What is formula for boiler efficiency?

boiler efficiency calculation methods:

1. Input-output method

η = Output / Input

Output is defined as the heat that is absorbed by working fluid. Input is defined as the chemical heat of fuel plus the heat that is added to working fluid, air, gas and other fluid circuit in which the fluid circuit across thin layer.

1. Heat Loss Method

Heat loss method is the method that is used to calculate the percentage amount of heat which is not useful. This method is very effective used in an attempt to find potential savings of boiler with heat balance.

There are several factors act as the source of heat loss combustion. These factors will be used to calculate boiler efficiency based on heat loss method. The source of heat loss can be seen as following below:

a. Heat loss due to dry flue gas

Heat loss due to dry flue gas is the heat loss which is contained in dry flue gas such as CO2, O2 and N2. These gases are one of causes of heat loss in combustion process. The high temperature of flue gas coming out from boiler affect amount of heat loss.

The weight and heat loss of dry flue gas of combustion of coal can be calculated as following formula:

Wdfg = mCO2 + mSO2 + mO2 + mN2

Eloss dfg = Wdfg x Cp x (To - Ts)

Where:

Wdfg = weight of dry flue gas (kg/kg coal)

Eloss dfg = heat loss in dry flue gas (kJ/kg)

To = temperature of dry flue gas coming out from boiler

Ts = temperature of surrounding

by Gajanan Nalegaonkar