International Journal of Recent Development in Engineering and Technology [616963]

International Journal of Recent Development in Engineering and Technology
Website: www.ijrdet.com (ISSN 2347 -6435(Online) Volume 2, Issue 6, June 2014 )
89
Design and Construction of A Small Scale Charcoal Baking
Oven
D M K ulla1, I M EBEKPA2, M Sumaila3
Department of Mechanical Engineering, Ahmadu Bello University, Zaria. Nigeria
Abstract – The need for baked food has become a necessity
in disgust. Bread and cakes has become part of our lives, as
such an oven for baking of bread/cake become important.
The production of different types of oven has grown rapidly
over the years particularly baking oven for domestic use.
But in our society today these ovens have been crippled by
electricity power instability in the urban settlement and
lack of electricity in the rural settlement because they
largely depend on electricity. Therefore the need for baking
oven not depending on electricity arises. Charcoal oven
which i s one of such oven, is cheap and efficient and can be
used both in the rural and urban settlement for domestic
consumption and small -scale business this oven uses little
quantity of charcoal to bake at a short time.
Keywords – baking , charcoal ,oven, Tempe rature , Time
I. INTRODUCTION
Baking refers to a process “to cook by dry heat “and is
therefore next to cooking another essential way of
preparing food from raw staple crops. During the baking
process the dough is transformed into eatable food
(nutritional improvements) and at the same time,
microorganisms causing spoilage are destroyed
prolonging keeping time of the product (food
preservation). Unlike other cooking methods, baking
does not alter the nutritional value of the food item, e.g.
the fat and calor ie content of the food [1, 3, 4] . Usually,
baking takes place in an oven or on a hotplate, but also in
hot ashes or on hot stones. During baking, the heating
process is done by a combination of three forms of heat:
by infra -red energy that is radiated from oven walls, by
circulating hot air; and by conduction through the baking
pan or tray [3]. That means the efficiency of the baking
process depends on the optimal use of three different
parts of the device: the walls, the tray and the ventilation
system [2, 10].
The dry heat of baking changes the structures of
starches in the food and gives its outer surface a brown
colour, giving it an attractive appearance and taste, while
partially sealing in the food's moisture. The browning is
caused by caramelization of sugars and the Maillard
reaction. Moisture is never really entirely "sealed in",
however over time an item being baked will become dry.
This is often an advantage, especially in situations where
drying is the desired outcome, for example in drying
herbs or in roasting certain types of vegetables [5, 12] .

II. BAKING USING CHARCOAL
Charcoal is a black substance that resembles coal and
is used as a source of fuel. Charcoal is generally made
from wood that has been burnt, or charred, while being
deprived of oxygen so that what's left is an impure
carbon residue. While charcoal is used in the
manufacture of various objects from crayons to filters, its
most common use is as a fuel [7]. One of charcoal's most
common fuel uses is for cooking. Charcoal produces a
heat that is hotter and burns cleaner than wood, making it
ideal for cooking. Though charcoal as a heat source has
been around for centuries, Henry Ford is credited with
cornering the U.S market for mass produced charcoal for
backyard grilling.The charcoa l burns (oxidizes) provided
there is sufficient oxygen at the fire -bed. At temperatures
around 800 C, the carbon monoxide produced reacts with
oxygen (again provided oxygen is available) just above
the fire bed to give carbon dioxide. The charcoal will
usually continue to burn long after the volatiles have
been used up. A charcoal fire requires oxygen both at the
fire bed (primary air) and just above the coals (secondary
air). If there is insufficient secondary air, the fire will
give off carbon monoxide, w hich can be dangerous to the
stove user especially in enclosed spaces [8].
Charcoal oven has proven to be more efficient and
effective than expected. Baking with charcoal gives you a
lot of advantages, particularly in this part of the world
where electricit y power supply is a problem. The baking
oven could be used both in the rural and urban settlement
for small -scale business and also for domestic use. To
solve our domestic need, a small -scale oven, which can
be used at home, is needed and to a large extent a small –
scale business can actually emerge and help in providing
extra money for the family.
III. METHODOLOGY
3.1 Theory of Heat
Heat is energy in transit under the motive force of a
temperature difference. Any theory should be able to
explain the facts below;
i. Whenever there is an exchange of heat is
consumed (heat lost by the hot body always equal
to heat gained by the cold body
ii. The heat flow takes place from higher to lower
temperature.

