JPS63167230A - Liquid resistance type temperature measuring instrument - Google Patents

Abstract

PURPOSE:To eliminate the influence of variation in environmental temperature and to preclude mismeasurement due to the breakage of a probe by detecting a pressure drop at the area contraction part atop the probe, and calculating temperature from the detected value and also detecting the probe breakage. CONSTITUTION:An internal cylinder 4 which has an area contraction part 2 atop is inserted into an external cylinder 6 which is closed at one end to constitute the probe 1. A working liquid supply source 9 is connected to the working liquid supply port 8 of the probe 1 through a working liquid supply pipe 10, which is provided with a pressure reduction valve 11, a pressure controller 12, and a mass flow rate controller 13. A differential pressure gauge 20 detects the pressure drop at the area contraction part 2 and a temperature arithmetic means 21 computes the temperature from its output; and the temperature is displayed on a temperature display part 22 and a probe breakage detecting means 23a detects the probe breakage, thereby generating a warning by a warning means 26.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a fluid resistance temperature measuring device that measures, for example, the temperature inside a furnace or the temperature of molten metal by utilizing changes in state due to the temperature of a fluid. .

(Prior Art and its Problems) Conventionally, thermocouples, resistance thermometers, and the like have been generally used to measure the temperature of molten metal or high-temperature parts such as inside a furnace. However, these thermometers are not suitable for long-term use because the material of the temperature sensing part that is exposed to high temperatures is limited in principle, and it is difficult to take measures against oxidation and other causes that shorten the lifespan. there were.

For this reason, a fluid resistance type temperature measuring device has been developed which has the advantage that the material of the sensor, which is the temperature sensing portion, can be freely selected from the viewpoint of life span without being restricted by the principle of measurement. This fluid resistance type temperature measuring device utilizes the temperature dependence of the viscosity coefficient of gas, and for example,
A probe l having a capillary tube 2 which is a constriction part inside as shown in Fig. 11 is used as a temperature sensor. The purpose is to determine the temperature from the change in pressure loss when the gas (working fluid) passes through the capillary tube 2.

This fluid resistance type temperature measuring device is specifically constructed as shown in FIG. This temperature measuring device supplies a working fluid such as Ar gas from a working fluid supply source 31 to a sensitivity adjustment valve 33 and a supply valve 3 at a constant pressure via a pressure control device 32.
The difference between the pressure loss ΔP of the capillary tube 2 in the probe l and the pressure loss of the trim valve 35, that is, the secondary side of the trim valve 35 and the secondary side of the capillary tube 2, is The pressure difference ΔPc between the two sides is amplified by the fluid element 36, converted into an electrical signal by the pressure sensor 37, and output.

Electrically speaking, the configuration of this system is a type of Wheatstone Blitz, and the sensitivity adjustment valve 33. A slight fluctuation in the pressure loss in the supply valve 34 or the trim valve 35
This has a significant effect on the pressure signal from the fluidic element 36. Therefore, the state change of the working fluid due to the environmental temperature is caused by the six valves 33,34.

35, and the apparent pressure drop ΔP of the capillary tube 2 of the probe 1 varies, that is, the probe! Therefore, the measuring device of this method has the disadvantage of being susceptible to the influence of the environmental temperature.

In addition, in the fluid resistance thermometer, if the probe l, which is the temperature sensor, is damaged such as cracks or holes, the working fluid may leak as shown in Figure 15 (arrow C9d). ) or because the atmosphere enters the probe l (arrow e), the signal output from the pressure sensor 37 continues to be output in a state that does not correctly correspond to the temperature to be measured.

Breakage of the probe of a fluid resistance temperature measurement device is equivalent to disconnection of a thermocouple. However, when a thermocouple is disconnected, no signal is output, whereas a fluid resistance temperature measuring device continues to output an erroneous signal as described above. Therefore, it is difficult to detect damage to the probe 1. For example, when temperature is measured and controlled by a fluid resistance type temperature measuring device, the temperature is controlled to a value different from the set value. This is a significant drawback of fluid resistance temperature measuring devices.

