A Mixed Air Temperature (MAT) Calculator is a useful tool for HVAC (heating, ventilation, and air conditioning) professionals and enthusiasts. It helps determine the temperature of air when two different air streams mix together. This is particularly important in managing indoor climate and ensuring efficient energy use.
Inputs
- Temperature of Outside Air (OA): The temperature of the air outside the building, measured in either Fahrenheit (°F) or Celsius (°C).
- Temperature of Return Air (RA): The temperature of the air returning from the indoor space, also measured in Fahrenheit (°F) or Celsius (°C).
- Percentage of Outside Air (%OA): The proportion of outside air in the mixed air, expressed as a percentage.
Formula: The Mixed Air Temperature (MAT) is calculated using the following formula: MAT=(OA temperature×%OA)+(RA temperature×(1−%OA))\text{MAT} = (\text{OA temperature} \times \% \text{OA}) + (\text{RA temperature} \times (1 – \% \text{OA}))MAT=(OA temperature×%OA)+(RA temperature×(1−%OA))
Calculation Steps:
- Multiply the Outside Air temperature by the Percentage of Outside Air (OA×%OA\text{OA} \times \% \text{OA}OA×%OA).
- Multiply the Return Air temperature by the complement of the Percentage of Outside Air ((1−%OA)×RA(1 – \% \text{OA}) \times \text{RA}(1−%OA)×RA).
- Add the results of steps 1 and 2 to get the Mixed Air Temperature (MAT).
Step-by-Step Examples
Let’s go through a practical example to see how the MAT Calculator works.
Example 1:
- OA temperature: 80°F
- RA temperature: 70°F
- %OA: 20%
Calculation:
- Multiply the Outside Air temperature by the Percentage of Outside Air: 80°F×0.20=16°F80°F \times 0.20 = 16°F80°F×0.20=16°F
- Multiply the Return Air temperature by the complement of the Percentage of Outside Air: 70°F×0.80=56°F70°F \times 0.80 = 56°F70°F×0.80=56°F
- Add the results of step 1 and step 2: 16°F+56°F=72°F16°F + 56°F = 72°F16°F+56°F=72°F
So, the Mixed Air Temperature (MAT) would be 72°F in this example.
Example 2:
- OA temperature: 90°F
- RA temperature: 75°F
- %OA: 30%
Calculation:
- Multiply the Outside Air temperature by the Percentage of Outside Air: 90°F×0.30=27°F90°F \times 0.30 = 27°F90°F×0.30=27°F
- Multiply the Return Air temperature by the complement of the Percentage of Outside Air: 75°F×0.70=52.5°F75°F \times 0.70 = 52.5°F75°F×0.70=52.5°F
- Add the results of step 1 and step 2: 27°F+52.5°F=79.5°F27°F + 52.5°F = 79.5°F27°F+52.5°F=79.5°F
So, the Mixed Air Temperature (MAT) would be 79.5°F in this example.
Relevant Information Table
Here is a table summarizing the relevant data for these examples:
| OA Temperature (°F) | RA Temperature (°F) | %OA | MAT (°F) |
|---|---|---|---|
| 80 | 70 | 20% | 72 |
| 90 | 75 | 30% | 79.5 |
Conclusion: Benefits and Applications of the Calculator
The Mixed Air Temperature Calculator is a valuable tool for anyone involved in HVAC systems. It simplifies the process of calculating the temperature of mixed air, which is crucial for maintaining a comfortable and energy-efficient indoor environment. By accurately determining the MAT, HVAC professionals can ensure optimal performance of heating and cooling systems, leading to better climate control and energy savings. This calculator is easy to use, providing quick and reliable results, making it an essential tool for efficient building management.