Reading the psychrometric chart Which set of lines on a standard psychrometric chart are vertical and uniformly spaced, and what do they represent?

Introduction / Context:
Correctly interpreting the axes and families of lines on the psychrometric chart is essential for HVAC design and analysis.

Given Data / Assumptions:

• Standard ASHRAE-style psychrometric chart for moist air.
• Horizontal axis is dry-bulb temperature T_db.
• Vertical axis is humidity ratio w (kg water/kg dry air).

Concept / Approach:
Lines of constant dry-bulb temperature are vertical because the x-axis is T_db. These are typically uniformly spaced to scale temperature directly. Other property lines (relative humidity, wet-bulb, enthalpy) are inclined or curved.

Step-by-Step Solution:
Identify axes: T_db on the x-axis, w on the y-axis.Therefore, a constant T_db corresponds to a vertical line.Uniform spacing reflects the linear temperature scale used.

Verification / Alternative check:
Compare with chart legends: isohumes (constant w) are horizontal; relative humidity curves are curved lines; wet-bulb lines are diagonally inclined.

Why Other Options Are Wrong:
Wet-bulb and relative humidity are not vertical; dew point is read at saturation for a given w and aligns horizontally with constant humidity ratio.

Common Pitfalls:
Confusing constant wet-bulb (slanted) with constant enthalpy lines; they are nearly but not exactly coincident in some ranges.

Final Answer:
Vertical, uniformly spaced lines represent dry-bulb temperature.