Furthermore, if the outer cylinder of the probe is damaged, the atmosphere to be measured may be contaminated with the working fluid (arrow d in Figure 15), or the pressure and component ratio of the atmosphere to be measured may be changed (arrow in Figure 15). It also had the disadvantages of d and e).

However, conventional fluid resistance type temperature measuring devices do not have any means for detecting breakage of the probe, which has such a large effect. This point was the biggest obstacle to the practical application of fluid resistance temperature measuring devices.

(Object of the invention) The present invention has been made in view of the above-mentioned conventional problems, and
The object of the present invention is to provide a fluid resistance type temperature measuring device that is capable of measuring high temperatures without being affected by changes in the temperature of the working fluid, and is capable of preventing erroneous measurements by detecting breakage of the probe.

(Structure of the Invention) In order to achieve the above object, the present invention provides a probe formed by inserting an inner cylinder having a constricted portion at the tip into an outer cylinder whose one end is sealed, and a pressure control device connected to the probe. Damage to a working fluid supply pipe equipped with a device and a mass flow rate control device, a differential pressure gauge that detects pressure loss at the throttle section, a temperature calculation means that calculates a temperature based on a signal from the differential pressure gauge, and the probe. and probe breakage detection means for detecting.

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a fluid resistance type temperature measuring device according to the present invention, in which a probe l, which is a temperature-sensitive sensor, has a capillary tube 2, which is a form of a constriction part, inside, and a working fluid that has passed through the capillary tube 2, into the probe l. Working fluid discharge channel 3 for discharging to the outside
An outer cylinder 6 forms a working fluid supply channel 5 for guiding the working fluid to the capillary tube 2,
- For example, it is attached to the furnace wall 7 to measure the temperature inside the furnace. Further, a working fluid supply pipe IO from a working fluid supply source 9 that supplies high-pressure working fluid is connected to the working fluid supply port 8 of the probe l, and a pressure reducing valve 11, a pressure control device 12, and a mass A flow rate control device 13 is provided in series.

As shown in FIG.
4, the valve opening adjustment 515 compares it with a set mass flow rate value, and based on the result, the opening of the valve 16 is controlled to maintain a constant mass flow rate.

Furthermore, by providing a pressure detection tube 19 at the artificial part 17 of the working fluid supply channel 5 and the outlet section 18 of the working fluid discharge channel 3, and by connecting both pressure detection tubes 19 to the differential pressure gauge 20, The pressure loss Δ■ in the capillary tube 2 in the probe 1 is directly detected. Further, the differential pressure gauge 20 has an output signal of 7. A temperature calculation means 21 for calculating the H temperature is connected to a probe damage detection means 23a, and a temperature display 22 is connected to the temperature calculation means 2I. Then, the temperature calculation means 21 converts the pressure loss ΔP into temperature based on the relationship between pressure and temperature, which will be described in detail below, and the temperature display 22 displays the measured temperature, that is, the furnace temperature.

On the other hand, the probe damage detection means 23a includes a differentiating circuit 24,
The comparison arithmetic processing circuit 25a and the alarm means 26 are connected in this order, and the differential pressure gauge 20 is connected to the differential circuit 24. Then, the differential circuit 24 differentiates the pressure loss ΔP signal from the differential pressure gauge 20 with respect to time to calculate the fluctuation speed of the pressure loss ΔP, and the comparison calculation processing circuit 25a compares this fluctuation speed with a set standard fluctuation speed. , pressure loss Δ
If there is an abnormality in the fluctuation speed of P, an abnormality signal is generated and an alarm is issued by the alarm means 26.

Next, a temperature measuring method using the apparatus having the above configuration will be explained.

First, a high pressure working fluid, for example A, is supplied from the working fluid supply source 9.
Supply r gas. The supplied working fluid is applied to the pressure reducing valve 11.
．． The pressure is reduced to a predetermined pressure by the pressure control valve I2, and further controlled to maintain this pressure.
The working fluid is supplied to the working fluid supply channel 5 of.

