Air Stream Mixing Calculator
Mixed-air temperature and moisture when return and outdoor air streams combine.
Mixing is a straight line on the psych chart — the mixed point divides it in the flow ratio. The basis of every AHU mixing-box control loop.
Formula
Air Stream Mixing Calculator is a free mixed air temperature for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Air Stream Mixing Calculator
Mixed-air temperature and moisture when return and outdoor air streams combine. The calculation implements T_mix = ΣQᵢTᵢ/ΣQ; w_mix = ΣQᵢwᵢ/ΣQ (mass-flow weighted) (ASHRAE Fundamentals, ch. 1). Mixing is a straight line on the psych chart — the mixed point divides it in the flow ratio. The basis of every AHU mixing-box control loop.
How to use Air Stream Mixing Calculator
- 1Enter Stream 1 (return) flow in L/s.
- 2Enter Stream 1 temperature in °C.
- 3Enter Stream 1 humidity ratio in g/kg.
- 4Enter Stream 2 (outdoor) flow in L/s.
- 5Read Mixed temperature, Mixed humidity ratio, Outdoor-air fraction instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Air Stream Mixing Calculator?
- ✓Implements the standard formula — T_mix = ΣQᵢTᵢ/ΣQ; w_mix = ΣQᵢwᵢ/ΣQ (mass-flow weighted)
- ✓Reference cited on-page: ASHRAE Fundamentals, ch. 1
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Air Stream Mixing Calculator use?+
It computes T_mix = ΣQᵢTᵢ/ΣQ; w_mix = ΣQᵢwᵢ/ΣQ (mass-flow weighted), per ASHRAE Fundamentals, ch. 1. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
Mixing is a straight line on the psych chart — the mixed point divides it in the flow ratio. The basis of every AHU mixing-box control loop.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the Air Stream Mixing Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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