JP6177051B2 - Solid phase ratio measuring device, cooling system and solid phase ratio measuring method for solid-liquid two-phase fluid - Google Patents

Description

  The present invention relates to a solid-phase two-phase fluid solid phase ratio measuring device including a solid phase component and a liquid phase component, a cooling system including the solid phase ratio measuring device, and a solid-liquid two-phase fluid solid phase ratio. The present invention relates to the technical field of measurement methods.

  Slush nitrogen is widely known as an example of a solid-liquid two-phase fluid obtained by mixing a solid phase component and a liquid phase component. Slush nitrogen is a slurry of a mixture of atomized solid nitrogen and liquid nitrogen, and has a low temperature of 63 K and is suitable for cooling systems such as superconducting equipment because of its high fluidity. In particular, when cooling a superconducting power transmission cable that is an example of a superconducting device, it is assumed that the installation interval of the cooling station may reach several kilometers, but if a solid phase component remains on the cable outlet side several kilometers away The nitrogen temperature is kept at the melting temperature of 63K, and as a result, the superconducting cable can maintain its capacity, that is, the amount of power transmission corresponding to the critical current value at 63K.

  The ratio of the solid phase component in this solid-liquid two-phase fluid (that is, the solid phase ratio) is closely related to the heat load of the object to be cooled (the solid phase ratio indicates the mass ratio of the solid component, Since conversion of volume and mass can be easily performed, the following description will be made with the volume ratio as the solid phase ratio). For this reason, when the heat load to be cooled varies, it is important to control the solid phase ratio according to the variation. In such solid phase rate control, it is necessary to detect the solid phase rate as a reference with high accuracy.

  As a method of measuring the solid phase ratio of this kind of solid-liquid two-phase fluid, paying attention to the property that the solid phase component and the liquid phase component in the solid-liquid two-phase fluid have different relative dielectric constants, Some measure the solid phase ratio based on the change in the capacitance of a capacitor composed of a pair or a plurality of pairs of electrodes immersed in the substrate. FIG. 8 is a schematic diagram showing an example of this type of solid-phase rate measuring apparatus. In this example, a pair of electrodes 31 and 32 of the capacitor C are immersed in a solid-liquid two-phase fluid, and the capacitance of the capacitor C is measured by the detector 35 which is an LCR meter, so that the gap between the electrodes 31 and 32 is measured. The solid phase ratio can be determined by evaluating the relative dielectric constant of the solid-liquid two-phase fluid occupied. In Patent Document 1, the shape of the electrode is cylinder-to-plate-to-cylinder, and solid particles are more easily inserted between the electrodes than in the case of plate-to-plate, thereby improving measurement sensitivity.

  As described above, in FIG. 8, the capacitance of the capacitor is directly measured by the detector 35 such as an LCR meter. However, in Patent Document 2, the resonance characteristic of the resonance circuit formed by the capacitor C and the coil L is used. It is disclosed that the electrostatic capacitance C is measured. In particular, in Patent Document 2, an AC signal is applied to a resonance circuit immersed in a solid-liquid two-phase fluid, and a capacitance C is calculated by calculating a resonance frequency at which the echo signal is maximized. Is going.

Japanese Patent No. 3572200 JP 2010-223740 A

In general, the capacitance C is obtained by using the area S of the electrodes, the distance L between the electrodes, and the dielectric constant ε of the substance existing between the electrodes.
C∝εS / L (1)
It is expressed. As shown in the equation (1), since the capacitance C is proportional to the area S of the electrode, it is preferable to increase the area of the electrode in order to improve measurement sensitivity. However, when trying to measure the solid phase ratio of a solid-liquid two-phase fluid flowing in a narrow pipe, the electrode area must be reduced, and a minute change in capacitance will be measured. There is a problem that it is difficult to ensure.
On the other hand, since the capacitance C is inversely proportional to the distance L between the electrodes, it is preferable to reduce the distance L between the electrodes in order to improve the measurement accuracy of the solid phase ratio. However, in order to smoothly guide the solid-liquid two-phase fluid to be measured between the electrodes, it is necessary to ensure that the distance L between the electrodes is sufficiently larger than the particle size of the solid phase component contained in the solid-liquid two-phase fluid. There is. For this reason, there is a limit to improving the measurement accuracy by reducing the distance L between the electrodes. Improvement of measurement accuracy when measuring the solid phase ratio in a narrow pipe is a problem common to Patent Document 1 and Patent Document 2.

