JP2014231937A - Method and device for measuring moisture content of air in ice saturation or above below freezing point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for accurately measuring a moisture content of air in ice saturation or above below the freezing point.SOLUTION: In a method for measuring a moisture content of air in ice saturation or above below the freezing point, a fixed quantity of air is sucked in from a space 2 including measurement object air; the air sucked in is heated by a heating part 3 and turned into air in the ice saturation or below; humidity of the air in the ice saturation or below is measured by a humidity measuring part 6; and the moisture content of the measurement object air is determined from a measured value of the measured humidity.

Description

  The present invention relates to a method and an apparatus for measuring the moisture content of air, and more particularly, to a method and an instrument for measuring the moisture content of air that is below freezing point and above ice saturation.

  An artificial snowfall device that produces crystal-type artificial snow generates and grows crystal snow in low-temperature air with a high water content. Air suitable for such a snowfall device, more specifically, contains a water content at a low temperature and above water saturation or above water saturation, and more than supersaturated steam, supercooled water droplets, and The frozen icing is air in a single or mixed state. Further, the amount and crystal shape of crystal snow produced by the snowfall device are affected by the moisture content of the air used. For example, Non-Patent Document 1 discloses a method for producing crystal-type artificial snow, and the crystal shape of snow changes depending on the combination of the temperature of the place where the crystal is growing and the supersaturation degree of air. A diagram (Nakaya diagram) showing this is described. Therefore, it is desirable to supply air with a specific water content to a snowfall device that generates crystal snow.

  However, it is difficult to accurately measure the water content of air including water droplets and ice particles that are scattered, even if a conventional hygrometer or dew point meter is installed alone in the air. For example, Patent Document 1 discloses an artificial crystal snow manufacturing apparatus, which describes that this apparatus includes a humidifier that creates a saturated atmosphere that is equal to or higher than ice saturation. However, this apparatus does not include a means for measuring the water content of a saturated atmosphere that is above the ice saturation.

JP-A-9-329380

By Ukichiro Nakatani, “Yuki” Iwanami Shoten, October 17, 1994, p. 176

  A normal hygrometer or dew point meter is a measuring instrument equipped with a sensor for measuring humidity below ice saturation. In other words, a normal hygrometer or dew point meter can measure only air that has a humidity of less than 100% and does not contain water droplets or icing. Therefore, the measurement of air at the low temperature and above the ice saturation is out of the measurement specifications of those measuring instruments as described above. When such air is directly measured with a normal hygrometer or dew point meter, icing particles or supercooled water droplets in the air adhere to the sensor surface, or frost is formed due to the influence of supersaturated steam. Therefore, the hygrometer indicates that the range is over (impossible to measure). Further, the dew point temperature value indicated by the dew point meter is not the exact dew point temperature of the air, and the humidity value obtained based on the dew point temperature is not accurate.

  The reason why the artificial crystal snow manufacturing apparatus described in Patent Document 1 does not include means for measuring the water content of a saturated atmosphere that is equal to or higher than ice saturation is because the value cannot be accurately measured. In Patent Document 1, it is described that humidification pans are provided in multiple stages so as to humidify the entire flow path little by little in order to make the supplied air an air humidity higher than ice saturation. In Patent Document 1, it is considered that the supplied air has an air humidity higher than or equal to ice saturation, which is estimated from the amount of water input to the pan and the amount of snowfall. Such a method of estimating the water content of the supplied air from the amount of water to be introduced into the pan is merely a prediction, and does not measure the supplied air itself. However, in order to stably obtain crystal snow having a desired shape and amount, it is preferable to measure the water content of the supplied air and adjust the amount and temperature of water to be poured into the pan from the measured value.

  The method of estimating the water content of the supplied air from the amount of snowfall is not a method of obtaining the current value of the water content of the supplied air, but a method of obtaining a past value obtained from the snowfall result. In such a method, it is necessary to repeat the adjustment of the amount of water input and the analysis of the snow until a crystal snow having a desired shape is stably obtained, which requires a long time. In particular, in the case of a snowfall device that produces air for snowfall by mixing outside air and cold air in order to use the moisture of the outside air, it is necessary to adjust the amount of cold air mixed based on the moisture content of the supplied air In some cases, such a method has a large time lag and it is difficult to produce desired air for snowfall.

