JPH0933302A - Sprinkled state measuring method on vertical wetted wall - Google Patents

Abstract

(57) [Abstract] [Problem] The problem is to eliminate troublesome work and dangerous work associated with measurement of the flow rate of water flowing down a vertical wetting wall and water film thickness. [Structure] A process of obtaining a moving image of water flowing down by photographing the surface of a vertical wet wall 2 with a camera 4, and extracting a motion vector of a local attention area from adjacent frames fi and fi + 1 in the moving image. Using the process of calculating the flow velocity of water and the known correspondence relationship between the flow velocity and the flow rate, the process of calculating the flow rate from the calculated flow velocity, and the known correspondence relation between the flow amount and the water film thickness A method of measuring a water spray state on a vertical wetting wall, which comprises a step of calculating the thickness of a water film from the calculated flow rate. From this, in the present invention, the flow rate of water flowing down the vertical wetting wall can be measured in a non-contact manner by the moving image of the camera, which is simple and does not involve dangerous work. It is possible to simultaneously measure not only one location but also multiple locations or multiple locations. Automatic measurement by robot is possible. It is also possible to measure the water film in addition to the flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a sprinkling state such as a sprinkling amount in an apparatus for flowing a fluid along a vertical wetting wall such as a heat exchanger using seawater as a heat source. Is.

[0002]

2. Description of the Related Art In an apparatus such as an open rack type vaporizer in which heat is exchanged by flowing a fluid along a vertical wetting wall such as a panel, the flow rate of the fluid flowing along the wetting wall is Since it is related to the exchange amount, it is necessary to control the sprinkling state such as the flow rate and the thickness of the water film.

In the conventional measuring method for controlling the sprinkling state, first, for measuring the flow rate of water flowing down along a wet wall, a water collecting device such as a special stake is installed at an appropriate position on the wet wall. The flowing water for a unit time, for example, about 1 minute,
This is a method of actually collecting and measuring, that is, a so-called volume method, and for measuring the thickness of the water film, a worker actually puts a ruler on the wet wall and visually measures it.

[0004]

However, in such a conventional method, it is necessary to install a special instrument and apply a ruler, which is troublesome and involves a risk in the work. In order to compare the local flow rates at a plurality of positions having different positions, it is necessary to perform the measurement using the above-mentioned instrument or the like at each of the plurality of positions. And other issues. Therefore, the present invention is intended to solve such a problem.

[0005]

In order to solve the above-mentioned problems, according to the present invention, first, a process of obtaining a moving image of water flowing down by photographing the surface of a vertical wetting wall with a camera, and It consists of a process of calculating a flow velocity of water by extracting a motion vector of a local region of interest from an adjacent frame, and a process of calculating a flow amount from the calculated flow velocity by using a known correspondence relationship between the flow velocity and the flow amount. We propose a method of measuring sprinkling condition.

Further, according to the present invention, a process of taking a picture of the surface of the vertical wetting wall with a camera to obtain a moving image of water flowing down,
The flow rate is calculated from the above calculated flow rate by using the process of extracting the local motion vector of the region of interest from the adjacent frame in the moving image to calculate the flow rate of water and the known correspondence relationship between the flow rate and the flow rate. We propose a method for measuring the sprinkling state, which comprises a process and a process of calculating the thickness of the water film from the calculated flow rate by using the known correspondence relationship between the flow rate and the water film thickness.

In the above method, the surface of one vertical wetting wall is photographed by one camera, and the sprinkling condition at a suitable number of points on one vertical wetting wall is measured.
It can be configured such that the surface of a plurality of vertical wetting walls can be simultaneously photographed by one camera and the water sprinkling state on the plurality of vertical wetting walls can be simultaneously measured.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, FIG. 1 schematically shows a configuration to which the present invention is applied. Reference numeral 1 is an LN using seawater as a heat source as an example of a device such as a heat exchanger having a vertical wetting wall.
G vaporizer, open rack vaporizer.
This LNG vaporizer 1 sprinkles seawater from a trough 3 at the upper part onto a panel 2 as a vertical wetting wall to make it flow down.
LNG flowing from the bottom to the top of the LNG pipe of panel 2
It is configured to perform heat exchange with and vaporize.

Reference numeral 4 is a camera arranged so that the panel 2 of the LNG vaporizer 1 is the field of view.
The surface of the panel 2 is photographed and a moving image of the surface of the seawater flowing down there is obtained. The image of the surface of seawater means an image in which the flow of the surface is substantially visible, and does not necessarily have to be an image of the surface of seawater in a strict sense. Further, the field of view 5 of the camera 4 is the entire panel 2 in FIG. 1 as schematically shown by a chain double-dashed line, but it is also possible to set a desired local field of view.

