Method for estimating density of overheated steam, and method for measuring volumetric flow rate of overheated steam

Abstract

To provide a method for estimating a density of overheated steam, capable of easily grasping a density of overheated steam in a predetermined pressure state at a target predetermined temperature.SOLUTION: In a virtual density calculation step S11, a virtual density ρntp, which is a density of virtual overheated steam in a standard state, is calculated using an ideal gas equation of state, based on conditions of a temperature Tntp and a pressure Pntp in the standard state and a molecular weight of water M, assuming that the overheated steam is ideal gas and exists in the standard state. In a density estimation step S12, the virtual density ρntp calculated in the virtual density calculation step S11 is used to calculate a density ρest of overheated steam at a predetermined temperature Tpd and pressure Ppd based on Boyle's law, thereby estimating the density ρest of overheated steam at the predetermined temperature Tpd and pressure Ppd.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for estimating the density of superheated steam and a method for measuring the volumetric flow rate of superheated steam. [Background technology]

[0002] It is known to heat a workpiece with superheated steam to perform heat treatment on the workpiece (see, for example, Patent Document 1). Patent Document 1 discloses a steam reflow apparatus 1 that heat-treats a workpiece carried into a heating furnace 2 by heating the workpiece with superheated steam that is continuously supplied into the heating furnace 2. Only the temperature of the superheated steam continuously supplied to the heating furnace 2 is measured by a temperature sensor 4.

[0003] When heat treating a workpiece with superheated steam, depending on the type of heat treatment, it may be necessary to more accurately grasp the atmospheric conditions in the heat treatment chamber where the workpiece is heat treated. In this case, it is desirable to be able to measure and monitor the volumetric flow rate of the superheated steam continuously supplied into the heat treatment chamber. However, the steam reflow apparatus 1 disclosed in Patent Document 1 can only monitor the temperature of the superheated steam supplied to the heating furnace 2, and cannot measure and monitor the volumetric flow rate of the superheated steam.

[0004] A known method for measuring the amount of water vapor is disclosed in Patent Document 2. In the measurement method disclosed in Patent Document 2, a gas having a known amount of water vapor is mixed with a high-temperature gas to be measured, the amount of water vapor in the mixed gas is made sufficiently smaller than that of the gas to be measured, the temperature of the mixed gas is lowered to a temperature at which the humidity can be measured with a hygrometer such as a wet-and-dry-bulb hygrometer or an electrical resistance hygrometer, and the amount of water vapor in the mixed gas is determined based on the measurement results from the hygrometer.Then, the mixing ratio of the gas to be measured and the gas having the known amount of water vapor is determined, and the amount of water vapor in the gas to be measured is determined based on this determined mixing ratio and the measured amount of water vapor in the mixed gas. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-2325 [Patent Document 2] Japanese Patent Publication No. 53-93089 Summary of the Invention [Problem to be solved by the invention]

[0006] The steam reflow apparatus 1 disclosed in Patent Document 1 can only monitor the temperature of the superheated steam supplied to the heating furnace 2, which is the destination of the superheated steam, and cannot measure and monitor the volumetric flow rate of the superheated steam. Furthermore, the measurement method disclosed in Patent Document 2 involves mixing the gas to be measured with a gas with a known amount of water vapor to lower the temperature, then using a hygrometer to determine the amount of water vapor in the mixed gas, and then measuring the amount of water vapor in the gas to be measured based on this and the mixing ratio of the mixed gas. Therefore, it is not possible to measure and monitor the volumetric flow rate of the superheated steam continuously supplied to the destination of the superheated steam.

[0007] In order to measure and monitor the volumetric flow rate of superheated steam continuously supplied to a destination, it is desirable to realize a flow meter capable of measuring the volumetric flow rate of superheated steam. The present inventors conducted extensive research into methods for realizing such a flow meter and discovered that it is possible to measure and monitor the volumetric flow rate of superheated steam by using an area flow meter. Meanwhile, designing an area flow meter requires knowing the density of the fluid to be measured. However, knowing the density of superheated steam at a given temperature and pressure requires the construction of a dedicated device for generating superheated steam at that temperature and pressure and measuring its density, which is not easily accomplished.