  Thus, for example, in an apparatus for generating crystal snow of crystal type artificial snowfall, it is necessary to supply air in the above-described state, and the water content of air above ice saturation is accurately and continuously measured below freezing point. Is important to ensure stable and high quality snowfall with the equipment. This invention is made | formed in view of this point, The subject is providing the moisture content measuring method and apparatus of the air more than ice saturation under exact freezing point.

The present invention includes the following aspects in order to solve the above problems.
(1) A method for measuring the moisture content of air that is below freezing and above ice saturation, inhaling a certain amount of air from the space containing the air to be measured, and heating the inhaled air to a temperature below ice saturation by the heating unit. The method for measuring the moisture content of air above the ice saturation below freezing point, wherein the humidity of the air below the ice saturation is measured, and the moisture content of the measurement target air is determined from the measured humidity value.
(2) The measurement target air is sprinkled with supercooled water droplets and / or ice particles, and heating of the inhaled air vaporizes the total amount of supercooled water droplets and / or ice particles and is below ice saturation. The method for measuring the water content of air that is not less than ice-saturated as described in (1) above.
(3) The temperature of the heating body surface that is in contact with the inhaled air of the heating unit is measured, and the measured value of the heating body surface temperature is calculated based on the measured value of the heating body surface temperature. The heating body surface temperature is controlled to be equal to or higher than the heating body surface temperature setting value Ts at which the total amount of moisture contained in the steam can be converted to water vapor, and the control is such that the measured value of the heating body surface temperature is the heating body surface When the temperature is less than the temperature setting value Ts, the amount of energy supplied to the heating unit is increased. When the measured value of the heating body surface temperature is equal to or higher than the heating body surface temperature setting value Ts, the amount of energy supplied to the heating unit is maintained. The method for measuring the water content of air above ice saturation as described in (1) or (2) above.
(4) When the measured value of the humidity of the air after heating is larger than the set value Hs, the heated body surface temperature set value Ts is increased, and when the measured value of the humidity is less than the set value Hs, the heated body surface temperature The method for measuring the moisture content of air above ice saturation as described in (3) above, wherein the measured value is controlled to be maintained at the heating body surface temperature set value Ts.
(5) Further, the temperature of the heated air is measured, and when the measured temperature value of the heated air is below freezing point, the heating body surface temperature set value Ts is increased, and the measured temperature value of the heated air is higher than the freezing point. The method for measuring the moisture content of air above ice saturation as described in (4) above, wherein the measured value of the heating body surface temperature is controlled to be maintained at the heating body surface temperature set value Ts.
(6) A part or all of the heated air whose temperature and / or humidity is measured is circulated in a space including the measurement target air, according to any one of (1) to (5). A method for measuring the moisture content of air above ice saturation.
(7) Crystal-type artificial snowfall method including generating crystal snow from measurement target air measured by the method for measuring water content of air above ice saturation according to any one of (1) to (6) .
(8) In order to measure the temperature of the surface of the heating body that comes into contact with the sucked air, and the heating section that includes a suction port for sucking the air to be measured, the heating body for heating the sucked air The heating body surface temperature measurement section, the humidity measurement section for measuring the humidity of the heated air, and the measured value of the heating body surface temperature are input, processed, and the moisture content value of the measurement target air is output. And an arithmetic unit for adjusting the amount of energy supplied to the heating unit to control the surface temperature of the heating body, and a discharge port for discharging the measured air. When the measured value is less than the set value Ts, the amount of energy supplied to the heating unit is increased, and when the measured value of the heating body surface temperature is equal to or greater than the set value Ts, the amount of energy supplied to the heating unit is maintained below freezing point. Equipment for measuring water content of air above ice saturation .
(9) Further, the control increases the set value Ts of the heating body surface temperature when the measured value by the humidity measuring unit is larger than the set value Hs, and heats when the measured value by the humidity measuring unit is less than the set value Hs. The water content measuring apparatus for air above ice saturation described in (8), which maintains the set value Ts of the body surface temperature.
(10) Further, a post-heating air temperature measurement unit for measuring the temperature of air after heating is provided, and the control sets the heating body surface temperature when the measured value by the post-heating air temperature measurement unit is below freezing point. The apparatus for measuring the moisture content of air above ice saturation as described in (9) above, wherein the value Ts is increased and the set value Ts of the heating body surface temperature is maintained when the measured value by the air temperature measuring unit after heating is higher than the freezing point.
(11) A crystal-type artificial snowfall device comprising the device for measuring water content of air above ice saturation according to any one of (8) to (10).