The camera 4 can be configured to obtain a monochrome image, that is, a gradation image by using, for example, a monochrome CCD camera, and can also be configured to obtain a color image by a color camera. The number can also be set appropriately.

The image signal from the camera 4 is input to the processing device 6, and the flow rate of seawater and the thickness of the water film are calculated by the process described later. The processing device 6 is schematically represented as two processing units, that is, an image processing unit 7 and a calculation unit 8, but these generally perform the following processing. First, the image processing unit 7 extracts the local motion vector of the region of interest from the adjacent frames in the moving image from the camera 4, and the velocity of a random pattern appearing in the image due to the flow of seawater, and thus the flow velocity of seawater. Then, in the calculation unit, the flow rate is calculated using the known correspondence relationship between the flow velocity and the flow rate, and if necessary, the water film thickness is calculated using the known correspondence relationship between the flow rate and the water film thickness. Calculate the The system resources constituting these are appropriate.

As described above, FIG. 2 schematically shows the process of obtaining the speed of a random pattern appearing in an image due to the flow of seawater. The left and right rectangular frames are i and i + 1 in the moving image, respectively. Th still image, i.e. frame fi,
fi + 1, which corresponds to the field of view of the camera 4. In these frames fi and fi + 1, a random pattern 9 that moves downward as seawater flows down appears, and this random pattern 9 is represented by a horizontal broken line in the figure. The movement of these random patterns 9 is analyzed using a known method in the field of moving image recognition. That is, the moving distance of the random pattern 9 between the adjacent frames fi and fi + 1 can be obtained by using a known method such as an inter-image correlation method.

In the inter-image correlation method, for example, a local attention area B is set at a desired portion of the frame fi, and the attention area B of this frame fi is scanned within the frame fi + 1 while the pixels in the attention area are scanned. The cross-correlation coefficient of the tone value of is calculated to obtain the area B ′ of the frame fi + 1 having the highest degree of coincidence with the attention area B, that is, the area B ′ having the maximum cross-correlation coefficient. The moving distance of the random pattern 9 on the screen between the frames fi and fi + 1 can be obtained from the shift amount of B and B'on the screen. Then, the actual movement distance on the panel 2 can be obtained from the movement distance on the screen. The position of the attention area B can be set at a proper position in the frame, and the number of pixels and the aspect ratio in the attention area B can be appropriately set.

In addition to the above, the movement distance of the random pattern 9 between the frames fi and fi + 1 is calculated from the best matching position by using the degree of coincidence of the attention area B as in the inter-image correlation method. Other methods of obtaining the corresponding points between fi + 1 and the shift amount can be used. As this method, for example, the sum of the absolute values of the difference gradation values of the pixels in the attention area B is calculated, and the closer the value is to 0, the higher the degree of coincidence, and the corresponding point is calculated. The absolute value of the difference in gradation value is calculated and this is 0
The closer the value is, the higher the degree of matching is, and the method of obtaining the corresponding points, the absolute value of the difference between the standard deviations of the gradation values of the pixels in the attention area B is obtained. Can be applied, and a method of finding the degree of coincidence with the Fourier series of the gradation values of the pixels in the attention area B can be applied. In addition to the method using the degree of coincidence of the attention area B as in the above method, the gradient proposed by HHNagel using the relationship between the spatial gradient of brightness and the temporal gradient in each pixel of each frame of a moving image. Laws and the like can also be applied.

By the above method, it is possible to obtain the moving distance between the frames fi and fi + 1 of the random pattern that moves downward on the panel 2 as the sea water flows down, that is, the sea water flowing down distance. The distance is frame fi,
The flow velocity of seawater can be calculated by dividing the time by fi + 1.

FIG. 3 shows the result of actually measuring the relationship between the flow velocity of seawater flowing down the panel 2 and the local flow velocity of the panel 2 in the panel 2 of the LNG vaporizer 1. In this case, the flow velocity of the sea water is shown. Is obtained by applying the present invention, and the local flow rate is obtained by the conventional volume method described above.
As shown in this figure, there is a significant correspondence between the surface flow velocity and the local flow rate, which can be approximated by the following equation. v≈1.49 × q ⁰ · ⁶⁷³ (1) where v: surface velocity [m / sec], q: local flow rate [kg /
sec · m]. Therefore, by applying the seawater flow velocity calculated using the above method to this equation (1),
The local flow rate can be calculated. The flow rate calculated in this way is the flow rate of the region of interest B. Therefore, by appropriately setting the region of interest B within the field of view 5 of the camera 4, the flow velocity at a desired location on the panel 2 and the flow rate are calculated. be able to. As described above, the attention area B can be set at a proper place in the frame, and the number of pixels in the attention area B can be set appropriately. At the same time, the number of regions of interest B for which the flow velocity and the flow rate are calculated is appropriate, and the flow velocity and the flow rate at many appropriate points can be calculated at the same time.

