calculated based on the partial pressure of the non-condensable gas, thereby solving the problem that the existing device for measuring the concentration of non-condensable gas in a gas-liquid two-phase system cannot perform online measurement.

[0010] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0011] In the first aspect, the present invention proposes an online device for measuring the concentration of non-condensable gas in a gas-liquid two-phase system, including an absolute pressure sensor and a temperature sensor. Both the absolute pressure sensor and the temperature sensor are inserted into the pipeline perpendicular to the pipeline wall, and the insertion depth of the two is equal to the radius length of the pipeline; the absolute pressure sensor measures the total absolute pressure of the pipeline, and the temperature sensor measures the saturated steam temperature in the pipeline. Both the absolute pressure sensor and the temperature sensor are connected to a microprocessor, and the microprocessor calculates the saturated steam pressure based on the saturated steam temperature, and then calculates the non-condensable gas partial pressure and non-condensable gas concentration in the pipeline based on the total absolute pressure of the pipeline.

[0012] As a further technical solution, the microprocessor calculates the saturated vapor pressure of the working fluid in the pipeline using the data measured by the temperature sensor and the saturated vapor pressure line.

[0013] As a further technical solution, the absolute pressure sensor and the temperature sensor are arranged in parallel and closely fitted along the radial direction of the pipeline.

[0014] As a further technical solution, the temperature sensor is located on a side close to the flow direction of the working fluid.

[0015] As a further technical solution, an extension pipeline is arranged on the side of the pipeline, and the absolute pressure sensor and the temperature sensor are both arranged in the extension pipeline.

[0016] As a further technical solution, the absolute pressure sensor and the temperature sensor are both arranged along the axial direction of the extension pipeline.

[0017] As a further technical solution, the absolute pressure sensor and the temperature sensor are fixed to the end of the extension pipeline through a flange.

[0018] In a second aspect, the present invention provides a method for measuring the concentration of non-condensable gas in a gas-liquid two-phase system online using the above-mentioned device, comprising the following steps:

[0019] According to the saturated steam temperature T in the pipeline measured by the temperature sensor, the saturated pressure Pvapor of the pipeline is calculated;

[0020] The total absolute pressure P0 of the pipeline is measured by the absolute pressure sensor minus the saturated pressure Pvapor of the pipeline, and the partial pressure Pair of the non-condensable gas is obtained, and then the volume concentration C of the non-condensable gas is calculated;

[0021] Using the ideal gas state equation, we can calculate the partial pressure Pa_std of non-condensable gas under standard conditions and the volume concentration C' of non-condensable gas under standard conditions;

[0022] The partial pressure of non-condensable gas under standard conditions is used as the set value, and the partial pressure Pair of non-condensable gas is compared with the set value. If the partial pressure Pair of non-condensable gas is higher than the set value, the pipeline is maintained.

[0023] As a further technical solution, firstly, according to the Clapeyron-Clausius equation, the saturated pressure Pvapor is calculated using the saturated steam temperature T, and the partial pressure Pair of the non-condensable gas is obtained by subtracting the saturated pressure Pvapor from the total absolute pressure P0;

[0024] Then, the volume concentration C of the non-condensable gas is calculated using Dalton's law of partial pressure:

[0025] C = Pair / P0*100%.

[0026] As a further technical solution, according to the saturated steam temperature T and the partial pressure Pair of the non-condensable gas, the partial pressure Pa_std of the non-condensable gas under standard conditions is obtained by using the ideal gas state equation:

[0027] Pa_std=(273.15+20) / (273.15+T)*Pair;

[0028] Then use Dalton's law of partial pressure to calculate the volume concentration C' of non-condensable gas under standard conditions:

[0029] C'=Pa_std / P0*100%.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention uses a temperature sensor to measure the saturated steam temperature, and uses an absolute pressure sensor to measure the total absolute pressure value of the gas-liquid two-phase system. Through the cooperation of the absolute pressure sensor, the temperature sensor and the microprocessor, the partial pressure and volume concentration of the non-condensable gas can be calculated using the total pressure of the steam in the pipeline and the steam temperature. The use of the sensor does not require the extraction of the working fluid, and can be directly measured online in the pipeline or container, which is more convenient to operate and has higher accuracy.

[0032] The absolute pressure sensor and the temperature sensor of the present invention are both inserted into the pipeline perpendicular to the pipeline wall, and the insertion depth is the radius of the pipeline, which can reduce the influence of the pipeline wall on the static pressure and saturated steam temperature measurement and ensure the accuracy of the measured data.

