KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY
COLLEGE OF ENGINEERING
MECHANICAL ENGINEERING DEPARTMENT
ME 296
MECHANICAL ENGINEERING LAB II
REPORT ON
CALORIFIC VALUE OF A LIQUID FUEL
BY
ADDAE- MENSAH SAMUEL
5918711
CALORIFIC VALUE OF A LIQUID FUEL
INTRODUCTION
One of the most important characteristics of any combustible fluid is the quantity of energy or
heat that it releases as it burns. This value is referred to as either heat of combustion or the
calorific value of the fuel and is usually expressed in British thermal units (Btu) per pound or
ton, or in calories per gram. The calorific value of solid and liquid fuel is routinely determined in
order to establish the price of the fuel, as well as to serve as a basis for calculating the overall
efficiency of a power generating facility engine.
Calorimetry is the study of heat as contrasted with temperature. The oxygen bomb calorimeter,
which is used to determine calorific value of fuels, is only one of many types of calorimeters.
To determine the calorific value of a fuel, a representative sample is burned in a high pressure
oxygen atmosphere within a metal bomb or pressure vessel. The energy released is absorbed
within the calorimeter and measured in terms of temperature change within the calorimeter. The
calorific value of the sample is obtained by multiplying the temperature rise of the calorimeter by
a previously determined energy equivalent or heat capacity of the instrument. Corrections are
applied to adjust these values for any heat transfer occurring in the calorimeter as well as for any
side reactions which are unique to the bomb combustion process.
OBJECTIVE
To determine, neglecting special corrections, the Gross Calorific Value (G.C.V) or Higher
Calorific Value of a sample of Diesel Oil.
APPARATUS
Bomb calorimeter: any oxygen –bomb calorimeter consist of four essential parts;
1. Bomb or vessel in which the combustible charge is burned (crucible).
2. A bucket or container which holds the bomb as well as a measured quantity of water
to absorb the heat released from the bomb and a stirring device to assure thermal
equilibrium.
3. A jacket for protecting the bucket from transient thermal stress.
4. A calorimeter thermometer for measuring temperature changes within the bucket.
THEORY
The Gross Calorific Value (G.C.V) or Higher Calorific Value (H.C.V) is the quantity of heat
liberated when unit mass of fuel is combusted at constant volume in oxygen saturated with
water vapour, and the products of combustion contain carbon dioxide (CO 2), sulphur dioxide,
oxygen and nitrogen.
In an experiment to determine the calorific value in accordance with the above
definition it is necessary to make detailed corrections for the following:
 Sulphur in the fuel does not burn to SO 2 but appears finally as H 2SO4 as distilled
water (15mls) is placed inside the “bomb”.
 Nitrogen originally present in the “bomb” prior to pressure charging with oxygen,
finally finishes as HNO 3.
 Losses to atmosphere by radiation and convection.
The energy content of a given liquid fuel (Diesel oil) is determined by burning a small
sample of the fuel in a device called a bomb calorimeter, which is basically a wellinsulated rigid tank. The tank contains a small combustion chamber surrounded by water.
The fuel is ignited and burned in the combustion chamber in the presence of excess
oxygen, and the energy released is transferred to surrounding water. The energy content
of the fuel is calculated on the basis of the conservation of energy principle by measuring
the temperature rise. The carbon in the fuel is converted to CO2 and sulphur to SO2..Any
H2O not originally present as vapour will be present as liquid.
METHOD
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The crucible was weighed empty; 0.7 gram of oil was added and reweighed to
determine the correct weight of the oil.
The crucible was positioned with oil in the seating of the bomb cover, and a suitable
piece of ignition wire was attached across the terminals but touching the oil surface.
15mls of distilled water was poured into the base of the bomb. The bomb was
assembled carefully and charged with oxygen to 25 atmospheres and tested under
water for leaks.
The calorimeter vessel was weighed and 2400mls of water was added and reweighed
to determine the correct weight of the water.
The calorimeter vessel was positioned in the water filled jacket which is to provide
the sensibly constant temperature environment, the bomb was set in place in the
calorimeter vessel and the electrical leads, stirrer and Beckmann thermometer was
connected to it and the stirring gear was set in motion.
The thermometer readings were observed at one minute interval for a preliminary
period of five minutes, and the firing circuit was completed. The thermometer
readings were continually observed at one minute intervals until the maximum
temperature was attained. The temperature was observed for a further five minutes at
one minute intervals.
After the combustion was complete, the apparatus was dismantled.
TABLE OF EXPERIMENTAL VALUES
Time/ min
Temperature/ °C
0
23.57
1
23.59
2
23.60
3
23.61
4
23.63
5
23.65
6
24.93
7
25.91
8
26.18
9
26.30
10
26.35
11
26.38
12
26.40
13
26.41
14
26.42
15
26.43
A GRAPH OF TEMPERATURE (°C) AGAINST TIME (min)
27
26,5
Temperature /ºC
26
25,5
25
Y-Values
24,5
24
23,5
23
0
2
4
6
8
10
12
14
16
Time /min
CALCULATIONS
W f  Q  (Ww  Wa )( rise in temperature)C  4.2
The maximum temperature in the experiment is 26.43°C
The minimum temperature in the experiment is 23.57°C
Therefore rise in temperature is 26.43 - 23.57 = 2.86°C
Volume of water in the bomb calorimeter = 2400ml = 2400x10-6m3
Weight of fuel: Wf = 0.7g = 0.7x10-3kg
Weight of water: Ww =Density of water x volume
Ww = 1000 x 2400 x10-6 = 2.4kg
Weight equivalent of the apparatus: Wa = 482g = 0.482kg
0.7x10-3×Q = (2.4+0.482) × (2.86) × 4.2
Q = 49455.12 kJ/kg
Q=calorific value.
COMMENTS
It can be observed from the graph that combustion was very slow at the beginning that resulted
in slow rise in temperatures between the 0th – 5th minutes. Rapid combustion took place during
the intermediate time period, from the 6th – 10th minutes which saw to the rapid rise in
temperature. After that, combustion of the fuel was very slow from the 11th – 15th time period
which also saw to slow rise in temperature. The After Period can be constant depending on the
room temperature.
PRECAUTIONS
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1. The cover bomb must be tight.
2. The crucible is checked for leakage so that the fuel will not be filled with water.
CONCLUSION
The value we had as compared to the standard value help as to know that our experiment was
successful
The calorific value obtained is a High Calorific Value (49455.12kJ/kg), since it is almost equal
to the standard HCV of diesel which is 46536kJ/kg, unlike the standard Low Calorific value
(LCV) that is 43448Kj/kg of diesel 0il.
REFERENCE

Laboratory Instructors’ Manual ̶ Mr. Anokye Boateng

Energy Technology Handbook – By Considine

Google search: http://www.transportation.anl.gov/software/GREET/index.html