Experiment No. 5
TEST OF OXYGEN BOMB CALORIMETER: OBTAINING THE CALORIFIC VALUE
OF FUEL
Course Code: MEF420L2Program: BSME
Course Title: ME Laboratory 2Date Performed: February 11,
2015
Section: ME42FA1Date Submitted: March 1, 2015
Members: 1. Zafra, Charles Jourdan M. (Leader)Instructor: Engr.
Nelson DelaPea Jr.
2. Arcay, Andrew
3. Caringal, John Martin U. (Safety Officer)
4. Dela cruz, John Kelvin B.
5. Gaela, Vanjochris
6. Macapagal,Roel U. (Quality Control)
1. Objective(s):
The activity aims to demonstrate how to determine the calorific
value of different types of fuel.
2. Intended Learning Outcomes (ILOs):
The students shall be able to:2.1 Perform the procedure of
operating an oxygen bomb calorimeter.2.2 Determine the calorific
value of different types of fuel.2.3 Develop professional work
ethics, including precision, neatness, safety and ability to follow
instruction.
3. Discussion:
Calorimetry is a fundamental test of great significance to
anyone concerned with the production or utilization of solid or
liquid fuels.
One of the most important tests in the evaluation of materials,
which are burned, as fuels, is the determination of the heat of
combustion, or calorific value. These measurements can be made in
the Bomb Calorimeter Set for Testing Calorific Value of Fuels,
TBCF.
The Bomb Calorimeter is a classic device used to determine the
heating or calorific value of solid and liquid fuel samples at
constant volume. Basically, this device burns a fuel sample and
transfers the heat into a known mass of water. From the weight of
the fuel sample and temperature rise of the water, the calorific
value can be calculated. The calorific value obtained in a bomb
calorimeter test represents the gross heat of combustion per unit
mass of fuel sample. This is the heat produced when the sample
burns, plus the heat given up when the newly formed water vapor
condenses and cools to the temperature of the bomb. Determining
calorific values is profoundly important; fuels are one of the
biggest commodities in the world, and their calorific value.
The Bomb Calorimeter study is carried out to gain a better
understanding of the working principles behind the bomb calorimeter
and also to find out the gross calorific values of different types
of liquid fuel.
Description:The unit comprises the calorimeter, a calorimeter
vessel, an outer double walled water jacket, control unit to switch
on/off the stirrer and the ignition device, a Beckman type
thermometer, and charging unit with pressure gauges to facilitate
the charging of the calorimeter with oxygen. The particular
features of the calorimeter bomb are the method of sealing and the
method of ensuring ignition. The calorimeter vessel and outer
jacket wall are manufactured in stainless steel. The calorimeter
bomb is a container made of stainless steel that can support high
pressures. It is sealed by a screw top. The bomb is charged with
gas (oxygen) through the filling valve. This bomb is introduced
inside a calorimeter vessel made of stainless steel that is filled
with water, and at the same time it is introduced inside a double
walled water jacket.
The rod of the calorimeter supports a metallic crucible. The
calorimeter bomb, which contains the fuel sample to be burned, is
hermetic to the gas by closing the filling valve and its cover.
Combustion is started through a thin wire that is red hot-heated up
momentarily due to the passing of an electrical current that flows
through an isolated terminal and the rod, which is electrically
connected to the cover.
The water in the calorimeter vessel is agitated automatically
with a stirrer driven by a small motor. The top of the double
walled jacket is closed with a cover that has some orifices. A
Beckman thermometer to measure the temperature of the calorimeter
vessel passes through one of these orifices. Other orifices are
used to fasten the jacket to the cover. Also, one of these holes is
used to insert the wire that supplies the electric current to the
rod. The unit includes a control unit that switches on/off the
stirrer and the ignition device through the heating up of the thin
wire, and a load unit with pressure gauges to make the filling with
oxygen of the calorimeter easier.
Specifications:
Calorimeter for testing calorific value of fuels, including: 1.
