What Is Dry Bulb Temperature?

Dry bulb temperature is a value read from a dry bulb temperature meter exposed to the air and not directly exposed to the sun. It is the temperature measured by the thermometer in ordinary air, which is the temperature often used in our general weather forecast. Dry bulb thermometer temperature is the temperature measured by the thermometer's free exposure to the air, and it should avoid the interference of radiation and moisture. The dry-bulb thermometer temperature is usually regarded as the actual temperature of the measured air, which is the true thermodynamic temperature. It is the temperature measured by an ordinary thermometer when exposed to airflow. Unlike a wet bulb thermometer, the temperature of a dry bulb thermometer is independent of the current humidity value in the air.

(1) In wood drying production, it is often necessary to determine the relative humidity of the air, referred to as humidity. The instrument for measuring air humidity is a hygrometer.
The commonly used hygrometer consists of two calibrated thermometers. The mercury ball of one thermometer is covered with gauze. The gauze is immersed in clean water. The mercury ball of the other thermometer is not covered with gauze. The thermometer with a mercury ball wrapped in wet gauze is called a wet bulb thermometer, and the temperature measured with it is called the wet bulb temperature, which is expressed by t wet; the thermometer with no mercury gauze is called a dry bulb thermometer, and the temperature measured with it is called a dry ball Use t to dry the table. When the humidity of the air is low, the moisture contained in the gauze wrapped around the wet bulb will evaporate into the air. When the water evaporates, it absorbs heat from the wet bulb, so that the wet bulb temperature is lower than the dry bulb temperature, that is, lower than the temperature of the air. The difference between dry bulb temperature and warm bulb temperature is called hygrometer difference, or dry and wet bulb temperature difference. Because it is related to evaporation capacity, the value of hygrometer difference can also be dried, that is: = t dry-t wet, the drier the air, the larger the hygrometer value, the stronger the air's ability to contain water vapor, and the faster the moisture in the wet wood evaporates. Conversely, the wetter the air and the smaller the hygrometer value, the weaker the air's ability to contain water vapor, and the slower the water evaporation from the wet wood. When the air is completely saturated with water vapor, the humidity = 100%, the dry bulb temperature and the wet bulb temperature are equal, and the hygrometer difference is zero. At this time, the moisture in the wet wood stops evaporating or the air and water vapor on the wood surface In a state of dynamic balance. In wood drying production, the humidity value of the air can be checked on a humidity table based on the two values of dry bulb temperature t dry and hygrometer difference. ^[3]

(2) Dry bulb temperature (air temperature) is one of the conventional elements to be measured in surface meteorological observations. ^[4]

(3) One of the influencing factors and research principles of the cooling capacity of wet air coolers. ^[5]

(4) The simplified distribution model of dry bulb temperature throughout the year can be used to estimate the energy consumption of HVAC buildings, calculate the number of days and temperature frequency, and can be used for the design and operation of HVAC systems. ^[6]