[0008] The present invention aims to provide a method for estimating the density of superheated steam, which allows easy determination of the density of superheated steam at a given target temperature and pressure, and a method for measuring the volumetric flow rate of superheated steam using an area flow meter designed using the density estimated using this estimation method. [Means for solving the problem]

[0009] (1) In order to solve the above problem, the method of estimating the density of superheated steam of the present invention is to estimate a virtual density ρ of the superheated steam at a standard state, assuming that the superheated steam is an ideal gas and exists at a standard state. ntp (kg / m 3 ) at the temperature T ntp (K) and pressure P ntp a virtual density calculation step of calculating the virtual density ρ from the equation of state of an ideal gas based on the condition of (Pa) and the molecular weight M (g / mol) of water; ntp Using the specified temperature T pd (K) at a given pressure P pd The density ρ of the superheated steam in (Pa) est (kg / m 3 ) based on Boyle's law, the predetermined temperature T pd At the predetermined pressure P pd The density ρ of the superheated steam in the state est and a density estimation step of estimating

[0010] (2) In the virtual density calculation step, the virtual density ρ is calculated using the following formula (1): ntp Calculate. JPEG2025167842000002.jpg33121 where R is the gas constant (J / (K·mol)).

[0011] (3) In the density estimation step, the predetermined temperature T pd At the predetermined pressure P pd The density ρ of the superheated steam in the state est is calculated using the following formula (2). JPEG2025167842000003.jpg33121

[0012] (4) In order to solve the above problem, the method for measuring the volumetric flow rate of superheated steam of the present invention is a method for measuring the density ρ of superheated steam estimated by the above-mentioned method for estimating the density of superheated steam. est A flow meter designed to measure a fluid at a predetermined pressure P pd and the predetermined temperature T pd The volumetric flow rate of the superheated steam passing through the area flow meter is measured by the area flow meter. [Effects of the Invention]

[0013] According to the present invention, a method for estimating the density of superheated steam can be provided, which makes it possible to easily grasp the density of superheated steam at a given target temperature and a given pressure, and further, a method for measuring the volumetric flow rate of superheated steam using an area flow meter designed using the density estimated using this estimation method can be provided. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart illustrating a method for estimating the density of superheated steam according to an embodiment of the present invention. [Figure 2] 1 is a flowchart illustrating a method for measuring a volumetric flow rate of superheated steam according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram schematically illustrating an area flow meter for measuring the volumetric flow rate of superheated steam. [Figure 4] FIG. 4(A) is a cross-sectional view showing a schematic internal structure of the area flow meter, and FIG. 4(B) is a cross-sectional view taken along the line XX in FIG. 4(A). [Figure 5] FIG. 1 is a diagram showing a system configuration for measuring the volumetric flow rate of superheated steam. [Figure 6] FIG. 10 is a diagram showing the measurement results of the volumetric flow rate of superheated steam. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present invention can be widely applied to various uses as a method for estimating the density of superheated steam and a method for measuring the volumetric flow rate of superheated steam. In the following description, first, the method for estimating the density of superheated steam according to this embodiment will be described, then the method for measuring the volumetric flow rate of superheated steam according to this embodiment will be described, and finally, a system for measuring the volumetric flow rate of superheated steam by applying the method for measuring the volumetric flow rate of superheated steam according to this embodiment will be described.

[0016] [Method for estimating the density of superheated steam] Superheated steam is water vapor in a gaseous state heated to a temperature higher than the boiling point, and is dry water vapor at a temperature higher than the boiling point. Because superheated steam is dry water vapor at a temperature higher than the boiling point, it does not exist under standard conditions (0°C, 1 atmosphere). However, in the method for estimating the density of superheated steam of this embodiment, the superheated steam is regarded as an ideal gas, and a virtual density ρ is used as the density of virtual superheated steam assuming that the superheated steam exists under standard conditions. ntp Then, in the method for estimating the density of superheated steam according to the present embodiment, the calculated virtual density ρ ntp Based on Boyle's law, the density of the superheated steam of interest is calculated at a predetermined temperature T pd At a given pressure P pd For superheated steam in this state, its density ρ est Estimate.

[0017] Fig. 1 is a flowchart for explaining a method for estimating the density of superheated steam according to an embodiment of the present invention. Referring to Fig. 1, the method for estimating the density of superheated steam according to this embodiment includes a virtual density calculation step S11 and a density estimation step S12.