The working fluid supplied to the working fluid supply channel 5 at a constant mass flow ff1Q passes through the capillary tube 2 and is discharged into the atmosphere from the outlet section 18. At this time, a pressure loss ΔP occurs in the capillary tube 2, so this pressure loss ΔP is measured by the differential pressure gauge 20.
The temperature is directly detected, and the temperature calculation means 21 calculates the temperature based on this detected value.

Therefore, a method for determining the furnace temperature T inside the probe l from this pressure loss ΔP will be explained.

The working fluid supplied to the probe 1 from the working fluid supply port 8 flows through the working fluid supply channel 5 and is heated from the furnace atmosphere through the outer cylinder 6 of the probe 1 between the filters, and the temperature inside the furnace T increases. and is guided into the capillary tube 2.

Since the flow in the capillary tube 2 can generally be assumed to be a Hagen-Boiseuille flow, the pressure loss occurring in the capillary tube 2 can be expressed by the following equation.

Yu, = 8 "blade ■", - uniform, (1) π・[d/2]
'ρ(T) However, ρ and d indicate the length and inner diameter of the capillary, respectively, and μ(1") and ρ(T) indicate the viscosity coefficient and density of the working fluid at the furnace temperature T. Also, Q is It shows the mass flow rate of the working fluid, which is a constant here because it is controlled to be constant by the mass flow rate controller 13.

Strictly speaking, the length ρ or the inner diameter d of the capillary tube 2 is also affected by temperature. Considering this, and since the kinematic viscosity ν(T) of the working fluid is ν(T)-μ(T)/ρ(T), equation (1) can be rewritten as follows.

+28Q Q Δ1)=□・−・ν(′1”) π d4 28Q ΔP=□・f(T) (2) π Therefore, it can be seen that ΔP is a function of the furnace temperature T.

In general! 2. Since the temperature dependence of d is often smaller than that of ν(T), it can be expressed as (3). From this equation (3), it can be said that the pressure loss ΔP occurring in the capillary tube 2 is proportional to the kinematic viscosity ν(T) of the working fluid when it passes through the capillary tube 2.

Since the kinematic viscosity ν(T) of the working fluid is a function of temperature, the pressure loss ΔP is a function of the temperature of the working fluid when it passes through the capillary tube 2, that is, the temperature T in the furnace.

Therefore, regardless of whether it is expressed by equation (2) or (3), the furnace temperature T can be determined by measuring the pressure loss ΔP occurring in the capillary tube 2. In many cases,
&, the temperature dependence of d (i.e. the thermal expansion of probe l)
is lower than the temperature dependence of kinematic viscosity ν(T), so it can be considered that it is approximately expressed by equation (3).

As explained above, the pressure loss ΔP in the capillary tube 2 depends only on the temperature of the working fluid when it passes therethrough.

Therefore, it is not affected by the temperature history of the working fluid before it enters the capillary tube 2, the environmental temperature of the material of the probe I, atmospheric pressure, etc.

Next, as a specific example of the probe 1, as shown in FIG.
Thermal expansion coefficient 20 x 10-@/'C) is used.
Consider the case where Ar gas is used as the working fluid. The relationship between the pressure loss ΔP and the temperature T at this time is shown in FIG. 3 using the flow m of Ar gas (working fluid) as a parameter. The pressure loss ΔP occurring in the capillary tube 2 increases monotonically as the temperature increases.

Moreover, it can be seen from FIG. 3 that as the mass flow rate Q flowing through the capillary tube 2 becomes larger, the value of the pressure loss ΔP becomes larger (and the temperature dependence becomes stronger).

Based on this fact alone, it can be considered that the larger the mass flow rate Q, the better the measurement accuracy or temperature resolution of the thermometer. However, as the flow rate increases, the following problems become more prominent.

