📍 Location & Design Conditions

⏱️ Transient Load Simulation

Evaluate dynamic cooling/heating demands across a 24-hour cycle. Upload weather data to override Initial State (P0).
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Psychrometric Processes

Initial State (Point 0)

Calculated State Points

PtDescriptionT db (°C)T wb (°C)T dp (°C)RH (%)W (g/kg)H (kJ/kg)v (m³/kg)Flow (m³/h)

Calculated Process Changes & Power

ProcessTypeΔ T (°C)Δ W (g/kg)Δ H (kJ/kg)Power (kW)SHF
Add a process step to see changes.

User Guide: How to Use the Calculator

This psychrometric calculator is designed to provide rapid, high-precision thermodynamic state points and process evaluations for HVAC engineering.

1. Setting the Initial State (Point 0)

Begin by defining your primary airstream in the Initial State panel. You can manually input the Dry-Bulb Temperature and Relative Humidity (or toggle the dropdowns to input Wet-Bulb, Dew Point, or Enthalpy). Specify the System Air Flow to calculate total power requirements.

2. Adding Psychrometric Processes

Click + Add Process Step to simulate conditioning coils, mixing boxes, or heat recovery units. Select the process type from the dropdown:

  • Cooling/Heating Coils: Define the target off-coil temperature. The tool will calculate the sensible and latent load, total power (kW), and condensation rates.
  • Mixing Box: Input the secondary airstream parameters and volume. The calculator will determine the final mixed air state based on mass and energy conservation.

3. Transient Load Simulation

To evaluate system performance over a full day, use the Transient Load Simulation tool. Download the CSV template, populate it with 24 hours of local weather data, and upload it. The simulation will override your Initial State point hour-by-hour, generating a comprehensive table of dynamic cooling and heating demands.

Thermodynamic Theory & Core Principles

Psychrometry is the scientific study of the physical and thermodynamic properties of gas-vapor mixtures—most commonly, atmospheric air and water vapor. Understanding these properties is critical for designing efficient mechanical ventilation, sizing cooling coils, and ensuring occupant comfort.

Key Psychrometric Variables

  • Dry-Bulb Temperature (DBT): The ambient air temperature measured by a standard thermometer, unaffected by the moisture content of the air.
  • Wet-Bulb Temperature (WBT): The lowest temperature that can be reached by the evaporation of water. The difference between DBT and WBT indicates the air's potential to absorb more moisture.
  • Relative Humidity (RH): The ratio of the current moisture in the air to the maximum amount of moisture the air could hold at that specific temperature, expressed as a percentage.
  • Humidity Ratio (W): The actual mass of water vapor present per unit mass of dry air (typically measured in grams of moisture per kilogram of dry air).
  • Enthalpy (H): The total heat energy content of the moist air mixture, encompassing both sensible heat (temperature) and latent heat (moisture).

Calculation Methodology

The algorithms powering this tool are built upon universally accepted, relevant industry standards for thermodynamic formulations. The calculations account for the non-linear relationship between saturation vapor pressure and temperature, allowing for accurate plotting of specific volume curves, enthalpy lines, and saturation boundaries without the need for manual chart interpolation. By utilizing standard barometric pressure baselines, the tool ensures reliable state point extraction for commercial equipment sizing and energy auditing.