Psychrometric chart plotter

This app lets you plot air conditions on a psychrometric chart and instantly see values such as temperature, humidity, and enthalpy. It's free to use, and useful both for HVAC design work and for learning.

Free features

・Plot an air state point on the psychrometric chart from two inputs: temperature and relative humidity, or temperature and dew point.

・For each plotted point, view temperature [°C], relative humidity [%RH], absolute humidity [kg/kg-DA], dew point temperature [°C], and specific enthalpy [kJ/kg-DA] together.

・Plot up to 9 points (A-I) on the chart at the same time, and show or hide each point individually. Handy when comparing several air conditions side by side.

・Save plotted points under a name and reload them later. Keep multiple cases saved so you can come back and compare them.

・A built-in Compare feature lets you view saved points in a table, including the difference between two points (such as enthalpy difference), useful for rough heat-load estimates.

・Switch between SI units and imperial units (°F, gr/lb, etc.).

・Switch to a chart range designed for sub-zero, low-temperature conditions (with a logarithmic humidity axis). This helps in cold-climate cases where points would otherwise be squeezed against the edge of a standard chart.

・This is a free app supported by ads (the Pro features described below are paid).

Pro features (paid)

The two features below are Pro (paid) features. They're available via monthly/yearly subscription, a one-time lifetime purchase, or a 3-day pass. Ads are removed once purchased.

1) AHU Process Design

Starting from a single air condition (such as an outdoor air condition), simulate the process through an actual air handling unit (AHU): preheater, steam humidifier, air washer, cooling coil, and reheater, in sequence, calculating the air state at each unit's outlet and visualizing it on the psychrometric chart. You can set target conditions (setpoints) and tolerance ranges for each unit, letting you quickly check a process design close to real control logic. You can also compare two conditions side by side.

2) Annual HVAC Simulation

Choose a location from the bundled city database or your current GPS location, then fetch a full year of real hourly weather data (8,760 hours, from NASA POWER's public dataset) for that location. Specify the air to be treated (outdoor air only, or a mix of outdoor and return air) and your target indoor conditions (setpoints, which can be prioritized and set for multiple cases). The app automatically determines, hour by hour, whether heating, cooling and dehumidification, humidification, or no treatment is required, and tallies the annual energy consumption (cooling electricity, heating, reheat, and humidification separately) based on equipment COP. Results can be viewed as a psychrometric chart plot color-coded by month, and can also be saved to your device and shared as a CSV file. In addition to SI units, imperial units such as CFM, Btu/h, refrigeration tons, and lb/h are supported.

Languages and more

The app supports 32 languages, including English and Japanese. Core features useful in HVAC and environmental engineering - switching between imperial and SI units, and viewing temperature, humidity, dew point, and specific enthalpy - are all free. For more advanced work, try the Pro features above.

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