Psychrometric relationships — select all correct statements Which of the following statements about moist-air properties and chart lines are correct?

Introduction / Context:Engineers rely on the psychrometric chart to visualize moist-air processes such as cooling and dehumidification, evaporative cooling, and reheat. Understanding how enthalpy, wet-bulb temperature, and saturation are related is critical for quick, accurate analysis.

Given Data / Assumptions:

• Standard atmospheric pressure psychrometric chart conventions.
• Definitions of dry-bulb temperature, wet-bulb temperature, relative humidity, and specific enthalpy.

Concept / Approach:Lines of constant wet-bulb temperature on the chart nearly coincide with constant enthalpy lines (minor deviations exist but are negligible for HVAC calculations). At saturation, evaporation from a wetted wick ceases, making wet-bulb equal to dry-bulb. Because wet-bulb embodies both sensible and latent effects, it closely tracks the enthalpy of moist air, serving as a convenient field indicator for energy content.

Step-by-Step Solution:Evaluate (a): On the chart, h ≈ constant along constant T_wb lines → commonly used for adiabatic process plotting.Evaluate (b): Saturation line (RH = 100%) shows T_db = T_wb.Evaluate (c): Enthalpy changes correlate strongly with T_wb because evaporative processes approximate constant h.Conclusion: All statements are concurrently valid for HVAC practice.

Verification / Alternative check:Run a quick calculation: adiabatic humidification follows nearly constant h and constant T_wb, confirming the practical equivalence.

Why Other Options Are Wrong:(e) is incorrect because at least one—and in fact all—statements are true. Choosing any single statement alone misses the comprehensive relationship among these properties.

Common Pitfalls:Over-interpreting small chart discrepancies between exact constant-h and constant-T_wb lines; for design estimates, their coincidence is sufficiently accurate.

Final Answer:all of the above