JP2003106975A - Thermal property measuring method and measuring device using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement accuracy by accurately measuring a diametral change of a droplet and easily measure it in a short time without degrading the measurement accuracy in a measuring method for surface tension or the like using a suspended droplet vibrating method. SOLUTION: A laser beam L is irradiated from a one end side of a hollow tube 2, the droplet d of a specimen is suspended in the hollow tube 2, the diametral change of the droplet d is measured from a shadow of the droplet d by the laser beam L, and at least one of surface tension, density or a viscosity coefficient of the specimen is measured. It is favorable to measure the diametral change of the droplet d in a free falling state from a perspective of improving the measurement accuracy by conglobating the droplet d.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring surface tension, density and viscosity using a floating droplet vibration method and a measuring device using the method.

[0002]

2. Description of the Related Art Thermophysical property values of a melt are indispensable for optimizing industrial processes such as micro joining of electronic parts. Until now, the sessile drop method has been generally used to measure the thermophysical properties of surface tension and density. This method is a method in which a droplet is placed on a substrate and the surface tension or the like is obtained from the change in curvature of the contour of the droplet. According to this method, the thermophysical property can be measured with a variation of about ± 5% or less in the case of a material having a low melting point, but in the case of a material having a high melting point, the reaction between the substrate and the liquid droplets proceeds to such an extent that it cannot be ignored. Since the droplets are contaminated, there is a problem that the thermophysical properties of highly pure materials cannot be measured.

Therefore, in recent years, a floating droplet vibration method has attracted attention, in which a droplet is floated by electromagnetic force or electrostatic force to freely vibrate, and thermophysical properties such as surface tension are measured from its vibration frequency. According to this method, since the droplet does not come into contact with the substrate, the thermal characteristics of the material can be measured in a highly pure state.

[0004]

However, in the conventional measurement by this method, the diameter change of the droplet is measured by photographing with a high-speed video camera or by using a photodiode. The speed was not fast enough and satisfactory measurement accuracy was not obtained.

Another problem is that when the measurement is performed under gravity, the accuracy of measurement is lowered because the droplet does not become spherical due to the influence of gravity. In order to solve this problem, the measurement should be performed in a weightless state. That is, the liquid droplets may be allowed to fall freely and the frequency of vibration during that period may be measured. Since the droplets are minutely affected by gravity even during the free fall, this free fall may be referred to as “microgravity environment” below. Based on such an idea, the present inventors have conducted various experiments using the facilities of the underground gravityless experimental center, and have clarified that surface tension and viscosity can be measured with high accuracy in a microgravity environment.
In the experiment using the above facility, each device was allowed to fall freely, so that preparation required a great deal of time and labor, and also required a high cost.

The present invention has been made in view of such a conventional problem, and in a method of measuring thermophysical properties such as surface tension of a droplet using a floating droplet vibration method, it is possible to accurately measure a change in droplet diameter. The purpose is to improve the accuracy of the measurement.

Another object of the present invention is to provide a method and an apparatus capable of easily measuring thermophysical properties in a short time without lowering measurement accuracy.

[0008]

In order to achieve the above object, in the thermophysical property measuring method according to the first invention, a laser beam is irradiated from one end side of the hollow tube, and the test substance in the form of droplets is collected. In a state of being suspended in the hollow tube, with a line sensor provided on the other end side of the hollow tube, the diameter change of the droplet is measured from the shadow of the droplet by laser light, and the surface tension and density of the test substance are measured. The configuration is such that at least one of the viscosity is measured. The floating state in the present invention means a state in which the liquid droplet is floating without any support, and the liquid droplet is not only statically floating but also dynamically floating. Including the state (free fall).

Here, from the viewpoint of making the droplets spherical and improving the measurement accuracy, it is recommended to adopt a state in which the droplets fall freely as the suspended state.

In the thermophysical property measuring method according to the second aspect of the present invention, laser light is irradiated from one end of the hollow tube, and the test substance that has turned into liquid droplets in the hollow tube is allowed to fall freely, whereby the hollow tube At the other end of the tube, measure the diameter change of the droplet from the shadow of the droplet by laser light, the surface tension of the test substance, the density,
It was configured to measure at least one of the viscosity.

