Btu/hr To Cfm Calculator

CFM Formula:

\[ CFM = \frac{BTU/h \times 1.08}{\Delta T} \]

Airflow (CFM):

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1. What is the BTU/hr to CFM Formula?

The BTU/hr to CFM formula calculates the required airflow (in cubic feet per minute) needed to transfer a specific heating load (in British thermal units per hour) given a temperature difference. This is essential for HVAC system design and sizing.

2. How Does the Calculator Work?

The calculator uses the airflow formula:

\[ CFM = \frac{BTU/h \times 1.08}{\Delta T} \]

Where:

\( CFM \) — Cubic feet per minute (airflow)
\( BTU/h \) — British thermal units per hour (heating load)
\( \Delta T \) — Temperature difference in degrees Fahrenheit
\( 1.08 \) — Constant factor derived from air properties

Explanation: 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, converted to hourly basis.

3. Importance of Airflow Calculation

Details: Proper airflow calculation is crucial for designing efficient HVAC systems, ensuring adequate heating/cooling capacity, maintaining indoor air quality, and optimizing energy consumption in residential and commercial buildings.

4. Using the Calculator

Tips: Enter heating load in BTU/h and temperature difference in °F. Both values must be positive numbers. The temperature difference is typically the difference between supply and return air temperatures.

5. Frequently Asked Questions (FAQ)

Q1: What does the constant 1.08 represent?
A: The constant 1.08 combines the specific heat of air (0.24 BTU/lb·°F) and standard air density (0.075 lb/ft³), multiplied by 60 minutes: 0.24 × 0.075 × 60 = 1.08.

Q2: When is this calculation typically used?
A: This calculation is commonly used in HVAC design for sizing ductwork, selecting fans, and determining airflow requirements for heating systems.

Q3: What is a typical temperature difference for heating systems?
A: For forced air heating systems, typical temperature differences range from 30°F to 70°F, depending on the system type and design.

Q4: Can this formula be used for cooling calculations?
A: Yes, the same formula applies for sensible cooling loads, though the temperature difference would be reversed (cooler supply air).

Q5: What factors affect the accuracy of this calculation?
A: Altitude, humidity, air density variations, and non-standard air conditions can affect accuracy. The formula assumes standard air conditions at sea level.