Practical Engineering Software
Psychrometrics
LITE BETA
Project Information
Client project identifier
Drawing or doc ref
Responsible engineer
Site or city
Search a city; sets altitude (sea level default). Override below for exact project altitude.
Actual installed altitude — overrides preset. ISO 2533 Patm correction.
P_atm (kPa)Calculated from altitude
101.325
RemarksOptional — duty notes, design basis, assumptions
Any-Two-Property Calculator
Select first known property
Numeric value for property 1
Controls chart shape & colour
Select second known property
Numeric value for property 2
Short identifier for chart
Optional airflow at this point — used to size process capacity (kW)
Interactive Psychrometric Chart
Compute a Process

Pick a process type and enter conditions to compute a stage. Each computed stage creates its state points, adds to the chain below, plots on the chart, and lights up the schematic. To link points you already have, use Manual Connections below.

12 psychrometric processes
System design airflow rate
Process Chain Summary
#ProcessAirflow L/skg/sEnter DB °CLeave DB °CEnter h kJ/kgLeave h kJ/kgEnter W g/kgLeave W g/kgQ_s kWQ_l kWQ_t kWTR
Saved State Points
#LabelSourceTypeDB °CWB °CRH %W g/kgh kJ/kgv m³/kgFlow L/s
No state points saved yet.
Manual Chart Connections

Link any two saved points into a process. Pick From and To and a process type below; the connection draws on the chart and its Δh and capacity appear in the table. Processes computed in Build Cycle auto-connect — add manual links here for points the calculator didn't chain.

FromToTypeΔh kJ/kgCapacity kW
AHU Cycle Schematic — Once Return

Run a process to generate schematic.

Save points and run processes to generate report.

Point Type Legend

Select a point type below — each gives the point a unique shape and colour on the chart. Process calculators auto-assign types; you can override here.

Room
Indoor design condition. SHR protractor anchors here.
Outside Air
Outdoor design DB/WB from ASHRAE or local code.
Mixed
Result of mixing OA + Return air streams.
On-Coil
Air entering a cooling or heating coil.
Off-Coil
Air leaving a cooling coil (typically 12–14°C, 90–95% RH).
Supply
Final conditioned air delivered to the room.
ADP
Apparatus Dew Point — condition line meets saturation curve.
Return
Air returning from conditioned space (≈ Room condition).
Exhaust
Air discharged outdoors. Used in ERV calculations.
Preheat
Air after preheat coil, before main cooling.
Reheat
After reheat coil — raises DB post-overcooling for humidity control.
ERV-SA
Supply-side air leaving the energy recovery wheel.
ERV-EA
Exhaust-side air leaving the energy recovery wheel.
Humidifier
Air leaving spray or steam humidification stage.
Dehumidifier
Air leaving desiccant or chemical dehumidification.
Custom
Any arbitrary reference or comparison marker.