Further, in the thermophysical property measuring apparatus according to the present invention, a hollow tube, a laser beam irradiating means provided at one end of the hollow tube, and a test substance suspended in the hollow tube are suspended. Floating means for, and provided on the other end side of the hollow tube, a detecting means for detecting the shadow of the droplet by the laser light, the surface tension of the test substance from the diameter change of the droplet while floating, The configuration is such that at least one of the density and the viscosity is measured.

From the viewpoint of improving the measurement accuracy,
As the floating means, a means for allowing the liquid droplets to fall freely is desirable, and as the detection means, a line sensor is desirable.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have made earnest studies to improve the accuracy of thermophysical property measurement such as surface tension by a floating droplet vibration method, and as a result, use a laser beam and a line sensor to measure the measurement speed. The inventors of the present invention have found that the measurement speed can be increased, the droplets can be freely dropped, and measurement can be performed easily in a short time without lowering the measurement accuracy, and the apparatus can be downsized.

First, the measuring method according to the first invention will be described. A major feature of the measuring method according to the present invention is a line sensor in which a droplet in a state of being suspended in a hollow tube is irradiated with laser light from one end side, and a shadow of the droplet by the laser light is provided on the other end side. This is to measure the vibration frequency, volume, and amplitude attenuation rate from the change in the diameter of the droplet, and to introduce these into the following theoretical formula to calculate the surface tension, density, and viscosity. It should be noted that the surface tension requires a correction formula because the droplet does not become spherical when measured under the influence of gravity.

Surface tension γ = 3/8 × π × M × ν ² (1) (M: mass, ν: vibration frequency) Density ρ = M / V (2) (M: mass, V: volume) viscosity η = 3 / (20π) × (1 / τ) × (M / R) (3) (1 / τ: logarithmic attenuation rate, M: mass, R: droplet radius)

Conventionally, a change in diameter of a suspended liquid droplet has been conventionally photographed by a high-speed video camera for analysis and measurement. When shooting with such a video camera, even at high speeds, at most 2
The frequency is about 0.00 to 2,000 frames / sec. For example, when the droplet is about 1 to 2 mm, it vibrates at 1,000 Hz (the smaller the droplet diameter, the higher the frequency). Could not be measured correctly. On the other hand, in the measuring method of the present invention, since the shadow of the liquid drop due to the laser light is measured by the line sensor provided on the other end side, 70,
Information of 000 to 80,000 frames / sec can be obtained and sufficient measurement can be performed even with a droplet vibration of 1,000 Hz.

FIG. 1 shows an example of a measuring apparatus using this measuring method. In the apparatus of FIG. 1, a He—Ne laser device (laser irradiation means) 1 is arranged at the lower end of a hollow tube 2 made of quartz or alumina, and laser light emitted from the laser device 1 having a diameter of about 1 mm is used. L is the beam expander 42
After expanding the diameter to 3 to 8 mm, the prism 43 allows the light to enter the hollow tube 2 from the opening at the lower end in parallel to the axial direction.
On the other hand, in the hollow tube 2, a droplet (here, pure water) d having a diameter of about 1 to 2 mm, which is formed by the dropping device 41, is statically suspended. Specifically, under gravity, the pair of supports S having needle-like tips support the droplet d, and the entire apparatus is allowed to fall freely, that is, after the microgravity environment is reached, the support S drops. The droplet is floated by removing it from d. As described above, in this device, since the whole device is freely dropped and measured, a device for statically suspending the liquid droplet is not particularly used, but the liquid droplet is statically suspended while the device is left stationary. For this purpose, conventionally known floating means such as electromagnetic force, electrostatic force and sound wave are required.

Then, the prism 44 provided at the upper end opening of the hollow tube 2 refracts the laser light L emitted from the hollow tube 2 substantially vertically and makes it enter the beam expander 45. Here, the diameter of the laser light L is further increased, and the cross section of the laser light L is made into a quadrangle through the slit 46, and then the laser light L is condensed in a line by the cylindrical lens 47, and the line sensor (detection means) 3 is used. Let it be detected.