  According to the moisture content measuring method and apparatus having the above-described configuration, it is possible to provide a method and apparatus for accurately measuring the moisture content of air above ice saturation under freezing point, which may include water droplets and ice flocculation. Become. In addition, since the air measured with a hygrometer / dew point meter can always be in an air condition that meets the specifications of the measuring instrument below ice saturation, the ice temperature is below the freezing point based on the value measured with a normal hygrometer / dew point meter. The water content of air above saturation can be accurately measured. In addition, since the water content of the current value can be measured by continuously inhaling part of the air to be measured, it can contribute to a control mechanism for ensuring snowfall quality when used in the control of a snowfall device.

It is a block diagram which shows the one aspect | mode of the moisture content measuring device which concerns on this invention. It is a flowchart which shows the one aspect | mode of the control process of the heating part which concerns on this invention. It is a flowchart which shows another aspect of the control process of the heating part which concerns on this invention. It is a flowchart which shows another aspect of the control process of the heating part which concerns on this invention.

  The method for measuring the moisture content of air below freezing point below the freezing point of the present invention draws a certain amount of air from a space containing air below freezing point and above freezing point (hereinafter sometimes referred to as “measurement target air”). Then, the inhaled air is heated by the heating unit to become air below ice saturation, the humidity of the air below ice saturation is measured, and the moisture content of the measurement target air is obtained from the measured humidity value.

  The air to be measured by the water content measuring method of the present invention is air that is below freezing point and above ice saturation. Air that is below freezing and above ice saturation is one that has a temperature below freezing and that contains supersaturated vapor that is above freezing, or that has a temperature below freezing and that is above ice saturated or above ice saturation, and has scattered. It contains supercooled water droplets and / or icing. Here, below freezing refers to 0 ° C. or less at normal pressure.

  This measurement target air is, for example, mixed with air that is lower than water saturation and air that is lower than that air and cooled, or, as described in Cited Document 1, at a temperature of 40 ° C. or lower. It is obtained by blowing below-freezing air into a pan containing water. Specifically, in the former method, for example, when air at a temperature of 20 ° C. and a relative humidity of 65% (absolute humidity 0.01 kg / kg (DA)) is cooled by mixing with air at −20 ° C., It becomes air saturated with water at about 8 ° C. Here, kg (DA) indicates the mass of dry air. Further cooling results in a transient state of air that contains water saturated steam or water supersaturated steam and possibly water saturation or higher air in which water droplets are scattered. When further cooled to below freezing point, the water droplets become supercooled or frozen, and air above ice saturation is obtained below freezing point, which is a transitional state including ice saturated vapor or ice supersaturated vapor. More specifically, the air that is above the freezing point below freezing point is, for example, 0.0015 kg of dry air having a temperature of −16 ° C. and moisture of 1 kg.

  The method for measuring the water content of air below the freezing point below the freezing point of the present invention will be further described with reference to the drawings. FIG. 1 is a block diagram showing an aspect of an apparatus used in the water content measuring method of the present invention. The moisture content measuring apparatus shown in FIG. 1 includes an inlet 5 for inhaling air to be measured, a heating unit 3 having a heating body for heating the inhaled air, and the inhaled air of the heating body. A heating body surface temperature measuring unit 8 for measuring the temperature of the contacting surface, a humidity measuring unit 6 for measuring the humidity of the heated air, and a measured value of the heating body surface temperature are input and processed. The calculation unit 9 for outputting the moisture content value of the air to be measured, adjusting the amount of energy supplied to the heating unit to control the surface temperature of the heating body, and the discharge port 10 for discharging the measured air Is provided.