[0018] In the virtual density calculation step S11, first, the superheated steam is regarded as an ideal gas and the superheated steam is in a standard state (i.e., the temperature is 0°C (273.15K) and the pressure is 1 atmosphere (1.01325 × 10 5Let us consider a hypothetical superheated steam that is assumed to exist at a standard temperature (Pa). Then, let us consider a hypothetical density ρ as the density at standard temperature of the hypothetical superheated steam that is assumed to exist at standard temperature. ntp (kg / m 3 ) at standard temperature T ntp (K) and pressure P ntp It is calculated from the ideal gas equation of state based on the condition of (Pa) and the molecular weight of water, M (g / mol).

[0019] Assuming 1 mol of hypothetical superheated steam in a standard state, the following equation (a) can be derived from the ideal gas equation using the gas constant R (J / (K·mol)) for 1 mol of hypothetical superheated steam in a standard state. JPEG2025167842000004.jpg33121 Here, the pressure P under the above standard conditions ntp For example, P ntp =1.01325×10 5 (Pa). The molecular weight M of water is set as the molar mass, for example, M = 18 (g / mol). The gas constant R is, for example, R = 8.31 (J / (K·mol)). The temperature T ntp For example, T ntp =273.15(K).

[0020] From the above equation (a), the virtual density ρ of superheated steam, which is assumed to exist under standard conditions, is ntp (kg / m 3 ) is calculated using the following formula (b). JPEG2025167842000005.jpg33121

[0021] Pressure P under standard conditions ntp For example, P ntp =1.01325×10 5 (Pa), the molecular weight of water M is, for example, M = 18 (g / mol), the gas constant R is, for example, R = 8.31 (J / (K·mol)), and the temperature at standard conditions T ntp As, T ntp= 273.15(K), the hypothetical density ρ of hypothetical superheated steam at standard state, which is assumed to exist at standard state, is ntp For example, ρ ntp ≒0.8035(kg / m 3 ) is calculated as

[0022] In the density estimation step S12, the virtual density ρ calculated in the virtual density calculation step S11 is ntp Using the specified temperature T pd (K) at a given pressure P pd Density ρ of superheated steam in (Pa) est (kg / m 3 ) based on Boyle's law, the temperature at a given temperature T pd At a given pressure P pd The density of superheated steam in this state is ρ est The temperature T pd and a given pressure P pd is the density of superheated steam ρ est The temperature T of the superheated steam at the state at which it is desired to estimate pd and pressure P pd is.

[0023] 1 mol of hypothetical superheated steam at standard temperature and 1 mol of water at a given temperature T pd At a given pressure P pd Assuming superheated steam in this state, the following equation (c) can be derived based on Boyle's law. JPEG2025167842000006.jpg33138

[0024] From the above formula (c), the predetermined temperature T pd At a given pressure P pd The density of superheated steam in this state is ρ est is calculated using the following formula (d). JPEG2025167842000007.jpg33138

[0025] The virtual density ρ is the density of the virtual superheated steam assumed to exist at standard conditions. ntp For example, the ρ calculated in the above examplentp =0.8035(kg / m 3 ) and the pressure P ntp For example, P ntp =1.01325×10 5 (Pa), and the temperature at standard ntp For example, T ntp = 273.15 (K) (i.e., 0°C), and the given pressure P pd For example, P pd =1.01325×10 5 (Pa) at a given temperature T pd For example, T pd = 453.15 (K) (i.e., 180°C), the given temperature T pd At a given pressure P pd The density of superheated steam in this state is ρ est For example, ρ est ≒0.4843(kg / m 3 ) is calculated as

[0026] As described above, according to the method for estimating the density of superheated steam of this embodiment, the virtual density ρ ntp is calculated from the equation of state of an ideal gas, and its virtual density ρ ntp Based on Boyle's law, the temperature T pd At a given pressure P pd The density of superheated steam in this state is ρ est Therefore, the predetermined temperature T pd At a given pressure P pd There is no need to construct a dedicated device for generating superheated steam in the state of pd At a given pressure P pd The density of superheated steam in this state is ρ est can be easily grasped.