Main metallic elements in stainless steel. 2. Diagram with a
distribution of the elements similar than the one in the real unit.
3. Calorimeter bomb. 4. Calorimeter vessel. Characteristics: o
Stainless steelMaximum volume: 4 litters. 5. Double walled outer
jacket in stainless steel, with water inlet and outlet. 6. Electric
stirrer with one rod and two blades. Characteristics: 330rpm. 7.
Control unit to switch on/off the stirrer and the ignition device
8. Beckman thermometer. Range: 6C. 9. Charging unit with pressure
gauges. 10. One nickel crucible. 11. Reel of Nickel-Chrome
wire.
Dimensions: 500 mm x 400 mm x 1000 mmVolume: 0.2 m3 Weight: 40
kgElectrical Supply: single-220V/50Hz or 110V/60HzWater: 7.7
LiterOxygen CylinderSeveral Types of Fuel: Benzoic Acid
(C7H6O2)
Theoretical Consideration:Almost all chemical reactions adsorb
or release energy, generally as heat. Heat is the thermal energy
transfer between two bodies whose temperatures are different. Heat
flow from a hot body to a cold one is frequently mentioned.
Generally, absorbed heat or released heat is used to describe the
energy changes that take place during a process.
Reactions that take place during a process can be endothermic,
if they absorb heat, or exothermic, if they release heat.
Endothermic changes are expressed with a positive sign, and
exothermic changes with a negative sign, according to the first law
of thermodynamics. The enthalpy change occurred in the direct
reaction is exactly opposed in the inverse reaction. This thermal
effect is the same regardless whether the reaction takes place in
one or several stages. The magnitude of the change depends on the
composition, the physical state of the reagents and products and
the stoichiometric expression.
Thermal changes can happen at constant pressure or at constant
volume and are expressed with the following equations:
H = qp = 0
E = qv = 0
Where: H represents the enthalpy change and E represents the
energy change. The H can be experimentally determined by measuring
the heat flow that accompanies a constant pressure reaction, and
the E a constant volume.
Heat changes of physical or chemical processes are measured with
a calorimeter, which is a closed vessel specifically designed for
that purpose. The calorimetry study, that is to say, the
measurement of heat changes, depends on the understanding of
specific heat and heat capacity. The specific heat (cp) of a
substance is the amount of heat required to increase one Celsius
degree the temperature of one gram of the substance. The heat
capacity (Q) of a substance is the amount of heat required to
increase one CelsiusDegree the temperature of a certain amount of
substance. The relationship between the heat capacity and the
specific heat of a substance is:
Q = mcpWhere m is the mass of the substance in grams and cp is
the specific heat of a substance
The Heat of Combustion and Its Determination:Fuels are those
substances predominantly containing carbon, or carbon and hydrogen,
or carbon, hydrogen and oxygen, which are utilized for the energy
they produce upon union with oxygen. The products of combustion are
carbon dioxide, water and other oxides. The amount of heat given
out in a chemical reaction depends on the conditions under which
the reaction is carried out. The standard heat of reaction isthe
heat released when the reaction is carried out under standard
conditions: pure components, pressure (1 atm.) and temperature,
usually but not necessarily, at 25C.
The Heat of Combustion (Calorific Value or Heat Value) of a
compound is the standard heat of reaction for complete combustion
of the compound with oxygen. The terms higher calorific value (HCV)
and lower calorific value (LCV) are used, respectively, to
distinguish the cases in which any water formed is in the liquid or
gaseous phase. The two calorific values are related as follows:
HCV = LCV + (mw x LH)
Where mw is the mass of water produced per unit mass of fuel and
LH is the latent heat of evaporation of water.
