The Complete Guide to Circulation Pump Selection: A Real-World Case Study
Why Circulation Pump Selection Matters
A mismatched pump can lead to:
Cold spots from insufficient flow
Higher energy bills from overpowered pumps
Premature wear on pipes and components
Key Factors for Circulation Pump Selection
1. Flow Rate Calculation
G = 3.6 × Q / (C × (Tg - Th))
Where:
Q = 1.2 × 1.2 × q × A (kW)
q = Heat demand (60 kcal/m²)
A = Floor area (m²)
Where:
Q = 1.2 × 1.2 × q × A (kW)
q = Heat demand (60 kcal/m²)
A = Floor area (m²)
2. Head Pressure Requirements
Hf = λ × (L/D) × (V²/2g)
ΔP = 102 × (G/KV0.01)²
ΔP = 102 × (G/KV0.01)²
Case Study: 120m² Home in Beijing
System Configuration
Condensing boiler + 6-loop underfloor heating
Supply/return temperatures: 50℃/40℃
Pipe length: 140m (25mm diameter)
Step 1: Flow Rate Calculation
Q = 1.2 × 1.2 × 60 × 120 = 12 kW
G = 3.6 × 12 / (4.1868 × 10) = 1.032 m³/h
Step 2: System Resistance Analysis
Frictional loss: 0.235m
Local loss: 0.156m
Total resistance: 4.29mH₂O
Step 3: Pump Performance Comparison
| Pump Head | Flow Range | Recommendation |
|---|---|---|
| 5m | 0.55-1.05 m³/h | Insufficient capacity |
| 6m | 0.6-1.45 m³/h | Optimal selection |
| 7m | 0.65-1.8 m³/h | Overpowered |
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