JP2579265B2 - Method for measuring thermal conductivity of fluid and apparatus for measuring state of fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid that utilizes a property value of a fluid obtained from the difference between the temperature of the heat sensor and the temperature of the fluid when the heat sensor in thermal contact with the fluid generates heat. TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring the thermal conductivity of an object. For example, the thermal conductivity of various fluids is a management item of a production facility in various industries, and the measurement of the production facility is important because the thermal conductivity varies depending on the temperature and composition of the fluid. As a specific example, if a change from a monomer to a polymer in a polymerization reaction can be measured from a change in thermal conductivity or the like, reaction control in a line can be simplified.

[0002]

2. Description of the Related Art Hitherto, for example, the following means have been proposed as means for measuring the thermal conductivity of a fluid by the unsteady fine wire method. 1. “Study on high-precision measurement of thermal conductivity of fluid” Yuji Nagasaka, Akira Nagashima Japan Society of Mechanical Engineers Vol. 47, No. 417 (Showa 56-5), pp. 821-829 2. “Study on high-precision measurement of thermal conductivity of fluid” Yuji Nagasaka, Akira Nagashima Japan Society of Mechanical Engineers, Vol. 47, No. 419 (Showa 56-7), pp. 1323-1331. “Thermophysical Handbook” edited by The Society of Thermophysical Properties of Japan 1990.5.30 Published by Yokendo
68-573

[0003] Here, the measurement of the thermal conductivity of a fluid is classified into an unsteady method and a steady method. The unsteady method in the thin wire heating method using a heating element is such that the temperature rise gradient of the heating element temperature from the start of the heating. This is a method that utilizes the temperature change caused by time-dependent heating, and the steady state method refers to a state in which the temperature stabilizes at a constant level over time after passing through an unsteady state, and depends on time. It is a method that uses a temperature field that does not. Generally, the steady-state method is susceptible to the effects of convective heat transfer due to convection phenomena caused by the temperature rise of the fluid to be measured, and this effect must be removed. Due to the merit of being detectable, measurement of thermal conductivity is mainly performed by the unsteady method. Literatures 1 and 2 are representative examples of publications, in which a current is applied to a thin metal wire arranged vertically in a sample, and a method of calculating thermal conductivity from the calorific value and temperature of the thin wire at this time is used.
It is reported in detail. Reference 3 describes known examples of both the stationary method and the non-stationary method. In particular, the method related to the present invention is a description relating to a measurement method called a concentric cylinder method. This is a measurement method using a stationary method of measuring the temperature using the method. In addition, JP-A-1-180444, JP-A-3-17542
No. is raised. Japanese Patent Application Laid-Open No. 1-180444 discusses a measurement error caused by electric resistance in a bridge circuit for reading a signal from a sensor in a measurement method using a non-stationary thin wire heating method. JP-A-3-175
No. 42 is a method of measuring the thermal conductivity by obtaining the linear relationship between the temperature rise and the logarithm of the current conduction time in order to suppress the thermal convection of the fluid when measuring using the unsteady fine wire heating method.

[0004]

The method of measuring the thermal conductivity by the non-stationary method described in the literature is introduced based on a measuring technique called a thin wire heating method. Uses a few microns.
For this reason, the measurement operation is performed by separately preparing the sample and cannot be configured in-line. This can be said for the stationary method introduced in Reference 3. That is, a configuration and a method for measuring the thermal conductivity of a fluid in-line at a production site have not been studied so far. In addition, as for the steady-state method used in the present invention, the method introduced in the literature has a complicated configuration of a measuring device, which is not only difficult to arrange in-line, but also has a corresponding capability for cleaning when configured in-line. There is no one. The known measuring device used in the concentric cylinder method of the literature similar to the present invention has a complicated and expensive structure in which a plurality of thermometers are arranged, and a silver cell is used to make the sample temperature uniform.

JP-A-1-180444 and JP-A-3-180444
No. 17542 uses an unsteady method, and is an application relating to a high degree of thermal conductivity measurement. Basically, the present invention is not related to these prior arts because it uses a stationary method,
A disadvantage of using the unsteady method is that it is necessary to process the measured values in order to obtain the thermal conductivity. In particular, as shown in JP-A-1-180444, there are still problems to be considered in the thin wire heating method, such as resistance change, temperature change, and temperature range. Further, it is difficult to dispose the measuring device in-line by these methods. This is because the measurement method is a batch process, the measurement device uses a thin wire that is weak to vibration, and the measurement device itself is easily affected by a temperature change of the environmental temperature.

