Inputs
Illustrative example · editable
Starts with a 100-ton cooling load, 44°F supply, 56°F return, plain-water factor, and an example pipe diameter. These are editable planning examples, not site operating data.
Planning estimate
Chilled-water flow requirement
Cooling load converts to flow using the entered fluid factor and water temperature difference.
- Cooling load
- 1,200,000 BTU/hr
- Equivalent load
- 100.00 tons
- ΔT
- 12 °F
- Flow
- 200.0 GPM
- Metric flow
- 12.62 L/s
- Metric flow
- 45.4 m³/h
- Pipe velocity
- 5.04 ft/s
Calculation details
Estimate formula
- Load in BTU/hr = tons × 12,000; kW thermal × 3,412.142; or BTU/hr as entered.
- ΔT (°F) = return − supply.
- Flow (GPM) = BTU/hr ÷ (fluid factor × ΔT). Equivalent water expression: GPM = tons × 24 ÷ ΔT.
- Flow (L/s) = GPM × 0.0630902.
- Flow (m³/h) = GPM × 0.2271247.
- If pipe ID is entered, velocity (ft/s) = 0.4085 × GPM ÷ ID².
Current calculation
100 tons × 12,000 = 1,200,000 BTU/hr56 − 44 = 12°F ΔT1,200,000 ÷ (500 × 12) = 200 GPM100 tons × 24 ÷ 12 = 200 GPM (water expression)200 × 0.0630902 = 12.62 L/s; 200 × 0.2271247 = 45.4 m³/h0.4085 × 200 ÷ 4.026² = 5.04 ft/s
Assumptions
- Sensible load carried by the water loop at steady state.
- The 500 factor assumes water near 60°F and changes slightly with temperature and more with glycol.
- Velocity uses the pipe's inside diameter and a full pipe.
Sources
- ASHRAE Handbook—Fundamentals (hydronic heat-transfer relationship q = 500 × GPM × ΔT)
- ASHRAE Handbook—HVAC Systems and Equipment, hydronic heating and cooling chapter
Planning estimate only. Pump selection, pipe sizing and balancing need a mechanical engineer's design and manufacturer data.