CN214309056U - Temperature control system of additional volume position in pVTt method gas flow standard device - Google Patents
Temperature control system of additional volume position in pVTt method gas flow standard device Download PDFInfo
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- CN214309056U CN214309056U CN202120585787.8U CN202120585787U CN214309056U CN 214309056 U CN214309056 U CN 214309056U CN 202120585787 U CN202120585787 U CN 202120585787U CN 214309056 U CN214309056 U CN 214309056U
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Abstract
The utility model relates to a temperature control system suitable for additional volume department of pVTt method gas flow standard device can realize the temperature compensation through additional volume department behind the Critical Flow Venturi Nozzle (CFVN) of being surveyed, realizes the temperature control to additional volume department, reduces the thermal balance time of the gaseous standard device of pVTt method, promotes the measurement of efficiency of the gaseous flow standard device of pVTt method.
Description
Technical Field
The utility model relates to a temperature control system especially relates to a temperature control system of additional volume department in pVTt method gas flow standard device.
Background
Gas flow measurement is widely used in flow monitoring in the fields of energy, environment, medical treatment and the like, in particular, in gas measurement, particularly for detection of household gas meters; in the metering of ambient gases, for monitoring of exhaust gases; in gas metering in the medical field, for monitoring the gas materials used; and can also be used for process control in industrial manufacturing of medicines, semiconductors, steel, petrochemicals and the like. Therefore, the accuracy of gas flow measurement plays an important role in the development of economy in China.
The internal geometry of a Critical Flow Venturi Nozzle (CFVN) is a differential pressure flow meter of the convergent-divergent type, the smallest cross section of which is called the throat, which tapers from the inlet to the throat and tapers from the throat to the outlet, including a convergent section, throat and divergent section. The CFVN has the characteristics of simple structure, no movable part, high accuracy, good repeatability and the like, and is used as a transmission standard for transmitting the measurement value of other types of gas flow meters. Meanwhile, the CFVN can be directly traced to the national gas flow primary standard device. Therefore, the sonic nozzle occupies an important position in a gas flow quantity value traceability system, and is a key link for ensuring the accuracy and reliability of gas flow measurement and the uniformity of the quantity value.
The pVTt method gas flow device is a common gas flow reference device and is a source for unifying gas flow quantity values. The pVTt gas flow device mainly comprises a CFVN, a switch valve (an additional timer), a standard container with a known volume, a valve, a vacuum pump, a pressure and temperature measurement and control system for realizing data acquisition and storage. When a pVTt method gas flow device is used for detecting the CFVN, due to the special geometrical structure of the nozzle, the sectional area of the nozzle is reduced in the process that gas flows from an inlet to a throat, so that the flow velocity of the gas is rapidly increased, the pressure is reduced, and the temperature is reduced; the increase in cross-sectional area as the gas flows from the throat to the outlet brings about a recovery of pressure and, at the same time, a recovery of temperature, which, however, does not fully return to the stagnation temperature of the inlet. Furthermore, when a gas with a certain velocity flows through an additional volume into a standard container, a drastic change in the velocity of the gas itself causes an increase in the temperature of the gas.
Therefore, after the gas enters the standard container from a stagnation state, the temperature of the gas can be changed drastically, so that the heat balance time of the pVTt method gas flow standard device is longer, and the experimental efficiency is lower.
SUMMERY OF THE UTILITY MODEL
The utility model aims at implementing temperature control system in additional volume department to reduce pVTt method gas flow standard device thermal equilibrium time, improve pVTt method gas flow standard device's detection efficiency.
The utility model provides a temperature control system at an additional volume part in a pVTt method gas flow standard device, which comprises a critical flow Venturi nozzle, a switch valve, a standard container and a control system; an additional volume between the critical flow venturi nozzle and the on-off valve; one end of the additional volume is connected with the critical flow Venturi nozzle, and the other end of the additional volume is connected with the switch valve; a temperature control system is disposed at the additional volume, the temperature control system regulating a temperature at the additional volume.
Wherein, the switch valve is provided with a timer for controlling the measurement initiation of the pVTt method gas standard device and recording the gas inlet time.
