Chiller Flow Rate Calculator
Required Flow Rate:
How to Calculate Chiller Flow Rate
In HVAC and industrial process cooling, determining the correct chilled water flow rate is critical for equipment efficiency and system longevity. If the flow rate is too low, the chiller may trip on low-pressure faults; if it is too high, it leads to excessive energy consumption and potential tube erosion.
The Chiller Flow Formula
The relationship between cooling capacity, temperature difference, and flow rate is governed by the principles of heat transfer. For water-based systems, the standard formula used in North America is:
Where:
- GPM: Gallons per minute of chilled water.
- Tons: The cooling capacity of the chiller (1 Ton = 12,000 BTU/hr).
- ΔT (Delta T): The difference between the Entering Water Temperature (EWT) and the Leaving Water Temperature (LWT).
- 24: A constant derived from the weight and specific heat of water (500 / 20.83).
Step-by-Step Calculation Example
Let's say you have a 50-ton chiller and your system design requires a 10°F temperature drop (returning at 55°F and leaving at 45°F).
- Identify Capacity: 50 Tons.
- Identify ΔT: 10°F.
- Apply Formula: (50 × 24) / 10 = 1,200 / 10 = 120 GPM.
In this scenario, your pump must be capable of delivering 120 GPM to ensure the chiller operates within its design parameters.
Common Design Standards
Most commercial comfort cooling systems are designed around a ΔT of 10°F or 12°F. However, High Delta T systems (using 15°F to 20°F) are becoming more popular in large-scale district cooling to reduce pipe sizes and pumping energy. Always verify your specific chiller's manufacturer data sheet for minimum and maximum allowable flow rates.