  In the method for measuring the moisture content of air below freezing point below the freezing point of the present invention, first, a constant amount of air is passed through the suction port 5 from the space 2 containing air above freezing point below the freezing point to be measured. Inhale to. Although the suction means is not particularly limited, usually, the fan 4 or the like is used to make the air pressure in the water content measuring device 1 negative from the space including the measurement target air, and a part thereof is sucked from the suction port 5. The amount of suction per unit time can be adjusted by changing the output of the fan 4 and the opening degree of the damper 10 and the damper 11. Before the air to be measured is heated by the heating unit 3, the fan 4 is prevented from being oversaturated by an impact or the like, from being overcooled by a supercooled water droplet, or from being attached to a wall surface. It is preferable to provide on the downstream side of the heating unit 3.

  Next, the inhaled measurement target air is heated by the heating unit 3 so that the humidity is equal to or lower than ice saturation. When water droplets and / or ice particles are scattered in the measurement target air, the heating unit 3 vaporizes the entire amount of the water droplets and / or ice particles. The heating unit 3 is not particularly limited as long as it can change the air above the ice saturation below the freezing point to an air whose humidity is below the ice saturation, and examples thereof include an electric heater and a heat exchanger (steam coil, etc.). . In particular, the heating unit measures the temperature of the surface of the heating body included in the heating unit, and the temperature measurement unit 8 contacts the measurement target air, and supplies the temperature to the heating unit based on the surface temperature measurement value. It is preferable that the surface temperature of the heating body can be controlled by adjusting the amount of energy.

  Although it does not specifically limit as the temperature measurement part 8 which measures a heating body surface temperature, For example, using non-contact-type temperature sensors, such as contact temperature sensors, such as a resistance temperature detector, a thermocouple, and a thermistor, and an infrared sensor. Can do. The temperature measuring unit 8 is preferably a sensor that can measure the surface temperature of the heating body and output a temperature signal. The contact-type temperature sensor can be measured by being fixed to the surface of the heating body by soldering or the like.

  Next, the humidity of the air heated by the heating unit 3 and below ice saturation is measured using the humidity measuring unit 6 provided downstream of the heating unit 3. Although the humidity measuring unit 6 is not particularly limited, a moisture meter, a telescopic hygrometer, an electric hygrometer, a dew point meter, a polymer humidity sensor, or the like can be used. Among them, a humidity sensor that can measure humidity and output a humidity signal is preferable.

The moisture content of the air to be measured is determined from the humidity measurement value obtained in this way. Specifically, when the measured value of humidity is obtained as absolute humidity x (kg / kg (DA)), the water content of the measurement target air is x (kg) with respect to 1 (kg) of dry air. Moreover, when the measured value of humidity is obtained at relative humidity φ (% RH), for example, “Air Conditioning and Sanitary Engineering Handbook 13th Edition”, Air Conditioning and Sanitary Engineering Association, Maruzen Publishing, November 2001, Volume 1 , P. The absolute humidity x (kg / kg (DA)) can be calculated from the relative humidity φ and the air temperature T (K) at which the humidity is measured by the relational expression described in 76-80. The water content of the target air is x (kg) with respect to 1 (kg) of dry air.
Specifically, the saturated vapor pressure P _s (kPa) of water at that temperature is obtained from the temperature T (K) and the Wexler-Hyland equation (1),
When in contact with liquid water (0.01 ° C. or higher): ln (10 ³ P _s ) = − 0.58002206 × 10 ⁴ /T+0.139149993×10−0.48640239×10 ⁻¹ T + 0.417676868 × 10 ⁻⁴ T ² −0.14452093 × 10 ⁻⁷ T ³ + 0.654595973 × 10 × lnT, in contact with ice (below 0.01 ° C.): ln (10 ³ P _s ) = − 0.567745359 × 10 ⁴ / T + 0. 63925247 × 10−0.96778430 × 10 ⁻² T + 0.6221215701 × 10 ⁻⁶ T ² + 0.20747825 × 10 ⁻⁸ T ³ −0.94840 240 × 10 ⁻¹² T ⁴ + 0.416335019 × 10 × lnT Formula (1)
By the P _s and the equation (2), the water vapor partial pressure p _ws (kPa) of saturated air at the temperature T is obtained,
p _ws = P _s (2)
The water vapor partial pressure p _w (kPa) is obtained from the p _ws and the relative humidity φ and the equation (3),
φ = 100 p _w / p _ws Formula (3)
From the sea level Z (m) and the standard atmospheric pressure P ₀ (= 101.325 (kPa)) and the equation (4), the atmospheric pressure P (kPa) is obtained,
P = P ₀ (1-2.558 × 10 ⁻⁵ Z) ^5.2559 Expression (4)
The p _w , the P, the average molecular weight M _a of dry air (= 28.9645 (g / mol)), the molecular weight M _{w of} water vapor (= 18.0153 (g / mol)) and the formula (5), Absolute humidity x (kg / kg (DA)) can be obtained, and the water content of the measurement target air is x (kg) with respect to 1 (kg) of dry air.
_{x = M w / M a ×} p w / (P-p w) ··· (5)