International Journal of Recent Development in Engineering and Technology
Website: www.ijrdet.com (ISSN 2347 -6435(Online) Volume 2, Issue 6, June 2014 )
90
iii. The substances expand on heating.
iv. In order t o change the state of a body from solid
to liquid or liquid to gas without rise in
temperature, certain amount of heat is required.
v. When a body is heated or cooled its weight does
not change.
According to the modern or dynamical theory of heat,
Heat is a form of energy. The mean kinetic energy per
molecule of the substance is proportional to its absolutes
temperature [9].
3.2 Heat Transfer
Heat transfer many be defined as the transmission of
energy from one region to another as a result of
temperatu re gradient.
Heat transfer is as a result of temperature gradient. It
takes place by the following three modes: (i) Conduction
(ii) Convection (iii) Radiation.
Heat transmission in majority of real situations occurs
as a result of combustion of the modes of heat transfer in
a baking, heat transfer from the charcoal to the baking
space and heat conduction through the oven walls. Heat
always flows in the direct of lower temperature.
3.2.1 Conduction
Conduction is the transfer of heat from one part of a
substance to another part of the same substance, or from
one substance to another in physical contact without
appreciable displacement of molecules forming the
substance.
In solid, the heat is conducted by the following two
mechanisms:
i. By lattice Vib ration (the faster moving molecules or
atoms in the hottest part of a body transfer heat by
impacts some of their energy to adjacent molecules.
ii. By transfer of free electrons (free electrons provide
an energy flux in the direction of decreasing
temp erature for the major portion of the heat flux
except at low temperature.
In case of gases, the mechanism of heat conduction is
simple. The kinetic energy of a molecule is a function of
temperature. These are in continuous random motion
exchanging energy a nd momentum. When a molecule
from the high temperature region collides with a
molecule from the low temperature region, its looses
energy by collisions.
3.2.1.1 Fouriers Laws Of Heat Conduction
Fourier’s laws of heat conduction are an empirical law
base on observation and state as follows:
The rate of flow of heat through a simple
homogeneous solid is directly proportional to the area of
the section at right angles to the direction of heat flow
and to changes of temperature with respect to the length
of the path of the heat flow. Mathematically, it can be represented by the equation
[9]
dxdtA Q
– – – (3.1)
Where Q = heat flow through a body per unit time (watt)
A = surface area of heat flow (perpendicular to the
direction of flow) m2
dt = temperature difference of the face of block
(homogeneous solid) of thickness dx through which heat
flows
or oK
dx = thickness of body in the direction of flow, m.
Thus
, where K = constant of
proportionality and is known as the rmal conductivity of
the body.
For composite materials:
Total heat flow is given by [9]

RdT


RTT2 1 – (3.2)
Where

R =
AkL
AkL
AkL
AhAhcc
ob
aa
o i1 1 – (3.3)
Where:
R=resistance to h eat flow
Hi and ho = inner and outer convective heat transfer co –
efficient
A= cross sectional area
la, lb and lc= thickness of materials a, b, c
Ka, kb and kc =conductive heat transfer co -efficient
for materials a, b, c
3.2.2 Convection
Convection is the transfer of heat with a fluid by
mixing of one portion of the fluid with another.
Convection constitutes the macro form of the heat
transfer since macroscopic particles of a fluid moving in
space cause the heat exchange.
The effectiveness of heat transfer by convection
depends largely upon the mixing motion of the fluid.
This mode of heat transfer is met within situation
where energy is transferred as hear to flowing fluid at
any surface over which fluid occurs. This mode is
basically conduction in a thin fluid layer at the surface
and them mixing caused by the flow. The heat flow
depends on the properties of the fluid and is independent
of the properties of the material of the surface.
However, the shape of the surface will influence the
flow and hence th e heats transfer.