  In Patent Document 2, since the LCR meter measures the capacitance between the respective electrodes via the lead wire connected to the electrode, the measured value of the LCR meter includes the stray capacitance generated between the wires. . This stray capacitance typically has a magnitude of about several pF. On the other hand, when the capacitor C is installed in the pipe in order to measure the solid phase ratio of the solid-liquid two-phase fluid flowing in the narrow pipe, the electrode size of the capacitor C is limited. About 10 pF. Therefore, there is a problem that it is difficult to accurately measure the solid phase ratio because the ratio of the stray capacitance in the measured value is large.

  The present invention has been made in view of the above problems, and a solid-liquid two-phase fluid solid-phase ratio measuring apparatus capable of measuring the solid-phase ratio of a solid-liquid two-phase fluid with high accuracy and the solid-phase ratio. It aims at providing a cooling system provided with a measuring device.

  In order to solve the above problems, a solid-liquid two-phase fluid measuring device for measuring a solid phase ratio of a solid-liquid two-phase fluid containing a solid phase component and a liquid phase component is provided. A solid-phase ratio measuring apparatus comprising: a measuring circuit in which a resistor is connected in series to a parallel circuit including a capacitor and a crystal resonator connected in parallel to the capacitor; and the measuring circuit has a predetermined frequency A signal generator for inputting an AC signal, an impedance converter connected to both ends of the parallel circuit and the resistor, a voltage across the parallel circuit and a voltage across the resistor via the impedance converter A phase difference detector that detects a phase difference between the phase difference detector, and a calculation unit that calculates a solid phase ratio of the solid-liquid two-phase fluid based on the phase difference detected by the phase difference detector. The measurement circuit is connected to the solid-liquid two-phase Based on the phase difference detected by the phase difference detector when an AC signal having a parallel resonance frequency of the crystal resonator is input from the signal generator, the solid-liquid two-phase fluid is immersed in a body. The solid phase ratio is calculated.

In the present invention, a measurement circuit composed of a capacitor, a crystal resonator, and a resistor is immersed in a solid-liquid two-phase fluid to be measured, and a phase difference when an AC signal is applied is detected, so that the gap between the electrodes of the capacitor is The change in the solid phase ratio of the occupied solid-liquid two-phase fluid can be regarded as the change in the capacitance of the capacitor, and the solid phase ratio can be measured. In particular, by setting the frequency of the AC signal input to the measurement circuit to the parallel resonance frequency of the crystal resonator, the following expression Δθ∝Δc is established between the phase difference variation Δθ and the capacitance variation Δc in the measurement circuit. (2)
The proportional relationship is established. Therefore, the solid phase ratio can be accurately measured without complicated calculations in the calculation unit.
In addition, the output impedance is reduced by detecting the phase difference between the voltage across the parallel circuit and the voltage across the resistor via the impedance converter, reducing measurement errors due to noise and wiring stray capacitance on the phase difference detector side. In addition, good measurement accuracy can be obtained.

In one aspect of the present invention, the phase difference detection is performed when the measurement circuit is immersed in a fluid including only the liquid phase component and an AC signal having a parallel resonance frequency of the crystal resonator is input from the signal generator. The phase difference detected by the detector is obtained in advance as a reference phase difference, and the calculation unit is configured to determine the phase difference detected by the phase difference detector based on the amount of change from the reference phase difference. Measure the solid fraction of the phase fluid.
According to this aspect, in order to further improve the measurement accuracy, the phase difference obtained when immersed in a fluid consisting only of the liquid phase component (that is, the solid phase ratio is zero) is obtained in advance as the reference phase difference θ _0. Based on the amount of change Δθ (= θ−θ ₀ ) between the phase difference θ obtained when the measurement circuit is actually immersed in the solid-liquid two-phase fluid to be measured and the reference phase difference, The amount of change in capacitance Δc can be obtained by the equation (2), and the solid phase ratio can be measured.