Wherein the control system of the standard device measures the upstream stagnation temperature and stagnation pressure of the critical flow Venturi nozzle, and simultaneously records the air inlet time recorded by a timer and the initial and final temperature and pressure in a standard container.
And the temperature control system regulates and controls the temperature according to the flow of the critical flow Venturi nozzle to be measured.
The utility model also provides a pVTt method gas flow standard device's additional volume department temperature control system, it includes:
the heating part is directly connected with the nozzle outlet at one end and is connected to the refrigerating part in an extending way at the other end; the heating quantity is controlled by the heating power of the electric heating wire;
one end of the refrigerating part is connected with the heating part, the other end of the refrigerating part is connected with a standard container of a pVTt method gas standard device, and the refrigerating capacity of the refrigerating part is controlled by the flow of the cooling circulating water;
the control system of the device controls and records stagnation parameters of the sonic nozzle, an air inlet switch valve, air inlet time, a temperature control system at the additional volume and thermodynamic parameters in the standard container.
The utility model discloses a temperature control system that one set was applicable to additional volume department among the pVTt method gas flow standard device has been established, through this temperature control system, the temperature of control entering standard container to the thermal balance time of temperature in the standard container after the reduction admits air effectively improves standard device's detection efficiency.
Drawings
FIG. 1 is a schematic diagram of a pVTt method gas flow standard device system of the present invention;
FIG. 2 is a schematic view of a temperature control system at an additional volume of the pVTt method gas flow calibration apparatus of the present invention;
fig. 3 illustrates a method for controlling the temperature at the additional volume according to the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention, and should not be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled," it can be directly connected or coupled to the other element or intervening elements may also be present.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In order to facilitate understanding of the embodiments of the present invention, the following description will be given by taking specific embodiments as examples with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of the pVTt method gas flow rate standard device of the present invention. As shown in fig. 1, the pVTt method gas flow calibration device comprises a Critical Flow Venturi Nozzle (CFVN) and an on-off valve with a timer for the initial control of the measurement of the pVTt method gas calibration device and the recording of the intake time, there being an additional volume between the Critical Flow Venturi Nozzle (CFVN) and the on-off valve, said additional volume being connected at one end to the Critical Flow Venturi Nozzle (CFVN) and at the other end to the on-off valve; upstream of the Critical Flow Venturi Nozzle (CFVN) is atmospheric air and the stagnation temperature is T0Stagnation pressure of p0(ii) a Downstream connected by an additional volume to a standard vessel, the temperature in the standard vessel being T and the pressure being p; the standard container is connected to a vacuum pump, and a valve is arranged between the standard container and the vacuum pump.
Considering that the additional volume is connected with the standard container, in the early stage of gas inlet, because the pressure at the additional volume is lower, the temperature at the additional volume is lower to reduce the dominant factor; with increasing inlet time, the pressure in the additional volume and in the standard container increases gradually, the temperature in the additional volume increasing as a dominant factor. Therefore, in order to reduce the heat balance time of the pVTt method gas flow standard device and improve the detection efficiency, in the gas inlet process, when the pressure in the standard container is lower, the heating part of the temperature control system at the additional volume part needs to be started; when the pressure in the standard container reaches a certain threshold, the refrigeration portion of the temperature control system at the additional volume needs to be turned on. The threshold is determined in close relation to the flow rate of the sonic nozzle and in close relation to the structural parameters at the additional volume.
A temperature control system is arranged at the additional volume and used for regulating and controlling the temperature at the additional volume; the temperature control system comprises a heating part and a refrigerating part, wherein the heating part preferably adopts an electric heating wire with adjustable heating power, and the refrigerating part preferably adopts refrigerating liquid for circulating cooling and further preferably adopts circulating water for cooling; the control system of the standard device automatically measures and records the parameters of the upstream stagnation temperature and pressure of a Critical Flow Venturi Nozzle (CFVN) and the temperature and pressure in a standard container; the diameter of the throat part of the detected critical flow Venturi nozzle is input into a control system, and the control system automatically calculates the size of the heat exchange quantity based on the parameters of the control system of the standard device, compensates the temperature change at the additional volume and effectively reduces the heat balance time of the standard container.