International Journal of Recent Development in Engineering and Technology
Website: www.ijrdet.com (ISSN 2347 -6435(Online) Volume 2, Issue 6, June 2014 )
91
1. Free or natural convection -: free or natural
convection occurs when the fluid calculates by virtue of
the natural differences in densities of hot and cold fluid;
the denser portions of the fluid move downward because
of the greater f orce of gravity, as compared with the force
on the less dense.
2. Forced convection: – When the work is done to blow or
pump the fluid, it is said to be forced convection.
3 Newton law of cooling : states that the heat transfer
from a solid surface of area A at a temperature t w, to a
fluid of temperature t, is given by
Q = hA (t w-t) -(3.4)
Where h is called the heat transfer co -efficient. It is
used for heat transfer from a solid to a liquid and vice –
versa.
3.2.3 Radiation
Radiation is the transfer of heart through space or
matter by means other than conduction or convection.
Radiation heat is thought of as electromagnetic waves
or quanta; an emanation of the same nature as light and
radio waves. All bodies radiate heat so a transfer of heat
by radiatio n occurs because hot body emits more heat
than it receives and a cold body receives more heat than
it emits. Radiant heat energy (being electromagnetic
radiation) requires no medium for propagations and will
pass through vacuum.
The properties radiant heat in general is similar to
those of light.
Some of its properties are:
1. It does not require the presence of a material
medium for its transmission.
2. Radiant heat can be reflected from the surface and
obey the ordinary laws of reflection.
3. It travels with ve locity of light.
4. Like light, it shows, interference, diffraction and
polarisation
5. It follows the inverse square laws. The wavelength
of heat radiations is longer than that of light waves;
hence they are invisible to the eye.
3.2.3.1 Laws of Radiation
1. Wien’s law: – it states that the wavelength ۸m
corresponding to the maximum energy is inversely
proportional to the absolute temperature T of the
hot body
2. Kirchoffs law: – it states that the emissivity of the
body at a particular temperature is numerically
equal to its absorptivity for radiant energy from
body at the same temperature.
3. The Stefan Boltzmann law: – states that the
emissive power of a black body is proportional to
fourth power of its absolute temperature. I.e.
T4
F
A (T 14
T24 ) – (3.5)
F= a factor depending on geometry and surface
properties
Stefan – Boltzmann constant = 5.67
–
8w/m2k4
A = area, m2
T1, T2= Temperature degree Kelvin (K)
This equation can also be re -written as;

=
212
11
T TTT
 – – (3.6)
Where denominator is radiation thermal resistance
(RTh) rad = F
A (T 1
T2) (T2
1
T22) – – (3.7)
F =1 for simple cases of black enclosed by other
surface
F = emissivity
– for no n
black surface enclosed by
other surface.
Emissivity (
) is defined as the ration of heat radiated
by a surface to that of an ideal surface.
3.3 Calculations
3.3.1 Heat Emitted by Charcoal : The heat emitted by
charcoal of recommended mass of 0.5kg was 17,220 kJ.
3.3.2 Heat Loss to Baking Space . The heat loss to baking
space as calculated was found to be 9, 284 kJ.
3.3.3 Thickness of Insulation : The thickness of the
insulation was calculated to be approximately 25 mm.
3.4 Construction
The materials used in the fabrication of the oven are:
mild steel, angle iron, flat bars and square pipes.
Aluminum foil was also used. The choice of these
materials was based on their availability and
affordability. Aluminium foil is also widely used for
thermal insulation (barrier and reflectivity), heat
exchangers (heat conduction) and cable liners (barrier
and electrical conductivity). The oven was constructed in
the Depart mental workshop of Mechanical Engineering,
Ahmadu Bello University Zaria using standard
fabrication tools. Plate 1 to Plate 3 shows the views of
the oven.
3.4.1 Oven Box: The oven box was made from one –
millimetre (1mm) mild steel. Basically cutting and
joining the metals together to make the box. The method
of joining is Lapp joint. This method involves the
bending and hammering the joint together. The choice of
this metal sheet is because it is relatively light so that the
box becomes easy to carry. The d imensions of the box
are 80 x 50 x50 cm.

