Flow Rate Calculator
What is the flow rate through this pipe? Used for refrigerant line sizing, hydronic systems, and condensate drain calculations.
Enter pipe diameter and fluid velocity to calculate flow rate.
What to do with this number
- Use for refrigerant line sizing. Match the flow rate to the manufacturer's recommended pipe diameter for the refrigerant type and distance. Undersized lines cause excessive pressure drop and reduced capacity.
- Check velocity against manufacturer specs. Most refrigerant systems require minimum velocity to ensure oil return to the compressor. Too slow and oil accumulates in the lines. Typical minimum: 500–700 FPM for suction lines.
- Watch the Reynolds number. Above 4,000 means turbulent flow, which increases pressure drop and noise. Below 2,300 is laminar (smooth) flow. Between 2,300 and 4,000 is transitional and unpredictable.
- This is a planning estimate. Always verify final pipe sizing with manufacturer engineering tables that account for equivalent length, fittings, elevation changes, and refrigerant properties at operating conditions.
These calculations use ASHRAE fundamentals and standard fluid mechanics. For refrigerant line sizing, verify with manufacturer specifications and pressure drop tables.
Sources (2)
- ASHRAE Fundamentals — pipe flow and fluid mechanics
- Crane TP-410 — pipe flow handbook