Cooling system according to the present invention, the solid-liquid two-phase fluid a cooling system for cooling a thermal load is provided on the circulation circuit for circulating a refrigerant, into the circulation times path, the solid-liquid two-phase fluid A generating device to be generated, a solid-phase ratio measuring device for a solid-liquid two-phase fluid according to claim 1 or 2 installed on the downstream side of the generating device, and based on a measurement value of the solid-phase rate measuring device And a control unit that controls an operation state of the generation device.
According to this cooling system, when the solid-liquid two-phase fluid measuring device (including the various aspects described above) is provided, the solid-liquid two-phase fluid generator is controlled when the solid-liquid two-phase fluid generator is controlled. Since the solid phase ratio of the liquid two-phase fluid can be accurately grasped in real time, the distribution of the solid phase ratio of the cooling system can be maintained in an optimum state. In particular, when the thermal load changes with time, the solid phase ratio of the solid-liquid two-phase fluid flowing through the circulation path also changes. However, the solid-liquid two-phase fluid of the present invention is By accurately determining the solid phase ratio, the generator is controlled to achieve the optimal solid phase ratio according to the thermal load at that time, and a cooling system that takes advantage of the characteristics of the solid-liquid two-phase fluid is realized. be able to.

In order to solve the above problems, a solid-liquid two-phase fluid measuring method for measuring a solid-phase ratio of a solid-liquid two-phase fluid including a solid-phase component and a liquid-phase component is provided. A solid phase ratio measuring method for immersing a measuring circuit in which a resistor is connected in series to a parallel circuit including a capacitor and a crystal resonator connected in parallel to the capacitor in the solid-liquid two-phase fluid. A first step, a second step of inputting an AC signal having a parallel resonance frequency of the crystal resonator to the measurement circuit, and detecting a phase difference between the voltage across the parallel circuit and the voltage across the resistor And a fourth step of calculating a solid phase ratio of the solid-liquid two-phase fluid based on the detected phase difference.
In one aspect of the present invention, the phase difference when the measurement circuit is immersed in a fluid composed only of the liquid phase component and an AC signal having a parallel resonance frequency of the crystal resonator is input is obtained in advance as a reference phase difference. The method further includes a step, wherein the fourth step measures the solid phase ratio of the solid-liquid two-phase fluid based on a change amount of the phase difference obtained in the third step from the reference phase difference.

  The solid phase ratio measuring method for a solid-liquid two-phase fluid according to the present invention can be preferably carried out by the above-described solid phase ratio measuring apparatus (including the above-described various aspects).

In the present invention, a measurement circuit composed of a capacitor, a crystal resonator, and a resistor is immersed in a solid-liquid two-phase fluid to be measured, and a phase difference when an AC signal is applied is detected, so that the gap between the electrodes of the capacitor is The change in the solid phase ratio of the occupied solid-liquid two-phase fluid can be regarded as the change in the capacitance of the capacitor, and the solid phase ratio can be measured. In particular, by setting the frequency of the AC signal input to the measurement circuit to the parallel resonance frequency of the crystal resonator, a proportional relationship is established between the phase difference variation Δθ and the capacitance variation Δc in the measurement circuit. . Therefore, the solid phase ratio can be accurately measured without complicated calculations in the calculation unit.
In addition, the output impedance is reduced by detecting the phase difference between the voltage across the parallel circuit and the voltage across the resistor via the impedance converter, reducing measurement errors due to noise and wiring stray capacitance on the phase difference detector side. In addition, good measurement accuracy can be obtained.