[0033] The absolute pressure sensor and the temperature sensor of the present invention are arranged in parallel and closely fitted along the radial direction of the pipeline, so that the data measured by the two are as much as possible data at the same position, thereby ensuring the reliability of the data.

[0034] The present invention installs the temperature sensor on the side close to the flow direction of the working fluid. The temperature sensor is closer to the flow direction than the absolute pressure sensor, so that the heat exchange coefficient between the temperature sensor and the working fluid is as large as possible, and the influence of the absolute pressure sensor can be avoided. The temperature sensor is more sensitive to changes in the fluid temperature, and the accuracy of the measured data is further guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] Figure 1 It is a schematic diagram of the overall structure of a device for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system according to one or more embodiments of the present invention;

[0037] In the figure: the distances or sizes between parts are exaggerated to show the positions of the parts, and the schematic diagram is for illustration only;

[0038] Among them, 1. pipeline; 2. absolute pressure sensor; 3. temperature sensor; 4. microprocessor; 5. flange; 6. data cable. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] As introduced in the background technology, the current device for measuring the concentration of non-condensable gases in a gas-liquid two-phase flow system cannot extract the working fluid because the internal pressure of the loop heat pipe system is negative when it is not put into use, and forced extraction will affect the gas-liquid interface of the loop heat pipe, making it impossible to measure online. The method for measuring the condenser outlet temperature cannot achieve accurate measurement, etc. In order to solve the above technical problems, the present invention proposes a device and method for online measuring the concentration of non-condensable gases in a gas-liquid two-phase system.

[0041] Example 1

[0042] In a typical embodiment of the present invention, Figure 1 As shown, a device for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system is proposed, which can be used in situations where the fluid in the pipe is saturated steam and the non-condensable gas content in the steam needs to be detected. The device includes: an absolute pressure sensor 2, a temperature sensor 3 and a microprocessor 4.

[0043] The liquid phase may be any liquid, and the gas phase may be any non-condensable gas.

[0044] The absolute pressure sensor 2 and the temperature sensor 3 are connected to the microprocessor 4 via the data line 6 respectively, so that the measured data is transmitted to the microprocessor 4 via the data line 6, and the microprocessor 4 processes and calculates the obtained data.

[0045] The absolute pressure sensor 2 is mainly used to measure the static pressure at the measuring point in the pipeline or container. The measured static pressure is the total absolute pressure in the pipeline or container.

[0046] The temperature sensor 3 is mainly used to measure the temperature at the measuring point in the pipeline or container. The measured temperature is the saturated steam temperature in the pipeline or container. The microprocessor 4 can calculate the saturated pressure of the steam based on the received saturated steam temperature.

[0047] In this embodiment, the temperature sensor 3 is a thermal resistor temperature sensor. In other embodiments, other types of temperature sensors such as thermocouples may also be used, and no excessive restrictions are made here.

[0048] The absolute pressure sensor 2 and the temperature sensor 3 are both inserted into the pipeline 1 vertically through the pipeline wall to measure the static pressure and saturated steam temperature of the fluid in the pipeline. The insertion depth is equal to the radius length of the pipeline. This can reduce the influence of the pipeline wall on the static pressure and saturated steam temperature measurement and ensure the accuracy of the measured data.

[0049] Specifically, the absolute pressure sensor 2 and the temperature sensor 3 are arranged in parallel and closely fitted along the radial direction of the pipeline 1, and are fixed in position by the flange 5 after being inserted into the pipeline, and the temperature sensor 3 is located on the side close to the flow direction of the working fluid.

[0050] The absolute pressure sensor 2 and the temperature sensor 3 are both arranged perpendicular to the flow direction in the pipeline 1. In the specific arrangement, an extension pipeline can be arranged on the side of the pipeline 1, and the absolute pressure sensor and the temperature sensor are arranged in the extension pipeline, and the two are arranged along the axial direction of the extension pipeline, and the flange is fixed to the end of the extension pipeline. The absolute pressure sensor and the temperature sensor are extended from the extension pipeline to the position of half the diameter in the pipeline 1.

[0051] The close fitting arrangement of the absolute pressure sensor 2 and the temperature sensor 3 makes the data measured by the two to be as close to the same position as possible, thus ensuring the reliability of the data; the temperature sensor 3 is closer to the incoming flow direction than the absolute pressure sensor 2, so that the heat transfer coefficient between the temperature sensor 3 and the working fluid is as large as possible, which can avoid the influence of the absolute pressure sensor 2, making the temperature sensor 2 more sensitive to changes in the fluid temperature, further ensuring the accuracy of the measured data.

