How is wet bulb temperature measured

A cooling tower cools water by evaporation to temperatures that are lower than the ambient temperature and that approach the wet bulb temperature. But what exactly is the wet bulb temperature and how do you calculate it? Heat is required to evaporate water. If this evaporation is adiabatic, the heat is extracted from the environment e.

The same thing happens when we step out of the shower or the swimming pool. The water on our body evaporates, extracts heat from our body and we get cold. The wet bulb temperature can be measured with a thermometer whose mercury reservoir is contained in a cotton stocking. It is kept wet by connecting it to a water tank with a cotton thread.

The thermometer is placed in an air stream. Because the water evaporates, heat is extracted from the environment, including the mercury reservoir, and the measured temperature will decrease. When the air is dry, more water can evaporate and the wet bulb temperature will be lower. The greater the difference between the dry bulb temperature or the normal temperature and the wet bulb temperature, the drier the air is and the more water can evaporate.

The wet bulb temperature is not the same as the dew point temperature. The dew point is the temperature at which water vapor begins to condense by cooling the air lower enthalpy without adding or removing moisture absolute humidity remains constant. Since cooling tower cells cool water by evaporation, the wet bulb temperature is the critical design variable. When selecting a cooling tower cell, the highest wet bulb temperature in your geographical area must be used.

Highest wet bulb temperatures occur during the summer, when air temperatures and humidity are highest. At a higher wet bulb temperature, the tower cell capacity to produce colder water decreases. Every location has a unique design worst case wet bulb temperature that is published by organizations such as ASHRAE and can be obtained easily. Industrial cooling tower performance is tied to ambient wet bulb conditions.

Higher wet bulb temperatures occur in the summer when higher ambient and relative humidity occurs. Initial system design and proper system maintenance are critical to be certain your cooling tower is providing desired cooling. Delta, the technology-leading cooling tower manufacturer in USA, is here to help. These applications will - due to browser restrictions - send data between your browser and our server.

We don't save this data. Google use cookies for serving our ads and handling visitor statistics. AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information. If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. Make Shortcut to Home Screen? Sponsored Links. Dry Bulb Temperature - T db The Dry Bulb temperature, usually referred to as "air temperature" , is the air property that is most commonly used.

Dew Point Temperature - T dp The Dew Point is the temperature where water vapor starts to condense out of the air the temperature at which air becomes completely saturated. Dew Point Temperature Charts Dew point temperatures from dry and wet bulb temperatures are indicated in the charts below. Privacy We don't collect information from our users. Citation This page can be cited as Engineering ToolBox, Modify access date. Scientific Online Calculator.