Psychrometric chart reading: The inclined, non-uniformly spaced straight lines on a standard psychrometric chart represent constant wet-bulb temperature (WBT). State whether this statement is correct.

Introduction / Context:
Psychrometric charts are essential tools in HVAC engineering for visualizing moist-air properties. Each family of lines corresponds to a specific property. Recognizing which lines represent the wet-bulb temperature helps engineers quickly estimate processes like adiabatic saturation, evaporative cooling, and cooling with dehumidification.

Given Data / Assumptions:

• Standard SI psychrometric chart for atmospheric pressure near 1 atm.
• Families of lines: dry-bulb temperature (DBT), wet-bulb temperature (WBT), relative humidity (RH), humidity ratio (w), enthalpy (h), and specific volume (v).
• Graphical conventions follow widely used HVAC charts.

Concept / Approach:
On most charts, constant DBT lines are vertical; constant humidity ratio lines are horizontal; constant RH lines are curved; constant enthalpy and constant WBT lines are inclined and nearly coincident. The WBT lines are drawn as straight, slanted lines that are not uniformly spaced because the psychrometric relationships are nonlinear.

Step-by-Step Solution:
Identify the vertical axis (humidity ratio) and horizontal axis (dry-bulb temperature).Observe the family of slanted straight lines labeled with values such as 15 °C WB, 20 °C WB, etc.Note the spacing varies with DBT and RH due to nonlinear moist-air behavior; hence, lines are non-uniformly spaced.Conclusion: These inclined straight lines represent constant wet-bulb temperature.

Verification / Alternative check:
Trace an adiabatic saturation (constant WBT) process line during evaporative cooling; it should follow one of these inclined lines, confirming identification.

Why Other Options Are Wrong:

• Disagree / conditional options: WBT lines exist over the normal chart domain, not limited to specific RH or subfreezing ranges.

Common Pitfalls:
Confusing constant enthalpy lines with constant WBT lines; in many charts they coincide or are almost coincident, but they are explicitly labeled—always read the legend.

Final Answer:
Agree