Hygrometer dictionary
In the metrology method, humidity is defined as the "amount of object state". The humidity referred to in daily life is relative humidity, expressed as %rh. In summary, the percentage of the amount of water vapor (water vapor pressure) in a gas (usually in air) and the amount of saturated water vapor (saturated water vapor pressure) in the same condition as air.
History of humidity measurement
Humidity and temperature have a close relationship with life long ago, but it is more difficult to express it by quantity. The history of hygrometers can be traced back to China's Libra type (179 BC) as the earliest humidity meter. (The thermometer can be traced back to the recorded Greek era thermometer.)
The mass per unit volume (1 m3) contains the mass (g) of water vapor.
Indicates: D=g/m3
However, even if the amount of water vapor is the same, the volume of the gas changes due to changes in temperature and pressure, that is, the absolute humidity D changes. D is the volume reference.
The ratio of the water vapor pressure (e) in the gas to the saturated water vapor pressure (es) of its gas is expressed as a percentage.
Indicates: rh=e/es×100%
However, changes in temperature and pressure result in a change in saturated water vapor pressure, and rh will change accordingly.
Saturated water vapor pressure
The amount of water vapor contained in the gas is limited, and the state in which the limit is reached is called saturation, and the water vapor pressure at this time is called saturated steam pressure. The physical quantity also changes with temperature and pressure, and the saturated water vapor pressure (esw) coexisting with water and the saturated water vapor pressure (esi) coexisting with ice are different at 0 ° C or lower, even at the same humidity, usually The saturated water vapor pressure (esw) coexisting with water is used. The saturated water vapor pressure gauge JIS-Z-8806 corresponding to each temperature is described at the end of the volume.
The gas with higher temperature has more water vapor. After the gas is cooled, the amount of water vapor does not change, and the relative humidity increases. When a certain temperature is reached, the relative rh reaches 100% saturation. If cooling is continued, some of the water vapor will condense into dew. The temperature at this time is the Dew Point Temperature. When the dew point freezes below 0 °C, it is Frost Point.
The term unpleasant index, popular in the living environment, was used in the 1959 US Meteorological Agency. Expressed as: THI = (dry bulb temperature td + wet bulb temperature tw) × 0.72 + 40.6, this data 70 ~ 75 is half unpleasant, 80 or more is basically unhappy, and recently, the market has an unpleasant index to be sold .
The unpleasant index is a simple representation of the human body's perceptible index. This term was created with the recent development of air-conditioning technology, temperature and humidity, and the introduction of wind-speed and other human-perceived items. There is little difference between the index and the unpleasant index, and the changes are relatively close.
A term that includes the elements of effective temperature (temperature, humidity, airflow) and four elements such as radiation.
For air below 1 kg of water vapor (dry air), water vapor of Xkg ratio is included, and the mass ratio X (kg/kg) is a mixing ratio, and even if the temperature and pressure change, as long as the amount of water vapor does not change, The mixing ratio is unchanged. Therefore, in order to facilitate calculation, the mixing ratio is industrially referred to as absolute humidity. X is the weight standard.
That is, a line graph showing the nature of air (moisture) containing water vapor, the horizontal axis represents the enthalpy (I), and the vertical axis represents the mixing ratio (X), and the state of the air at all points in the figure is called For the state point, this state point is known, and the dry bulb temperature, wet bulb temperature, ludian temperature, mixing ratio, relative humidity, and enthalpy of the air can be calculated.
※? The enthalpy (kcal/kg)...the sensible heat of the dry air and the sensible heat of the steam + the latent heat. (ie the total heat of moisture).
That is, water vapor (kg) contained in moisture (1 kg). Expressed in kg/kg.
That is, the amount of vapor contained in 1 kg of dry gas (absolute X of moisture) and the ratio of the amount of saturated steam (the absolute humidity Xs of saturated air) of 1 kg of dry gas at the same temperature are 100 times.
φ = X / Xs × 100% or Saturation degree, that is, φ = 0 is dry air, and φ = 100 is saturated air.
