In these notes Boiler efficiency, Boiler trial and Heat balance related with Boiler performance are explained.

1. Boiler performance (Part 2) - Boiler
efficiency, Boiler trial and Heat
balance
Presentation by:
Avdhesh Tyagi
Asst. Prof.
Department of Mechanical Engineering
G. L. Bajaj Institute of Technology & Management, Greater Noida
Disclaimer: The materials provided in this presentation and any comments or information provided
by the presenter are for educational purposes only. Nothing conveyed or provided should be
considered legal, accounting or tax advice.

2. Name of Subject: Applied Thermodynamics
Subject Code: KME401
Department of Mechanical Engineering
G. L. Bajaj Institute of Technology and Management,
Greater Noida, Uttar Pradesh
College code: 192
Affiliated to Dr. A.P.J. Abdul Kalam Technical University (Formerly UPTU Lucknow).
Unit 3
Topic covered: Boiler efficiency, Boiler trial
and Heat balance

3. Boiler efficiency
It is defined as the ratio of heat actually utilized in
steam generation to the heat supplied by the fuel
during same time duration.
Mathematically
η 𝑏𝑜𝑖𝑙𝑒𝑟 =
𝑚 𝑎 ℎ − ℎ 𝑤
𝑚 𝑓x 𝐶𝑉
Where CV = Calorific value of fuel in kJ/kg
• If Boiler, superheater and economizer are
considered as single unit, above formula gives the
overall efficiency of boiler plant.

4. Heat balance sheet
A heat balance sheet represents the complete account of
heat supplied by 1 kg of dry fuel and the consumption of
this supplied heat.
The heat supplied is used for steam generation in boiler
and the remaining heat is lost. Various heat losses are:
1. Heat lost in dry flue gases
2. Heat lost in moisture in fuel
3. Heat lost due to steam in flue gases
4. Heat lost due to unburnt carbon in ash pit
5. Heat lost due to incomplete combustion
6. Heat lost due to convection, radiation and other
unaccounted losses (By difference)

5. Heat balance sheet
Heat supplied by fuel
Supplied
percentage
Heat distribution (kJ) Percentage (%)
𝑸 𝒇𝒖𝒆𝒍 = 𝒎 𝒇 𝐱 𝐂𝐕 100%
Heat used in steam generation X1
Heat lost in dry flue gases X2
Heat lost in moisture present in
fuel
X3
Heat lost due to steam in flue
gases
X4
Heat lost due to unburnt carbon
in ash pit
X5
Heat lost due to incomplete
combustion
X6
Heat lost due to convection,
radiation and other
unaccounted losses (By
difference)
X7 = 100 – (X1+X2+X3+X4+X5+X6)
Overall heat supplied 100% Overall heat distribution X1+X2+X3+X4+X5+X6+X7=100%

6. Boiler trial
Boiler trial refers to running the boiler under test
conditions for assessment of its performance. The
objectives of a boiler trial are:
• To determine the steam generation capacity of
the boiler.
• To determine the thermal efficiency of the plant
while working at a certain pressure.
• To prepare the heat balance sheet for the boiler.
During trial the boiler is generally run for 4 to 6
hours duration so as to attain steady state.

7. Boiler trial
Duration of boiler run for attaining steady state
changes from boiler to boiler (Oil fired and coal fired
types). Observations are taken after the boiler attains
steady state for a duration ranging from 10 to 15
minutes.
Measurements are made for fuel supply, combustion
analysis, steam generation rate and its quality/state,
flue gas and their analysis, temperature and pressure
at salient locations and all other measurements as
required for heat balance sheet preparation.

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