Air-conditioning process insight: During purely sensible cooling of air (no moisture removal), how does the wet-bulb temperature behave?

Introduction / Context:
On the psychrometric chart, different HVAC processes trace different paths. For sensible cooling, the air's dry-bulb temperature drops without changing its humidity ratio, a key concept for diagnosing coil performance and reheating needs.

Given Data / Assumptions:

• No condensation occurs (constant humidity ratio).
• Process line is horizontal to the left on the chart.
• Air properties are measured in steady state.

Concept / Approach:
The wet-bulb temperature is a measure related to the adiabatic saturation state. For a constant humidity ratio, the adiabatic saturation temperature stays fixed, and so does the wet-bulb temperature. Therefore, WB remains the same while DB reduces in a sensible-only process.

Step-by-Step Solution:

Verification / Alternative check:
Compute humidity ratio from measured DB/WB pairs before and after. If the ratio is unchanged and no condensate forms, WB should remain the same within instrument accuracy.

Why Other Options Are Wrong:

Increase/decrease implies moisture exchange, which contradicts the definition of sensible cooling.“Varies unpredictably” ignores psychrometric relationships.Equalling dew point happens only at saturation; not the case here.

Common Pitfalls:
Assuming WB always follows DB; in reality, WB is tied to moisture content and will not change in truly sensible-only cooling.

Final Answer:

remains constant