The Bomb Calorimeter:The heat of combustion is a required value
in the design of any type of combustion system. There are two
methods for its determination one by calculation based on the
chemical composition and other by actual combustion in a bomb
calorimeter. For fuels with complex chemical formulae, it is more
reliable and simpler to evaluate the heat of combustion by doing a
bomb calorimeter test. Further, if there is any doubt in the
composition and structure of a fuel or the formula for calculating
the heat of combustion, it may prove more reliable to perform the
bomb calorimeter test, as it is a direct measure of the heat of
combustion.
Bomb calorimeters for rapid combustion are composed of a
combustion chamber (bomb) and a calorimeter vessel, usually a
cylinder surrounding the bomb and containing a known quantity of
water. The elevation in temperature of that water will be measured.
The combustion is made in oxygen, pure or diluted. Combustion
chambers are either under a constant pressure or with a constant
volume. The results obtained with a calorimeter of constant volume
are not exactly the same as those obtained with constant pressure,
but for solid or liquid substances the difference is too small to
consider.
Set of Bomb CalorimeterThe instrument consists of (1) the bomb;
(2) the water container where the bomb is placed and (3) a
surrounding compartment of temperature controlled water. The bomb
is a small cylindrical pressure vessel with a tight fitting head
clamped on the external face of the bomb by a screw cap, a port for
a pressure relief valve and two ports for the two electrodes. The
material to be combusted is placed in a metal cup that is suspended
in the bomb by two supports that also are part of the electrical
circuit containing the fuse wire. The fuse wire spans across the
top of the metal cup. When current is passed through the fuse wire,
it heats up rapidly and ignites the fuel.The bomb is placed in a
container with a known amount of water, together with an agitator
and a thermometer. The agitator is used to maintain a uniform
temperature in the water and aids the heat transfer
from the bomb. The thermometer measures the water temperature
(its range is from 24C to 30C with 0.01C accuracy). There is an air
gap between the water vessel and the water jacket, which is an
excellent heat insulator. When the calorimeter is running, the
temperature of the calorimeter body is automatically maintained at
the same temperature than that of the water container that holds
the bomb. This provides an adiabatic condition and, thus, no heat
is transferred to or from the container of water, except from the
heat released in the bomb.
4. Materials and Equipment:
Bomb Calorimeter Set for Testing Calorific Value of Fuels, TBCF
Different kinds of fuels
5. Procedure:
1. Prepare the fuel sample by placing it in a crucible and
weighing it on a balance. Ensure that the weight of the fuel does
not exceed 1.1 g. Note down the weight of the fuel sample (mf) and
place the crucible containing the fuel gently in the loop holder.
When starting tests with new or unfamiliar materials, it is always
best to use samples of less than 0.7 of a gram, with the
possibility of increasing the amount if a preliminary test
indicates no abnormal behavior.
2. The bomb head has been pre-attached with a 10 cm long fuse
wire between the two electrodes. Bend the fuse wire down just above
the liquid fuel sample. The wire must not make contact with the
fuel crucible. To attach the fuse to quick-grip electrodes, insert
the ends of the wire into the eyelet at the end of each stem and
push the cap downward to pinch the wire into place. No further
threading or twisting is required.
3. It is not necessary to submerge the wire in a powdered
sample. In fact, better combustions will usually be obtained if the
loop of the fuse is set slightly above the surface. When using
pelleted samples, bend the wire so that the loop bears against the
top of the pellet firmly enough to keepit from sliding against the
side of the capsule.
4. Care must be taken no to disturb the sample when moving the
bomb head from to the calorimeter bomb. Check the sealing ring to
be sure that it is in good condition and moisten it with a bit of
water so that it will slide freely into the body of the calorimeter
bomb, then slide the head into the bomb and push it down as far as
it will go. Set the screw cap on the bomb and turn it down firmly
by hand to a solid stop. When properly closed, no threads on the
bomb should be exposed.
5. Oxygen for the bomb can be drawn from a standard commercial
oxygen cylinder. Connect the regulator to the cylinder, keeping the
0-55 atm. in an upright position.