It is a schematic diagram which shows the whole structure of the solid-phase-ratio measuring apparatus which concerns on a present Example. It is a circuit block diagram showing a solid-phase-ratio measuring apparatus as an equivalent circuit. It is a graph which shows the relationship between the input frequency with respect to the measurement circuit immersed in liquid nitrogen in the case of calibration, and phase (theta) detected by a phase difference detector. The relationship between the input frequency to the measurement circuit immersed in slush nitrogen with a solid phase ratio f = 0.1 and the phase θ detected by the phase difference detector, and the phase difference Δθ between the solid phase ratio f = 0 and It is a graph shown together. FIG. 5 is an enlarged view of the vicinity of the parallel resonance frequency in FIG. 4. It is a graph which shows the relationship of the variation | change_quantity of a solid-phase rate and a detection phase difference. It is a schematic diagram which shows the whole structure of the cooling system which concerns on a present Example. It is a schematic diagram which shows an example of a solid-phase-ratio measuring apparatus.

  Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. This is just an example.

  In the following embodiment, as a solid-liquid two-phase fluid, slash nitrogen including solid nitrogen as a solid phase component and liquid nitrogen as a liquid phase component will be described as an example. Needless to say, the present invention can be similarly applied to other solid-liquid two-phase fluids such as slush hydrogen.

(Solid ratio measurement device)
FIG. 1 is a schematic diagram showing an overall configuration of a solid phase ratio measuring apparatus 1 according to the present embodiment.
The solid phase ratio measuring device 1 includes a storage tank 2 in which slush nitrogen as a measurement target is stored, a measurement circuit 3 immersed in the storage tank 2, and a signal generator 4 that inputs an AC signal to the measurement circuit 3. A phase difference detector 5 that detects a phase difference, a calculation unit 10 that calculates a solid phase ratio based on the detection result of the phase difference detector 5, and a measurement error due to noise in the sensor output or wiring stray capacitance And an impedance converter 9 for reducing the above.

とすると、その差分ΔＶは次式

ただし、

となる。差分信号の振幅Ａ_２はＡ₀とＡ₁の値によって依存し、

の場合に最小値

となる。つまり、各信号をアンプ等で増幅し、信号の差分の振幅Ａ_２が最小となるように、各増幅率を調整することで、得られる差分信号の振幅は入力信号の振幅と位相差の積となる。位相差の検出は、アンプ利得を調整した場合における、差分信号の最小振幅を計測する簡単なアナログ回路にて実現できる。位相差検出器５では、電圧Ｖ_０、Ｖ_１を取り込み、（３）式に基づいて演算することによって位相差θを検出する。 Measurement circuit 3 includes a parallel circuit 6 and a crystal oscillator S and the capacitor C is connected in parallel with a predetermined natural frequency, and a resistor R _m which is serially connected to said parallel circuit 6 It is configured. Signal generator 4 is inputted to both ends of the measuring circuit 3 and AC signal (e.g., sine wave) having a predetermined frequency, the voltage across V ₁ of the phase difference detector 5 and the voltage across V ₀ which parallel circuit 6 resistor R _m Phase difference θ (that is, impedance deviation angle) is detected.
For example, the voltage V ₀ across the parallel circuit 6 and the voltage V ₁ across the resistor R _m are respectively

Then, the difference ΔV is given by

However,

It becomes. Amplitude A ₂ of the difference signal is dependent on the value of A ₀ and A _1,

Minimum value in case of

It becomes. That is, by amplifying each signal with an amplifier or the like and adjusting each amplification factor so that the amplitude A ₂ of the signal difference is minimized, the amplitude of the obtained difference signal is the product of the amplitude of the input signal and the phase difference. It becomes. The detection of the phase difference can be realized by a simple analog circuit that measures the minimum amplitude of the difference signal when the amplifier gain is adjusted. The phase difference detector 5 detects the phase difference θ by taking in the voltages V ₀ and V ₁ and calculating based on the equation (3).

