Convert kg/h to kW for steam using typical boiler enthalpies, or for fuel, heated fluids or any energy per kg, and convert kW back to kg/h of steam.
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kg/h to kW Formula
For sensible heat with no phase change and a representative mean specific heat, use the following steady-flow heat-transfer formula. Mass flow alone cannot determine power.
Variables:
- P is the power output (kW)
- แน is the mass flow rate (kg/h)
- c is the specific heat of the fluid (kJ/kgยทK)
- ฮT is the temperature change (K)
To calculate sensible heat-transfer rate in kilowatts, convert kg/h to kg/s by dividing by 3600, then multiply by mean specific heat and outlet minus inlet temperature. Positive means heating the flowing substance; negative means cooling. A Celsius difference equals a kelvin difference; a Fahrenheit difference is multiplied by 5/9 without a 32-degree offset. For other bases, P(kW) = mass(kg/h) ร transferred energy(kJ/kg) / 3600. Thus specific energy in kWh/kg multiplies kg/h directly, while fuel calorific value in MJ/kg is divided by 3.6. Fuel results are energy-input rate before losses; use a consistent HHV or LHV. Steam requires the relevant enthalpy difference, not absolute enthalpy. Latent heat applies only to the specified pressure and phase-change conditions. Reverse flow divides power by the nonzero energy-per-mass basis, with matching signs. See Spirax Sarcoโs steady-flow heat and steam balances and NIST unit conversions.
| Mass Flow Rate (kg/h) | Power (kW) |
|---|---|
| 50 | 1.163 |
| 75 | 1.744 |
| 100 | 2.326 |
| 150 | 3.488 |
| 200 | 4.651 |
| 250 | 5.814 |
| 300 | 6.977 |
| 400 | 9.302 |
| 500 | 11.628 |
| 600 | 13.953 |
| 750 | 17.442 |
| 1,000 | 23.256 |
| 1,500 | 34.883 |
| 2,000 | 46.511 |
| 2,500 | 58.139 |
| 3,000 | 69.767 |
| 4,000 | 93.022 |
| 5,000 | 116.278 |
| 7,500 | 174.417 |
| 10,000 | 232.556 |
| * Rounded to 3 decimals. Formula: P (kW) = (แน (kg/h) / 3600) ร c (kJ/kgยทK) ร ฮT (K). Assumes water: c = 4.186 kJ/kgยทK and ฮT = 20 K. | |
What is Specific Heat?
Specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius or one kelvin. It is a property that describes how much energy a substance can absorb before its temperature changes. The specific heat of a substance can vary depending on its state (solid, liquid, or gas) and temperature.
How to Calculate Power Output from Mass Flow Rate?
The following steps outline how to calculate the power output from a mass flow rate in kg/h.
- First, determine the mass flow rate (แน) in kg/h.
- Next, determine the specific heat (c) of the fluid in kJ/kgยทK.
- Next, determine the temperature change (ฮT) in kelvin.
- Next, gather the formula from above: P (kW) = (แน / 3600) * c * ฮT.
- Finally, calculate the power output (P) in kilowatts.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Mass flow rate (แน) = 5000 kg/h
Specific heat (c) = 4.2 kJ/kgยทK
Temperature change (ฮT) = 50 K
Using sensible-heat mode: P = (5000 รท 3600) ร 4.2 ร 50 = 291.666667 kW. The table above uses a different explicitly stated mean specific heat and temperature difference; its numbers are conditional examples, not a universal conversion factor.
