The Mixed Air Calculator is a tool designed to simplify the complex process of determining the temperature and specific humidity of air resulting from the mixture of two different air streams. This kind of calculation is crucial in Heating, Ventilation, and Air Conditioning (HVAC) applications, especially for engineers and technicians who work on optimizing indoor air quality and climate control. The calculator uses specific formulas to compute the final properties of mixed air, assuming an adiabatic process—meaning no heat is lost or gained during the mixing.
Purpose and Functionality
The primary purpose of the Mixed Air Calculator is to calculate the temperature and specific humidity of air that results from combining two distinct air streams. This situation is common in HVAC systems where outside air is mixed with recirculated indoor air to maintain indoor air quality and comfort levels. By inputting the temperature, specific humidity, and mass flow rate of each air stream, the calculator provides accurate and quick results. This not only saves time but also ensures precision in calculations that are critical for designing and optimizing HVAC systems.
Formulas Used in the Mixed Air Calculator
The calculator uses two main formulas:
- Mixed Air Temperature Formula:(1⋅1)+(2⋅2)1+2Tm=m1+m2(m1⋅T1)+(m2⋅T2)This formula calculates the temperature (Tm) of the mixed air based on the mass flow rates (1,2m1,m2) and temperatures (1,2T1,T2) of the two air streams.
- Mixed Air Specific Humidity Formula:(1⋅1)+(2⋅2)1+2wm=m1+m2(m1⋅w1)+(m2⋅w2)This formula calculates the specific humidity (wm) of the mixed air by considering the mass flow rates and specific humidities (1,2w1,w2) of both air streams.
Step-by-Step Examples
Let’s go through an example to understand how the calculator works:
Example 1:
- Air Stream 1: Mass flow rate = 2 kg/s, Temperature = 20°C, Specific Humidity = 0.008 kg/kg
- Air Stream 2: Mass flow rate = 3 kg/s, Temperature = 30°C, Specific Humidity = 0.010 kg/kg
Calculations:
- Mixed Air Temperature (Tm): (2⋅20)+(3⋅30)/(2+3)=28°(2⋅20)+(3⋅30)/(2+3)=28°C
- Mixed Air Specific Humidity (wm): (2⋅0.008)+(3⋅0.010)/(2+3)=0.0096(2⋅0.008)+(3⋅0.010)/(2+3)=0.0096kg/kg
Relevant Information Table
| Input Parameters | Air Stream 1 | Air Stream 2 |
|---|---|---|
| Mass Flow Rate (kg/s) | 2 | 3 |
| Temperature (°C) | 20 | 30 |
| Specific Humidity (kg/kg) | 0.008 | 0.010 |
| Output Parameters | Value |
|---|---|
| Mixed Air Temperature (°C) | 28 |
| Mixed Air Specific Humidity (kg/kg) | 0.0096 |
Conclusion
The Mixed Air Calculator offers a straightforward and efficient method for HVAC professionals to determine the properties of air resulting from the mixing of two different streams. Its ability to provide quick and accurate calculations not only facilitates better design and optimization of HVAC systems but also helps in ensuring the comfort and safety of indoor environments. By automating the calculation process, it eliminates errors associated with manual computations, making it an indispensable tool in the HVAC industry.