The present invention solves the problem of convective heat transfer caused by convection using a steady method in the thin wire heating method, obtains an index value having a good correlation with the thermal conductivity, and obtains an inexpensive production site. Another object of the present invention is to provide a method and an apparatus for measuring the thermal conductivity, which can perform in-line measurement.

[0007]

In order to achieve the above object, a heat generation sensor is disposed in a sealable line configured so that a fluid to be measured does not flow for a predetermined time, and the temperature in the line is controlled by a constant temperature facility. The temperature of the fluid to be measured was controlled, and the fluid to be measured was supplied to the line at regular intervals to measure the change in the thermal conductivity of the fluid to be measured. In addition, the clearance between the inner wall of the line and the outer wall of the heat sensor is set to a size that is not affected by convection heat transfer due to convection of the fluid to be measured generated by heat generation of the heat sensor, and that the fluid to be measured does not flow for a certain time. A heat-generating sensor having a heat-generating action and capable of measuring its own temperature is arranged in the configured line that can be closed, and a part or all of the line on which the heat-generating sensor is arranged is arranged in a constant-temperature facility, or An apparatus for measuring the state of the fluid coated by the equipment was constructed. And the clearance was set to 0.8 mm or less. In addition,
The temperature of the heat generating sensor may be a temperature of a heat generating element built in the sensor, or a sensor surface temperature calculated from the temperature and a condition of the sensor sheath. A method for determining the sensor surface temperature is disclosed in Japanese Patent Application Laid-Open No. 63-217261.
In the above paragraph, the present invention is proposed by the present applicant, but can also be obtained by analyzing heat transfer. Further, the temperature control of the constant temperature liquid supplied to the constant temperature bath as a constant temperature facility may be configured to follow the temperature of the sample fluid. The constant temperature equipment may be a device in which the sensor arrangement line is a double pipe and the constant temperature liquid flows to the outer pipe side. Further, the temperature of the fluid may be measured by another sensor, the temperature of the fluid may be measured by operating a heat generation sensor having a temperature measuring function used in the present invention, or supplied to a constant temperature facility. A constant temperature fluid temperature may be used. In the case of the device of the present invention, the clearance between the sensor and the inner diameter of the line becomes a problem as a method of eliminating the influence of convection heat transfer, but as the clearance becomes narrower, the influence of heat conduction from the heat generation sensor to the fluid increases, and the fluid temperature is measured. It is preferable that the temperature of the constant-temperature fluid be set to the fluid temperature in order to make it difficult. Considering the material of the measurement line as an apparatus configuration in this case is a matter within a range that can be considered by those skilled in the art.

[0008] The fluid temperature may be measured using another element or may be replaced with a constant temperature fluid temperature. However, the heat generation sensor is a sensor having a built-in heating element, has a heat generation function, and has its own temperature measurement. It is a sensor that can perform the function of a simple temperature measuring element by controlling the current to the sensor. By performing the function conversion operation by the current operation, it is possible to measure the temperature of the fluid to be measured when the element is a temperature measuring element and to measure the temperature of the heat generating sensor when the element is a heat generating sensor. The present invention is based on the fact that the index value of the thermal conductivity of the fluid to be measured is the temperature difference between the temperature of the heat generating sensor and the temperature of the fluid to be measured. May be used.

In the apparatus according to the present invention, the clearance between the sensor diameter and the inner diameter of the line in which the sensor is arranged has an important influence on the measurement. Convection is generated, and heat is transferred by convective heat transfer and conduction heat transfer. In particular, the transfer of heat by convective heat transfer affects the measurement of thermal conductivity, making measurement impossible. The smaller the clearance, the better, but if it is too small, it will increase the difficulty of sensor processing and line processing, and it will take time to replace the fluid to be measured, so it is better to be as large as possible within the allowable range. . Note that no matter how small the clearance is, the convection due to the heat conduction of the flowing fluid cannot be completely eliminated in the measurement using the steady-state method. The inventors have found from experiments that heat is negligibly small compared to conduction heat transfer, and that the correlation between thermal conductivity and index values is high.
The present invention utilizes this relationship. There are roughly two methods for determining this clearance. one,
This is a method for experimentally confirming that the temperature distribution is constant and no convection occurs while measuring the temperature distribution of the fluid. In this case, it is necessary to confirm each sensor and each fluid, and there is a drawback in that the reliability is high, but the determination takes time. If the temperature distribution is possible, it is determined that there is an effect of convective heat transfer due to convection. Secondly, after changing the clearance at each sensor diameter and obtaining an index value using a standard material, the correlation coefficient between the thermal conductivity of the standard material and the index value is obtained by a general method, and this phase relationship is obtained. This is a method of determining the clearance by obtaining the diameter and clearance in a range that guarantees a measured value and the correlation coefficient. In the method using this correlation coefficient, when the viscosity of the fluid to be measured is low, the clearance is determined from the one with a high correlation coefficient, and when the viscosity of the fluid is high, the clearance can be determined even with a low correlation coefficient. . In addition, even if the fluid has a low viscosity, if a high degree of accuracy cannot be obtained, a fluid having a low correlation coefficient can be arbitrarily used. As described above, the clearance can be set by analysis from the sensor diameter, but the applicant has experimentally set the clearance to 0.8 mm or less for a sensor of 3.5 mm or less, and convection due to heat transfer action in the sample occurs when the clearance is 0.8 mm or less. It was also confirmed that a steady state where the influence of convective heat transfer could be neglected was maintained. When this confirmation was compared with the correlation coefficient, it was found that there was almost no problem in determining the clearance if the correlation coefficient was 0.995 or more. Therefore, as long as the correlation coefficient is obtained, the clearance of any sensor diameter can be determined within a range not affected by convective heat transfer due to convection.