[0027] [Method for measuring the volumetric flow rate of superheated steam] Next, a method for measuring the volumetric flow rate of superheated steam according to an embodiment of the present invention will be described. In the method for measuring the volumetric flow rate of superheated steam according to this embodiment, first, the density ρ estimated by the above-mentioned method for estimating the density of superheated steam is calculated. est Fabricate and prepare a variable area flow meter fm designed to measure a fluid with a density ρ est A variable area flow meter fm is designed to measure a fluid at a given pressure P pd and a given temperature T pd The volumetric flow rate Q of the superheated steam passing through the area flow meter fm is measured by the area flow meter fm.

[0028] 2 is a flowchart for explaining the method for measuring the volumetric flow rate of superheated steam according to this embodiment. When the method for measuring the volumetric flow rate of superheated steam according to this embodiment is carried out, first, a predetermined pressure P pd and a given temperature T pd The superheated steam adjusted to the predetermined pressure P pd and a given temperature T pd The superheated steam in this state is generated by a superheated steam generator that is composed of a boiler and a superheater. In the superheated steam generator, the boiler heats and evaporates water to generate saturated steam at a temperature close to the boiling point, and the superheater further heats the saturated steam generated in the boiler to generate a predetermined pressure P pd At a given temperature T pd Heat it until it reaches a predetermined pressure P pd At a given temperature T pd Superheated steam in this state is generated.

[0029] Given pressure P pd At a given temperature T pd When the superheated steam in this state is generated, the superheated steam is supplied to the area flow meter fm (step S22). The area flow meter fm measures the density ρ est The pressure and temperature of superheated steam are determined by the temperature and pressure.pd At a given temperature T pd The density of superheated steam in this state is the density ρ est In other words, the area flow meter fm is pd At a given temperature T pd In the state of density ρ est It is designed to measure the volumetric flow rate of superheated steam.

[0030] Given pressure P pd and a given temperature T pd and density ρ est The superheated steam in this state has a density of ρ est The superheated steam is fed into and passes through an area flow meter fm, which is designed to measure the volumetric flow rate of the superheated steam at a given pressure P pd and a given temperature T pd and density ρ est The superheated steam in this state passes through the area flow meter fm, and the volumetric flow rate Q of the superheated steam is measured (step S23). The superheated steam whose volumetric flow rate Q has been measured flows out of the area flow meter fm and is supplied to the supply destination of the superheated steam (step S24).

[0031] where density ρ est The area flow meter fm for measuring the volumetric flow rate of superheated steam in this state will be further described. Fig. 3 is a diagram that schematically shows the area flow meter fm for measuring the volumetric flow rate of superheated steam. Fig. 4(A) is a cross-sectional view that schematically shows the internal structure of the area flow meter fm, and Fig. 4(B) is a cross-sectional view taken along the arrow XX in Fig. 4(A). Referring to Figs. 3 and 4, the area flow meter fm is connected to an upstream pipe 11, and receives a fluid having a predetermined temperature T pd and a given pressure P pd The superheated steam adjusted to a predetermined temperature T pd and a given pressure P pdThe superheated steam in this state passes through the area flow meter fm, which measures the volumetric flow rate Q of the passing superheated steam. The area flow meter fm is connected to the downstream pipe 12, and the superheated steam that has passed through the area flow meter fm and whose volumetric flow rate Q has been measured flows out from the area flow meter fm to the downstream pipe 12 and is supplied to the destination of the superheated steam through the downstream pipe 12.

[0032] The area flow meter fm includes a flow meter body 13, a tapered tube 14, a float 15, etc. The flow meter body 13 connects the upstream pipe 11 and the downstream pipe 12, and is provided as a housing that houses the tapered tube 14. The upstream pipe 11 and the downstream pipe 12 connected to the flow meter body 13 are connected to the tapered tube 14 inside the flow meter body 13. A scale 13a is provided on the front of the flow meter body 13 for reading the volumetric flow rate Q of the superheated steam measured by the area flow meter fm.

[0033] The tapered pipe 14 of the area flow meter fm is installed inside the flow meter body 13, extending in the vertical direction, and is provided as a pipe through which superheated steam supplied from the upstream pipe 11 passes from bottom to top. The tapered pipe 14 is tapered so that its cross-sectional area gradually increases from its bottom to its top. The lower end of the tapered pipe 14 is connected to the upstream pipe 11, and the upstream pipe 11 and the interior of the tapered pipe 14 are in communication. The upper end of the tapered pipe 14 is connected to the downstream pipe 12, and the interior of the tapered pipe 14 is in communication with the downstream pipe 12. The superheated steam supplied from the upstream pipe 11 to the lower end of the tapered pipe 14 flows from bottom to top through the tapered pipe 14 and then flows from the upper end of the tapered pipe 14 to the downstream pipe 12. In FIG. 4(A), the flow direction of the superheated steam is indicated by a dashed arrow.

