【Mechanical Equipment Technology Edition】Daily Question 201709029: Principles of Refrigeration

Dry bulb temperature, wet bulb temperature, and dew point temperature are all physical quantities related to the measurement of air humidity. A common method for measuring air humidity is the dry-wet bulb method, which involves using a dry bulb thermometer and a wet bulb thermometer to measure these temperatures respectively; the actual relative humidity of the air is then determined based on the dry bulb temperature and the difference between the two temperatures. The wet-bulb thermometer shows a lower temperature than the dry-bulb thermometer because heat is drawn away by the evaporation of water; the lower the air humidity, the greater the amount of evaporation, and thus the larger the difference between the wet-bulb and dry-bulb temperatures. Therefore, the wet-and-dry-bulb method is an effective way to measure air humidity. Dew point temperature is another way of expressing relative humidity of air; it is the temperature at which condensation occurs when the water vapor content in the air remains constant. Since a higher water vapor content in the air makes condensation more likely, the dew point temperature is also higher. Therefore, the dew point temperature is a commonly used method for measuring air humidity. The wet-bulb temperature is higher than the dew point

Dry-bulb temperature is the value read from a dry-bulb thermometer that is exposed to the air but not directly exposed to sunlight. The wet-bulb temperature refers to the air temperature at which the water vapor in the air reaches saturation under conditions of the same enthalpy. On an air enthalpy-humidity diagram, it is determined by moving from the air condition point along the isenthalpy line until reaching the 100% relative humidity line, and the dry-bulb temperature at that corresponding point. In simple terms, the wet-bulb temperature is the lowest temperature that an environment can reach through evaporation alone. The dew point (or frost point) temperature refers to the temperature at which air becomes saturated when cooled, with no changes in its water vapor content or pressure. Put simply, the temperature at which water vapor in the air turns into dew drops is called the dew point temperature. For unsaturated air: dew point temperature

The wet-bulb temperature is the temperature resulting from the cooling effect on the dry-bulb temperature due to the heat absorbed by water evaporation. The dew point temperature is related only to the moisture content of moist air. By keeping the moisture content constant and cooling the moist air until water vapor just begins to condense, the temperature at that point is the dew point temperature.

Dry bulb temperature, wet bulb temperature, and dew point temperature are all physical quantities related to the measurement of air humidity. A common method for measuring air humidity is the dry-wet bulb method, which involves using a dry bulb thermometer and a wet bulb thermometer to measure these temperatures respectively; the actual relative humidity of the air is then determined based on the dry bulb temperature and the difference between the two temperatures. The wet-bulb thermometer shows a lower temperature than the dry-bulb thermometer because heat is drawn away by the evaporation of water; the lower the air humidity, the greater the amount of evaporation, and thus the larger the difference between the wet-bulb and dry-bulb temperatures. Therefore, the wet-and-dry-bulb method is an effective way to measure air humidity. Dew point temperature is another way of expressing relative humidity of air; it is the temperature at which condensation occurs when the water vapor content in the air remains constant. Since a higher water vapor content in the air makes condensation more likely, the dew point temperature is also higher. Therefore, the dew point temperature is a commonly used method for measuring air humidity. The wet-bulb temperature is higher than the dew point

Dry-bulb temperature is the value read from a dry-bulb thermometer that is exposed to the air but not directly exposed to sunlight. The wet-bulb temperature refers to the air temperature at which the water vapor in the air reaches saturation under conditions of the same enthalpy. On an air enthalpy-humidity diagram, it is determined by moving from the air condition point along the isenthalpy line until reaching the 100% relative humidity line, and the dry-bulb temperature at that corresponding point. In simple terms, the wet-bulb temperature is the lowest temperature that an environment can reach through evaporation alone. The dew point (or frost point) temperature refers to the temperature at which air becomes saturated when cooled, with no changes in its water vapor content or pressure. Put simply, the temperature at which water vapor in the air turns into dew drops is called the dew point temperature. For unsaturated air: dew point temperature

Dry-bulb temperature is the value read from a dry-bulb thermometer that is exposed to the air but not directly exposed to sunlight. The wet-bulb temperature refers to the air temperature at which the water vapor in the air reaches saturation under conditions of the same enthalpy. On an air enthalpy-humidity diagram, it is determined by moving from the air condition point along the isenthalpy line until reaching the 100% relative humidity line, and the dry-bulb temperature at that corresponding point. In simple terms, the wet-bulb temperature is the lowest temperature that an environment can reach through evaporation alone. The dew point (or frost point) temperature refers to the temperature at which air becomes saturated when cooled, with no changes in its water vapor content or pressure. Put simply, the temperature at which water vapor in the air turns into dew drops is called the dew point temperature. For unsaturated air: dew point temperature

Dry bulb temperature, wet bulb temperature, and dew point temperature are all physical quantities related to the measurement of air humidity. A common method for measuring air humidity is the dry-wet bulb method, which involves using a dry bulb thermometer and a wet bulb thermometer to measure these temperatures respectively; the actual relative humidity of the air is then determined based on the dry bulb temperature and the difference between the two temperatures. The wet-bulb thermometer shows a lower temperature than the dry-bulb thermometer because heat is drawn away by the evaporation of water; the lower the air humidity, the greater the amount of evaporation, and thus the larger the difference between the wet-bulb and dry-bulb temperatures. Therefore, the wet-and-dry-bulb method is an effective way to measure air humidity. Dew point temperature is another way of expressing relative humidity of air; it is the temperature at which condensation occurs when the water vapor content in the air remains constant. Since a higher water vapor content in the air makes condensation more likely, the dew point temperature is also higher. Therefore, the dew point temperature is a commonly used method for measuring air humidity.

The air temperature measured with a thermometer is called the dry-bulb temperature t, while the air temperature measured with a thermometer wrapped in gauze is called the wet-bulb temperature ts. The temperature at which moist air becomes saturated is known as the dew point temperature tl. Under normal circumstances: t is greater than ts, which is greater than tl ； At saturated air: t=ts=tl.

The temperature at which water vapor in the air turns into dew drops is called the dew point temperature. The temperature of a dry-bulb thermometer is usually considered the temperature of the air, and it represents the true thermodynamic temperature. The wet-bulb temperature is also known as the thermodynamic wet-bulb temperature. The wet-bulb temperature is a method for calibrating relative air humidity. For unsaturated air, dew point temperature

Dry-bulb temperature is the value read from a dry-bulb thermometer that is exposed to the air but not directly exposed to sunlight. The wet-bulb temperature refers to the air temperature at which the water vapor in the air reaches saturation under conditions of the same enthalpy. On an air enthalpy-humidity diagram, it is determined by moving from the air condition point along the isenthalpy line until reaching the 100% relative humidity line, and the dry-bulb temperature at that corresponding point. Dew point temperature refers to the temperature at which air reaches saturation when its water vapor content and pressure remain unchanged.