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BTU to GPM Formula:
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The BTU to GPM formula calculates the flow rate (gallons per minute) required to transfer a specific heating load (BTU per hour) with a given temperature difference for water systems. This is essential for HVAC and plumbing system design.
The calculator uses the BTU to GPM formula:
Where:
Explanation: The formula converts heating capacity to water flow rate, considering that 1 pound of water requires 1 BTU to raise its temperature by 1°F, and 1 gallon of water weighs approximately 8.33 pounds.
Details: Accurate flow rate calculation is crucial for proper sizing of pumps, pipes, and heat exchangers in heating and cooling systems. It ensures efficient heat transfer and prevents system inefficiencies.
Tips: Enter BTU/hr (heating load) and ΔT (temperature difference) in positive values. The calculator provides the required flow rate in gallons per minute for water-based systems.
Q1: What does the constant 500 represent?
A: The constant 500 comes from water's specific heat (1 BTU/lb-°F) multiplied by water's density (8.33 lb/gal) and conversion factor (60 min/hr): 8.33 × 60 ≈ 500.
Q2: Can this formula be used for other fluids?
A: No, this specific formula is designed for water. Other fluids require different constants based on their specific heat and density properties.
Q3: What is a typical ΔT for HVAC systems?
A: Typical ΔT values range from 10°F to 20°F for chilled water systems and 20°F to 40°F for heating water systems, depending on system design.
Q4: How accurate is this calculation?
A: The calculation is accurate for water systems under standard conditions. For precise engineering applications, additional factors like pipe friction and elevation changes should be considered.
Q5: What if I need to calculate BTU/hr from GPM?
A: You can rearrange the formula: BTU/hr = GPM × ΔT × 500. This calculates the heating capacity from flow rate and temperature difference.