[0034] The float 15 of the area flow meter fm is disposed inside the tapered pipe 14. The float 15 is provided as a sphere made of, for example, metal, ceramic, or resin. The float 15 is configured to move up and down according to the volumetric flow rate Q of the superheated steam flowing inside the tapered pipe 14.

[0035] A given temperature T pd and a given pressure P pd The superheated steam adjusted to the above is introduced from the upstream pipe 11 to the lower end of the tapered pipe 14 and flows upward through the tapered pipe 14. As the superheated steam flows upward through the tapered pipe 14, the float 15 is positioned at a position where it is in equilibrium with the tapered pipe 14 in accordance with the volumetric flow rate Q of the superheated steam flowing upward, in relation to the pressure difference between the upper and lower parts of the float 15 and the gravity and buoyancy acting on the float 15. Then, the volumetric flow rate Q of the superheated steam flowing upward through the tapered pipe 14 is measured based on the position where the float 15 is in equilibrium with the tapered pipe 14. The volumetric flow rate Q of the superheated steam is measured by reading the scale 13a at the position where the float 15 is in equilibrium.

[0036] The superheated steam supplied to the area flow meter fm is heated to a predetermined temperature T pd and a given pressure P pd is adjusted to a predetermined temperature T pd and a given pressure P pd The density of the superheated steam adjusted to ρ is calculated by the method shown in the flowchart in Figure 1. est The area flow meter fm is pd At a given pressure P pd The density ρ est The system is set up to measure the volumetric flow rate Q of the superheated steam.

[0037] In the area flow meter fm, the volumetric flow rate Q of the superheated steam measured is expressed by the following equation (e) based on the balance of the forces of the float 15 in the tapered tube 14. JPEG2025167842000008.jpg35154 In the above formula (e), "C" is the discharge coefficient, which is an adjustment coefficient between the theoretical formula and the flow rate obtained by an actual test under the conditions of the area flow meter fm. "A" represents the flow area, which is the area through which superheated steam flows between the inner circumference of the tapered tube 14 and the outer circumference of the float 15 when the float 15 is in balance. In other words, "A" is the area of ​​the difference between the cross-sectional area of ​​the inner circumference of the tapered tube 14 when the float 15 is in balance and the cross-sectional area of ​​the maximum diameter part of the float 15, and is the area indicated by the symbol A in Figure 4(B). "g" is the gravitational acceleration. "V f " is the volume of the float 15. "A f " is the cross-sectional area of ​​the maximum diameter part of the float 15, and in Figure 4(B) f The area of ​​the region indicated by the symbol ρ f " is the density of the float 15. "ρ est " is the density used in the design of the area flow meter fm, and is the density of the superheated steam that the area flow meter fm is intended to measure, and is the density of the superheated steam that the area flow meter fm is intended to measure at a predetermined temperature T pd and a given pressure P pd is the density of superheated steam in this state.

[0038] In the above equation (e), the flow coefficient C, the gravitational acceleration g, and the volume V of the float 15 f , the cross-sectional area A of the maximum diameter part of the float 15 f , and the density ρ of float 15 f is a fixed value, and the density ρ of the superheated steam to be measured est Even if the superheated steam reaches a predetermined pressure P pd and a given temperature T pd Therefore, in the area flow meter fm, there is a fixed relationship between the flow area A, which is determined by the position of the float 15 in the tapered tube 14, and the volumetric flow rate Q of the superheated steam passing through, and the volumetric flow rate Q of the superheated steam can be measured by detecting this position.

[0039] In the area flow meter fm, for example, the flow rate display value displayed corresponding to the scale 13a for reading the measured volumetric flow rate Q of superheated steam is displayed so that the volumetric flow rate Q is read as a volumetric flow rate converted to a standard state, assuming that the superheated steam is in a standard state. Furthermore, the measurement of the volumetric flow rate Q of superheated steam in the area flow meter fm does not have to be performed by reading the scale 13a. For example, a magnet may be provided in the float 15, and the position of the float 15 relative to the tapered tube 14 may be magnetically detected by detecting the magnitude of the magnetic force from the magnet, thereby measuring the volumetric flow rate Q of the superheated steam. In this case, the area flow meter fm is configured to display the measured value of the volumetric flow rate Q measured by magnetically detecting the position of the float 15 relative to the tapered tube 14.

