Question

In drying process, which of the following parameters is same as the adiabatic saturation temperature:

• A. Absolute humidity
• B. Dew point
• C. Relative humidity
• D. Wet bulb temperature

Answer 1

The Correct Option is D

The correct option is (D): Wet bulb temperature.

Answer 2

The question asks which humidity-related parameter is numerically equal to the adiabatic saturation temperature during drying. Let's examine each option.

1. Absolute humidity: This is simply the mass of water vapor present per unit mass (or volume) of dry air. It is a moisture content measurement, not a temperature, so it cannot be equal to a temperature value.
2. Dew point: This is the temperature at which air becomes saturated with water vapor upon cooling at constant pressure, without any evaporation happening into it. It is a distinct thermodynamic quantity from adiabatic saturation temperature in general, so it does not fit here.
3. Relative humidity: This is a ratio, expressed as a percentage, of the actual vapor pressure to the saturation vapor pressure at the same temperature. It is not a temperature at all.
4. Wet bulb temperature: This is the steady temperature reached by a thermometer bulb covered in a wet wick when air flows past it and water evaporates from the wick. For the air-water system specifically, the heat and mass transfer coefficients work out such that the wet bulb temperature equals the adiabatic saturation temperature, a result known as the Lewis relation.

Because of the Lewis relation holding for air-water systems, the wet bulb temperature and the adiabatic saturation temperature turn out to be numerically the same value.

Therefore, the correct answer is Wet bulb temperature.