First, the first problem is that the heat transfer within the probe 1 cannot be followed, and the difference between the working fluid and the temperature inside the furnace increases, making it impossible to accurately display the temperature inside the furnace, especially when the temperature inside the furnace changes rapidly. The longer the delay, the greater the delay.

The second problem is that compared to the pressure loss ΔP in the capillary tube 2, the probe tip or working fluid inlet 17 of the probe l
The ratio of the magnitude of pressure loss at bends, constrictions, etc. becomes relatively large, and as a result, the temperature dependence of pressure loss ΔP in the capillary tube 2 becomes relatively small.

The third problem is probe! tip or probe l
Bent portions such as the working fluid inlet portion 17 of.

Since the flow becomes unstable at the throttle part, the pressure loss ΔP fluctuates.

Therefore, it is considered that there is an upper limit value for the flow rate of the working fluid, which is restricted by the above problem.

The mass flow rate of the working fluid should be determined from the measurement temperature range, the range of the differential pressure gauge 20, the measurement resolution, etc. within an appropriate flow rate range that does not exceed the above-mentioned upper limit.

Note that the appropriate flow rate of the working fluid varies greatly depending on the type of working fluid and the structure, shape, and dimensions of the probe.
Should be determined experimentally.

Further, according to this temperature measuring device, only the tip of the probe l is exposed to the high temperature part. From the measurement principle,
The material of the probe l does not affect measurement accuracy, so any material that can withstand the measurement temperature range may be used. This is one of the advantages over thermocouples, which require a combination of metals that can withstand the measurement temperature range and generate electromotive force.

Next, the principle of operation of the probe breakage detection means 23a will be explained using the above embodiment as an example.

As described above, in this case, the working fluid is flowing in the direction from the outer cylinder 6 into the inner cylinder 4. Further, the pressure inside the furnace is assumed to be higher than the pressure inside the probe l.

Consider a case where the probe 1 shown in FIG. 1 is damaged 27 as shown in FIG. 4. Since the furnace pressure Pa is higher than the probe internal pressure P, the gas in the furnace atmosphere flows into the probe 1 as indicated by the arrow r and passes through the capillary tube 2 together with the working fluid.

Therefore, the pressure loss value ΔP measured by the differential pressure gauge 20 increases instantaneously at the same time as the probe l is damaged, and is greater due to the pressure loss change rate corresponding to the pressure loss value ΔP measured by the differential pressure gauge 20 at that time. That is, even if the temperature inside the furnace changes instantaneously from T to T, the pressure loss generated in the capillary tube 2 of the probe l will change to Pl! The detection is as follows: ■ Time required for the outer surface of the outer cylinder of probe 1 to change from temperature TI to temperature T: tl ° ■ Time required for the inner surface of the outer cylinder of probe 1 to reach temperature T: t.

(2) A time delay occurs, which is the time required for the working fluid to reach the temperature T = L3. By the way, the time delay mentioned above,
is greatly affected by the atmospheric components, pressure, flow conditions, etc., and the time delay t3 mentioned above is greatly influenced by the pressure of the working fluid, flow conditions, etc., and is difficult to predict or understand in reality. However, since the temperature conductivity α of the probe I and the meat 17Q are known, the time delay in (2) above can be predicted by the following equation (4).

t2=J! /+6α...(4)
Therefore, the pressure loss value of the pressure loss value ΔP12 is ΔP1%, the pressure loss value corresponding to the furnace temperature T2 is ΔP,
Then, it can be expressed by the following equation (5).

(5) Equation (5) above means that if the probe 1 is not damaged, the pressure loss change rate measured by the differential pressure gauge 20 will not change.

On the other hand, the pressure loss value corresponding to the upper limit temperature Tmax of the temperature measurement range of the fluid resistance type temperature measurement device may be 8P.

The pressure loss value corresponding to the lower limit temperature Tm1n can be expressed by the following equation (6).

