1. What is an Air Handling Unit Calculator?

Definition: This calculator determines the required air flow (CFM) for an air handling unit based on cooling load and temperature difference.

Purpose: It helps HVAC professionals and engineers properly size air handling systems for buildings and spaces.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q_{cfm} \) — Air flow (cubic feet per minute)
• \( Q_{btu} \) — Cooling load (BTU per hour)
• \( \Delta T \) — Temperature difference (°F)
• 1.08 — Constant for air at standard conditions

Explanation: The formula converts cooling capacity to required air flow based on the temperature difference between supply and return air.

3. Importance of Air Flow Calculation

Details: Proper air flow calculation ensures efficient HVAC operation, adequate cooling capacity, and proper air distribution throughout the space.

4. Using the Calculator

Tips: Enter the cooling load in BTU/h and the desired temperature difference (typically 15-25°F for comfort cooling). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the 1.08 constant in the formula?
A: It's derived from the specific heat of air (0.24 BTU/lb-°F) and standard air density (0.075 lb/ft³), converted to minutes: 0.24 × 0.075 × 60 = 1.08.

Q2: What's a typical temperature difference for comfort cooling?
A: Most comfort cooling systems use ΔT of 15-25°F, with 20°F being a common design value.

Q3: How do I find the cooling load for my space?
A: Use a Manual J calculation or cooling load estimation tool to determine the BTU/h requirement for your space.

Q4: Does this account for humidity control?
A: This basic calculation doesn't account for latent load (humidity). For precise calculations, consider both sensible and latent heat ratios.

Q5: What if my air density isn't standard?
A: For high-altitude or non-standard conditions, adjust the 1.08 constant based on actual air density.