JPH06249796A - Apparatus and method for measuring moisture evaporation amount - Google Patents

Abstract

PURPOSE:To provide a moisture-evaporation-amount measuring apparatus wherein it measures the evaporation amount of moisture evaporated from the surface of soil, bedrock, fiber and the like and to provide its measuring method. CONSTITUTION:The title apparatus is provided with a detection part 4 in which two sets of temperature and humidity sensors having integrated temperature sensors la, 2a and humidity sensors 1b, 2b used to measure a temperature value and a humidity value are installed at prescribed intervals so as to be arranged at a distance difference with reference to a measuring face, with a first operation circuit 9 which finds respective humidity values on the basis of a saturated vapor pressure, a standard atmospheric pressure and the like with reference to respective relative humidity values and measured temperature values detected by the detection part 4, with a second operation circuit 10 which finds an absolute humidity gradient from the difference in the relative humidity values found by the first operation circuit and from the distance difference between both temperature and humidity sensors for the detection part and which finds an evaporation amount from the molecular diffusion coefficient of moisture in the air and with a display part 11 which displays the evaporation amount found by the second operation circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture evaporation measuring device for measuring the amount of moisture evaporated from the surface of soil, bedrock, fibers, concrete, plants, wood, paper, paint, food, resin, etc. It relates to a measuring method.

[0002]

2. Description of the Related Art There are several conventional methods for measuring the amount of water evaporation. A method using a large-scale evaporometer. This evaporometer is filled with water in a white-painted bowl-shaped container with a caliber of 120 cm, and the height of the water surface in this container is read to 1/10 mm by a gauge, and the same time as the previous day. It is a method of measuring the amount of evaporation per day by the difference with the read data of. This method has a large measurement point due to its large basin, and has a problem in accuracy because it is an indirect measurement, not a method for directly measuring the evaporation amount from the ground surface. The water balance method, which measures the inflow and outflow of water and estimates it from the decrease in water storage, but this method also estimates it from the decrease in water volume per unit area.
Similar to the method using a large-scale evaporator, the measurement points are large, and there is a problem in accuracy due to indirect measurement.

Energy balance method, which is a method of estimating the evaporation amount by measuring the balance amount of thermal energy such as solar radiation, radiation, and heat conduction. Similar to the method described in the above, this method also targets the zone instead of the point measurement, and there is a problem such as time loss because it is analyzed from long-term data. The gravimetric method (lysimeter) is a method in which a material such as soil at a measurement point is put in an appropriate container and the evaporation amount is calculated from the weight change at regular time intervals. This method can measure the minute amount of evaporation, but since it will destroy the soil,
There was a problem that the correct amount of evaporation could not be measured.

[0004]

The present invention, as described above, is a problem in the conventional method for measuring the evaporation amount, that is, it is inaccurate because it is an indirect measurement or estimation method, that the measurement point is wide, and that the measurement point is large. It takes a long time to complete, the measuring device is large and difficult to carry, etc., and it aims to measure the amount of water evaporation directly from the measurement surface of the object to be measured with a completely new idea. It is the one. Therefore, soil, bedrock,
This makes it possible to accurately measure the water evaporation amount of any substance such as fiber, concrete, and plants.

[0005]

In the apparatus for measuring the amount of water evaporation of the present invention, two sets of temperature / humidity sensors, which are integrated with a temperature sensor and a humidity sensor for measuring temperature and relative humidity, are placed at a distance from a measurement surface. The first calculation for obtaining the absolute humidity from the relative humidity detected by this detection unit and the saturated water vapor pressure, the standard atmospheric pressure, etc. with respect to the measured temperature, which are provided at predetermined intervals because they are arranged with a difference The absolute humidity gradient is obtained from the circuit and the difference in absolute humidity obtained by the first arithmetic circuit and the distance difference between both temperature / humidity sensors of the detection unit, and from the molecular diffusion coefficient of moisture in the air. A second arithmetic circuit for obtaining the evaporation amount and a display section for displaying the evaporation amount obtained by the second arithmetic circuit are provided, and the two sets of temperature /
A humidity sensor is arranged in the laminar flow layer on the surface of the substance to be measured to measure the evaporation amount. In addition, the method for measuring the amount of water evaporation of the present invention is to measure the temperature and relative humidity of each by two sets of temperature / humidity sensors provided with a certain distance difference in the laminar flow layer on the surface of the substance to be measured. The absolute humidity is calculated from the humidity and the saturated vapor pressure, the standard atmospheric pressure, etc. with respect to the measured temperature, and the absolute humidity gradient is calculated from the difference between the absolute humidity and the distance difference between the two temperature / humidity sensors. The amount of evaporation is obtained by multiplying by the molecular diffusion coefficient of water in the air.