  The temperature of the air after heating is not particularly limited, but is preferably a freezing point or higher. When the temperature is above the freezing point, it is possible to prevent water vapor from becoming water droplets or icing, even when the temperature of the heated air is lowered due to cooling by the housing of the measuring device. The temperature of the air after heating can be measured by the temperature measuring unit 7 provided on the downstream side of the heating unit. Although it does not specifically limit as the temperature measurement part 7, For example, non-contact-type temperature sensors, such as contact-type temperature sensors, such as a resistance thermometer, a thermocouple, a thermistor, and an infrared sensor can be used. The temperature measuring unit 7 is preferably a sensor that can measure the surface temperature of the heating body and output a temperature signal.

  In the measuring method of the present invention, as shown in FIG. 2, the temperature of the heating body surface of the heating unit is measured by the temperature measuring unit 8, the temperature signal output from the temperature measuring unit 8 is input to the calculating unit 9, and the heating is performed. Based on the body surface temperature measurement value, the measurement value of the heating body surface temperature is controlled to be equal to or higher than the heating body surface temperature setting value Ts that can change the total amount of moisture contained in the measurement target air to water vapor. preferable. Here, the heating body surface temperature set value Ts varies depending on the amount of measurement target air to be sucked in, the water content, and the temperature. For example, the temperature is 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher. It is. In this control, for example, when the measured value of the heating body surface temperature is less than the heating body surface temperature set value Ts, the amount of energy supplied to the heating unit 3 is increased, and the measured value of the heating body surface temperature is greater than or equal to the set value Ts. In this case, the amount of energy supplied to the heating unit is maintained or reduced. The amount of energy supplied to the heating element can be increased or decreased, for example, by adjusting the current when the heating element is an electric heater or the like, and adjusting the temperature or flow rate of water vapor when the heating element is a heat exchanger or the like.

  The initial measured value of the heating body surface temperature is, for example, room temperature. The heating body surface temperature can be raised to the set value Ts before inhaling the measurement target air, or can be raised to the set value Ts while inhaling the measurement target air.

  When the measurement target air is inhaled, the measurement target air comes into contact with the surface of the heating body. When the amount of energy supplied to the heating body is constant, the surface temperature of the heating body decreases due to sensible heat or latent heat and becomes less than the set value Ts. The heating body surface temperature is measured, and when the heating body surface temperature measurement value is less than the set value Ts, the amount of energy supplied to the heating body is increased by the calculation unit 9. When this process is repeated and the heating body surface temperature measurement value is equal to or higher than the set value Ts, the amount of energy supplied to the heating body is maintained or reduced to that value, and then the heating body surface temperature measurement value is continuously monitored, The amount of energy supplied to the heating element of the heating unit is controlled so as to maintain a constant value. Thus, based on the measured value of the heating body surface temperature, when the amount of energy supplied to the heating body is gradually increased and the heating body surface temperature is set to the set value Ts, the total amount of moisture contained in the measurement target air is changed to water vapor. It is possible to minimize the amount of energy supplied to the heating body that is necessary for the purpose. Therefore, according to such control, for example, the amount of energy supplied to the heating body is fixed to a value such that the temperature of the heating body surface is about 250 ° C. without inhaling the measurement target air. Because it is less, it is energy saving. In addition, water content can be accurately measured because it is possible to prevent the amount of heat and air flow from becoming insufficient, or from insufficient vaporization of water droplets and icing due to heat leakage from outside the path. .