In such an apparatus, a laser beam L incident from the lower end opening of the hollow tube 2 and parallel to the axial direction of the hollow tube
However, when it collides with the floating droplet d, the laser beam is blocked only in that portion and a shadow is detected by the line sensor 3. A schematic diagram of detection by the line sensor 3 is shown in FIG. As is apparent from FIG. 2, the line sensor 3 can detect the maximum diameter of the droplet d at any position in the radial direction of the hollow tube 2. Further, since the laser beam L is used, even if the droplet d moves in the tube axis direction of the hollow tube 2, its maximum diameter can be correctly detected.

Here, the measurement error of the maximum diameter of the droplet is set to 0.1.
In order to reduce the percentage to less than 100%, it is necessary for the line sensor to have shadows of droplets of 1,000 pixels or more. For this purpose, a 2048-pixel line sensor must be used. Further, in order to reduce the reading error of the droplet to 0.1% or less, the reading error of the phase needs to be ± 2.5 ° or less. In other words, during one amplitude of the surface vibration of the droplet, 71
Need to record more than once. Therefore, the frequency 1,0
In order to measure the surface vibration of the liquid droplets at about 00 Hz within the above error, a line sensor capable of recording at 71,000 frames / sec or more must be used. As a line sensor having such performance, for example, "CT manufactured by DALSA Co., Ltd.
-F3-2048W "(2048 pixels, 83,000 frames / sec) and the like.

Further, the measuring apparatus of FIG. 1 uses only one line sensor, but in order to further improve the measurement accuracy, two or more line sensors are used, and the laser light is spectrally incident on each line sensor. Of course it does not matter if you do so.

Next, an example of a method for calculating the thermophysical property value from the data obtained by the measuring device will be described. FIG. 3 shows the change over time in the diameter of the droplet detected by the line sensor, with the vertical axis representing the droplet diameter and the horizontal axis representing the time. From this figure, changes in the vibration frequency and amplitude of the droplet can be calculated. FIG. 4 shows the vibration frequency distribution obtained from the data of FIG. 3 at each time interval from the start of measurement. Is 0 to 0.28 sec
Vibration frequency distribution curve between is 0.07 to 0.35se
The vibration frequency distribution curve between c is shown, and the larger the sign is, the more the vibration frequency distribution curve becomes after the start of measurement. According to this figure, after the start of measurement ~
In the vibration frequency distribution curve of, the surface vibration is not only in two directions (“L = 2” in the figure) but also in three directions and four directions (“L = 3” and “L = 4” in the figure). A peak is observed. Therefore, to eliminate the effects of such noise,
It is desirable to calculate the thermophysical property value using the data after a predetermined time has elapsed from the start of measurement.

FIG. 5 is a diagram showing the time-dependent change in the amplitude of the droplet surface vibration, which is obtained from the data of FIG. From this figure,
It can be seen that the surface vibration amplitude attenuates with time. The formula of the approximation curve is calculated from this data as follows.

[0024] y = 0.364exp (-1.7394x)

The exponent (-1.7394) in the above equation corresponds to the logarithmic decay rate (1 / τ). Substituting this into the equation (3) to calculate the viscosity yields 0.92 × 10 ⁻³ Pa · s, which is the known viscosity of pure water (0.924 × 10 ⁻³ Pa · s).
s) was almost the same. Here, the viscosity coefficient is obtained as an example, but the surface tension and density of the droplet can be calculated by obtaining the vibration frequency and diameter of the droplet from the data of FIG. 3 and substituting them into the above equations (1) and (2). Needless to say.