[0040] [Volumetric flow measurement system] Next, a system for measuring the volumetric flow rate Q of superheated steam by applying the method for measuring the volumetric flow rate of superheated steam according to this embodiment will be described.

[0041] 4 is a diagram showing the configuration of a volumetric flow measurement system 20 for measuring the volumetric flow rate Q of superheated steam by applying the method for measuring the volumetric flow rate of superheated steam of this embodiment. The volumetric flow measurement system 20 includes a superheated steam generator 21, an upstream pipe 11, an area flow meter fm, a downstream pipe 12, a controller 22, etc. The volumetric flow measurement system 20 measures the volumetric flow rate Q of superheated steam at a predetermined temperature T pd and a given pressure P pd The generated superheated steam is supplied to an area flow meter fm, which measures the volumetric flow rate Q. The superheated steam with the measured volumetric flow rate Q is then supplied to a heat treatment device 30, which is the destination of the superheated steam. The heat treatment device 30 is configured as a device that heats a ceramic or metallic workpiece with superheated steam to perform heat treatment on the workpiece. In the heat treatment device 30, the workpiece is continuously supplied with superheated steam via the volumetric flow rate measuring system 20, thereby performing heat treatment on the workpiece.

[0042] In the superheated steam generator 21, a predetermined temperature Tpd and a given pressure P pd The superheated steam generator 21 is configured to include a boiler and a superheater, and the operations of the boiler and the superheater are controlled by a controller 22. The controller 22 controls the temperature of the boiler to a predetermined temperature T pd and a given pressure P pd The superheated steam generator 21 is controlled so as to generate superheated steam in the above state.

[0043] The upstream pipe 11 connects the superheated steam generator 21 and the area flow meter fm, and the superheated steam generated by the superheated steam generator 21 is heated to a predetermined temperature T pd and a given pressure P pd The superheated steam in this state is supplied to the area flow meter fm. In addition, a temperature sensor 23 and a pressure sensor 24 are provided in the upstream pipe 11. The temperature sensor 23 and the pressure sensor 24 are provided in the vicinity of the part of the upstream pipe 11 that is connected to the area flow meter fm, and detect the temperature and pressure, respectively, of the superheated steam supplied from the upstream pipe 11 to the area flow meter fm. The temperature sensor 23 and the pressure sensor 24 are electrically connected to the controller 22, and the temperature detected by the temperature sensor 23 and the pressure detected by the pressure sensor 24 are sent to the controller 22. The controller 22 controls the boiler and superheater of the superheated steam generator 21 based on the detected values ​​of the temperature sensor 23 and the pressure sensor 24, and controls the superheated steam generated in the superheated steam generator 21 to reach a predetermined temperature T pd and a given pressure P pd Furthermore, a heater 25 is provided in the upstream pipe 11. The heater 25 is provided to prevent a drop in the temperature of the superheated steam passing through the upstream pipe 11 by heating the upstream pipe 11 from the surroundings. The heater 25 is electrically connected to the controller 22, and the operation of the heater 25 is controlled by the controller 22.

[0044] The area flow meter fm is pd and a given pressure P pdThe superheated steam adjusted to the density ρ is supplied from the upstream pipe 11, and the volumetric flow rate Q of the superheated steam passing through the tapered pipe 14 of the area flow meter fm is measured, and the superheated steam whose volumetric flow rate Q has been measured is supplied to the downstream pipe 12. The area flow meter fm measures the density ρ estimated by the method shown in the flowchart of FIG. est The superheated steam supplied to the area flow meter fm is heated to a predetermined temperature T pd At a given pressure P pd and the density ρ est It is superheated steam at a given temperature T pd At a given pressure P pd In the state of density ρ est As the superheated steam passes through the area flow meter fm, the volumetric flow rate Q of the passing superheated steam is measured.