[0006]

The present invention was made by paying attention to the fact that the amount of water evaporated from the surface of a substance is affected by the temperature of air, relative humidity, and wind speed. According to the experience of the inventor, generally, at an air temperature of about 20 ° C. and a relative humidity of about 60%, a maximum evaporation amount of about 30 mg / m ² / s was observed. 85% inside and outside 3 ~
An evaporation amount of about 4 mg / m ² / s was observed. And
The amount of evaporation is based on the theory that it becomes equal to the amount of water carried in the air in the direction orthogonal to the ground surface. Therefore, it was discovered that the water evaporation amount can be obtained by measuring the water transportation amount near the ground surface. Specifically, a thin laminar flow layer is formed on the ground surface.In the laminar flow layer, the flow is along the ground surface, and water transport in the air in the direction orthogonal to the ground surface is carried out by molecular diffusion. Be seen. Therefore, if the humidity change along the ground surface is small, this water transport amount qn, in other words, the water evaporation amount Ev
Is expressed by the following equation.

## EQU1 ## qn = Ev = Dm.Δθ / Δn (1) Dm is the molecular diffusion coefficient of moisture in the air, and Δθ is between two points at different distances from the ground surface (measurement surface). The amount of change in absolute humidity, Δn, is the distance difference between two points in the direction orthogonal to the ground surface.

[0007]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 is a first temperature / humidity sensor in which a temperature sensor 1a and a humidity sensor 1b are integrally fixed in a substantially coplanar manner. Reference numeral 2 is a second temperature / humidity sensor in which the temperature sensor 2a and the humidity sensor 2b are integrally fixed in a substantially same plane. The first and second temperature / humidity sensors shown in FIG.
As shown in the plan view of FIG. 2A and the side view of FIG. 2B, one detection unit 4 is fixed by a fixture 3 so that its sensor surfaces have a predetermined interval and their surfaces do not overlap.
Becomes It should be noted that the temperature sensors 1a and 2a are made of platinum resistance temperature detectors and have a flat plate shape of about 2 mm × 4 nm, and the humidity sensors 1b and 2b are made of a polymer film or the like and have a thickness of about 3 mm.
The sensor is a flat plate of mm × 5 mm, and these sensors are arranged and protected in the center of the protective cover 5, respectively. The dimensions of the temperature / humidity sensors 1 and 2 are, for example, about 10 mm in width and about 5 mm in thickness. The mutual arrangement relationship is that the distance between the temperature / humidity sensors 1 and 2 in the direction orthogonal to the measurement surface, that is, the distance difference A is about several mm, and the distance B in the horizontal direction is about 15 mm. Each sensor has a measuring circuit and a connecting line 6 which will be described later.
Connected by. Further, the size of the mutual arrangement relationship can be appropriately changed by the fixing tool 3. Further, the protective cover 5 is provided with air circulation windows on the upper, lower, left and right sides thereof.

The temperature / humidity sensors 1 and 2 are connected to an A / D conversion circuit 8 of the apparatus main body 7, and each measurement data is digitized and added to an absolute humidity calculation circuit 9. This absolute humidity calculation circuit 9 is composed of humidity sensors 1b and 2b.
Relative humidity H, saturated water vapor pressure es determined by the temperature t measured by the temperature sensors 1a, 2a, temperature t, standard atmospheric pressure Po
From the above, each absolute humidity θ can be obtained based on the following equation.

[Number 2] _{θ = 804 · H · e s} / 100 · (1 + 0.00366t) · Po ... (2)

Next, the absolute humidity θ1 and θ2 of both the temperature / humidity sensors 1 and 2, the distances n1 and n2 (distance difference A) from the surface of the substance to be measured to the temperature / humidity sensors 1 and 2, the molecular diffusion coefficient. From this, the water evaporation amount calculation circuit 11 obtains the water evaporation amount Ev based on the following equation. In this case, it is assumed that the temperature / humidity sensor 2 is located near the surface of the substance to be measured and the temperature / humidity sensor 1 is located far away.

