1. What is CFM?

CFM (Cubic Feet per Minute) is a measurement of airflow volume, indicating how much air flows through a space in one minute. It's commonly used in HVAC systems to measure air flow rates.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

Where:

• \( Q \) — Heat flow rate (BTU/h)
• \( \Delta T \) — Temperature difference (°F)
• \( 1.08 \) — Constant factor

Explanation: The equation calculates the required airflow (in cubic feet per minute) needed to achieve a certain heat transfer given the temperature difference.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for proper HVAC system design, ensuring adequate ventilation, and maintaining desired temperature conditions in a space.

4. Using the Calculator

Tips: Enter heat flow rate in BTU/h and temperature difference in °F. All values must be valid (greater than 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the 1.08 constant in the formula?
A: The 1.08 constant comes from the product of air's specific heat (0.24 BTU/lb-°F) and density (0.075 lb/ft³), multiplied by 60 minutes/hour.

Q2: What are typical CFM values for residential HVAC?
A: Typical residential systems range from 400-2000 CFM, depending on the size of the home and system capacity.

Q3: How does CFM relate to air velocity?
A: Air velocity (in feet per minute) can be calculated by dividing CFM by the cross-sectional area of the duct (in square feet).

Q4: Why is CFM important in HVAC design?
A: Proper CFM ensures adequate air circulation for both comfort and equipment efficiency, preventing issues like hot/cold spots or excessive energy use.

Q5: Can this formula be used for any air temperature?
A: The formula works best for standard air conditions (around 70°F at sea level). Significant variations in temperature or altitude may require adjustments.