Enter the quantity of steam generated, the enthalpy of the steam and water, the gross calorific value (GCV) of the fuel, and the fuel consumption to determine the boiler efficiency.

Boiler Efficiency Calculator

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Boiler Efficiency Formula

The following formula is used to calculate the direct efficiency of a boiler. 

E = [ Q * (H-h) / (q*GCV) ] * 100
  • Where Q is the quantity (or flow rate) of steam generated (kg/hr)
  • H is the enthalpy of steam (kcal/kg or kJ/kg)
  • h is the enthalpy of feedwater (kcal/kg or kJ/kg)
  • GCV is the gross calorific value (higher heating value) of the fuel (kcal/kg or kJ/kg)
  • q is the quantity (or flow rate) of fuel consumed (kg/hr)

Boiler Efficiency Definition

Boiler efficiency is defined as the percentage of input energy that a boiler can convert into output energy in the form of steam.

How to calculate boiler efficiency?

First, determine the quantity of steam the boiler generated. For this example, the quantity of steam generated by the boiler is 10 kg/hr.

Next, determine the enthalpy of the steam that is generated. For this example, we will use the enthalpy of saturated steam at standard atmospheric pressure ≈ 2676 kJ/kg.

Next, determine the enthalpy of the water input into the boiler. For this problem, the input water is at 60 degrees Celsius. At this temperature, water has an enthalpy of about 251.18 kJ/kg.

The next step is to determine the gross calorific value of the fuel. This boiler uses natural gas to heat the water which has a gross calorific value of 12,500 kcal/kg (≈ 52,300 kJ/kg).

Next, determine the quantity of fuel. To match the steam production rate given above, we will use a fuel consumption of 0.6 kg/hr of natural gas.

Finally, calculate the efficiency using the formula above:

E = [ Q * (H-h) / (q*GCV) ] * 100

= [ 10 * (2676-251.18) / (0.6*52,300) ] * 100

= 77.26%.