Mixed Air Temperature Guide
A mixed air temperature calculator helps estimate the final temperature after two or more air streams combine. It is useful for ventilation checks, economizer review, and simple energy planning. The method uses weighted averages. Each stream contributes by flow, density, and heat capacity. When these properties are similar, airflow weights usually give a close field estimate.
Why mixed air matters
Heating and cooling equipment rarely handles one pure air source. Most systems blend outdoor air with return air before conditioning. A wrong mixed temperature can cause coil sizing errors. It can also hide damper faults or excess leakage. This calculator makes those effects visible. You can compare outdoor, return, and leakage streams in one view.
What inputs mean
Temperature is the measured air temperature for each stream. Airflow describes how much air enters the mixing box. Density lets the tool account for altitude, pressure, or different operating assumptions. Specific heat adjusts the heat carried by each kilogram of air. The optional adjustment adds fan heat rise, sensor correction, or another known change after mixing.
Formula context
The main calculation is a heat balance. Each stream has a heat weight equal to airflow times density times specific heat. The final temperature is the sum of weighted temperatures divided by the sum of all heat weights. This approach works best when air is well mixed. It also assumes no moisture condensation or heat loss through duct walls.
Practical use
Measure airflow from reliable test data when possible. Use the same airflow unit for all entries. Enter leakage flow only when a third stream is known. Leave it at zero otherwise. Check the outdoor air fraction after calculation. It shows whether the blend matches the design target. Export the result when you need a quick record for reports or service notes.
Accuracy tips
Field sensors should be stable before recording values. Place probes away from stratified spots. Very large humidity differences may require a psychrometric calculation. For normal dry bulb checks, this calculator gives a fast and transparent estimate. Review the example table before starting. It shows typical values and expected trends for common mixed air cases. Save every run to support checks, audits, and repeat comparisons later clearly.