## EQU00003 ## Ev = Dm.multidot. (. Theta.2-.theta.1) / (n1-n2) ... (3) In the equation (3), (.theta.2-.theta.1) / (n1-n).
2) represents an absolute humidity gradient, and this absolute humidity gradient is multiplied by the molecular diffusion coefficient Dm to obtain the water evaporation amount Ev. The molecular diffusion coefficient Dm can be obtained as follows.

[Equation 4] Dm = 1.6375 × 10 ⁻⁷ × t + 2.1325 × 10 ⁻⁵ (m ² / s) …… (4)

According to the present invention, the water evaporation amount Ev
However, there are various methods for displaying, recording, and transmitting the measurement result as needed. In the embodiment of the water evaporation measuring apparatus shown in FIG. 1, the measurement result at every certain time interval is displayed on the display unit 11, and the D / A conversion circuit 12 is also provided if necessary.
And record it on an automatic recording device, etc. via RS-2.
The data may be transmitted via the 32C output circuit 13 and input to a remote information processing device. Further, the above-mentioned measurement result may be obtained as a moving average value for each predetermined time by the moving average calculation circuit 14, and this data may be displayed or recorded. Further, in the process of obtaining the water evaporation amount Ev from the relative humidity H and the like described above, the wind speed and the atmospheric pressure in the measurement environment that affect the result are measured by the wind speed sensor 1.
5. The wind speed data may be used for correction of the molecular diffusion coefficient and the atmospheric pressure data may be used for correction of the absolute humidity as measured by the atmospheric pressure sensor 16 to improve the accuracy of the moisture evaporation amount measurement. Of course, if the measurement is performed in a windless environment or under standard atmospheric pressure, the above-mentioned correction is not necessary.

The measurement logic relating to the above-described embodiment of the present invention will be described in more detail. In equation (3), θ
2-θ1 / n1-n2 = Δθ / Δn, where n1 and n2 are the height from the ground surface to each measurement point (n1> n2), θ
1 and θ2 are absolute humidity at each position, and Δθ and Δn are absolute humidity difference and altitude difference, respectively. Absolute humidity is calculated by multiplying the amount of saturated water vapor determined by the temperature by the relative humidity. Therefore, in the measurement, the temperature and the relative humidity are obtained at two points. The molecular diffusion coefficient Dm described above can be expressed as a function of temperature. Since the amount of water evaporation from the ground surface can be obtained from the weight change of the small cup, the absolute humidity distribution in the vertical direction is measured on the small cup. In the laminar layer, the absolute humidity decreases linearly with the height, and outside the laminar layer, water transport is strongly affected by turbulent diffusion, so the absolute humidity decrease rate relative to the height increase. Is smaller than in the laminar flow layer. Therefore, the thickness of the laminar flow layer can be obtained by obtaining the change point of the gradient from the relationship between the altitude and the absolute humidity.

The absolute humidity distribution, in other words, the relative humidity and temperature distribution is measured by simultaneously measuring the relative humidity and temperature at two points and calculating the absolute humidity and the absolute humidity gradient from these values. Is something that can be done. And this absolute humidity gradient can be obtained by multiplying the molecular diffusion coefficient of the moisture in the air with respect to the measured temperature to obtain the moisture evaporation amount.The measurement of the moisture evaporation amount of the present invention uses the method according to this logic. It was what I had. Fig. 3 shows the wind speed Vo directly above the ground surface.
And an example of the distribution of the vertical absolute humidity θ is shown. That is, the wind speed Vo at the position of 3 mm above the ground surface is 0.0 m /
Absolute humidity θ when s, 0.28 m / s, 1.5 m / s
Of the vertical distribution of, up to height Hi for each wind speed,
The absolute humidity θ is greatly reduced linearly. The value of the height Hi tends to decrease as the wind speed increases, but the height H
Above i, the rate of decrease with respect to the height of the absolute humidity θ becomes small, and the distribution shows a straight line as a whole. This is because the area above the height Hi is affected by turbulence,
It can be interpreted that a large amount of water is transported by turbulent diffusion. In this way, the region below the height Hi is a measurable range as a laminar flow region (in the laminar flow layer) in which molecular diffusion is dominant. Further, when the wind speed is too high to measure in the laminar flow region, the turbulent diffusion coefficient can be taken into consideration for the calculation.

