JP5257812B2 - How to measure the air volume in the wind path - Google Patents

Description

  The present invention relates to an air volume measuring method for measuring the velocity and flow rate of gas flowing in an air passage.

  Various measurement methods have been proposed as conventional air volume measuring means in an air passage. In particular, the mixed dilution method is a method that can accurately measure the air volume in a complex combined airway, unlike the other measurement methods that use pitot tubes or orifices, without the need to rectify the airway. It is.

  For example, in Patent Document 1, while measuring the air volume of the measurement target air passage temporarily using the mixed dilution method, the detected differential pressure from the fluid pressure detection device separately provided on the air passage is examined, The relationship is clarified once, and the device for performing the subsequent air volume measurement with the detection differential pressure of the fluid pressure detection device is devised.

  However, even in the use of such a mixed dilution method, the fact is that it has not been adopted even in a field that actually requires airflow measurement because it has the following problems.

First, since the tracer gas is gasified from the liquefied state in the gas cylinder and injected into the air passage, the gas temperature in the cylinder is rapidly decreased by the heat of vaporization, and the pressure in the cylinder is decreased. Due to this phenomenon, the gas injection pressure into the air passage fluctuates, and the gas cannot be stably injected into the air passage. In order to prevent this, the internal pressure in the cylinder is kept constant by, for example, winding a heater around the cylinder. As the air volume increases, the amount of tracer gas injected also increases, requiring a large-capacity heater, increasing the size of the apparatus itself, and causing problems that are difficult to use in fields that actually require air volume measurement.
JP2008-185515

  Due to the problems with the conventional air volume measurement method using the mixed dilution method, a large amount of tracer gas is injected into the air path with a simple device when measuring a large air volume, and the tracer gas is liquid in the air path. Therefore, there has been a demand for a method capable of adjusting the amount of injection when injecting into a tube and obtaining a stable injection state with a simple mechanism.

  In view of this point, the present invention provides a method for injecting a large amount of tracer gas into the air passage with a simple device when measuring a large air volume, and a constant amount when injecting the tracer gas into the air passage in liquid form. Another object of the present invention is to provide a method for reducing the amount of tracer gas cylinders brought into the measurement field, which is a practical burden.

  In order to achieve the above object, according to the present invention, in the mixed dilution method, which is a method for measuring the amount of air in an air passage, the tracer gas is injected into the air passage to be measured in a liquefied state. This is a characteristic airflow measurement method.

  A second aspect of the present invention is the air volume measuring method according to the first aspect, wherein the amount of injection into the air passage is adjusted by the hole diameter of the spray nozzle and the number of nozzles installed.

  A third aspect of the invention is a method of measuring the air volume in which the liquid tracer gas is injected according to the first aspect, and the injection in a liquefied state is possible by using a general gas cylinder in an inverted manner.

  In the method of the present invention, the air passage includes not only a duct-like one but also a clean room or the like.

  As described above, the air volume measuring method of the present invention can send a large amount of tracer gas into the air passage with a simple device by injecting the tracer gas in a liquefied state.

  In addition, when injecting the tracer gas in the liquefied state, the injection amount can be maintained by adjusting the hole diameter of the spray nozzle and the number of nozzles installed based on the relational expression described in claim 2. .

  Further, by using the tracer gas cylinder in an inverted state, the tracer gas can be injected in a liquid state more easily.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows a state where the tracer gas is injected into the air passage 100 in a liquefied state. The tracer gas in the liquefied state is spray-injected into the air passage 100 from the spray nozzle 13 via the header 12 from the injection tube 11.

  Further, a primary side sampling pipe 14 is installed upstream of the point where the tracer gas is injected. A plurality of primary side air suction holes 14a for sucking air in the air passage are formed in the primary side sampling tube 14 at appropriate intervals.

  A small amount of air is sampled using this primary air suction hole 14a. This sampling air is sent to a gas concentration analyzer, and the concentration of the same gas component as the tracer gas 1 existing in the air of the fluid to be measured is measured.

  On the other hand, the secondary side air sampling pipe 15 is also installed downstream of the point where the tracer gas 1 is injected. Similar to the primary side air sampling pipe 14, a secondary side air suction hole 15a is provided to sample a small amount of air. This sampling air is also sent to the gas concentration analyzer, and the concentration of the tracer gas 1 mixed and diluted with air as the fluid to be measured is measured.

  If the difference in the tracer gas concentration between the primary side air and the secondary side air measured in this way and the amount of tracer gas injected into the wind path are known, the air volume in the wind path can be determined.

  By injecting the tracer gas in a liquefied state as shown in FIG. 1, a large amount of the tracer gas 1 can be stably injected into the air passage, and the air flow measurement of a large air passage with a large air flow can be easily performed.

  For example, when carbon dioxide is used as the tracer gas, most of the liquefied carbon dioxide changes to dry ice due to a sudden pressure drop and temperature drop immediately after being sprayed from the spray nozzle 13. Furthermore, this dry ice immediately exchanges heat with air, which is the fluid to be measured, and changes to carbon dioxide gas. Such a series of phase changes is smoothly promoted by spray injection using the spray nozzle 13.

ガス液化状態の密度（ｋｇ／ｍ^３）、Ｐはヘッダーの内圧（Ｐａ）、Ｎはノズル設置数、ｋは比例定数とし取り得る範囲は次の通りとする。０．１＜ｋ＜０．９In FIG. 1, in order to stably inject the tracer gas supplied in a liquefied state into the air passage 100, the amount of the tracer gas injected, the hole diameter of the spray nozzle 13 provided in the header 12, and the number of nozzles provided are as follows. Adjust with the relational expression.

