Question

The dry bulb temperature of an air-water vapour mixture is equal to the dew point temperature when the relative humidity is -

• A. Less than 100
• B. More than 100
• C. Equal to 100
• D. Equal to 50

Hint:

At any relative humidity less than \(100\%\), the dry bulb temperature is always higher than the wet bulb temperature, which in turn is higher than the dew point temperature (\(\text{DBT} > \text{WBT} > \text{DPT}\)).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Psychrometrics is the study of the physical and thermodynamic properties of air-water vapor mixtures, which is essential for understanding food drying, dehydration, and storage processes.

Step 2: Detailed Explanation:
- Dry Bulb Temperature (DBT): The actual air temperature measured by a standard thermometer.
- Dew Point Temperature (DPT): The temperature to which air must be cooled (at constant pressure) to become fully saturated with water vapor, leading to condensation.
- When the air is fully saturated, it is carrying the maximum possible water vapor, which means the Relative Humidity (RH) is exactly \(100\%\).
At this \(100\%\) saturation limit, the dry bulb temperature, wet bulb temperature, and dew point temperature are all identical.

Step 3: Final Answer:
The relative humidity is equal to 100, which corresponds to option (C).