[0010]

The thermal conductivity measurement of the present invention is used for two measurement purposes. One is a method in which the correlation between the thermal conductivity of various fluids and the index value is obtained by a measuring method in a standard state, and the thermal conductivity of the fluid in the line is measured using the correlation in an actual line. This can also be used to determine the liquid in the line. The other is to measure a change in the structure or component composition of the fluid to be measured in a standard state, or to measure the thermal conductivity of the fluid to be measured at that time. When measuring the change of the structure or the composition of the component, the temperature of the fluid to be measured is controlled by a constant temperature fluid at a constant measurement environment temperature and measured, and the change of the thermal conductivity at that time is estimated. The latter thermal conductivity measures a change in thermal conductivity due to a temperature change of the fluid to be measured. In this case, it is necessary to control the temperature of the constant temperature fluid to the fluid temperature. The method of controlling the constant temperature fluid according to the purpose is solved by a known technique. The standard state refers to a state at a temperature of 298 K and a pressure of 101 KPa, and the physical property values of various fluids at this time are referred to “Thermophysical Handbook” edited by The Japan Society for Thermophysical Properties (Yokendo).

[0011]

Embodiments of the present invention will be described below. As shown in FIG. 1, a line 2 containing a sensor 1 is provided inside a constant temperature layer 3. Reference numerals 4 and 5 denote an inlet and an outlet of the liquid to be measured flowing into the line 2. The liquid to be measured is guided from the inlet 4 to the line 2 by the pressure of the pump. After closing, the valve 7 on the inlet 4 side is closed to stop the flow of the liquid in the line 2. In addition, without using the valves 6 and 7 as described above, for example,
The liquid may be sent to the line 2 using a stepping motor or the like, and the liquid may be intermittently stopped in the line 2. Further, it is desirable that the sensor 1 is disposed vertically as shown in the figure. This is to prevent bubbles and the like in the liquid to be measured from staying on the surface of the sensor 1 and to maintain the uniformity of the liquid to be measured, thereby preventing an error from occurring. In particular, when the sensor 1 is thin, the clearance with the inner wall of the line 2 is small, and the liquid to be measured needs to be sent at a certain pressure or higher. In such a case,
The deformation can be prevented by arranging the sensor 1 vertically so that the pressure of the liquid to be measured is applied in the sensor axis direction.

As shown in FIG. 2, the sensor 1 is a heating element 1
0 is covered with an insulating material 11 and the heating element 1
In this configuration, a current can be supplied from a lead wire 13 to a heating wire (thin metal wire) 12 buried inside the wire. The above configuration is basically the same as that of the sensor disclosed in JP-A-64-44838. Then, such a sensor 1 is disposed inside the line 2 in which the sensor 1 is disposed, a current is supplied from the lead wire 13 to cause the heating element 10 to generate heat, and the temperature of the sensor 1 is measured from a change in the resistance value of the heating wire 12. I do. Then, the temperature of the fluid to be measured in the line 2 is kept constant by the constant temperature water (for example, water) flowing through the constant temperature layer 3 to prevent the temperature of the fluid to be measured from rising due to the heat generation of the sensor. The thermal conductivity of the fluid to be measured is measured from the temperature difference of the fluid to be measured.