[0052] It is understandable that in other embodiments, the absolute pressure sensor 2 and the temperature sensor 3 may be connected to the pipeline by means of threads, welding or grooves, etc., as long as the position of the sensors can be fixed, and no excessive restrictions are imposed here.

[0053] The microprocessor 4 is mainly used to receive the static pressure and saturated steam temperature data transmitted from the absolute pressure sensor 2 and the temperature sensor 3, and process and calculate the received data.

[0054] Among them, the microprocessor 4 stores data points on the saturated vapor pressure curve of the working fluid, and the data between the points are obtained by linear calculation to obtain the saturated vapor pressure of the working fluid. The microprocessor 4 can also use the saturated vapor pressure data to calculate a piecewise linear saturated vapor pressure line, and the microprocessor 4 can also modify the saturated vapor pressure data stored therein.

[0055] The microprocessor 4 calculates the saturated vapor pressure of the working fluid in the pipeline or container of the measured system using the data measured by the temperature sensor 3 and the saturated vapor pressure line.

[0056] Furthermore, the microprocessor 4 can calculate the non-condensable gas partial pressure and non-condensable gas concentration in the pipeline or container of the measured system using the data measured by the absolute pressure sensor 2 and the calculated saturated vapor pressure of the working fluid in the pipeline or container of the measured system.

[0057] In this embodiment, the microprocessor 4 includes a digital display recorder, which is mainly used to record the calculation results of the microprocessor 4 and present them to the outside.

[0058] Specifically, the digital display recorder can display the time, the temperature of the working fluid in the pipeline or container of the measured system, the total pressure of the steam, the saturated vapor pressure, the non-condensable gas pressure and the concentration of the non-condensable gas; and can record and transmit data to the outside in real time, and can also export the stored data.

[0059] The digital display recorder can also be used as an interface to modify the working fluid saturated vapor pressure curve in the microprocessor 4 and the settings of related displays and hardware.

[0060] Through the cooperation of the absolute pressure sensor 2, the temperature sensor 3 and the microprocessor 4, the partial pressure and volume concentration of the non-condensable gas can be calculated using the total pressure and temperature of the steam in the pipeline 1. The use of the sensor does not require the extraction of the working fluid and can be measured directly in the pipeline or container, which is more convenient to operate and has higher accuracy.

[0061] Example 2

[0062] In another typical embodiment of the present application, a method for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system is provided, using the measuring device described in Example 1, as follows:

[0063] In a gas-liquid two-phase system, at a certain temperature, when the liquid phase no longer evaporates, the gas-liquid two-phase system reaches phase equilibrium, and the system is said to have reached a "saturated state", and the pressure in this state is called the "saturated pressure".

[0064] Therefore, this embodiment uses the absolute pressure sensor 2 to measure the total absolute pressure (hereinafter referred to as the total pressure) of the working fluid in the pipeline 1 or the container. The total pressure P0 is composed of two parts: the saturated pressure Pvapor of the vapor and the partial pressure Pair of the non-condensable gas; the measurement value of the temperature sensor 3 is the saturated vapor temperature T.

[0065] The microprocessor 4 can calculate the partial pressure Pair of the non-condensable gas and the volume concentration C of the non-condensable gas at the temperature T using the total pressure P0 measured by the absolute pressure sensor 2 and the vapor temperature T measured by the temperature sensor 3 .

[0066] First, according to the Clapeyron-Clausius equation, the saturated steam temperature T can be used to calculate the saturated pressure Pvapor. The partial pressure Pair of the non-condensable gas can be obtained by subtracting the saturated pressure Pvapor from the total pressure P0.

[0067] Then, using Dalton's law of partial pressure, the volume concentration C of the non-condensable gas can be calculated as:

[0068] C=Pair / P0*100% (1)

[0069] For the same working fluid, the saturation pressure at different temperatures is different, that is, one temperature corresponds to one saturation pressure.

[0070] In addition, using the ideal gas state equation, the partial pressure Pa_std of non-condensable gas under standard conditions can be calculated:

[0071] Pa_std=(273.15+20) / (273.15+T)*Pair (2)

[0072] Then, using Dalton's law of partial pressure, we can calculate the volume concentration C' of non-condensable gas under standard conditions:

[0073] C'=Pa_std / P0*100% (3)

[0074] The larger the non-condensable gas content, the greater the adverse effect on the heat exchange of the two-phase circuit system. In order to ensure the heat exchange performance of the two-phase circuit, the non-condensable gas content cannot exceed a certain limit;

[0075] In this scheme, the measured partial pressure of non-condensable gas is first calculated by measuring the pressure and the saturated pressure of water vapor calculated according to the temperature T, and then the ideal gas state equation is used to calculate the partial pressure of non-condensable gas under standard conditions. The content of non-condensable gas in the two-phase loop system can be quantitatively determined. The partial pressure of non-condensable gas under standard conditions is used as the set value, and the data obtained twice are compared. Therefore, if the content of non-condensable gas is lower than the set value, no operation and maintenance are required. If it is higher than the set value, maintenance operations such as vacuuming the pipeline are required.