6. The pressure connection to the bomb is made with a slip
connector on the oxygen hose which slides over the gas inlet
fitting on the bomb head. Slide the connector onto the inlet valve
body and push it down as far as it will go.
Close the outlet valve on the bomb head; then open or crack the
oxygen tank valve not more than one-quarter turn. Open the filling
connection control valve slowly and watch the gage as the bomb
pressure rises to the desired filling pressure (30 atm.); then
close the control valve. The bomb inlet check valve will close
automatically when the oxygen supply is shut off, leaving the bomb
filled to the highest pressure indicated on the 0 - 55 atm. Release
the residual pressure in the filling hose by pushing downward on
the lever attached to the relief valve. The gage should now return
to zero.
7. Fill the calorimeter vessel by first taring the empty vessel;
then add 3700 grams of water. Note the exact mass of the water.
8. Introduce the bomb calorimeter inside the calorimeter vessel.
Handle the bomb carefully during this operation so that the sample
will not be disturbed.
9. Check the bomb for leaks before firing. If any gas leakage is
indicated, no matter how slight, DO NOT FIRE THE BOMB. Instead
remove it from the water bath; release the pressure and eliminate
the leak before proceeding with combustion test.
10. Fill the jacket with water.
11. Put the cover on the jacket. Turn the stirrer by hand to be
sure that it runs freely and start the motor. Install the Beckman
thermometer; this thermometer should be immersed in water and not
close to the bomb.
12. Let the stirrer run for at least 5 minutes to reach
equilibrium before starting a measured run.
13. The scanning of the temperature data is pre-set to be done
once a minute. At the start of the 5th minute, fire the charge by
pressing the firing button on the control unit, keeping the circuit
closed for about 5 seconds.
14. The vessel temperature will start to rise within 20-30
seconds after firing. This rise will be rapid during the first few
minutes; then it will become slower as the temperature approaches a
stable maximum as shown by the typical rise curve shown in Figure.
Accurate time and temperature observations must be recorded to
identify certain points needed to calculate the calorific value of
the sample.
15. Usually the temperature will reach a maximum; then it will
drop very slowly. But this is not always true since a low starting
temperature may result in a slow continuous rise without reaching a
maximum. As stated above, the difference between successive
readings must be noted and the readings continued until the rate of
the temperature change becomes constant over a period of 5
minutes.
16. After the last temperature reading, stop the stirrer. Let
the bomb stand in the calorimeter vessel for at least 3 minutes.
Then, remove the jacket cover and extract the bomb calorimeter.
Wipe the bomb with a clean towel.
17. Open the valve knob on the bomb head slightly to release all
residual gas pressure before attempting to remove the screw cap.
This release should proceed slowly over a period of not less than
one minute to avoid entrainment losses. After all pressure has been
released, unscrew the cap; lift the head out of the cylinder. Do
not twist the head during removal. Pull it straight out to avoid
sticking. Examine the interior of the bomb for soot or other
evidence of incomplete combustion. If such evidence is found, the
test will have to be discarded.
18. Remove all unburned pieces of fuse wire from the bomb
electrodes.
19. On completion of experiment, wash all inner surfaces of the
bomb and the combustion crucible with a jet of distilled water and
collect the washings. Keep the bomb set dry and clean with some
wiping tissue.
6. Data and Results:
Method of Obtaining the Calorific Value from the Obtained
Data:
To illustrate the method of working out the calorific value, the
following example of a test is given:
Weight of fuel oil = Weight of crucible and fuel sample - Weight
of crucible
Total equivalent weight of water = Weight of water in
calorimeter + Water value of unit
Time and Temperature Readings:
Preperiod:
Time (minutes)Thermometer Readings (C)
0
25.3
1
25.3
2
25.4
3
25.5
4
25.6
5
25.6
Rise Period:Time (minutes)Thermometer Readings (C)
5.3025.9
626
726.1
826.2
926.3
1026.4
1126.5
1226.6
1326.6
1426.6
1526.6
1626.6
1726.6
1826.6
1926.6
2026.6
2126.6
2226.6
2326.6
2426.6
2526.6
2626.6
2726.6
2826.6
2926.6
3026.6
3126.7
3226.7
3326.7
3426.7
3526.6
Radiation Correction:The radiation correction is calculated from
the knowledge of the rates of change of temperature of the water
before igniting the fuel sample and after the attainment of the
maximum temperature. Let: n= number of minutes between the ignition
and the attainment of the maximum temperaturetf= rate of
temperature fall in degrees per minute at the end of the
exercisetr= rate of temperature rise in degrees per minute at the
beginning of the exercise.