Here, the clearance between the heat generating sensor 1 and the inner wall of the line 2 is designed to have a size such that the measured fluid whose temperature has risen due to the heat generated by the heat generating sensor 1 generates convection and does not affect the convective heat transfer. There is a need to. The clearance is basically determined by the diameter of the sensor 1 and the inner diameter of the line 2. However, the clearance greatly changes depending on the viscosity of the fluid. If the fluid has a high viscosity, convection hardly occurs, so that the clearance can be increased. . Further, the influence of the amount of heat generated by the heat generation sensor 1, the shape of the heat generation sensor 1, the length of the heat generating body 12 inside the heat generation sensor, and the like are also factors that determine the clearance.

The method of determining the clearance includes an experimental method and a method of determining the clearance from a correlation coefficient. Here, an example of determining the clearance using the correlation coefficient will be described. FIG. 3 shows that the diameter of the sensor 1 is 1 mm, 1.25 mm, and 2.5 mm, respectively.
5 shows the result of calculating the correlation coefficient in the case of 5 mm and 5 mm. As shown in the figure, when the clearance is 0.8 mm or less, the correlation coefficient becomes 0.995 or more, and it can be determined that it is usable. If the accuracy is neglected, a clearance of about 2 mm is possible, but the correlation coefficient is 0.995 or more in a range in which convective heat transfer is not affected by heat transfer by convective heat transfer. Thus, the clearance is preferably 0.8 mm or less.

FIG. 4 shows the relationship between the diameter of the heat generating sensor 1 and the clearance under the condition that the correlation coefficient is 0.995, the fluid is water, and the calorific value is constant. Shows clearance.
According to this figure, it can be understood that the clearance can be set only up to 0.8 mm in water in order to secure a correlation coefficient of 0.995. In this figure, the diameter is 0.35
The analysis is based on the analysis of average heat transfer in a sensor of mm or less, and the numerical value of the clearance tolerance when the sensor diameter is changed at a correlation coefficient of 0.995 was obtained. This figure also agrees with the experimental results when the diameter is 0.35 mm or less, indicating that there is no problem in setting the clearance by the correlation coefficient.

Here, it is known that the following equation holds between the temperature difference ΔθW measured in a steady state in the apparatus as shown in FIG. 1 and the thermal conductivity λ of the fluid to be measured. Therefore, it can be seen from the above equation that the thermal conductivity λ can be obtained from the temperature difference ΔθW. As can be seen from the equation, instead of the correlation between the temperature difference ΔθW and the thermal conductivity λ, the heat value Q
It is also possible to obtain the thermal conductivity λ from the correlation between the thermal conductivity λ and the thermal conductivity λ. In this case, the correlation between the change in the heat value Q and the thermal conductivity λ is obtained by controlling the temperature difference ΔθW to be constant. In this embodiment, a description will be given of a correlation between the temperature difference ΔθW and the thermal conductivity λ. 5 and 6 show the difference ΔθW between the temperature of the sensor 1 and the temperature of the fluid to be measured, measured in a steady state while maintaining the temperature in the thermostatic layer 3 at 25 ° C. in the apparatus as shown in FIG. 1, and the thermal conductivity of the fluid to be measured. (FIG. 5 and FIG. 6 show different scales of axes, FIG. 5 shows a liquid portion, and FIG. 6 shows a gas portion). Each point in the figure shows the relationship between the temperature difference △ θW and the thermal conductivity λ measured for each substance in FIG. 7 (Table 1), black circles are experimental measurement values, and white circles are obtained by numerical analysis. Indicates the value to be set. As shown in the figure, the result of the numerical analysis and the result of the experiment are in good agreement, and it can be seen that the measured value can be predicted by the numerical analysis.

As described above, in order to measure the thermal conductivity λ of the fluid in a state where convection does not occur and in a steady state,
As described above, it is important to set the clearance to a desired size. Therefore, the results of experiments were conducted with the clearance set so that convection does not occur, or even if convection occurs, heat transfer due to convection heat does not affect the measurement of thermal conductivity. FIG. 8 (Table 2). FIGS. 9 and 10 show the results in a graph.
By examining such a relationship in advance, it is possible to determine what the fluid to be measured is by measuring the temperature difference ΔθS and determining the thermal conductivity of the fluid in the line. Therefore, when various fluids are intermittently changed and flow into the line, the type of fluid can be determined. Needless to say, it is possible to measure the thermal conductivity of a specific fluid whose thermal conductivity changes, but in such a case, the correlation between the change in the thermal conductivity of the fluid and the temperature difference ΔθS is separately obtained. Need to be kept. In this case, it is possible to detect, for example, a change in the concentration of the fluid or a change in the structure or composition of the component from the change in the thermal conductivity. Is also possible. Although a specific example is not shown, for example, it is conceivable to detect a change in concentration as a change in thermal conductivity and control the flow rate of the line based on the degree of the change. As described above, in the thermal conductivity measurement in this case, the temperature of the constant temperature fluid is kept constant or the temperature of the fluid to be measured is controlled according to the purpose.

