Mechanical Engineering Department
Bharathiyar College of Engineering & Technology
Karaikal - 609 609.
e-Mail : firstname.lastname@example.org
Part - 1
The entropy of substances at the absolute zero of temperature,
called absolute entropy (third law of thermodynamics).
A combustion reaction is a chemical reaction in which
products are formed from reactants with the release
or absorption of energy as heat is transferred to as
from the surroundings
The numerical coefficients in the equation,
which precede the chemical symbols to give
equal amounts of each chemical element on
both sides of the equation, are called
the total mass of reactants must equal the total mass of products
Since 1 kmol of H2 equals 2 kg, 1 2 kmol of O2 equals 16 kg, and
1 kmol of H2O equals 18 kg,
The air–fuel ratio is simply the ratio of the
amount of air in a reaction to the amount of
fuel. The ratio can be written on a molar basis
(moles of air divided by moles of fuel)
or on a mass basis (mass of air divided by mass
The minimum amount of air that supplies
sufficient oxygen for the complete combustion
of all the carbon, hydrogen, and sulfur present
in the fuel is called the theoretical amount of air
Gas Molar Weight
Carbon dioxide 44.01
Stoichiometric (or chemically correct) mixture of
air and fuel is one that contains just sufficient
oxygen for complete combustion of the fuel.
A weak mixture is one which has an excess of air.
A rich mixture is one which has a deficiency of air
The ratios are expressed as follows :
For gaseous fuels :By volume
For solid and liquid fuels : By mass
• air-fuel ratio can be calculated by the
following methods :
1. Fuel composition known
(i) Carbon balance method
(ii) Hydrogen balance method
(iii) Carbon-hydrogen balance method.
2. Fuel composition unknown
(i) Carbon-hydrogen balance method.
Carbon balance method : combustion takes place
with excess air and when free (solid) carbon is not
present in the combustion products.
Hydrogen balance method is used when solid
carbon is present in the combustion product.
Carbon-hydrogen balance method: This method
may be employed when there is some uncertainty
about the nitrogen percentage reported by the
ANALYSIS OF EXHAUST AND FLUE GAS
Wet analysis : An analysis which includes the
steam in the exhaust.
Orsat apparatus : is used for the analysis of
ENTHALPY OF FORMATION
The enthalpy of formation (∆Hf) is the increase in
enthalpy when a compound is formed from its
constituent elements in their natural form and in a
standard state. The standard state is 25°C, and 1 atm.
∆ 0 = ∆ 0
− ∆ 0
∆ 0 = . ∆ 0
− . ∆ 0
n – number of moles
Also Enthalpy of formation of elements in its elemental form is
zero. For example H2,O2 ext
Enthalpy of formation of elements in its elemental form
is zero. For example H2,O2 ext
• Moran, M. J. 2011. Fundamentals of engineering thermodynamics. Wiley,
• Rajput, R. K. 2010. Engineering thermodynamics. Jones and Bartlett
Publishers, Sudbury, Mass.
• Nag, P. K. 2002. Basic and applied thermodynamics. Tata McGraw-Hill, New