Results:
Understanding the Mixed Air Calculator
The Mixed Air Calculator is a fundamental tool in HVAC (Heating, Ventilation, and Air Conditioning) systems. It helps engineers and technicians determine the resulting temperature and flow rate when two air streams with different temperatures and flow rates are combined.
How it Works:
The calculation is based on the principle of conservation of energy. When two streams of air mix, the total thermal energy of the combined stream is the sum of the thermal energies of the individual streams. This leads to the following formulas:
- Total Mixed Air Flow Rate: $Q_{total} = Q_1 + Q_2$
- Mixed Air Temperature: $T_{mixed} = \frac{(T_1 \times Q_1) + (T_2 \times Q_2)}{Q_{total}}$
Where:
- $T_1$ is the temperature of the first air stream (°C).
- $Q_1$ is the flow rate of the first air stream (m³/s).
- $T_2$ is the temperature of the second air stream (°C).
- $Q_2$ is the flow rate of the second air stream (m³/s).
- $T_{mixed}$ is the resulting mixed air temperature (°C).
- $Q_{total}$ is the total flow rate of the mixed air (m³/s).
Applications in HVAC:
This calculator is crucial for:
- Ventilation Systems: Determining the temperature of outside air being mixed with recirculated indoor air to maintain comfortable and healthy indoor environments.
- Air Handling Units (AHUs): Calculating the temperature of air entering cooling or heating coils after mixing return and outside air.
- System Balancing: Ensuring that the mixed air conditions meet the design specifications for the building.
Example Calculation:
Let's consider a scenario where an air handling unit mixes return air with fresh outside air:
- Supply Air (e.g., fresh outside air) Temperature ($T_1$): 10 °C
- Supply Air Flow Rate ($Q_1$): 1.2 m³/s
- Return Air Temperature ($T_2$): 24 °C
- Return Air Flow Rate ($Q_2$): 2.5 m³/s
Using the calculator:
- Total Mixed Air Flow Rate ($Q_{total}$) = 1.2 m³/s + 2.5 m³/s = 3.7 m³/s
- Mixed Air Temperature ($T_{mixed}$) = ((10 °C × 1.2 m³/s) + (24 °C × 2.5 m³/s)) / 3.7 m³/s
- $T_{mixed}$ = (12 + 60) / 3.7
- $T_{mixed}$ = 72 / 3.7 ≈ 19.46 °C
The resulting mixed air will have a temperature of approximately 19.46 °C and a total flow rate of 3.7 m³/s, which is essential information for the subsequent stages of the HVAC system.