FIGS. 9 and 10 show the relationship between the temperature difference ΔθS and the thermal conductivity λ obtained by the numerical analysis. However, the thermal conductivity obtained by the numerical analysis and the thermal conductivity of the actually measured value are almost the same. The coincidence is as shown in FIGS. Also,
The experiments in the above examples were conducted under the conditions of a sensor diameter of 1 mm, a clearance of 0.25 mm, and a heating value of 20 W. When a regression equation for obtaining the thermal conductivity λ was obtained from the measured values shown in FIG. 8 (Table 2), the following equation was obtained. λ = 1 / (A + B × {θW + C × {θW ² + D ×}}
θW ³ ) The values of the coefficients A, B, C, and D are as follows. A = -1.0398 E1 B = 6.1081 E-1 C = -6.1724 E-3 D = 8.2584 E-5

When convection occurs, heat transfer due to convective heat transfer affects the measurement of thermal conductivity.
In such a case, it can be determined from the fact that the correlation between the temperature difference ΔθS and the thermal conductivity λ varies as shown in FIGS. FIG. 11 shows a liquid portion,
FIG. 12 shows a gas portion.

[0020]

According to the present invention, the thermal conductivity of a fluid can be easily measured in-line. Therefore, process management becomes easy. In addition, since the measurement is performed while maintaining the temperature at a constant temperature in the constant temperature layer, the measurement can be performed accurately with little error and without being affected by a temperature change in a place where the measurement equipment is arranged. In particular, when the thermal conductivity is obtained from the relationship between the temperature difference and the thermal conductivity as in the present invention, complicated numerical processing and arithmetic circuits are not required for measurement, and the measuring device itself can be configured at low cost. Can be. In addition, the structure is simpler than that of a conventional measuring device using the stationary method, and cleaning and maintenance are easy. Therefore, it can be arranged directly in an actual production facility.

[Brief description of the drawings]

FIG. 1 is a sectional view of a measuring device.

FIG. 2 is a sectional view of a sensor.

FIG. 3 is a graph showing a relationship between a clearance and a correlation coefficient.

FIG. 4 is a graph showing a relationship between a diameter of a heat generation sensor and a clearance.

FIG. 5 is a graph showing a relationship between a temperature difference and a thermal conductivity of a fluid to be measured.

FIG. 6 is a graph showing a relationship between a temperature difference and a thermal conductivity of a fluid to be measured.

FIG. 7 is a table 1 showing the thermal conductivity of each substance.

FIG. 8 is a table showing the thermal conductivity and temperature difference of each substance.

FIG. 9 is a graph showing a relationship between a temperature difference and a thermal conductivity obtained by numerical analysis.

FIG. 10 is a graph showing a relationship between a temperature difference and a thermal conductivity obtained by numerical analysis.

FIG. 11 is a graph showing a relationship between a temperature difference and a thermal conductivity of a fluid to be measured in a state where heat transfer due to convective heat transfer affects thermal conductivity measurement.

FIG. 12 is a graph showing a relationship between a temperature difference and a thermal conductivity of a fluid to be measured in a state where heat transfer due to convective heat transfer affects the measurement of thermal conductivity.

[Explanation of symbols]

 1 Heat generation sensor 3 Constant temperature layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-191852 (JP, A) JP-A-3-175334 (JP, A) JP-A-3-24448 (JP, A) JP-A 64-64 32120 (JP, A) JP-A-60-146118 (JP, A) JP-A-2-306152 (JP, A)

Claims (3)

(57) [Claims] 1. A method for preventing a fluid to be measured from flowing for a certain period of time.
Place the heat sensor in the configured line that can be closed,
And the temperature of the fluid to be measured in the line is controlled by a constant temperature facility.
Control and supply the fluid to be measured to the line at regular intervals
Fluid thermal conductivity measurement to measure changes in fluid thermal conductivity
Method. 2. A connection between an inner wall of a line and an outer wall of a heat generation sensor.
The measured fluid is generated by the heat generated by the heat sensor.
Size not affected by convective conduction due to convection
And the measured fluid does not flow for a certain period of time.
It has a heating effect in the line that can be closed and
A heat sensor capable of measuring temperature is arranged, and the heat sensor
A part or all of the line where the
In the state of the fluid
measuring device. 3. The clearance is set to 0.8 mm or less.
The fluid state measuring device according to claim 2.