FIG. 2 is a circuit diagram showing the solid phase ratio measuring apparatus 1 as an equivalent circuit. In FIG. 2, the crystal resonator S is represented by connecting a capacitor C ₀ in parallel to a series circuit in which an inductance component L ₁ , a capacitance component C _1, and a resistance component R ₁ are connected in series. As shown in FIG. 1, the signal generator 4 is connected to both ends of the measurement circuit 3 via wirings 7a and 7b, and the phase difference detector 5 is connected to wirings 8a and 8b and impedance converters 9a and 9b. Te are respectively connected to both ends of both ends and a resistor R _m of the parallel circuit 6. There is a considerable amount of stray capacitance between these wirings 7a, 7b, 8a, 8b. Since the impedance due to the wiring stray capacitance between 8a and 8b affects the measured value, signal amplification is required. Therefore, impedance converters 9a and 9b are connected to both ends of the sensor, and the sensor output is input to the converter. By making the output impedance of the sensor very small, the impedance due to wiring stray capacitance can be ignored. Since the impedance converter is used in a cryogenic environment (in liquid nitrogen or slush nitrogen), for example, a drain common circuit of a MOS transistor or the like is used. In FIG. 2, the stray capacitance generated between the wirings 7 a and 7 b is represented as a capacitance C _f connected in parallel to the signal generator 4.
When the impedance converter is used in this manner, the influence of the wiring stray capacitance can be reduced, so that the wiring length between the impedance converters 9a and 9b and the phase difference detector 5 for detecting the phase difference can be increased. Incidentally, in the case of obtaining a higher accuracy, impedance converter 9a, the wiring length between the 9b parallel circuit 6 and the series resistance R _m may be as short as possible is naturally.

となる。 Here, the impedance Za of the crystal resonator S is expressed by the following equation:

It becomes.

ただし、

である。ω_s０を基準角周波数と呼ぶ。 Here there resonance frequency two crystal resonator S, the series resonance frequency f _s and the parallel resonance frequency f corresponding to the _p angular frequency omega _s of each crystal resonator _S, is omega _p. Each resonance angular frequency is

However,

It is. ω _s0 is called a reference angular frequency.

と整理できる。これは図５（ａ）に相当する。 Here, the declination of Za uses p, Q, and _ωs0 ,

Can be organized. This corresponds to FIG.

となる。これは図５（ｃ）に相当する。 Here, the impedance deviation angle when the parallel capacitance C ₀ → C ₀ (1 + Δc) of the circuit is changed.
arg (Za ') is

It becomes. This corresponds to FIG.

となる。これは、図５（ｂ）に相当する。ただし、（９）式において

とした。 The phase difference Δθ (ω, Δc) between the equations (7) and (8) is

It becomes. This corresponds to FIG. However, in equation (9)

It was.

と仮定すると、最終的に（９）式は以下のように近似される。

従って（１０）式によれば、キャパシタの静電容量Ｃが一定である場合（すなわちΔｃ＝０の場合）には位相差θの変化量はΔθ＝０であるが、静電容量Ｃが変化した場合には、その変化量Δｃに比例する変化量Δθが生じることとなる。
本実施例に係る固相率測定装置１では、位相差検出器５によって位相差の変化量Δθを検出することによって、（１０）式に基づいて、対応する静電容量の変化量Δｃを算出する。そして、（１）式で示した静電容量と誘電率との関係に当てはめることによって、静電容量の変化量を更に誘電率εの変化に換算する。スラッシュ窒素の比誘電率ε_ｓｌは、固体窒素の比誘電率ε_ｓ、液体窒素の比誘電率ε_ｌ、固相率ｆ（０≦ｆ≦１）とすると、次式
ε_ｓｌ＝ｆ×ε_ｓ＋（１−ｆ）×ε_ｌ （１１）
により表される。従って、静電容量の変化量Δｃに対応するスラッシュ窒素の誘電率ε_ｓｌの変化量に基づいて、固相率ｆが求められることとなる。 here,

Assuming that, equation (9) is finally approximated as follows.

Therefore, according to equation (10), when the capacitance C of the capacitor is constant (that is, when Δc = 0), the change amount of the phase difference θ is Δθ = 0, but the capacitance C changes. In this case, a change amount Δθ proportional to the change amount Δc is generated.
In the solid phase ratio measuring apparatus 1 according to the present embodiment, the phase difference detector 5 detects the phase difference change amount Δθ, thereby calculating the corresponding capacitance change amount Δc based on the equation (10). To do. Then, by applying the relationship between the capacitance and the dielectric constant shown in the equation (1), the amount of change in capacitance is further converted into a change in dielectric constant ε. The relative permittivity ε _sl of slush nitrogen is given by the following formula: ε _sl = f × ε, where the relative permittivity ε _s of solid nitrogen, the relative permittivity ε _l of liquid nitrogen, and the solid phase ratio f (0 ≦ f ≦ 1) _s + (1−f) × ε _l (11)
It is represented by Therefore, the solid phase ratio f is obtained based on the amount of change in the dielectric constant ε _sl of slush nitrogen corresponding to the amount of change Δc in capacitance.

