In 2025, smartphone apps like Akton or CoolSelector do instant calculations. So why learn manual plotting?
(Answers at the end of this article.)
(e.g., winter comfort)
| Property | What it tells you | How to find on chart | | :--- | :--- | :--- | | | Sensible heat level | Vertical line from bottom | | Wet Bulb (WB) | Potential for evaporative cooling | Diagonal line to saturation | | Dew Point (DP) | Temperature where condensation starts | Horizontal line to 100% RH |
Plot the point on the psychrometric chart where the dry-bulb temperature is 20°C and the humidity ratio is 8 g/kg. Read off the relative humidity, enthalpy, and specific volume from the chart. psychrometric chart tutorial
Here are a few example problems to illustrate the use of the psychrometric chart:
But here’s the truth: It tells you everything about a parcel of air—how hot it is, how wet it is, and how much energy it holds. In 2025, smartphone apps like Akton or CoolSelector
To read the chart effectively, you must first recognize its seven primary components. Each represents a specific thermodynamic property of the air. 1. Dry-Bulb Temperature (DBT) Why Learn Psychrometrics? | ashrae.org
If dew point is high (e.g., >65°F), air feels muggy. If dew point is low (<40°F), air feels dry, even if dry-bulb is 75°F. Read off the relative humidity, enthalpy, and specific
Find the 60% RH curve (it looks like a line bowing to the right). Follow that curve until it crosses the vertical 85° line.
The far-left curved boundary representing 100% relative humidity, where the air can hold no more moisture. 2. Reading the Key Properties