  Furthermore, in the measuring method of the present invention, as shown in FIG. 3, when the measured value of the humidity of the heated air measured by the humidity measuring unit 6 is larger than the set value Hs, the heating body surface temperature set value Ts is increased, When the measured value of humidity is equal to or lower than the set value Hs, it is preferable that the calculation unit 9 controls the measured value of the heated body surface temperature to be maintained at the heated body surface temperature set value Ts. The set value Hs is, for example, a relative humidity of 100%, which is a saturated humidity, or a high humidity equivalent thereto (for example, a relative humidity of 90%). If the measured value of the humidity of the air after heating indicates high humidity, heating by the heating unit may be insufficient and water droplets may not evaporate completely, or the humidity measurement accuracy may be reduced. By performing the above, it is possible to ensure that the entire amount of water droplets and ice particles contained in the air that is above the ice saturation below the freezing point evaporates, and the humidity measurement accuracy can be improved. In addition, when the heating body surface temperature setting value Ts is gradually increased based on the humidity measurement value by the above-described control, the water content can be accurately measured with the minimum energy amount, which is energy saving. .

  Furthermore, in the measurement method of the present invention, as shown in FIG. 4, the temperature measurement unit 7 provided downstream of the heating unit measures the temperature of the heated air, and when the measured temperature value of the heated air is below freezing point, When the heating body surface temperature set value Ts is increased and the measured temperature value of the air after heating is higher than the freezing point, it is preferable to control the measured value of the heating body surface temperature to maintain the set value Ts. By performing such control, when the heating amount is insufficient with respect to the moisture amount and the air amount, or due to heat leakage from the outside of the path, the steam is recondensed into water droplets downstream of the heating unit, The water droplets can be prevented from freezing and the amount of water can be measured accurately. In addition, the water content can be accurately measured with the minimum amount of energy by performing control to gradually increase the heating body surface temperature setting value Ts until the temperature measurement value of the air after heating becomes higher than the freezing point, It is energy saving.

  The air heated using the moisture content measuring method of the present invention is discharged to the outside through the damper 10 provided in the moisture content measuring device 1 according to the present invention. Moreover, as shown in FIG. 1, it can return and circulate to the space 2 containing measurement object air via the damper 11 with which the moisture content measuring device 1 was equipped. In the water content measurement method of the present invention, a part of the measurement target air is heated with a minimum amount of energy that can accurately measure the water content, and therefore when the heated air is returned to the measurement target air. Are better. In the case of circulation, if necessary, the fan 12 can be cooled or humidified through the device 13 for producing air above ice saturation to be air above ice saturation and then returned to the space 2 containing the measurement target air. it can. The device 13 that produces air that is above ice saturation can use the humidity measurement value measured by the humidity measurement unit 6 as a control value. The space 2 including the measurement target air can be, for example, a space including snowfall air included in the crystal type artificial snowfall device.

  It is possible to generate snow by making crystal snow from the air measured by the water content measuring method of the present invention and above the freezing point and above the ice saturation. According to this crystal-type artificial snowfall method, it is possible to use air above ice saturation below freezing point, which has been confirmed by accurately and continuously measuring that the temperature and water content are specific values. It is possible to obtain artificial snowfall with uniform and excellent quality.

  The water content measuring method and apparatus of the present invention are suitable for measuring the water content of snowing air in a snowfall device, but are not limited by the measurement target, and are not limited to supersaturated steam, supercooled water droplets above ice saturation, or In all cases where air is frozen or mixed in a mixed state, for example, it is mounted on a balloon and used to measure air in clouds, or it is used to measure air containing snow in natural snowfall. You can also.