Subsequently, the procedure for measuring the solid fraction of slush nitrogen using such a solid fraction measurement apparatus 1 will be specifically described.
(Calibration)
First, as a premise for performing solid phase ratio measurement, calibration is performed using slush nitrogen (that is, liquid nitrogen) having a solid phase ratio f = 0 as a reference point. In the calibration, the storage tank 2 is filled with liquid nitrogen (solid phase ratio f = 0) instead of slush nitrogen, and the measurement circuit 3 is immersed. Then, after inputting an AC signal having a predetermined frequency from the signal generator 4, the phase difference detector 5 detects the phase difference θ.

Here, FIG. 3 is a graph showing the relationship between the input frequency to the measurement circuit 3 immersed in liquid nitrogen and the phase difference (impedance deviation angle) θ detected by the phase difference detector 5 during calibration. In FIG. 3, the horizontal axis indicates the frequency normalized with the reference frequency f _s0 of the crystal resonator S.
As you changing the frequency of the alternating current signal inputted from the signal generator 4, the phase difference θ becomes zero at the parallel resonance frequency f _p of the crystal oscillator S. In the calibration, thus the phase difference θ at the parallel resonance frequency f _p of the crystal oscillator S is based on the characteristic that the zero, to verify that the reference phase difference is zero.

However, in actual measurement, and measurement environment conditions (temperature and pressure), by a variety of factors such as the influence of the stray capacitance C _f between the wires, the reference phase difference in some cases deviates from zero. In calibration, the measurement accuracy can be improved by correcting such a shift in the reference phase difference using liquid nitrogen having a solid phase ratio f = 0. A specific method for correcting the shift of the phase θ includes, for example, fine frequency adjustment of the signal generator 4, but is not limited thereto.

(Solid fraction measurement)
After calibration, the storage tank 2 is filled with slush nitrogen having a solid phase ratio f (> 0) to be measured, and the measurement circuit 3 is immersed. Similarly to the calibration described above, an AC signal having a predetermined frequency is input from the signal generator 4, and then the phase difference θ is detected by the phase difference detector 5.

FIG. 4 shows (a) the relationship between the input frequency to the measurement circuit 3 immersed in slush nitrogen having a solid phase ratio f = 0.1 and the phase difference (impedance deviation angle) θ detected by the phase difference detector 5; (B) It is a graph which shows together the variation | change_quantity (DELTA) (theta) of a phase difference with the case where a solid-phase rate f = 0 (refer FIG. 3). Further, FIG. 5 shows an enlarged parallel resonance frequency f _p vicinity of Figure 4, in each case (a) the solid phase ratio f = 0.1, in the case of (c) fraction solid f = 0 , The phase difference θ detected by the phase difference detector 5 with respect to the input frequency, and (b) is the amount of change in the phase difference when the solid phase ratio changes from f = 0 to f = 0.1. Δθ is shown.

When the solid phase ratio f> 0, when the frequency of the AC signal input from the signal generator 4 is changed, the phase difference θ is zero at the series resonance frequency f _s as in the case of the solid phase ratio f = 0. become, but shows values parallel resonance frequency f a phase difference at _p theta deviates from zero. This is evidenced by Δθ as shown in FIG. 4 indicates a large peak at a parallel resonance frequency f _p vicinity. Assuming that the capacitance C ₀ changes by Δc due to the change in the solid phase ratio f from 0 to 0.1, the phase difference proportional to the change amount Δc is obtained as shown in the above equation (11). This reflects the appearance of the change amount Δθ of. An example of the amount of change in the solid phase ratio and the phase difference is shown in FIG.

