Engineering tools · Free to use

Adiabatic Moist Air Mixing Calculator

Estimate the condensation-free mixed state of two air streams from their states and dry-air mass flow rates.

Inputs

Inputs and calculations stay in this browser.

Mixed state

Dry-bulb temperature— °C

Relative humidity— %

Humidity ratio— g/kg dry air

Specific enthalpy— kJ/kg dry air

Total dry-air mass flow— kg/s

Flow, humidity ratio and enthalpy use a dry-air mass basis.

Method

Apply steady dry-air, water-vapour and enthalpy balances. Calculate temperature from the mixed humidity ratio and enthalpy, then check saturation.

Applicability

Common absolute pressure and steady, adiabatic mixing, without external heat, added moisture, condensation, frost, droplets or significant kinetic-energy changes. Each input must be within −20 to 50 °C and 1–100% relative humidity; pressure must be 50–120 kPa. Either stream flow may be zero, but total flow must be positive. Input and output relative humidity use saturation vapour pressure at each state’s dry-bulb temperature: over ice at or below 0.01 °C and over liquid water above 0.01 °C. Humidity relative to supercooled liquid water cannot be entered directly as an ice-based value; supercooled droplets and frost formation are not simulated.

Software license

Worked example

At a common absolute pressure of 101.325 kPa, mix two streams each carrying 1 kg/s dry air: stream 1 is 25 °C at 50% relative humidity and stream 2 is 10 °C at 50%. For steady adiabatic mixing without condensation, PsychroLib gives approximately 17.542 °C, 54.931% relative humidity, 6.8364 g/kg dry air, 34.968 kJ/kg dry air and 2 kg/s total dry-air flow.

For engineering estimates; check operating conditions and applicable requirements for design.