Fig. 2 is a schematic structural diagram of the additional volume temperature control system of the pVTt method gas flow calibration apparatus of the present invention. As shown in fig. 2, the temperature control system includes: a heating part (a) with one end directly connected to the nozzle outlet and the other end extending close to the refrigerating part (b), wherein the heating amount in the heating part is controlled by the heating power of an electric heating wire wound on the additional volume, preferably a pipeline; one end of the refrigerating part is adjacent to the heating part, the other end of the refrigerating part is close to a standard container of the pVTt method gas standard device, and the refrigerating capacity of the refrigerating part is controlled by the flow of cooling circulating water; the refrigeration part comprises a water pump, a cooling water tank and a cooling water pipe, wherein the cooling water pipe is wound on the additional volume, and the additional volume is cooled through the cooling water pipe. The control system of the standard device controls and records stagnation parameters of the sonic nozzle, an air inlet switch valve, air inlet time, a temperature control system at the additional volume and thermodynamic parameters in the standard container.
The following introduces the temperature control method of the additional volume of the pVTt method gas flow calibration apparatus of the present invention, and the steps of the control method include:
firstly, starting a vacuum pump to vacuumize the standard container;
the control system of the standard device measures the temperature and pressure in the standard container in real time, and records the temperature and pressure in the standard container after the temperature and pressure parameters are balanced, wherein the temperature and pressure are expressed as initial temperature and pressure, namely Ti，pi(ii) a The pressure in the standard vessel of the pVTt method gas flow standard device is preferably pumped to 200Pa, i.e. pi<200Pa；
Opening a switch valve, and simultaneously starting to record air inlet time and stagnation parameters at the upstream of a nozzle;
starting the heating part of the temperature control system at the additional volume, the magnitude of the heating quantity, Δ H, can be roughly determined by
ΔH＝kh·m·Cp·ΔT (2)
The heating quantity and the flow (m) of the tested nozzle, and the specific heat (C) of the gas of the system to be testedp) And a heat transfer coefficient (k) dependent on the influence of the geometrical parameters and material properties of the standard deviceh) And the difference (Δ T) between the temperature at the additional volume and the stagnation temperature.
When the pressure in the standard container reaches a certain pressure value, usually not exceeding 15kPa, the refrigerating part is started, the heating part is turned off, the magnitude of the refrigerating capacity, ac, can be estimated by the following formula,
ΔC＝kc·m·Cp·ΔT (3)
the refrigerating capacity and the flow (m) of the tested nozzle, and the specific heat (C) of the gas of the system to be testedp) And a heat transfer coefficient (k) dependent on the influence of the geometrical parameters and material properties of the standard devicec) And the difference (Δ T) between the temperature at the additional volume and the stagnation temperature.
The heating amount and the refrigerating amount in the standard container change with the pressure, as shown in fig. 3, when the pressure in the standard container reaches a first preset value, the heating part is closed, the refrigerating part is started, and the heat exchange amount is controlled to change with the increase of the pressure.
Based on the final pressure in the standard container reaching about 50kPa, i.e. p, when the pressure in the standard container reaches a predetermined valuef<50 kPa; closing the switch valve, and simultaneously stopping recording time to obtain the air inlet time t of the standard device; and calculating to obtain the average value of the stagnation parameters in the air intake time to obtain T0，p0；
The control system of the standard device measures the temperature and pressure in the standard container in real time, and records the temperature and pressure in the standard container after the temperature and pressure parameters are balanced, namely the ending temperature and pressure, namely Tf，pf；
Obtaining the outflow coefficient of the nozzle based on the throat diameter of the nozzle to be measured, CdNamely, it is
Wherein q ismActual mass flow through the nozzle measured for the pVTt apparatus; q. q.smiIs the desired mass flow through the nozzle; ruIs the universal gas constant; m is molecular weight; c*Is a critical flow function; d is the throat diameter of the nozzle; v is the standard volume of the pVTt method gas flow standard device; p is a radical of0Is stagnation pressure; t is0Is the stagnation temperature; p is a radical ofi、pfThe initial pressure and the final pressure of the gas in the standard container are set; t isi、TfThe starting temperature and the ending temperature of the gas in the standard container; zi、ZfThe compression factors of the starting and ending of the gas in the standard container.