That is, in the solid phase ratio measuring apparatus 1 according to the present embodiment, when the solid phase ratio f is changed from 0 to 0.1, the frequency of the AC signal output from the signal generator 4 is changed to the parallel resonance frequency f. _{In addition} to setting to _p , the calculation unit 10 obtains the change amount Δθ of the phase difference θ measured by the phase difference detector 5, thereby obtaining the change amount Δc of the capacitance from the equation (10). The computing unit 10 obtains the solid phase ratio of the solid-liquid two-phase fluid based on the capacitance change Δc thus obtained.

静電容量がΔｃ変化した場合に、そのときの位相変化量がθ_ｑを超えている必要があるが、その条件を満たす運転周波数の範囲は、

となる。すなわち、信号発生器４の出力周波数を（１２）式を満たす範囲に設定すれば、十分な測定感度を得ることができる。 Thus in measuring the solid fraction in a solid phase rate measuring device 1, the output frequency of the signal generator 4 will be set to the parallel resonance frequency f _p of the crystal oscillator S. On the other hand, when the measured frequency deviates from the parallel resonant frequency f _p, since the measurement sensitivity of the solid fraction is reduced, the measurement frequency must fall within a certain tolerance from the parallel resonance frequency f _p.
The relationship between the frequency and the measurement sensitivity should be defined based on the expected change amount Δc of the capacitance and the minimum resolution (that is, the minimum detectable phase) θ _q of the phase difference detector 5. Can do.
For example, (10), the phase change amount when the frequency omega = omega _alpha is the maximum value Δθmax next, its value is expressed by the following equation.

When the capacitance changes by Δc, the amount of phase change at that time needs to exceed θ _q .

It becomes. That is, if the output frequency of the signal generator 4 is set in a range that satisfies the equation (12), sufficient measurement sensitivity can be obtained.

(Cooling system)
Then, the cooling system provided with the said solid-phase-ratio measuring apparatus is demonstrated. The cooling system according to this embodiment performs cooling by circulating and supplying slush nitrogen, which is a solid-liquid two-phase fluid, to a thermal load such as a superconducting cable. FIG. 7 schematically shows the overall configuration. Show.

  The cooling system 100 has a circulation path 110 through which slush nitrogen as a refrigerant circulates. A circulation pump 120 for pumping slush nitrogen from the upstream side on the circulation path 110 and a generator for generating slush nitrogen. 130 and a superconducting cable 140 that is a thermal load are provided. The generation device 130 has a vacuum heat insulating container 131 that stores slush nitrogen flowing through the circulation path 110 while preventing heat from entering from the outside, and a refrigerant cooled by the refrigerator 136, thereby introducing the inside of the vacuum heat insulating container 131. The fluid coagulation heat exchanger 132 that exchanges heat with the slush nitrogen stored in the motor and the motor 133 that operates with external electric power are connected and driven via the shaft 134 to be solidified by the fluid coagulation heat exchanger 132. The heat exchanger surface scraping blade 135 for atomizing and stirring the solid nitrogen formed in this manner is provided. The solid phase ratio measuring apparatus 1 described above is installed in the vicinity of the outlet of the vacuum heat insulating container 131, and in particular, the pair of electrodes constituting the capacitance C is installed at the inlet of the outlet pipe. As a result, the solid phase ratio of slush nitrogen generated by the generator 130 can be monitored in real time.

The controller 160 is a control unit of the cooling system 100, acquires the solid phase ratio data measured from the solid phase ratio measuring apparatus 1, and the refrigerating capacity of the refrigerator 136 so that the acquired value becomes a preset target value. By controlling the operation of the motor 133 and the like, the solid phase rate of slush nitrogen flowing through the circulation path 110 is appropriately maintained.
In the cooling system 100 according to the present embodiment, the solid phase ratio of slush nitrogen used for controlling the generator 130 can be accurately measured by using the above-described solid phase ratio measuring device. Optimal control according to the thermal load state can be performed. In particular, when the thermal load changes with time as in a superconducting power transmission cable, the solid fraction of slush nitrogen flowing through the circulation path 110 changes sequentially. Even in such a case, the solid-phase ratio is accurately measured in real time by the solid-phase ratio measuring device 1, and the optimum solid-phase ratio distribution of the cooling system is maintained by controlling the generator 130, and the superconducting power transmission Cooling and stable operation utilizing the characteristics of the solid-liquid two-phase fluid of the cable 140 can be performed.