In the apparatus shown in FIG. 1, the liquid droplets are statically suspended in a spherical shape by free-falling the entire apparatus, but a large-scale drop device must be used for free-falling the entire apparatus. This requires a lot of time, labor, and cost for measurement. Therefore, in the apparatus of FIG. 1, it is preferable that the droplets are allowed to freely fall while the apparatus is stationary to form spherical droplets. Of course, in the apparatus of FIG. 1, the droplet may be statically suspended by using a conventionally known floating means such as electromagnetic force, electrostatic force, or sound wave, but in this case, the droplet does not become spherical. A correction formula is required to calculate the surface tension from the formula (1). Further, in the apparatus of FIG. 1, the line sensor is provided at the upper end of the hollow tube and the laser device is provided at the lower end, but the arrangement positions may be reversed. Further, when the droplets are floated by using the floating means, it is not necessary to dispose the hollow tubes in the vertical direction, and for example, they may be arranged in the horizontal direction.

Next, the thermophysical property measuring method according to the second invention will be described. The major feature of the measuring method according to the present invention is to make the droplets to be spherical by free-falling the droplet-shaped test substance, and at the same time, to make apparent changes in the droplet diameter caused by the droplets falling, This is because it was prevented by using parallel laser light. According to this method, it is possible to accurately measure the diameter change of the spherical droplets in a microgravity environment, so that the measurement accuracy of thermophysical properties is improved. Moreover, since the liquid droplets are allowed to fall freely, the thermophysical properties can be easily measured in a shorter time than the conventional measurement in which the apparatus is allowed to fall freely. In addition, the measurement equipment can be downsized.

Although the measuring method according to the first aspect of the present invention has the same basic structure, the measuring method of the present invention is not limited to a line sensor as a means for detecting a change in the diameter of a droplet, and a conventionally known detecting means such as a high speed video camera. Is different from the measuring method according to the first invention. However, in order to reduce the size of the device and provide versatility, it is necessary to make the drop distance of the droplet as short as possible. Therefore, if the fall distance is about 1.5 m, the fall time is about 0.55.
In order to obtain the data necessary for accurately calculating the thermophysical property value in this short time, it is necessary to reduce the droplet diameter and set the vibration frequency to 1000 Hz or higher. In order to accurately measure such a high vibration frequency of a small droplet diameter, it is desirable to use a line sensor as the detection means, and the one exemplified in the first invention can be suitably used here.

FIG. 6 shows an example of a measuring apparatus using the measuring method according to the present invention. The measuring apparatus shown in FIG. 6 has a part of the basic configuration common to that of the measuring apparatus shown in FIG. First, one different configuration is that in the measuring device of FIG. Depending on the substance to be inspected, the electromagnetic levitation device 5 may be insufficient in heating amount depending on the substance to be inspected. Therefore, the infrared introducing and heating device 6 is additionally provided for assisting heating and melting. Further, in the apparatus of FIG. 6, the laser beam L is split into two using the half mirror 48, and the two line sensors (detection means) 3a and 3b detect the droplet diameters in two directions orthogonal to each other. This is for the purpose of improving the measurement accuracy, and one or three or more may be used.

Next, a specific measuring method in such a measuring device will be described. After the hollow tube 2 is evacuated, the test substance is heated and melted by the electromagnetic levitation device 5 to form droplets d. At this time, the effect of cleaning the surface of the droplet is additionally obtained.
Then, by turning off the power of the electromagnetic levitation device 5, the formed droplet d is allowed to fall freely inside the hollow tube 2. The droplet d is spherical because it is in a microgravity environment during free fall. The change in diameter of the liquid droplet d during this time is detected by the line sensors 3a and 3b as the shadow of the liquid droplet d caused by the laser light L. Then, the vibration frequency, the volume, and the damping rate of the amplitude of the droplet are obtained from the obtained change of the droplet diameter in the same manner as described above, and are substituted into the equations (1) to (3) to calculate each thermophysical property value. Good.

[0031]

In the measuring method according to the first aspect of the present invention, a laser beam is irradiated onto a liquid droplet suspended in a hollow tube, and the shadow of the liquid laser beam is measured by a line sensor to obtain the liquid droplet. Since the thermophysical property value is calculated from the change in diameter, the thermophysical property value can be obtained with high accuracy by measuring in a short time.

If the floating state of the droplets is the state of free fall, the droplets will be spherical and the thermophysical property value can be obtained with higher accuracy.