Coefficient of flow CdAs one of the important parameters of the flow-out characteristic of the sonic nozzle, the important parameter is used for correlating the actual mass flow and the ideal mass flow of the gas flowing through the sonic nozzle and ensuring the gas flow metering to be accurate, reliable and uniform in quantity valueThe key parameter is that the pVTt method gas flow standard device is the main standard device for detecting the outflow coefficient of the sonic nozzle, and the calculation formula is shown in formula (3). The utility model discloses the temperature control system of accessible additional volume department realizes pVTt method gas flow standard device thermal equilibrium time's reduction, improves detection efficiency. Based on the measurement capability of the pVTt method gas flow standard device, the initial parameters of the temperature control system can be prefabricated in the control system of the standard device, and the optimized control parameters are finally determined through typical experiments, so that the detection efficiency of the pVTt method gas flow standard device is reduced to a value within 10 minutes from the traditional hour magnitude, and the detection efficiency is greatly improved.
Although the present invention has been described in connection with the preferred embodiments, it is not intended to limit the invention to the specific embodiments described. To anyone skilled in the art, without departing from the scope of the present invention, the technical solution disclosed above can be used to make many possible variations and modifications to the technical solution of the present invention, or to modify equivalent embodiments with equivalent variations. Therefore, any simple modification, equivalent change and modification made to the above embodiments by the technical entity of the present invention all still fall within the protection scope of the technical solution of the present invention, where the technical entity does not depart from the content of the technical solution of the present invention.
Claims (4)
1. A temperature control system at an additional volume in a pVTt method gas flow standard device is characterized in that:
the pVTt method gas flow standard device comprises a critical flow Venturi nozzle, a switch valve, a standard container and a control system; an additional volume between the critical flow venturi nozzle and the on-off valve;
one end of the additional volume is connected with the critical flow Venturi nozzle, and the other end of the additional volume is connected with the switch valve;
a temperature control system is arranged at the additional volume and regulates and controls the temperature at the additional volume;
the temperature control system includes: one end of the heating part is directly connected with the nozzle outlet, the other end of the heating part extends to be close to the refrigerating part, the heating quantity in the heating part is controlled by the heating power of an electric heating wire, and the heating wire is wound on the additional volume; one end of the refrigerating part is adjacent to the heating part, the other end of the refrigerating part is close to a standard container of the pVTt method gas standard device, and the refrigerating capacity of the refrigerating part is controlled by the flow of cooling circulating water; the refrigeration part comprises a water pump, a cooling water tank and a cooling water pipe, wherein the cooling water pipe is wound on the additional volume, and the additional volume is cooled through the cooling water pipe.
2. The system for controlling temperature at an additional volume in a pVTt method gas flow calibration apparatus of claim 1, wherein: the switch valve is provided with a timer for controlling the measurement initiation of the pVTt method gas standard device and recording the gas inlet time.
3. The system for controlling temperature at an additional volume in a pVTt method gas flow calibration apparatus of claim 1, wherein: the control system of the standard device measures the stagnation temperature and the stagnation pressure at the upstream of the critical flow venturi nozzle, and simultaneously records the air inlet time recorded by the timer and the initial and final temperature and pressure in the standard container.
4. The system for controlling temperature at an additional volume in a pVTt method gas flow calibration apparatus of claim 1, wherein: and the temperature control system regulates and controls the temperature according to the flow of the critical flow Venturi nozzle to be measured.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115574899A (en) * | 2022-09-28 | 2023-01-06 | 中国计量科学研究院 | Temperature control system and method of passive piston gas flow standard device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115574899A (en) * | 2022-09-28 | 2023-01-06 | 中国计量科学研究院 | Temperature control system and method of passive piston gas flow standard device |
| CN115574899B (en) * | 2022-09-28 | 2023-04-04 | 中国计量科学研究院 | Temperature control system and method of passive piston gas flow standard device |
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