Then the radiation correction is:
Radiation Correction = n x tf+ (tf - tr)/2
This is an approximation to the Renault-Stohman-Pfaundler
formula, and is sufficiently accurate for all purposes other than
research.
7. Computation, Analysis and Interpretation of Data:
Reactant Product
C7H6O2 + xO2= yCO2 + zH2O
Balancing:
C7H6O2 + 7.5O2=7CO2 + 3H2O
C = 7, H = 6, O = 17
Lower Heating Value:
H2O(L) H2O(g) = 44.0 KJ
3H2O(L) 3H2O(g) = (3 x 44.0 KJ) = 132.0 KJ
LHV = 132.0 KJ
Mass of Water:
Q = mw Cpw (T2 T1)
HVacidmacid = mw Cpw (T2 T1)
mw =
mw =
mw = 4 418.677 g or 4.4187 kg
Higher Heating Value:
HHV = LHV + LH mw
HHV = 132.0 KJ + (2257 )(4.4187 kg)
HHV = 10 104.95 KJ
Molecular Formula (Benzoic Acid)
C7H6O2
Mass of Acid
0.7 gram
Heating Value of Acid26 430
Mass of Water
4.4187 kg
Specific Heat of Water 4.186
Temperature Change
1
LHV
132.0 KJ
HHV
10 104.95 KJ
In this given graph, the result successfully show that the fuel
(Benzoic Acid) was burned correctly. Though it only rises 1 due to
the mass of the fuel because the fuel contain in the crucible was
less than one gram. The graph of the fuel presents the before and
after burning the fuel. The first five minutes shows the graph of
the initial temperature of the water. The next minutes show the
rising temperature of the water; this is the time when the fuel is
burning. And the higher temperature shows the after burned of the
fuel.
8. Conclusion and Recommendation:
1. Objectives: The activity aims to demonstrate how to determine
the calorific value of different types of fuel.
Answer: In this experiment we perform and learned how to compute
and balance about the fuel being burn inside the bomb calorimeter.
By the use of the formulas and ideal in our subject internal
combustion engine.
2. Intended Learning Outcomes (ILOs):
The students shall be able to:
2.1 Perform the procedure of operating an oxygen bomb
calorimeter.
In Performing the procedure of an oxygen bomb calorimeter, we
can say it is patiently to perform because it has a lot of
procedure to make before we can determine the higher heating value
of the fuel. It needs a team work and follow the proper procedure
to do the experiment and make a result.
2.2 Determine the calorific value of different types of
fuel.
In this experiment, we only determine one type of fuel or acid
of calorific value which is benzoic acid. We determine the
calorific value by measuring the temperature of the water.
Measuring the temperature of the water before and after burst are
the given to calculate the result of a burning fuel.
2.3 Develop professional work ethics, including precision,
neatness, safety and ability to follow instruction.
2.3.1 Duties and Responsibility of a Leader. (Zafra, Charles
Jourdan M.)
As a Leader, I always assure that my group mates have their
designated task and discuss them what they task. I listen to my
instructor so we can perform our experiment right, and to avoid
accident. Before we start the experiment I read the procedures the
things we must do.
2.3.2 Duties and Responsibility of a Safety Officer. (Caringal,
John Martin U.)
