Psychrometrics concept check: At 100% relative humidity, the wet-bulb temperature is ________ the dew-point temperature.

Introduction / Context:Wet-bulb temperature (WBT) and dew-point temperature (DPT) are fundamental air properties in HVAC design. Their relationship simplifies under saturation conditions (100% relative humidity).

Given Data / Assumptions:

• Air–water vapor mixture at 100% relative humidity.
• Steady psychrometric conditions.
• Standard definitions of WBT and DPT.

Concept / Approach:At 100% RH, the air is saturated. For saturated air, dry-bulb temperature, wet-bulb temperature, and dew-point temperature all coincide. Evaporative cooling potential is zero, so the wet-bulb cannot be lower than dry-bulb; likewise, the dew point equals the current air temperature.

Step-by-Step Solution:Recognize 100% RH → saturated state.On a psychrometric chart, the state lies on the saturation curve.At this point, DBT = WBT = DPT.

Verification / Alternative check:Using sling psychrometer logic: with no evaporation from the wet wick (air already saturated), WBT equals DBT. Dew point equals DBT at saturation.

Why Other Options Are Wrong:

• Lower/higher/undefined/greater by a fixed value: contradict the saturation property relationship.

Common Pitfalls:Confusing near saturation (e.g., 95% RH) with full saturation; at near saturation, WBT is slightly below DBT and DPT is slightly below DBT, but they are not equal.

Final Answer:same as