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Water which are included for the air(humidity) and plant production

Caution: This page is made with the purpose of the plant production, and it has been designed for the use in the ordinary temperature in which the crop grows.

Produced By Hoshi, Takehiko, Ph.D. (Tokai University)

References:: Agri-Environment Experiment, Science House Pub. Ed. By Dr. Watanabe, Ichirou
Hand-Book for High-Tech. Agricultue production, Tokai Univ. Press Co., Ed. By Society of High-Technology in Agriculture

The humidity is important as an environmental condition which influences the growth of the plant with temperature and light. There is the relation which is profound with transpiration of the plant, generation of the disease, generation of the mists and fog, stresses of the plant, heating and cooling energy, etc. on the humidity in the air. And, there are various types, even if that the humidity is an index on the water which is included for the air goes to the draft with the humidity. In this page, it is made that the humidity is understood, though you measure the humidity actually, and though it is calculated, to be a purpose.

Measuring method of the humidity
Calculation of the various humidities
Description of the values concerning the humidity
Humidity calculation sheet

Measuring method of the humidity
Wet and dry bulb thermometers or thermometers and relative humidity meters are necessary in order to measure the humidity. The relative humidity meter is the instrument which measures the result of calling what is called "the 70% humidity", etc. with the humidity generally.
- Wet and dry bulb thermometer
  
  It is convenient to use the wet and dry bulb thermometer in order to the most accurately measure. This the gauze has been wound to temperature sensing element of another thermometer by the equipment that 2 thermometers were installed, and it is being inserted in the bottle. It puts the water in this bottle, and the gauze of the temperature sensing element would moisten in the capillarity. And, one side measures the temperature. Showing temperature of the thermometer which moistens in winding the gauze, is called the wet bulb temperature. And, one side is called dry-bulb temperature or temperature only.
  
  Though the simple wet and dry bulb thermometer does not pass the wind at temperature sensing element, it sends and ventilates the wind of about 5m/s wind velocity to the temperature sensing element in order to accurately measure. It is called conformer wet and dry bulb thermometer which ventilates this, and there is the Asman ventilation type wet and dry bulb thermometer as a representative thing.
- Thermometer and relative humidity meter
  Relative humidity meter is for measuring the relative humidity directly. The humidity is measured using the contraction of cellophane and hair, and the semiconductor is used, and there is relative humidity meter of various structure.

Calculation of the various humidities

To begin with, the dry-bulb temperature ( air temperature ) is measured, and thereupon, it is written with C. The person who uses wet and dry bulb thermometer in continueing, writes the field: C as wet bulb temperature, or the person who uses relative humidity meter a substitute for the wet bulb temperature writes the field: % as relative humidity. It has been written, and the button is pushed. Various humidity is obtained like the following, when it is done. It is the button, when it wants to already redo the once, and the filling up field is eliminated, and it is it good. Here, by assuming 1 atm (1013.25 hPa), the atmospheric pressure calculates it.

dry-bulb temperature wet bulb temperature relative humidity absolute humidity vapor pressure enthalpy specific volume percentage humidity dew-point temperature

Unit C C % kg/kgD.A. mmHg kJ/kgD.A. m³/kgD.A. % C

The meaning of each humidity is described well-informed in this after.

Description of the values concerning the humidity
- Preparation for the description
  It explains on the basis of the value measured actually. Please read, after the numerical value measured in the actually place in the field of following dry-bulb temperature and wet bulb temperature or relative humidity with the self is let in, and after "Explain" button is pushed.
  
  dry-bulb temperature wet bulb temperature relative humidity
  
  Unit C C %
- relative humidity
  For the pressure ( the saturated vapor pressure ) of the steam in containing the water to the limit the, whether there was the steam of the pressure of the what percent at present showed % by the relative humidity. The aerial relative humidity here is %. It becomes 0 %, when it becomes a case in which the water is contained to the limit for 100 %, and when it completely does not contain the water.
  This relative humidity is indicated, when it is generally called the humidity. However, the quantity of including water is be same, when the aerial temperature changes, and the value of the relative humidity changes. As the saturated vapor pressure changes on this by the aerial temperature, be.
- absolute humidity
  The aerial absolute humidity here is kg/kgD.A. This shows whether it includes the water of what kg for drying air 1kg. This absolute humidity is spent, when they want to accurately know the mass of the water which is included for the air.
  Usually, the volume of 1kg dry air becomes about 0.83m³ at 20 C in 1 atm. The water of weight (kg) over this numerical value will be included for the air in 1m cube in one side. The water of the quantity of surprising so that it may not see it as a water, is included.
- vapor pressure
  The pressure of the vapor which is included for the air is shown. The pressure of the steam which is included for this air is mmHg. The unit is the pressure which corresponds to the Torricelli's making length which is vacuum by the mercury. 760 mmHg is 1 atm, and it becomes that it is broken in 760 by putting on 1013.25 for this value, for the unit of hPa.
- enthalpy
  This shows the energy which the air has. This aerial enthalpy is kJ/kgD.A. 4.186 KJ becomes 1 kcal. Therefore, it can be converted into the kilo calorie, if it is sent, by dropping below calculated value in 4.186.
  For example, it is possible to measure the energy given to the air by the heating, if suction port of the heater and difference of the enthalpy of the outlet and aerial flow rate are obtained. It is an important index, when heating and cooling of greenhouses is considered.
- specific volume
  This aerial volume including 1kg wet air is shown. The value of the air here is m³/kg
- percentage humidity
  It is called the saturation. The mass of the possible steam of the water of containing for any air as a steam largest, for the mass ( specific humidity at satulation ) which is included at present is shown at the proportion. This air is %.
- dew-point temperature
  Since it appears as a liquid without not dissolving in the air, that it gives the dew in the glass window and that the mist comes out like ( condensation and dew condensation ) and bathroom happens. The possible quantity of the dissolution of the water as a steam in the air decreases, as the temperature lowers. So, the dew is easy to be given at the indifferent part. The fog may instantaneously arise, when the suddenly indifferent air is put in, by opening windows such as the greenhouse. Including water calls the fact of appearing temperature the dew-point temperature by the cooling of the air as it is as a liquid. With that the air in of today is cooled to 、C, the dew condensation is done, and the fog arises.

	dry-bulb temperature	wet bulb temperature	relative humidity	absolute humidity	vapor pressure	enthalpy	specific volume	percentage humidity	dew-point temperature
Unit	C	C	%	kg/kgD.A.	mmHg	kJ/kgD.A.	m³/kgD.A.	%	C

Humidity calculation sheet
It puts the numerical value in dry-bulb temperature and wet bulb temperature or relative humidity, and the calculation is possible, when "Calculate" button is pushed.

English | Japanese

Water which are included for the air(humidity) and plant production

Caution: This page is made with the purpose of the plant production, and it has been designed for the use in the ordinary temperature in which the crop grows.

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