The Feed Water Enthalpy Calculator helps calculate the thermal energy carried by water entering a boiler or heat exchanger. This is important in steam generation, power plants, and industrial thermal systems where precise energy balances are require. By knowing the specific enthalpy of feed water, engineers can evaluate energy efficiency and ensure optimal boiler operation.
This calculator is part of the Thermal Engineering and Power Plant Calculator category and is essential for those involved in steam systems, energy auditing, or heat exchanger performance assessments.
formula of Feed Water Enthalpy Calculator
Feed Water Enthalpy (hf) = Cp × T
Where:
- hf = specific enthalpy of feed water (in kJ/kg or Btu/lb)
- Cp = specific heat of water at constant pressure
Approx. 4.186 kJ/kg·°C (SI)
Approx. 1 Btu/lb·°F (Imperial) - T = temperature of feed water from 0°C (or 32°F)
Alternative Formula Using Steam Tables:
If you have boiler or system pressure data, use:
hf = hf(p)
Here, hf is retrieved directly from the saturated water property for the given pressure (in steam tables). This is more accurate than estimation when precision is required.
Optional Total Enthalpy Flow (Energy Rate):
Total Enthalpy Flow = hf × ṁ
Where:
- ṁ = mass flow rate (in kg/s or lb/hr)
This gives energy delivery in kW (SI) or Btu/hr (Imperial).
Table of Common Feed Water Enthalpy Values
| Temperature (°C) | hf (kJ/kg) | Temperature (°F) | hf (Btu/lb) |
|---|---|---|---|
| 0 | 0 | 32 | 0 |
| 25 | 104.65 | 77 | 45 |
| 50 | 209.30 | 122 | 90 |
| 75 | 313.95 | 167 | 135 |
| 100 | 418.60 | 212 | 180 |
| 120 | 502.32 | 248 | 216 |
This table helps users approximate enthalpy without detailed calculations.
Example of Feed Water Enthalpy Calculator
Suppose water enters a boiler at 75°C.
hf = Cp × T = 4.186 × 75 = 313.95 kJ/kg
If the mass flow rate is 1.5 kg/s:
Total Enthalpy Flow = hf × ṁ = 313.95 × 1.5 = 470.93 kW
This means the water brings about 470.93 kilowatts of thermal energy into the system per second.
Most Common FAQs
It shows how much heat energy is carried by the water entering a thermal system. It’s crucial for boiler efficiency, steam calculations, and heat exchanger sizing.
Yes. You can use temperature-based estimation. But for high-accuracy needs, especially in pressurized systems, steam tables should be used.
At higher pressures, water holds more energy at the same temperature. Steam tables account for this extra energy, giving more accurate values than Cp × T for pressurized systems.