The density in the gas liquefied state (kg / m ³ ), P is the internal pressure (Pa) of the header, N is the number of nozzles installed, k is a proportional constant, and the possible range is as follows. 0.1 <k <0.9

  Even if an attempt is made to adjust the flow rate of the tracer gas injected in the liquefied state by installing a valve or an orifice on the injection tube 11 between the spray port and the cylinder, the presence of these causes a local pressure drop, and vaporization occurs. It will cause a phenomenon. Since the heat of vaporization is deprived by this vaporization phenomenon, the tracer gas may change phase from a liquefied state to a solid state, block the injection tube 11 and cause a problem that stable tracer gas cannot be injected.

  Moreover, the following is mentioned as necessity of adjustment of tracer gas injection amount. First, the concentration of the tracer gas mixed and diluted with the fluid to be measured is measured by a gas concentration analyzer. However, since the measurement range of the gas concentration is usually limited, it is necessary to keep the concentration within that range.

  Furthermore, for example, when carbon dioxide is injected as a tracer gas, consideration for the environment is also necessary. Since the long-term stability limit for human carbon dioxide is said to be 5000 ppm, the amount of tracer gas to be injected should be adjusted so as to be kept below this limit concentration in a state of being mixed and diluted with air.

  In addition, although the direction of the spray nozzle 13 shown in FIG. 1 is installed so that spray injection is performed toward the upstream side, spray injection may be performed in any direction.

  In addition, the primary sampling tube 14 and the secondary sampling tube 15 are provided with air suction holes toward the upstream and the downstream, respectively, but may be directed in either direction.

  FIG. 2 shows a state in which the tracer gas cylinder 2 is used upside down in order to inject the tracer gas into the air passage 100 in a liquefied state. The cylinder is stood on the cylinder inverted stand 4 for the purpose of preventing the fall, and is on the weight scale 3. By inverting the cylinder 2, the tracer gas can be easily taken out in a liquefied state.

  The liquefied tracer gas is sent into the air passage 100 via the opening / closing cock 10 and the injection tube 11. The tracer gas injection amount in the liquefied state appears as a change in the weight measured by the weigh scale 3. By using the weigh scale 3, there is an advantage that the injection amount can be accurately measured regardless of the amount of injection, and the change in weight over time can be easily taken into a personal computer or the like as sequential data.

  When the air volume to be measured ranges from a small air volume to a large air volume, a small amount of tracer gas is injected in a gas state with a small air volume, and a large amount of liquid is injected into the air passage with a large air volume in order to simplify the device. Although it is preferable, the internal structure of the gas cylinder differs between the gaseous injection and the liquid injection, and it is necessary to prepare two types of cylinders of normal specification and siphon type specification. However, according to the present invention, the cylinder 2 can be used in an upright position with a small air volume, and can be used with one type because it is used upside down with a large air volume. Thereby, the amount of cylinders brought into the measurement field can be reduced.

  FIG. 3 shows an application example in the clean room 114. The clean room 114 is a circulatory air conditioning system in which return air and outside air are appropriately cleaned and adjusted in temperature and humidity by a filter, heat exchanger, etc., and has a high degree of air cleaning and a uniform air flow in the room. Is an important factor.

  In general, the air sent to the clean room 114 is pushed out by the blower 111, passes through the duct 110, reaches the clean room ceiling surface, and is sent from the air volume adjusting damper 112 to the room via the high performance filter 113.

  In such an environment, as a method of measuring the state of the airflow, first, the amount of air blown into the clean room 114 and the air volume distribution in the clean room 114 are measured.

  The measurement is performed by sampling the air for measuring the gas concentration of the same gas component as the tracer gas in the fluid to be measured by the primary side sampling pipe 14 provided on the discharge side of the blower 111, and the header provided in the downstream area thereof. The spray nozzle 13 disposed at 12 sprays the tracer gas into the air passage 110, and further samples the air in order to measure the degree of dilution of the tracer gas in the downstream side sampling pipe 15 to measure the gas concentration. Measure the air volume.

  Further, the air volume distribution can be obtained by measuring the arrival time and concentration of the tracer gas with a plurality of gas concentration analyzers 115 installed in the clean room 114.

It is sectional drawing which shows embodiment of this invention. It is a front view which shows embodiment of this invention. It is sectional drawing which shows the application example in a clean room.

Explanation of symbols

1 tracer gas 2 tracer gas cylinder 3 weigh scale 4 cylinder inverted base 10 opening / closing cock 11 injection tube 12 header 13 spray nozzle 14 primary side sampling pipe 14a primary side air suction hole 15 secondary side sampling pipe 15a secondary side air suction Hole 100 Airway 110 Duct 111 Blower 112 Airflow adjustment damper 113 High performance filter 114 Clean room 115 Gas concentration analyzer 116 Airflow adjustment damper for exhaust

Claims (3)

  The tracer gas is liquefied into the wind path when injecting the tracer gas upwind of the wind path and measuring the concentration of the tracer gas down the wind path to measure the air volume in the wind path. An air volume measuring method characterized by injecting. In claim 1, the amount of tracer gas injected into the air passage, the nozzle hole diameter of the spray nozzle disposed in the header provided in the air passage as an inlet, and the number of nozzles to be installed are represented by the following equation (1). A characteristic air flow measurement method.

Here, Iq is the tracer gas injection amount (kg / s), D is the nozzle hole diameter (m), ρ is the density in the tracer gas liquefied state (kg / m ³ ), P is the internal pressure (Pa) of the header, N is The number of nozzles installed, k is a proportional constant, and the possible range is as follows. 0.1 <k <0.9   3. The air volume measuring method according to claim 1, wherein when the tracer gas is injected, the gas cylinder is inverted and supplied to the nozzle region in a liquefied state.

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