The Feed Water Flow Calculator estimates how much water needs to enter a boiler or thermal system to support continuous steam generation. It factors in steam production, blowdown, and thermodynamic conditions to maintain a proper water-energy balance. This tool is vital in thermal engineering, steam plants, and boiler operations.
As part of the Thermal Systems & Boiler Calculators category, it ensures precise energy supply and helps engineers track and manage boiler performance more effectively.
formula of Feed Water Flow Calculator
Feed Water Flow Rate (ṁ) = Steam Flow Rate − Blowdown Flow Rate
Where:
- ṁ = feed water flow rate (kg/h, lb/h, or m³/h)
- Steam Flow Rate = amount of steam produced
- Blowdown Flow Rate = water discharged to remove dissolved solids
Energy Balance-Based Calculation
ṁ = Q / (hf₂ − hf₁)
Where:
- Q = total heat added to feedwater (kW or Btu/hr)
- hf₂ = enthalpy of saturated water at boiler pressure
- hf₁ = enthalpy of water at feed temperature
- ṁ = feed water flow rate (kg/s or lb/s)
This method gives a thermodynamically accurate result, especially when enthalpies are pulled from steam tables.
Volumetric Flow Conversion
Volumetric Flow Rate (V̇) = ṁ / ρ
Where:
- V̇ = flow in m³/h or gallons/min
- ρ = water density (approx. 998 kg/m³ at 20°C)
This converts mass flow into usable pipe or pump flow data.
Reference Table for Common Water Properties
| Temperature (°C) | Density (kg/m³) | Enthalpy (kJ/kg) |
|---|---|---|
| 20 | 998 | 83.91 |
| 50 | 988 | 209.30 |
| 75 | 974 | 313.95 |
| 100 | 958 | 419.04 |
| 120 | 943 | 502.32 |
These values help users calculate enthalpy difference (hf₂ − hf₁) and density for conversions.
Example of Feed Water Flow Calculator
Suppose a boiler produces 5,000 kg/h of steam and has a blowdown rate of 200 kg/h.
ṁ = 5,000 − 200 = 4,800 kg/h
If using energy balance, assume:
- Q = 3,200 kW
- hf₂ = 419 kJ/kg (from steam table)
- hf₁ = 210 kJ/kg (from feedwater temp)
ṁ = 3,200 / (419 − 210) = 3,200 / 209 ≈ 15.31 kg/s
Convert to hourly: 15.31 × 3600 = 55,116 kg/h
So, the feed water flow required is about 55,116 kg/h to supply 3,200 kW of heat.
Most Common FAQs
Feed water flow ensures that enough water enters the system to replace steam and maintain pressure and temperature balance. Without proper flow, the boiler can overheat or fail.
You can estimate it. Typical blowdown rates range from 3% to 10% of steam flow, depending on water quality and boiler design.
Yes. Use the volumetric flow formula: V̇ = ṁ / ρ, and convert cubic meters to liters (1 m³ = 1,000 L) or gallons (1 m³ = 264.17 gallons).