1. What is the AHU CFM Calculation Formula?

The AHU (Air Handling Unit) CFM calculation formula determines the airflow rate in cubic feet per minute required for cooling applications. This formula is essential for HVAC system design and sizing.

2. How Does the Calculator Work?

The calculator uses the AHU CFM formula:

Where:

• \( CFM \) — Airflow in cubic feet per minute
• \( BTU/hr \) — British Thermal Units per hour
• \( \Delta T \) — Temperature difference in degrees Fahrenheit
• \( 1.08 \) — Constant factor for air properties

Explanation: The formula calculates the airflow needed to remove heat based on the cooling load (BTU/hr) and the temperature difference across the cooling coil.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for proper HVAC system design, ensuring adequate cooling capacity, energy efficiency, and occupant comfort in buildings.

4. Using the Calculator

Tips: Enter BTU/hr (cooling load) and ΔT (temperature difference) in the appropriate units. Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What does the constant 1.08 represent?
A: The constant 1.08 accounts for the specific heat of air (0.24 BTU/lb·°F) and air density (0.075 lb/ft³) at standard conditions.

Q2: What is a typical ΔT for AHU systems?
A: Typical ΔT values range from 15°F to 25°F for standard comfort cooling applications, depending on system design and climate.

Q3: How does CFM relate to tonnage?
A: One ton of cooling equals 12,000 BTU/hr. For a typical ΔT of 20°F, this would require approximately 400 CFM (1.08 × 12,000 ÷ 20).

Q4: When is this formula most applicable?
A: This formula is most accurate for standard air conditioning applications with sensible cooling loads at sea level conditions.

Q5: What factors can affect CFM requirements?
A: Altitude, humidity levels, air density variations, and specific application requirements can all affect actual CFM needs.