How to Reading a Psychrometric Chart

How to Reading a Psychrometric Chart, this simulation shows to read a psychrometric chart. Click and drag the black dot to adjust the properties of ai

This simulation shows to read a psychrometric chart (also known as a humidity chart). Click and drag the black dot to adjust the properties of air. Unchecking the "relative humidity" (green) box removes the labels for the relative-humidity lines. Check the boxes for "enthalpy" (blue) and "specific volume" (purple) to display lines of constant enthalpy and constant volume, respectively. Check the box for "temperatures" to display dashed black lines that point to dry-bulb, wet-bulb and dew point temperatures that correspond to those values at the black dot. When the "temperatures" box is checked, move the mouse over each dashed line to identify which temperature it corresponds to. All temperatures are read on the axis. Check "display values" to see a table of the values obtained from the chart for the selected point; only the moisture content and the values whose boxes are checked are displayed. The values per kg are per kg of dry air.


Relative humidity is defined by:

where is the Pw partial pressure of the water and is Psatw the saturation pressure of water (bar). The saturation pressure is calculated from the Antoine equation:

where A, B and C are Antoine constants and T is temperature (°C).

• [accordion]
• 1. Fundamentals of psychrometrics
• 2. Applied Thermodynamics Software Solutions Psychrometrics Reactive systems
• 3. Understanding psychrometrics American Society of Heating
• 4. Handbook of Psychrometric Charts Humidity diagrams for engineers