As a safety officer, The operator must be aware of safety
precautions to prevent physical injury. Any pressure-containing
device can explode, rupture, or discharge its contents if it is
over pressurized. Take all necessary measures to avoid
over-pressurization. Operating, installing, or maintaining the unit
in any way that is not covered in this manual could cause death,
serious personal injury, or damage to the equipment. This includes
any modification to the equipment or use of parts not provided by
ITT. If there is a question regarding the intended use of the
equipment, please contact an ITT representative before proceeding.
This manual clearly identifies accepted methods for disassembling
units. These methods must be adhered to. Trapped liquid can rapidly
expand and result in a violent explosion and injury. Never apply
heat to impellers, propellers, or their retaining devices to aid in
their removal unless explicitly stated in this manual. If the
pump/motor is damaged or leaking, do not operate as it may cause an
electric shock, fire, and explosion, liberation of toxic fumes,
physical harm, or environmental damage. Correct/repair the problem
prior to putting back in service. Do not change the service
application without the approval of an authorized ITT
representative.
2.3.3 Duties and Responsibility of a Quality Control Officer.
(Macapagal,Roel U.)
As a quality inspector, I am responsible for the accuracy of the
data in order to acquire low percentage error. I monitor the
performers on their process on how they conduct the experiment. I
also compute the actual data to make sure that the computations are
correct.
3. Based on Observation:
During we perform the activity we can say that the temperature
difference after and before we turning on the machine is very
little almost no difference so we say that the amount of the fuel
being burn is too small and the amount of water inside the bomb
calorimeter is too big thats why the heat transfer of the fuel is
very small, we suggest that the amount of the fuel put inside the
bomb calorimeter must increase so that the temperature will also
increase and the data being gathered is more precise and
accurate.
Group Pictures:
Fig.1. Pouring the water in the bomb calorimeter. Fig.2.
Preparing the fuel (Benzoic Acid).
Fig.3. Measuring the initial temp. of the water. Fig.4. Starting
to burn the fuel.
Fig.5. Temp. result after burnt. Fig.6. Opening the vessel after
the experiment.
a.b.
Result of the experiment:Fig.a. The crucible.Fig.b. The inside
vessel.
9. Assessment Rubric:
T I P - V P A A 0 5 4 D Revision Status/Date:0/2009 September
09TECHNOLOGICAL INSTITUTE OF THE PHILIPPINESRUBRIC FOR LABORATORY
PERFORMANCECRITERIABEGINNER1ACCEPTABLE2PROFICIENT3SCORE
Laboratory Skills
Manipulative SkillsMembers do not demonstrate needed
skills.Members occasionally demonstrate needed skills.Members
always demonstrate needed skills.
Experimental Set-upMembers are unable to set-up the
materials.Members are able to set-up the materials with
supervision.Members are able to set-up the material with minimum
supervision.
Process SkillsMembers do not demonstrate targeted process
skills.Members occasionally demonstrate targeted process
skills.Members always demonstrate targeted process skills.
Safety PrecautionsMembers do not follow safety
precautions.Members follow safety precautions most of the
time.Members follow safety precautions at all times.
Work Habits
Time Management/Conduct of ExperimentMembers do not finish on
time with incomplete data. Members finish on time with incomplete
data.Members finish ahead of time with complete data and time to
revise data.
Cooperative and Teamwork Members do not know their tasks and
have no defined responsibilities. Group conflicts have to be
settled by the teacher.Members have defined responsibilities most
of the time. Group conflicts are cooperatively managed most of the
time.Members are on tasks and have responsibilities at all times.
Group conflicts are cooperatively managed at all times.
Neatness and OrderlinessMessy workplace during and after the
experiment.Clean and orderly workplace with occasional mess during
and after the experiment.Clean and orderly workplace at all times
during and after the experiment.
Ability to do independent workMembers require supervision by the
teacher.Members require occasional supervision by the
teacher.Members do not need to be supervised by the teacher.
Other Comments/Observations:TOTAL SCORE
RATING= x 100%