Work out mixing air streams instantly with clear inputs, formula shown and shareable results.
When two air streams merge, the mixed temperature is the flow-weighted average of the two. The outdoor air fraction that results is the quantity ventilation standards regulate, and the sensible penalty it imposes on the coil is 1.08 x outdoor CFM x the temperature gap it has to be pulled across.
Mixed condition
T mix = (Q1 T1 + Q2 T2) / (Q1 + Q2)
Outdoor air penalty
BTU/h = 1.08 x outdoor CFM x (outdoor T - return T)
T mix = (Q1 T1 + Q2 T2) / (Q1 + Q2). When two air streams merge, the mixed temperature is the flow-weighted average of the two.
Yes. Humidity ratio and enthalpy mix by the identical flow-weighted average, which is why the mixed point lies on the straight line joining the two states on a psychrometric chart.
This calculator takes 4 inputs: Return air flow, Return air temperature, Outdoor air flow, Outdoor air temperature. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.