Next, it was verified whether or not the measurement result according to the present invention is correct, that is, whether or not water is actually transported only by molecular diffusion in the region of the height Hi or lower. Therefore, the absolute humidity gradient obtained in the range lower than the height Hi and the water evaporation amount Evo obtained from the weight change of the small cup are substituted into Δθ / Δn and Ev in the equation (1), respectively, and the molecular diffusion is performed. As a result of back-calculating the coefficient Dm, the height H
It was confirmed that the region below i is the laminar flow region where molecular diffusion controls. That is, the result of this data comparison is
As is clear from FIG. 4, the moisture evaporation amount measurement output Ev (black dot) by the moisture evaporation amount measuring device of the present invention is also almost overlapped with the 45 degree dotted line of the moisture evaporation amount Evo obtained from the weight change of the small cup. Was obtained. In the method of obtaining the weight change of the small cup, it takes about 1 to 2 hours to measure the change clearly, but in the moisture evaporation measurement of the present invention, it is stable after the sensor is installed on the surface to be measured. It takes a very short time, for example, 60 seconds, until the target output can be measured, and a continuous change can be output after the start of the measurement.

[0014]

As described above in detail, the present invention has two advantages.
The detection unit equipped with a pair of temperature / humidity sensors is placed near the surface of the substance to be measured, and the amount of water evaporation is calculated from the measured data of the temperature / humidity sensor and the coefficient of relation. It has excellent effects. Since the amount of water evaporated from the surface to be measured such as the ground surface can be directly measured, it can be accurately measured without destroying the measurement point. Since the sensor portion is small, it is possible to perform a point measurement with a small surface of the substance to be measured.
Therefore, the measurement target can be applied to the measurement of various substances such as soil, bedrock, fiber, concrete, plant, wood, paper, paint, food and resin. Accurate measurement is possible even with a small amount of evaporation. The time from installation on the surface of the substance to be measured until the start of measurement is short, and continuous measurement is possible. It is possible to measure the amount of evaporation not only from the horizontal surface but also from the wall surface of rock. Since the measuring device is small and lightweight, it is extremely convenient to carry.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a temperature / humidity sensor portion of the present invention.

FIG. 3 is a distribution diagram of wind speed on the ground surface and vertical absolute humidity.

FIG. 4 is a diagram comparing an evaporation amount obtained from a change in weight with an evaporation amount measured by a water evaporation amount measuring device of the present invention.

[Explanation of symbols]

 1, 2 temperature / humidity sensor 1a, 2a temperature sensor 1b. 2b Humidity sensor 3 Fixture 4 Detecting part 5 Protective cover 6 Connection cord 7 Measuring device body 8 A / D conversion circuit 9 Absolute humidity calculation circuit 10 Moisture evaporation amount calculation circuit 11 Display part 12 D / A conversion circuit 13 RS-232C output Circuit 14 Moving average calculation circuit 15 Wind speed sensor 16 Atmospheric pressure sensor

Claims (3)

[Claims] 1. A detection provided at predetermined intervals so that two sets of temperature / humidity sensors, which are integrated with a temperature sensor and a humidity sensor for measuring temperature and relative humidity, are arranged with a distance difference with respect to a measurement surface. Section, a first arithmetic circuit for obtaining respective absolute humidity from the relative humidity detected by the detecting section, saturated water vapor pressure with respect to the measured temperature, standard atmospheric pressure, etc., and each obtained by the first arithmetic circuit. A second arithmetic circuit for obtaining an absolute humidity gradient from the difference in absolute humidity of the sensor and the distance difference between both temperature / humidity sensors of the detection unit, and also obtaining the evaporation amount from the molecular diffusion coefficient of moisture in the air; And a display section for displaying the evaporation amount obtained by the arithmetic circuit of 1., and the evaporation amount is measured by arranging the two sets of temperature and humidity sensors in the laminar layer on the surface of the substance to be measured. A device for measuring water evaporation. 2. A third arithmetic circuit for determining the evaporation amount obtained by the second arithmetic circuit as a moving average value for a predetermined time is added, and the evaporation amount obtained by the moving average by the third arithmetic circuit is added. The display is made on the display unit.
The apparatus for measuring the amount of water evaporation according to. 3. The temperature and relative humidity are measured by two sets of temperature / humidity sensors arranged with a certain distance difference in the laminar flow layer on the surface of the material to be measured, and saturated steam corresponding to the relative humidity and the measured temperature is measured. Each absolute humidity is calculated from the pressure, standard atmospheric pressure, etc., and the absolute humidity gradient is calculated from the difference between the absolute humidity and the distance difference between the two temperature / humidity sensors. A method for measuring the amount of evaporation of water by multiplying the molecular diffusion coefficient to determine the amount of evaporation.