An energy recovery wheel calculator is an invaluable tool for professionals in the heating, ventilation, and air conditioning (HVAC) industry. This calculator helps determine how efficiently an energy recovery wheel can transfer heat and moisture between incoming and outgoing air streams in building ventilation systems. Its use is crucial in designing systems that optimize energy usage while maintaining indoor air quality and comfort.
Purpose and Functionality
The main function of an energy recovery wheel is to conserve energy by recovering heat and moisture from the exhaust air in a building and using it to treat incoming fresh air. The calculator uses specific inputs related to air properties and system efficiency to predict how much energy can be saved through this process. These predictions are vital for HVAC system designers to ensure systems are both efficient and effective.
Key Inputs and Formulas
To understand the calculator’s workings, it’s important to know the inputs and the corresponding formulas used:
- Airflow Rate (Q): This measures the volume of air being processed, crucial for determining the potential amount of energy to be recovered.
- Inlet and Outlet Air Temperatures (T_in and T_out): These temperatures help calculate the heat that can be recovered or needs to be added.
- Inlet and Outlet Air Humidity Ratios (ω_in and ω_out): These ratios are used to compute the moisture exchange necessary for maintaining desired humidity levels.
- Wheel Efficiency (η): This percentage reflects how effectively the wheel transfers heat and moisture.
Formulas Used:
- Heat Recovery: \text{Heat Recovered (Q_h)} = 1.08 \times Q \times (T_{\text{out}} – T_{\text{in}}) \times \eta
- Humidity Recovery: \text{Moisture Recovered (Q_w)} = Q \times (ω_{\text{out}} – ω_{\text{in}}) \times \eta
- Total Energy Recovery: Total Energy Recovery=Q×(hout−hin)×η\text{Total Energy Recovery} = Q \times (\text{h}_{\text{out}} – \text{h}_{\text{in}}) \times \etaTotal Energy Recovery=Q×(hout−hin)×η
Step-by-Step Example
Let’s calculate using an example:
- Inputs:
- Airflow Rate: 3000 CFM
- Inlet Air Temperature: 32°F
- Outlet Air Temperature: 50°F
- Inlet Humidity Ratio: 0.005 g/kg
- Outlet Humidity Ratio: 0.007 g/kg
- Wheel Efficiency: 70%
- Calculations:
- Heat Recovered: Qh=1.08×3000×(50−32)×0.70=35,064 BTU/hQ_h = 1.08 \times 3000 \times (50 – 32) \times 0.70 = 35,064 \text{ BTU/h}Qh=1.08×3000×(50−32)×0.70=35,064 BTU/h
- Moisture Recovered: Qw=3000×(0.007−0.005)×0.70=4.2 pounds of water per hourQ_w = 3000 \times (0.007 – 0.005) \times 0.70 = 4.2 \text{ pounds of water per hour}Qw=3000×(0.007−0.005)×0.70=4.2 pounds of water per hour
- Total Energy Recovery:
- Assume enthalpy values from tables based on temperature and humidity.
Relevant Information Table
| Input | Unit | Example Value |
|---|---|---|
| Airflow Rate | CFM | 3000 |
| Inlet Air Temperature | °F | 32 |
| Outlet Air Temperature | °F | 50 |
| Inlet Air Humidity Ratio | g/kg | 0.005 |
| Outlet Air Humidity Ratio | g/kg | 0.007 |
| Wheel Efficiency | % | 70 |
Conclusion
The energy recovery wheel calculator is a critical tool for maximizing energy efficiency in HVAC systems. By calculating potential energy savings, it helps designers create systems that not only save costs but also contribute to environmental sustainability. Utilizing this calculator ensures that buildings are equipped with the best possible air handling systems, tailored to their specific needs and local climate conditions. This not only optimizes energy use but also enhances the comfort and health of building occupants.