DESCRIPTION OF SYMBOLS 1 Water content measuring apparatus 2 Space containing air more than ice saturation (measurement target air) 3 Heating unit 4, 12 Fan 5 Suction port 6 Humidity measuring unit 7, 8 Temperature measuring unit 9 Arithmetic unit 10, 11 Damper (exhaust port)
13 Equipment for producing air that is above ice saturation

Claims (11)

A method for measuring the water content of air that is below freezing and above ice saturation,
Inhale a certain amount of air from the space containing the air to be measured,
The inhaled air is heated by the heating unit to make the air below ice saturation,
Measure the humidity of air below the ice saturation,
A method for measuring the moisture content of air that is below freezing point and above ice saturation, wherein the moisture content of the air to be measured is obtained from the measured humidity value. In the measurement target air, supercooled water droplets and / or ice particles are scattered,
The method for measuring the moisture content of air above ice saturation according to claim 1, wherein the heating of the sucked air vaporizes the entire amount of supercooled water droplets and / or ice particles and makes the air below ice saturation. Measure the temperature of the heating body surface of the heating unit that is in contact with the inhaled air,
Based on the measured value of the heating body surface temperature, the measured value of the heating body surface temperature is equal to or higher than the heating body surface temperature setting value Ts that can change the total amount of moisture contained in the measurement target air to water vapor. The heating body surface temperature is controlled,
When the measured value of the heating body surface temperature is less than the heating body surface temperature setting value Ts, the control increases the amount of energy supplied to the heating unit,
The method for measuring the moisture content of air exceeding ice saturation according to claim 1 or 2, wherein the amount of energy supplied to the heating unit is maintained when the measured value of the heating body surface temperature is equal to or higher than the heating body surface temperature set value Ts. . When the measured value of the humidity of the air after heating is larger than the set value Hs, the heating body surface temperature set value Ts is increased,
When the measured value of the humidity is equal to or lower than the set value Hs, the measured value of the heated body surface temperature is controlled to be maintained at the set temperature of the heated body surface Ts. Water volume measurement method. Furthermore, the temperature of the heated air is measured,
When the temperature measurement value of the air after heating is below freezing point, the heating body surface temperature setting value Ts is increased,
5. When the measured temperature value of air after heating is higher than the freezing point, the measured value of the heated body surface temperature is controlled so as to be maintained at the heated body surface temperature set value Ts. Water volume measurement method.   The part of or the whole of the heated air whose temperature and / or humidity is measured is circulated in a space including the measurement target air. Water content measurement method.   A crystal-type artificial snowfall method comprising generating crystal snow from measurement target air measured by the water content measurement method for air above ice saturation according to any one of claims 1 to 6. An inlet for inhaling air to be measured;
A heating unit comprising a heating element for heating the inhaled air;
A heating body surface temperature measurement unit for measuring the temperature of the surface of the heating body that is in contact with the inhaled air; and
A humidity measuring unit for measuring the humidity of the heated air;
Calculation unit for controlling the heating body surface temperature by inputting the measured value of the heating body surface temperature, calculating and processing, outputting the moisture content value of the air to be measured, and adjusting the amount of energy supplied to the heating unit When,
An outlet for discharging the measured air;
The control includes
When the measured value of the heating body surface temperature is less than the set value Ts, increase the amount of energy supplied to the heating unit,
When the measured value of the heating body surface temperature is equal to or higher than the set value Ts, the amount of energy supplied to the heating unit is maintained.
A device for measuring the water content of air below freezing point below freezing point. Furthermore, the control
When the measured value by the humidity measuring unit is larger than the set value Hs, the set value Ts of the heating body surface temperature is increased,
When the measured value by the humidity measuring unit is equal to or lower than the set value Hs, the set value Ts of the heating body surface temperature is maintained.
The water content measuring device of air more than ice saturation according to claim 8. Furthermore, a post-heating air temperature measuring unit for measuring the temperature of air after heating is provided,
The control is
When the measured value by the air temperature measuring unit after heating is below freezing point, increase the set value Ts of the heating body surface temperature,
When the measured value by the air temperature measuring unit after heating is higher than the freezing point, the set value Ts of the heating body surface temperature is maintained.
The water content measuring device of air more than ice saturation according to claim 9.   A crystal-type artificial snowfall device comprising the device for measuring the water content of air above ice saturation according to any one of claims 8 to 10.

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