Wet-bulb Depression and Relative Humidity

The wet-bulb depression refers to the difference between the dry-bulb temperature and the wet-bulb temperature. It is a measure of the cooling potential of evaporation and can be used to determine the relative humidity of the air.

The wet-bulb temperature is the lowest temperature that can be reached by evaporating water into the air, while the dry-bulb temperature is the temperature of the air measured by a regular thermometer. The wet-bulb depression is calculated by subtracting the wet-bulb temperature from the dry-bulb temperature.

When the relative humidity is 100%, the air is saturated with moisture, and the wet-bulb temperature is equal to the dry-bulb temperature. In this case, the wet-bulb depression is zero because there is no potential for evaporation to occur. The air is already holding as much moisture as it can at that temperature.

Explanation:

- Wet-Bulb Depression and Evaporation: The wet-bulb depression is related to the cooling effect of evaporation. When water evaporates, it absorbs heat from the surrounding air, which results in a cooling effect. The greater the wet-bulb depression, the more potential for evaporation and cooling.
- Saturated Air: When the air is saturated, it cannot hold any more moisture at that temperature. This means that there is no potential for evaporation to occur because the air is already holding the maximum amount of moisture it can hold at that temperature.
- Relative Humidity: Relative humidity is a measure of the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a particular temperature. When the relative humidity is 100%, it means that the air is holding the maximum amount of moisture it can hold at that temperature.
- Wet-Bulb Temperature and Relative Humidity: The wet-bulb temperature is directly related to the relative humidity. When the air is saturated, the wet-bulb temperature is equal to the dry-bulb temperature. As the relative humidity decreases, the wet-bulb temperature becomes lower than the dry-bulb temperature, resulting in a positive wet-bulb depression.
- Conclusion: When the relative humidity is 100%, the air is saturated, and the wet-bulb temperature is equal to the dry-bulb temperature. Therefore, the wet-bulb depression is zero.