I. Introduction
The air around us is a mixed gas. The air contains water vapor. The degree of dryness and humidity of the air is related to the amount of water vapor contained in the air. The degree of dryness and humidity of the air is closely related to our life and production, so we know It is necessary to have some knowledge in this area.
(1) The humidity of the air
The humidity of the air can be understood as the degree of moisture in the air. It has absolute humidity and relative humidity.
1. Absolute humidity: The pressure of water vapor in the air is called the absolute humidity of the air.
The humidity of the air can be expressed by the density of the water vapor contained in the air, that is, the mass of the water vapor contained in the air per unit volume. It is difficult to directly measure the density of water vapor in the air, and the pressure of the water vapor varies with the water vapor density. Increases and increases, so the pressure of the water vapor in the air is usually used to indicate the humidity of the air, which is the absolute humidity of the air.
2, relative humidity
(1) Introduction of concept: The concept of introducing relative humidity in order to express the distance between water vapor in the air from saturation.
(2) Relative humidity B: The absolute humidity of air at a certain temperature and the percentage of saturated vapor pressure ps of water at the same temperature are called the relative humidity of the air at this time.
1 The saturated vapor pressure of water at different temperatures can be found in the table.
2 When the absolute humidity p is constant and the temperature is lowered, the relative humidity of the air is increased due to the decrease of the saturated vapor pressure of water.
The relative humidity of the 3 bedroom is more suitable for 60% to 70%.
(2) Dew point
1. Dew point: The temperature at which the water vapor in the air just reaches saturation is called the dew point.
(1) The saturated vapor pressure of water at the dew point temperature is the absolute humidity of the air.
(2) According to the difference between the dew point and the temperature, the relative humidity can be roughly judged. The larger the difference, the smaller the relative humidity.
2, the dew point can be measured.
3. According to the measured dew point, the relative humidity of the air can be determined. From the saturated vapor pressure gauge of the water, the saturated vapor pressure at the dew point (equal to the absolute humidity of the air at the original temperature) is detected, and then the saturated vapor pressure at the original temperature is detected. It can be found.
(three) hygrometer
1. The composition of the hygrometer: The hygrometer consists of two identical thermometers. One of the thermometers is a dry bulb thermometer and the other is a wet bulb thermometer.
2. The principle of measuring the relative relative humidity of the hygrometer: Since the temperature sensitive bubble of the wet bulb thermometer wraps the cotton yarn, the lower end of the cotton yarn is immersed in water, and the evaporation of the water makes the temperature of the wet bulb thermometer always lower than that of the dry bulb thermometer. The temperature difference (temperature) is related to the speed at which the water evaporates (ie the relative humidity at that time). According to the readings of the two thermometers, the relative humidity of the air can be detected from the table or curve.
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