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TECHNICAL TOOL / 02

Moist-air property converter

Convert one measured air state into the moisture quantities commonly used in HVAC, process, enclosure, and dehumidification work—without treating unlike units as interchangeable.

INPUTS

Pressure basis

Water-vapour density (g/m³), humidity ratio (g/kg dry air), and specific humidity (g/kg moist air) are different quantities. Humidity ratio, specific humidity, and enthalpy depend on total pressure.

CALCULATED RESULTS

Water-vapour density (absolute humidity)
—
Humidity ratio
—
Specific humidity
—
Dew / frost point
—
Water-vapour partial pressure
—
Moist-air enthalpy
—
Pressure used
—

METHOD AND BOUNDARY

Pressure is part of the conversion

Use measured local barometric pressure when available. The altitude option estimates standard-atmosphere pressure and is not a substitute for a site pressure measurement during unusual weather or pressurised operation.

Engineering range

The equations use the perfect-gas moist-air relations normally applied near atmospheric pressure. This release accepts 10–200 kPa and does not cover high-pressure process gases or non-air mixtures.

Calculation reference: ASHRAE Handbook—Fundamentals, Chapter 1 ↗ · PsychroLib API ↗

OTHER TECHNICAL TOOLS

Continue with another calculation

TECHNICAL TOOL / 01 Dew-point calculator → TECHNICAL TOOL / 03 Surface condensation risk check →

PROJECT REVIEW

A calculator defines a condition. Equipment selection needs the full operating context.

For a project review, include the enclosure or room, temperature and humidity range, target, moisture source, airflow, power, drainage, controls, quantity, and operating cycle.

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