[0045] The downstream piping 12 connects the area flow meter fm and the heat treatment device 30, and supplies superheated steam whose volumetric flow rate Q is measured by the area flow meter fm to the heat treatment device 30. The downstream piping 12 is also provided with a flow rate adjustment valve 26. The flow rate adjustment valve 26 is electrically connected to the controller 22, and its valve opening is adjusted based on commands from the controller 22. By adjusting the valve opening of the flow rate adjustment valve 26, the flow rate of superheated steam supplied from the downstream piping 12 to the heat treatment device 30 is controlled. The downstream piping 12 is also provided with a heater 27. The heater 27 heats the downstream piping 12 from the surroundings, thereby preventing a drop in the temperature of the superheated steam supplied to the heat treatment device 30 through the downstream piping 12. The heater 27 is electrically connected to the controller 22, and the operation of the heater 27 is controlled by the controller 22.

[0046] The above-described volumetric flow rate measuring system 20 is operated to implement the method for measuring the volumetric flow rate of superheated steam according to this embodiment, as shown in the flowchart of Fig. 2. The superheated steam generator 21 is operated under the control of the controller 22, and the superheated steam is heated to a predetermined temperature T pd and a given pressure P pdThe generated superheated steam is heated to a predetermined temperature T pd At a given pressure P pd The superheated steam in this state is passed through the upstream pipe 11 and is heated to a temperature of 10 ... est The superheated steam is supplied to an area flow meter fm designed to measure the temperature T pd At a given pressure P pd In the state of density ρ est The superheated steam passes through the area flow meter fm, and the volumetric flow rate Q of the superheated steam passing through the area flow meter fm is measured (step S23). The superheated steam whose volumetric flow rate Q has been measured flows out of the area flow meter fm and is supplied to the heat treatment device 30, which is the supply destination of the superheated steam (step S24).

[0047] The volumetric flow rate measuring system 20 was actually constructed, and an experiment was carried out to measure the volumetric flow rate of superheated steam. Figure 6 shows the measurement results of the volumetric flow rate of superheated steam. pd = 453.15(K) (i.e., 180°C) at a given pressure P pd =1.01325×10 5 (Pa) of superheated steam with density ρ est =0.4843(kg / m 3 ) was used. In the superheated steam generator 21, pd (453.15(K)) at a given pressure P pd (1.01325×10 5 (Pa) of superheated steam was generated, and the valve opening of the flow rate adjusting valve 26 was changed to measure the volumetric flow rate of the superheated steam with the area flow meter fm at various flow rates.

[0048] To estimate the volumetric flow rate of superheated steam actually supplied from the superheated steam generator 21 to the area flow meter fm, the amount of water actually consumed per unit time in the superheated steam generator 21 to generate superheated steam was measured, and a flow rate conversion value was calculated by converting the measured water amount into the volumetric flow rate of superheated steam. The volumetric flow rate of superheated steam actually supplied from the superheated steam generator 21 to the area flow meter fm was calculated by calculating this flow rate conversion value. Note that the measured value of the volumetric flow rate of superheated steam obtained by the area flow meter fm and the flow rate conversion value based on the actual amount of water consumed by the superheated steam generator 21 were calculated as volumetric flow rates converted to standard conditions, assuming that the superheated steam was in a standard state. In FIG. 6, the data for the measured value of the volumetric flow rate of superheated steam obtained by the area flow meter fm are indicated by triangle symbols, and the data for the flow rate conversion value based on the actual amount of water consumed by the superheated steam generator 21 are indicated by square symbols.

[0049] As shown in Fig. 6, the volumetric flow rate of superheated steam measured by the area flow meter fm is changed by changing the valve opening of the flow rate adjustment valve 26. As shown in Fig. 6, it was confirmed that the measured value of the volumetric flow rate of superheated steam measured by the area flow meter fm has a good correlation with the flow rate conversion value based on the actual amount of water consumed in the superheated steam generator 21 (i.e., the value obtained by calculating the volumetric flow rate of superheated steam actually supplied to the area flow meter fm based on the actual amount of water consumed in the superheated steam generator 21). Therefore, at a predetermined temperature T pd and a given pressure P pd The superheated steam adjusted to the density ρ est The volumetric flow rate of superheated steam can be suitably measured by measuring it with an area flow meter fm designed to measure the volumetric flow rate of superheated steam.

