Question

Consider the following statement and choose the correct one I. Dew point is reached by cooling the air at constant moisture content
II. Wet bulb temperature changes by addition of moisture at constant enthalpy
III. For saturated air, dry bulb, wet bulb and dew point temperatures are same
IV. Dehumidification of air is achieved by heating

• A. Only I and II
• B. Only I and III
• C. Only II and IV
• D. Only II and IV

Hint:

For air conditioning and humidity control, remember that dehumidification involves heating, and wet bulb temperature changes with the addition of moisture at constant enthalpy.

Answer 1

The Correct Option is B

Step 1: Statement I
Dew point is the temperature at which air becomes saturated and begins to condense. It is not related to the cooling of air at constant moisture content; therefore, Statement I is incorrect.
Step 2: Statement II
The wet bulb temperature changes when moisture is added to the air while maintaining constant enthalpy. This is because the addition of moisture increases the latent heat of evaporation, thus affecting the wet bulb temperature, so Statement II is correct.
Step 3: Statement III
For saturated air, the dry bulb, wet bulb, and dew point temperatures are the same. When air is saturated, the wet bulb temperature equals the dry bulb temperature, and the dew point also becomes equal. Therefore, Statement III is correct.
Step 4: Statement IV
Dehumidification is the process of removing moisture from the air, which is typically done by heating the air to increase its capacity to hold moisture. Therefore, Statement IV is correct. Conclusion The correct combination of statements is I and III. Hence, the correct answer is (2).