  The present invention relates to a solid-phase two-phase fluid solid phase ratio measuring device including a solid phase component and a liquid phase component, a cooling system including the solid phase ratio measuring device, and a solid-liquid two-phase fluid solid phase ratio. It can be used for the measurement method.

DESCRIPTION OF SYMBOLS 1 Solid-phase-ratio measuring apparatus 2 Reservoir 3 Measurement circuit 4 Signal generator 5 Phase difference detector 6 Parallel circuit 9 Impedance converter 10 Calculation part

Claims (5)

A solid-liquid two-phase fluid solid phase ratio measuring device for measuring a solid-phase ratio of a solid-liquid two-phase fluid containing a solid phase component and a liquid phase component,
A measurement circuit formed by connecting a resistor in series to a parallel circuit including a capacitor and a crystal resonator connected in parallel to the capacitor;
A signal generator for inputting an AC signal having a predetermined frequency to the measurement circuit;
An impedance converter connected to both ends of the parallel circuit and to both ends of the resistor;
A phase difference detector for detecting a phase difference between the voltage across the parallel circuit and the voltage across the resistor;
Based on the phase difference detected by the phase difference detector, comprising a calculation unit for calculating the solid phase ratio of the solid-liquid two-phase fluid,
The calculation unit is detected by the phase difference detector when the measurement circuit is immersed in the solid-liquid two-phase fluid and an AC signal having a parallel resonance frequency of the crystal resonator is input from the signal generator. A solid-phase ratio measurement apparatus for a solid-liquid two-phase fluid, wherein the solid-phase ratio of the solid-liquid two-phase fluid is calculated based on the phase difference. A phase difference detected by the phase difference detector when the measurement circuit is immersed in a fluid composed of only the liquid phase component and an AC signal having a parallel resonance frequency of the crystal resonator is input from the signal generator. Is determined in advance as a reference phase difference,
The said calculating part measures the solid-phase rate of the said solid-liquid two-phase fluid based on the variation | change_quantity from the said reference | standard phase difference of the phase difference detected by the said phase difference detector. The solid-phase ratio measuring apparatus of the solid-liquid two-phase fluid described in 1. A cooling system for cooling a heat load provided on a circulation circuit that circulates the solid-liquid two-phase fluid as a refrigerant,
In the circulation times the street,
A generating device for generating the solid-liquid two-phase fluid;
The solid-liquid two-phase fluid solid phase ratio measuring device according to claim 1 or 2 installed downstream of the generating device;
A cooling system comprising: a control unit that controls an operation state of the generating device based on a measurement value of the solid phase ratio measuring device. A solid-liquid two-phase fluid phase ratio measurement method for measuring a solid-phase ratio of a solid-liquid two-phase fluid containing a solid phase component and a liquid phase component,
A first step of immersing a measurement circuit formed by connecting a resistor in series with a parallel circuit including a capacitor and a crystal resonator connected in parallel to the capacitor in the solid-liquid two-phase fluid;
A second step of inputting an AC signal having a parallel resonance frequency of the crystal resonator to the measurement circuit;
A third step of detecting a phase difference between the voltage across the parallel circuit and the voltage across the resistor;
And a fourth step of calculating a solid phase ratio of the solid-liquid two-phase fluid based on the detected phase difference. The step of immersing the measurement circuit in a fluid composed only of the liquid phase component, and further obtaining in advance the phase difference when an AC signal having a parallel resonance frequency of the crystal resonator is input as a reference phase difference,
The fourth step is characterized in that the solid phase ratio of the solid-liquid two-phase fluid is measured based on a change amount of the phase difference obtained in the third step from the reference phase difference. 5. A method for measuring a solid phase ratio of a solid-liquid two-phase fluid according to 4.

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