1. What is a Heating Flow Rate Calculator?

Definition: This calculator determines the flow rate in gallons per minute (GPM) needed for a heating system based on heat transfer rate and temperature difference.

Purpose: It helps HVAC professionals and engineers size pumps and piping systems for heating applications like chilled water systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Flow rate (gallons per minute)
• \( Q_{btu} \) — Heat transfer rate (BTU per hour)
• \( \Delta T \) — Temperature difference (°F)
• 500.4 — Constant combining water properties and unit conversions

Explanation: The heat transfer rate is divided by the product of the temperature difference and the constant 500.4 to determine the required flow rate.

3. Importance of Flow Rate Calculation

Details: Proper flow rate calculation ensures efficient heat transfer, prevents pump oversizing, and maintains system performance while minimizing energy costs.

4. Using the Calculator

Tips: Enter the heat transfer rate in BTU/h and the temperature difference in °F. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the 500.4 constant derived from?
A: It combines the specific heat of water (1 BTU/lb-°F), water density (8.33 lb/gal), and unit conversion (60 min/h).

Q2: Can this be used for cooling systems?
A: Yes, the same formula applies to chilled water systems where heat is being removed rather than added.

Q3: What's a typical ΔT for heating systems?
A: Most systems are designed for 20°F ΔT, but this can range from 10°F to 30°F depending on the application.

Q4: How do I find the heat transfer rate?
A: Calculate building heat load or use equipment specifications. 1 ton of cooling = 12,000 BTU/h.

Q5: Does this account for system efficiency?
A: No, the formula gives theoretical flow rate. Actual systems may need adjustments for pump efficiency, pipe losses, etc.