[0050] [Effects of this embodiment] When superheated steam is continuously supplied to a heat treatment device to which the superheated steam is to be supplied, it is desirable to be able to measure the volumetric flow rate of the continuously supplied superheated steam. One possible method for measuring the volumetric flow rate of superheated steam is to use an area flow meter. In this case, in order to design the area flow meter, it is necessary to know the density of the superheated steam to be measured. According to this embodiment, a virtual density ρ, which is the density of virtual superheated steam assuming that the superheated steam exists in a standard state, is calculated. ntp is calculated from the equation of state of an ideal gas, and its virtual density ρ ntp Based on Boyle's law, the temperature T pd At a given pressure P pd The density of superheated steam in this state is ρ est Therefore, the predetermined temperature T pd At a given pressure P pd There is no need to construct a dedicated device for generating superheated steam in the state of pd At a given pressure P pd The density of superheated steam in this state is ρ est can be easily grasped.

[0051] Furthermore, according to this embodiment, the density ρ estimated as above est A flow meter fm is designed to measure superheated steam at a given temperature T pd and a given pressure P pd The area flow meter fm can measure the volumetric flow rate of the superheated steam passing through the area flow meter fm. According to this embodiment, when the superheated steam is continuously supplied to the heat treatment device 30, which is the destination of the superheated steam, the area flow meter fm can measure and monitor the volumetric flow rate of the continuously supplied superheated steam.

[0052] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, the following modifications may be made.

[0053] In the above embodiment, the predetermined temperature T pd As, T pd = 453.15 (K) is shown as an example, and the given pressure P pd As, P pd =1.01325×10 5 (Pa) as an example, the density of superheated steam ρ est However, these values ​​are merely examples and should not be used to estimate the predetermined temperature T pd and a given pressure P pd Any temperature and pressure can be selected as long as they are at a temperature and pressure at which superheated steam exists. pd and a given pressure P pd The density of superheated steam in this state is ρ est can be easily estimated and understood.

[0054] In the above embodiment, the float 15 of the area flow meter fm is a sphere, but this is not the only option. The shape of the float of the area flow meter fm may be various, and for example, a float with a shape that combines a conical shape and a cylindrical shape may be used. [Industrial Applicability]

[0055] The present invention can be widely applied as a method for estimating the density of superheated steam and a method for measuring the volumetric flow rate of superheated steam. [Explanation of symbols]

[0056] fm area flowmeter 11 Upstream piping 12 Downstream piping 13 Flow meter body 14 Tapered pipe 15 Float 20 Volumetric flow measurement system 21 Superheated steam generator 22 Controller 23 Temperature Sensor 24 Pressure Sensor 25, 27 Heater 26 Flow control valve 30 Heat treatment equipment

Claims

1. The virtual density ρ of the virtual superheated steam at the standard state, assuming that the superheated steam is an ideal gas and exists at the standard state. ｎｔｐ (kg / m ３ ) at the temperature T ｎｔｐ (K) and pressure P ｎｔｐ a virtual density calculation step of calculating the virtual density from the equation of state of an ideal gas based on the condition of (Pa) and the molecular weight M (g / mol) of water; The virtual density ρ calculated in the virtual density calculation step ｎｔｐ Using a predetermined temperature T ｐｄ (K) at a predetermined pressure P ｐｄ The density ρ of the superheated steam in the state of (Pa) ｅｓｔ (kg / m ３ ) based on Boyle's law, the predetermined temperature T ｐｄ The predetermined pressure P ｐｄ The density ρ of the superheated steam in the state ｅｓｔ a density estimation step for estimating A method for estimating the density of superheated steam, comprising:

2. 2. The method for estimating the density of superheated steam according to claim 1, In the virtual density calculation step, the virtual density ρ is calculated using the following formula (1): ｎｔｐ A method for estimating the density of superheated steam, comprising: where R is the gas constant (J / (K·mol)).

3. 2. The method for estimating the density of superheated steam according to claim 1, In the density estimation step, the predetermined temperature T ｐｄ The predetermined pressure P ｐｄ The density ρ of the superheated steam in the state ｅｓｔ A method for estimating the density of superheated steam, characterized by calculating the density of superheated steam by the following equation (2):

4. The density ρ estimated by the method for estimating the density of superheated steam according to any one of claims 1 to 3. ｅｓｔ The predetermined pressure P ｐｄ and the predetermined temperature T ｐｄ and measuring the volumetric flow rate of the superheated steam passing through the area flow meter using the area flow meter.

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