That is, the ratio of the water vapor pressure to the dry gas pressure ratio, that is, the molar ratio of the two.
Ie es-e or Ds-D. Discuss the evaporation of water and use it when drying.
Standard temperature and humidity status（JIS-8703）
Standard humidity status Level 1: Relative humidity 65±2%rh
Standard humidity condition Level 2: Relative humidity 65±5% rh
Standard humidity status Level 3: Relative humidity 65±20% rh
Usually the 3-stage humidity state is normally wet.
Standard temperature and humidity status Category 1: Temperature 20±1°C Relative humidity 65±2%rh
Standard temperature and humidity status Category 2: Temperature 20±2°C Relative humidity 65±2%rh
Standard temperature and humidity status Category 3: Temperature 20±2°C Relative humidity 65±5%rh
Normal temperature and humidity: temperature 20±15°C Relative humidity 65±20%rh
In contact with the gas and liquid in the externally insulated system, the gas conducts a certain amount of heat to the liquid, and the heated liquid partially evaporates, and the temperature (tw°C) of the gas temperature, humidity, and liquid temperature does not change. The wet bulb temperature of the state. That is, the gas temperature (t ° C) at that time is the dry bulb temperature (Chemical Engineering Dictionary)
Adiabatic Saturation temperature"ts"
The air comes into contact with water in a state of heat, called saturated air at the same temperature as the water. The temperature at this time is the heat-saturation temperature.
* The moisture on the surface of the wet bulb heat sensitive portion of the wet bulb thermometer evaporates to extract latent heat, and when it is heated to 5 m/sec or more with the surrounding air, it can be the same as the heat-off saturation temperature.
The moisture contained in the food is distinguished from the free water and is freely absorbed in the form of crystal water. Previously, the way to calculate the moisture content of food was to compare the weight of the food. The recent thermodynamic method of using free water and degrees of freedom to represent water activity is a reasonable method, and its value is Aw.
As the temperature of the object rises and falls, the heat/temperature of 1 kg of dry air is equivalent to ○0.24T sensible heat, and 0.24 is the weight specific heat of dry air (kcal/kg °C).
When the evaporation of the object changes and the condensation changes to each other, even if the heat/elevation of the incoming and outgoing air changes, the amount of heat entering and leaving does not change. The latent heat of 1 kg of water vapor at temperature T (597.3 + 0.44T). 597.3 is the latent heat of vaporization of steam.
That is, the total amount of heat retained by the object.return
When the unsaturated air receives heat and moisture from other objects (such as other air, water, water vapor, etc.), the ratio of the enthalpy change 空气i of the air to the change amount of the absolute humidity ⊿X
μ=⊿i／⊿X
A state in which water droplets are mixed in saturated air.
The state of snow and ice mixed in saturated air.
The specific weight γ of the standard state (temperature 0 ° C, pressure 760 mmHg, gravitational acceleration g = 980, 665 cm / S2) was 1.293 kg / Nm 3 . The weight of moisture in the air is about 1-2%. Of course, as the humidity changes, the air conditioning is more calculated with a humidity ratio of 1.2 kg/m3.
The volume of moisture contained in 1 kg of dry air. The inverse of the wet specific weight. Thus, 1/1.2 = 0.833 m3/kg [DA], where kg [DA] represents 1 kg of dry air.
It refers to the change in heat when the moisture temperature changes by 1 °C.
Cp=0.240+0.44χ
Cp at this time: constant pressure specific heat of moisture〔kcal/kg（DA）?℃〕
χ ：Absolute humidity of moisture〔kg/kg（DA）〕
The sensible heat ratio for total heat (thermal function) change when the temperature and humidity of the air change, ie: SHF=(Cp*⊿t)/⊿i
At this time Cp: constant pressure specific heat
⊿i：Caloric change
⊿t：Temperature change
Continuous drying in the winter takes a long time to prevent the occurrence of fire and to confirm the dryness of the wood.
E=(1-0.7)H0+0.7H1+(0.7)(0.7)H2
H0 at this time: relative humidity of the day
H1：Relative humidity of the previous day
H2：Relative humidity of the previous day