International Journal of Recent Development in Engineering and Technology
Website: www.ijrdet.com (ISSN 2347 -6435(Online) Volume 2, Issue 6, June 2014 )
92
3.4.2 Charcoal Tray: The tray is also made from 1mm
sheet of mild steel. It is formed by Lapp joint. The base
of the tray is perforated using a drilling machine. Its
dimensions are 80 x 40 x 20 cm.
3.4.3 Slide Door: The slide door is made from 1mm sheet
of mild steel. It is simply cut and curved at one end to the
handle. Its dimensions are 30 x 20 cm.
3.4.4 Asbestos: The inside of the oven box is lined with
double of asbestos board to provide the necessary
insulation for the oven.
3.4.5 Aluminium Foil: Aluminium foil is used to reduce
heat loss through the oven wall by reflecting the heat
back to the baking space.
3.4.6 Angle Iron: Angle iron is used to hold the
aluminium foil and asbestos firm to the oven wall. Holes
are drilled through the angle iron and oven wall. Screws
are used to hold it firm. The angle iron provides a means
of supporting the flat bars.
3.4.7 Flat Bars: The flat bar is used to support the baking
pan. It is placed on the angle iron.
3.4.8 Cost of Production: The total production cost of the
prototype oven was N5,200 ($30) only. However, with
mass production the unit production cost will be less.
This is because the material purchase will be in bulk and
there will be minimal waste.
IV. TESTI NG RESULT AND DISCUSSIONS
0.2kg of charcoal was used fo r the baking of bread. It
took 2 5 minutes to bake at 140 oC . The initial
temperature of the oven was 33 oC. The baking of the
bread took place after baking of the cake. The cake was
baked at a Teperature o f 120 oC and the time taken was
28 minutes. The maximum temperature of the oven was
220 oC The outer oven temperature was 63 oC. Mercury
in glass thermometer was used to determine the
temperatures of the oven (thermometer of range 0 -110 oC
and of range 140 -300 oC). Plate 4 to Plate 7 shows the
stages of the baking processes and the baked items. From
the test results, the charcoal oven prototype can be used
for baking both in rural and urban settlements e specially
in the Northern part of Nigeria. The results also agree
with [2, 6, 10, 11] recommendations respectively.
V. CONCLUSION
It was amazing to discover such an efficient and
highly economical oven. With a very small quantity of
charcoal, bread can be b aked in a short time. What is
even more interesting is that it does not depend on
electricity for heat supply. The charcoal provides the heat
supply and it is readily available at a cheap rate.
VI. RECOMMENDATION
This oven is a wonderful piece for small -scale
business. You have a combination of efficiency and
availability of raw materials. The oven can be used both
in rural and urban settlements. The oven is an advantage
largely because of electricity power instability. The
Federal and State Government sho uld assist in the mass
production of this oven to the end users.
REFERENCES
[1] Armando Manhiça, Fabião/ Lucas, Carlos/ Richards, Tobias
(2012): Wood consumption and analysis of the bread baking
process in wood -fired bakery oven. , Applied Thermal
Engineering, Volume 47, 5 December 2012, Pages 63 -72,
available at:
http://www.sciencedirect.com/science/article/pii/S1359431112001
627.
[2] Emma Christensen (2012) How To Bake a Potato in the Oven
www.thekitchn.com/how -to-bake -a-potato -in-the-oven -165615
[3] Fellows, Peter 2012: Baking. Technical Brief of Practical Action.
This is a technical brief about the baking process. March 2012,
available at: http://practicalaction.org/baking .
[4] Giz Hera (2014) Baking with Improved Ovens . Available online
at https://energypedia.info/wiki/Baking_with_Improved_O vens
[5] GIZ India (2011): Identification of Industrial Sectors Promising
for Commercialisation of Solar Energy, Commercialisation of
Solar Energy in Urban and Industrial Areas – ComSolar, New
Dehli, India. Available online at
http://www.giz.de/en/downloads/giz2011 -commercialisation –
solar -energy -india -en.pdf .
[6] Julia Layton (1998) Calculating Convection Oven Cooking
Times . Available online at
home.howstuffworks.com/…/calculating -convection -oven –
cooking -times ..
[7] Kulla, D. M (2011) :Technology improvement for safety and
economy in wood burning devices in Niger i., Ph.D Thesis,
Department of mechanical Engineering, A.B.U Zaria.
[8] Kulla, D M, Sumaila, M, Alabi A A and Bamshima A M (2014)
Evaluation of Cooking Energy Efficiencies and Emissions. 4th
Annual and International Conference of The Renewable and
Alternative Energy Society of Nigeria(RAESON) Imo State
University, Owerri, Nigeria Feb 23 -26 G27
[9] Rajput , R K. (2004) “Heat and Mass Transfer” S.Chand and
Company Limited, New Delh i.
[10] Stephane Jaworski (1997) Oven Baking Temperatures: joy of
baking.com :
http://www.joyofbaking.com/OvenTemperatures.html#ixzz35ugC
znVD
[11] The Independent Aquarius (TIA) (2012) oven – How to decide the
baking temperature Cooking Available online at
.stackexchange.com/…/how -to-decide -the-baking -temperature -w.
[12] UNIDO 2004: Smal l-scale Cereal Milling and Bakery Products,
Production Methods, Equipment and Quality Assurance Practices,
Technology Manual, UNIDO: Vienna. Available at:
http://www.unido.org/fileadmin/user_media/Publications/Pub_
free/Small_scale_cereal_milling_and_bakery_products.pdf

International Journal of Recent Development in Engineering and Technology
Website: www.ijrdet.com (ISSN 2347 -6435(Online) Volume 2, Issue 6, June 2014 )
93

Figure 1 : Baking Oven in Construction
Figure 2 : Baking Oven after Construction

Figur e 3: Ignited Charcoal before baking
Figure 4 : Dough before baking

International Journal of Recent Development in Engineering and Technology
Website: www.ijrdet.com (ISSN 2347 -6435(Online) Volume 2, Issue 6, June 2014 )
94

Figure 5 : Dough in oven before baking
Figure 6 : Cake in oven just after baking

Figure 7 : Cake after removal from oven
Figure 8 : Cake served and ready for eating