Therefore, based on the above equation (6), the set reference rate of change is differentiated with respect to time by the differentiating circuit 24, and if the measured pressure loading rate and the set reference rate of change are greater than the calculation process,
It is determined that the probe l is damaged, an abnormality signal is output, and an alarm is issued by the alarm means.

Next, contrary to the example described above, as shown in FIG. 5, the furnace pressure P is increased. A case will be explained in which the pressure inside the probe 1 is lower than the pressure P1. In this case, as soon as the probe 1 is damaged 27, a portion of the working fluid flowing inside the probe 1 flows out into the furnace as shown by arrow g. For this reason, the differential pressure gauge 20
The measured pressure loss value ΔP rapidly decreases at the same time as the probe I is damaged, and is larger than the set reference rate of change as shown in FIG.

Therefore, as in the case described above, the differential circuit 24 differentiates the output signal of the differential pressure gauge 20 with respect to time, and if the measured pressure is detected, it is determined that the probe l is damaged, an abnormality signal is output, and the alarm means 26 issues an alarm.

Therefore, the following equation If this holds true, an alarm will be issued.

In the above embodiment, the differential pressure gauge 20 is connected to the differential circuit 24, but as shown in FIG.
3b may be provided. In this case as well, after the measured pressure loss value ΔP is converted into temperature by the temperature calculation means 21, this temperature signal is input to the differentiator circuit 24, and the calculated temperature change rate is used instead of the change rate of the measured pressure loss value ΔP. Probe damage can be detected by calculating the temperature change rate and comparing the calculated temperature change rate with a reference change rate (calculated temperature change rate) in the comparison calculation processing circuit 25a.

Note that the set reference rate of change is not limited to the one based on this measuring device as described above, but can be selected as appropriate, such as the rate of change in pressure loss, the rate of temperature change, or the rate of temperature change that corresponds to the heat curve of the treated material. .

FIG. 7 shows a device that automatically stops measurement when damage to the probe l is detected as described above, and in addition to the device shown in FIG. Solenoid valves 28 and 29 are provided in the gas passages on the side and discharge sides. Then, by the comparison calculation processing circuit 25a,
When damage to the probe l is detected, the normally open solenoid valves 28 and 29 are closed to prevent the working fluid from flowing into the furnace atmosphere and the furnace atmosphere from flowing out of the furnace. be.

Furthermore, since the signal outputted from the comparison processing circuit 25a is an electrical signal, this signal can be inputted to other than the solenoid valves 28 and 29, for example, inputted to the control unit of the power source of the heater of the furnace. If the probe l is damaged, the solenoid valve 28.
Applications such as closing the switch 29 and turning off the power to the furnace heater are possible.

Incidentally, in each of the above embodiments, a device was shown in which damage to the probe I was detected from the pressure loss value ΔP at the probe I, but the present invention is not limited to this.
Probe from changes in the mass flow rate of the working fluid! This also includes the detection of damage.

Specifically, as shown in FIG.
0, and a probe breakage detection means 23 formed by connecting a comparison arithmetic processing circuit 25b to this mass flowmeter 30 and the mass flowmeter 14 of the mass flow rate control device 13.
c, and corresponding parts are given the same numbers. Then, the mass flow rate of the working fluid on the working fluid supply side and the discharge side of the probe l, that is, the mass flow meter 1
The flow rate signals from 4.30 are compared by the comparison arithmetic processing circuit 25b to detect damage to the probe l. That is, if the probe l is normal, the two signals will match, but if the probe l is damaged, the two signals should be different. Therefore, when the comparison arithmetic processing circuit 25b detects a discrepancy, an abnormality signal is outputted, and the alarm means 26 issues an alarm to inform the surroundings of the damage of the probe 1.

FIG. 9 corresponds to the above-mentioned FIG. 7, and shows the apparatus of FIG. 8 and the working fluid supply side of the probe I.

Solenoid valves 28 and 29 are provided in the gas flow path on the discharge side, so that when damage to the probe l is detected, the solenoid valves 28 and 29 are closed.