In the measuring method according to the second aspect of the invention, the thermophysical property value is calculated by allowing the droplet to freely fall in the hollow tube and measuring the change in diameter of the droplet during that time by the shadow of the droplet due to the laser light. The thermophysical property value can be measured with high accuracy. In addition, thermophysical property values can be measured in a shorter time and more easily than conventional measurements. In addition, the measurement equipment can be downsized.

In the measuring apparatus of the present invention, the droplets suspended in the hollow tube are irradiated with the laser beam, and the shadow of the droplets by the laser beam is measured by the detecting means to detect the change in the diameter of the droplets from the heat. Since the physical property values are calculated, the thermophysical property values can be obtained with high accuracy.

Here, if the diameter change of the liquid drop in the free-fall state is measured, or if a line sensor is used as the detection means, the thermophysical property value can be obtained with higher accuracy.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a measuring apparatus using a measuring method according to a first invention.

FIG. 2 is an explanatory diagram in which a line sensor detects a shadow of a droplet caused by laser light.

FIG. 3 is a diagram showing an example of a change in droplet diameter.

FIG. 4 is a vibration frequency distribution chart of droplets calculated from the data of FIG.

5 is a diagram showing a change over time in the vibration amplitude of a droplet calculated from the data of FIG.

FIG. 6 is a schematic view showing an example of a measuring device using the measuring method according to the second invention.

[Explanation of symbols]

1 Laser device (laser irradiation means) 2 hollow tubes 3 line sensor (detection means) 5 Electromagnetic levitation device (floating means) d droplet L laser light

Continued front page    (71) Applicant 501382052             Kiyoshi Nojo             11-1 Mihogaoka, Ibaraki City, Osaka Prefecture             Within the Institute of Advanced Science (72) Inventor Daihei Matsumoto             11-1 Mihogaoka, Ibaraki City, Osaka Prefecture             Within the Institute of Advanced Science (72) Inventor Hidetoshi Fujii             11-1 Mihogaoka, Ibaraki City, Osaka Prefecture             Within the Institute of Advanced Science (72) Inventor Masayoshi Kamai             11-1 Mihogaoka, Ibaraki City, Osaka Prefecture             Within the Institute of Advanced Science (72) Inventor Toyomasa Nakano             2-303, Isshiki Nishi, Hiraoka Town, Kakogawa City, Hyogo Prefecture             15 (72) Inventor Kiyoshi Nogi             11-1 Mihogaoka, Ibaraki City, Osaka Prefecture             Within the Institute of Advanced Science

Claims (6)

[Claims] 1. A laser beam is irradiated from one end side of the hollow tube, and the test substance in the form of droplets is provided on the other end side of the hollow tube in a state of being suspended in the hollow tube. A thermophysical property measuring method, characterized in that a line sensor measures a diameter change of a droplet from a shadow of the droplet caused by laser light, and measures at least one of surface tension, density, and viscosity of a test substance. 2. The thermophysical property measuring method according to claim 1, wherein the suspended state is a state in which a liquid droplet is allowed to fall freely. 3. A laser beam is radiated from one end side of the hollow tube, and a test substance that has been made into droplets inside the hollow tube is allowed to fall freely, and a droplet of the laser beam is emitted at the other end side of the hollow tube. Measure the diameter change of the droplet from the shadow of the, the surface tension of the test substance,
A method for measuring thermophysical properties, which comprises measuring at least one of density and viscosity. 4. A hollow tube, a laser beam irradiating means provided on one end side of the hollow tube, a floating means for suspending a test substance in the form of droplets in the hollow tube, and a hollow tube for the hollow tube. Equipped with a detection means provided on the other end side for detecting the shadow of the droplet due to laser light, and measuring at least one of the surface tension, density, and viscosity of the test substance from the diameter change of the droplet while floating A thermophysical property measuring device characterized by: 5. The thermophysical property measuring device according to claim 4, wherein the floating means is means for allowing the liquid droplets to fall freely. 6. The thermophysical property measuring device according to claim 4, wherein the detecting means is a line sensor.