[0076] For example: for an air-water system, when the total pressure P0 is 0.1 MPa, the non-condensable gas content at different temperatures is shown in Table 1 below.

[0077] Table 1 Non-condensable gas content of air-water system at different temperatures when the total pressure is 0.1 MPa

[0078]

[0079]

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for online measurement of the concentration of non-condensable gas in a gas-liquid two-phase system, characterized in that: It includes an absolute pressure sensor and a temperature sensor arranged on the loop heat pipe, the absolute pressure sensor and the temperature sensor are both inserted into the pipeline perpendicular to the pipeline wall, and the insertion depth of the two is equal to the radius length of the pipeline; the absolute pressure sensor measures the total absolute pressure of the pipeline, and the temperature sensor measures the saturated steam temperature in the pipeline, and the absolute pressure sensor and the temperature sensor are both connected to a microprocessor, and the microprocessor calculates the saturated steam pressure according to the saturated steam temperature, and then calculates the non-condensable gas partial pressure and non-condensable gas concentration in the pipeline according to the total absolute pressure of the pipeline; The absolute pressure sensor and the temperature sensor are arranged in parallel and closely fitted in the radial direction of the pipeline, and the depth of the temperature sensor inserted into the pipeline is lower than that of the absolute pressure sensor; The temperature sensor is located on a side close to the flow direction of the working fluid; The data measured by the absolute pressure sensor and the temperature sensor are data at the same location; The microprocessor stores data points on the saturated vapor pressure curve of the working fluid, and the data between the points are obtained by linear calculation to obtain the saturated vapor pressure of the working fluid, and the microprocessor calculates a piecewise linear saturated vapor pressure line using the saturated vapor pressure data, and the microprocessor has the function of modifying the saturated vapor pressure data stored therein; The microprocessor calculates the saturated vapor pressure of the working medium in the pipeline using the data measured by the temperature sensor and the saturated vapor pressure line.

2. The device for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system according to claim 1, characterized in that: An extension pipeline is arranged on the side of the pipeline, and the absolute pressure sensor and the temperature sensor are both arranged in the extension pipeline.

3. The device for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system according to claim 2, characterized in that: The absolute pressure sensor and the temperature sensor are both arranged along the axial direction of the extension pipeline.

4. The device for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system as claimed in claim 2, characterized in that: The absolute pressure sensor and the temperature sensor are fixed to the ends of the extension pipeline through flanges.

5. A method for measuring the concentration of non-condensable gas in a gas-liquid two-phase system using the device for online measuring the concentration of non-condensable gas in a gas-liquid two-phase system according to any one of claims 1 to 4, characterized in that: The following steps are involved: According to the saturated steam temperature T in the pipeline measured by the temperature sensor, the saturated pressure Pvapor of the pipeline is calculated; The total absolute pressure P0 of the pipeline is measured by the absolute pressure sensor minus the saturated pressure Pvapor of the pipeline, and the partial pressure Pair of the non-condensable gas is obtained, and then the volume concentration C of the non-condensable gas is calculated; Using the ideal gas state equation, we can calculate the partial pressure Pa_std of non-condensable gas under standard conditions and the volume concentration C' of non-condensable gas under standard conditions; The partial pressure of non-condensable gas under standard conditions is used as the set value, and the partial pressure Pair of non-condensable gas is compared with the set value. If the partial pressure Pair of non-condensable gas is higher than the set value, the pipeline is maintained.

6. The measuring method according to claim 5, characterized in that: First, according to the Clapeyron-Clausius equation, the saturated pressure Pvapor is calculated using the saturated steam temperature T. The partial pressure Pair of the non-condensable gas is obtained by subtracting the saturated pressure Pvapor from the total absolute pressure P0. Then, the volume concentration C of the non-condensable gas is calculated using Dalton's law of partial pressure: C = Pair / P0*100%.

7. The measuring method according to claim 5, characterized in that: According to the saturated steam temperature T, the partial pressure of non-condensable gas Pair, and the ideal gas state equation, the partial pressure of non-condensable gas under standard conditions Pa_std is obtained: Pa_std=(273.15+20) / (273.15+T)*Pair; Then use Dalton's law of partial pressure to calculate the volume concentration C' of non-condensable gas under standard conditions: C'=Pa_std / P0*100%.

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