Furthermore, the present invention provides a component for detecting damage to the probe l based on a change in the rate of fluctuation of the pressure loss value ΔP or a change in the rate of temperature fluctuation, and
It may be possible to have both components for detecting f1 loss, and FIG.
The probe breakage detection means 23d is composed of a probe breakage detection means 23c and a probe breakage detection means 23c.

Incidentally, in each of the above embodiments, the working fluid in the probe l was shown only when flowing in the direction from the outer cylinder 6 into the inner cylinder 4, but in the present invention, as shown in FIG. This also includes a case where the working fluid is made to flow in the direction from to the outer cylinder 6. In this case as well, damage to the probe 1 can be detected in the same manner as described above if there is either a pressure abnormality or a mass flow abnormality. The explanation will be omitted.

(Effects of the Invention) As is clear from the above description, the present invention provides a probe formed by inserting an inner cylinder having a constricted portion at the tip into an outer cylinder whose one end is sealed, and a probe that is connected to the probe to control pressure. Damage to a working fluid supply pipe equipped with a device and a mass flow rate control device, a differential pressure gauge that detects pressure loss at the throttle section, a temperature calculation means for calculating a temperature based on a signal from the differential pressure gauge, and the probe. and a probe breakage detection means for detecting the breakage of the probe.

Therefore, with a simple configuration, it is possible to operate at high temperatures (1500 to 3000℃) without being affected by the environmental temperature 1 working fluid temperature.
We need to be able to measure temperature with high reliability.

Further, if the probe is damaged, it can be detected, so that erroneous measurements can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a fluid resistance temperature measuring device according to the present invention, FIG. 2 is a detailed diagram of the mass flow rate control device of FIG. 1, and FIG. Figures 4 and 5 are partially enlarged views showing the state when the probe is broken, and Figures 6 to 10 are diagrams showing the relationship between pressure loss and temperature when using the probe shown in Fig. 5. A block diagram showing the embodiment, FIGS. 11 to 13 are partial sectional views showing the probe and the flow state of the working fluid, FIG. 14 is a block diagram of a conventional fluid resistance type temperature control device, and FIG. [7-B is a partially enlarged sectional view showing a damaged state. ■... Probe, 2... Capillary tube, 3... Working fluid discharge channel, 4... Inner cylinder, 5 - Working fluid supply channel, 6...
- Outer cylinder, 12... Pressure control device, I3... Mass flow rate control device, 19... Pressure detection tube, 20... Differential pressure gauge, 21
...Temperature calculation means, 23a, 23b, 23c, 23d
= Probe damage detection means. Patent applicant: Chugai Roko Kogyo Co., Ltd. Representative: Patent attorney Two idiots, Figure 1, Figure 2, I! 111 Maki 3 Figure i L Zuke T ("C1 4f!i!! Figure 5 Figure 6 Figure 71!llI Figure 8 Name 11 Ward Figure 12 Figure 131!! 11 Figure 15

Claims (3)

[Claims] (1) A probe formed by inserting an inner cylinder having a constricted portion at the tip into an outer cylinder with one end sealed, and connecting to this probe,
A working fluid supply pipe equipped with a pressure control device and a mass flow rate control device, a differential pressure gauge that detects pressure loss at the throttle section, a temperature calculation means that calculates a temperature based on a signal from the differential pressure gauge, and the probe. A fluid resistance type temperature measuring device comprising: a probe breakage detection means for detecting breakage of the probe. (2) The probe damage detection means includes means for calculating the rate of variation of the output signal from the differential pressure gauge, and means for comparing the calculated rate of variation with a set standard rate of change to determine whether or not it is normal. 2. A fluid resistance type temperature measuring device according to claim 1, wherein the fluid resistance type temperature measuring device is characterized in that: (3) The probe damage detection means is provided with means for comparing the mass flow rate of the working fluid supplied to the probe with the mass flow rate of the working fluid discharged from the probe to determine whether or not it is normal. Claim 1 characterized by
The fluid resistance type temperature measuring device according to any one of Items 1 and 2.