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Moist-Air Mixing Calculator — result sheet
Estimate the mixed dry-bulb temperature, humidity ratio, enthalpy, and relative humidity for two adiabatically mixed air streams.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: For each stream, pws(T) uses a Magnus saturation-pressure approximation, W=0.62198Pv/(P−Pv), and h=1.006T+W(2501+1.86T). The mixed W and h are dry-air-flow-weighted, and T is recovered from h and W.
Two moist-air streams mix along a psychrometric line when the process is steady and adiabatic. This implementation keeps dry-air flow, humidity ratio, and enthalpy explicit instead of averaging relative humidity directly. The saturation-pressure relation is a bounded educational approximation, so the result is a screening calculation rather than a full psychrometric design program.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Stream 1 dry-air mass flow — kg/s; minimum 1.0E-6; maximum 1000000
- Stream 1 dry-bulb temperature — °C; minimum -40; maximum 80
- Stream 1 relative humidity — %; minimum 0; maximum 100
- Stream 2 dry-air mass flow — kg/s; minimum 1.0E-6; maximum 1000000
- Stream 2 dry-bulb temperature — °C; minimum -40; maximum 80
- Stream 2 relative humidity — %; minimum 0; maximum 100
- Total pressure — kPa; minimum 60; maximum 120
Worked example
| Input | Value |
|---|---|
| Stream 1 dry-air mass flow | 1.2 |
| Stream 1 dry-bulb temperature | 24 |
| Stream 1 relative humidity | 50 |
| Stream 2 dry-air mass flow | 0.8 |
| Stream 2 dry-bulb temperature | 12 |
| Stream 2 relative humidity | 70 |
| Total pressure | 101.325 |
The two streams produce a mixed state near 19.20 °C; the page also reports the resulting humidity ratio, enthalpy, and relative humidity from the stated approximation.
Assumptions and limits
- The two flow inputs are dry-air mass flows on the same basis and both streams share the entered pressure.
- Mixing is steady, adiabatic, and complete with no coil, fan heat, condensate, or injected steam.
- Humidity ratio and enthalpy are calculated with a Magnus saturation-pressure approximation and standard moist-air constants.
- Temperature, pressure, and relative-humidity bounds keep the approximation inside a practical classroom/HVAC range.
- The calculator does not size equipment, approve ventilation, predict condensation risk in a real duct, or replace an ASHRAE psychrometric analysis.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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