When the local flow rate is obtained as described above,
The water film thickness can be calculated by applying Nusselt's theoretical formula showing the correspondence between the flow rate of the fluid flowing down the vertical wetting wall and the water film thickness. That is, Nussel
The theoretical formula of t) is expressed by the following formula. h = 0.909 × (4 ・ q / η) ^1/3 × [η ² / {gρL (ρL-ρG)}] ^1/3 where q: mass flow rate, η: coefficient of static viscosity, g: acceleration of gravity, ρL : Liquid density, ρG: Gas density

FIG. 4 shows an example of the installation form of the cameras 4 in the case where a large number of LNG vaporizers are arranged in a row. In this example, the cameras 4 are provided on each side of the panel 2 of each LNG vaporizer. Are arranged, and the above-mentioned measurement is performed with each of them as a visual field.

On the other hand, FIG. 5 shows another example of the installation form of the cameras 4 when a large number of LNG vaporizers are arranged in a row. In this example, one surface side of a plurality of target LNG vaporizers is shown. One common camera 4 is arranged in a viewable position, and one surface side of a plurality of LNG vaporizers corresponds to the field of view of one camera 4. In this configuration,
With respect to the LNG vaporizer farthest from the front side, only a part of each one side is imaged.

Although the panel of the LNG vaporizer has been described above as the vertical wetting wall, other suitable vertical wetting walls such as the outer wall of the tank for cooling the internal substance by the water film other than seawater are used. Can be applied to things. Further, the vertical wet wall literally includes not only a wall having an angle forming a right angle with the horizontal but also an inclined wall which may be regarded as substantially vertical.

[0021]

Since the present invention is as described above,
The following effects are obtained as compared with the above-mentioned conventional method. The flow rate of water flowing down the vertical wetting wall can be measured in a non-contact manner by a moving image of a camera, which is simple and does not involve dangerous work. It is possible to simultaneously measure not only one location but also multiple locations or multiple locations. Automatic measurement by robot is possible. It is also possible to measure the water film in addition to the flow rate.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a perspective view of applying the present invention.

FIG. 2 is a schematic diagram showing a process of obtaining the velocity of a random pattern appearing in an image due to the flow of seawater.

FIG. 3 is an explanatory diagram showing a result of measuring a correspondence relationship between a surface flow velocity and a local flow rate.

FIG. 4 is a schematic plan view showing an example of an installation form of a camera.

FIG. 5 is a schematic plan view showing another example of the installation form of the cameras.

[Explanation of symbols]

 1 LNG vaporizer 2 panel 3 trough 4 camera 5 field of view 6 processor 7 image processor 8 calculator 9 pattern f frame B area of interest

Claims (4)

[Claims] 1. A process of capturing a moving image of water flowing down by photographing the surface of a vertical wet wall with a camera, and a flow velocity of water by extracting a motion vector of a local region of interest from adjacent frames in the moving image. And a step of calculating the flow rate from the calculated flow rate by using a known correspondence relationship between the flow rate and the flow rate. 2. A process of obtaining a moving image of water flowing down by photographing the surface of a vertical wet wall with a camera, and a flow velocity of water by extracting a motion vector of a local attention area from adjacent frames in the moving image. Using the known correspondence relationship between the flow rate and the flow rate, the step of calculating the flow rate from the calculated flow rate, and the known correspondence relationship between the flow rate and the water film thickness,
A method of measuring a water sprinkling state on a vertical wetting wall, which comprises the step of calculating the thickness of a water film from the calculated flow rate. 3. The vertical according to claim 1, wherein the surface of one vertical wetting wall is photographed by one camera to measure the water sprinkling state at an appropriate number of points on the one vertical wetting wall. Method of measuring water sprinkling condition on wet wall 4. The camera according to claim 1, wherein the surfaces of a plurality of vertical wetting walls are simultaneously photographed by one camera, and the water sprinkling state on the plurality of vertical wetting walls is measured at the same time.
Method for measuring water sprinkling condition on vertical wet wall