EXPERIMENTAL PERFOMANCE EVALUATION OF CHARCOAL … · 2015. 9. 16. · 3 CERTIFICATION This is to certify that this work “Experimental Performance Evaluation Of Charcoal Stove”

1

EXPERIMENTAL PERFOMANCE EVALUATION OF

CHARCOAL-STOVE

BY

USMAN, OJONIMI YUSUF

REG.NO. PG/M.ENG/02/32816

DEPARTMENT OF MECHANICAL ENGINEERING

UNIVERSITY OF NIGERIA

NSUKKA

MAY 2011

2

EXPERIMENTAL PERFORMANCE EVALUATION OF

CHARCOAL-STOVE

A PROJECT REPORT SUBMITTED TO THE DEPARTMENT

OF MECHANICAL ENGINEERING UNIVERSITY OF

NIGERIA, NSUKKA IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR AWARD OF DEGREE OF MASTER

OF ENGINEERING (M.ENG.) IN MECHANICAL

ENGINEERING (ENERGY AND POWER TECHNOLOGY

OPTION)

BY

USMAN, OJONIMI YUSUF

REG. NO. PG/M.ENG/02/32816

SUPERVISOR: PROF. S.O. ENIBE

DEPARTMENT OF MECHANICAL ENGINEERING

UNIVERSITY OF NIGERIA,

NSUKKA

MAY 2011

3

CERTIFICATION

This is to certify that this work “Experimental Performance Evaluation Of

Charcoal Stove” is an original work by the student, Usman, Ojonimi Yusuf

withRegistration number PG/M.ENG./02/32816.

He has met the requirements in course work and in research work for the award

of the Master of Engineering, (M.Eng.) Degree in Mechanical Engineering.

______________________________ _____________ Prof. S.O. Enibe Date

(Supervisor)

______________________________ _____________ Prof. S.O. Onyegegbu Date

(Head of Department)

______________________________ _____________ External Examiner Date

4

DEDICATION

This work is dedicated to my wife and children and all who stood by my family

in the course of this study which was painfully prolonged by a number of bitter

circumstances.

5

ABSTRACT

An experimental evaluation of the performance of a charcoal stove designed to reduce human labour and health hazards associated with frying in open fire was carried out. The channel- type metallic stove was lagged with 2.54 mm thick glass wool. The charcoal grate is 160 mm from the floor and has 44 holes of 12 mm diameter each to serve as air holes and provide passage for ashes, drilled in it. The charcoal bed is 230 mm from the bottom of the pot and the channel gap is 8mm. A 300 mm high chimney of diameter 50 mm to enhance draft was incorporated. The stove has an internal diameter of 417 mm and a height of 460 mm. Water boiling tests were carried out in order to generate the data required for assessing the stove’s performance indices such as fire power, specific consumption and percent heat utilized. Evaluation of performance indices shows an average fuel firepower (f.p.) of 7.59 KW, an average specific fuel consumption (s.c.) of 0.11 Kg/kW hr, and an average percent heat utilized (p.h.u.) of 15% (or 15% thermal efficiency). The recorded experimental data shows that an average amount of 0.43 kg of charcoal would be required to be burnt for an average of twenty nine minutes to bring 3.6 kg of water to boil. The tests yielded an efficiency of 15%. Based on the results of the study, it can be seen that the performance of the charcoal stove is better than the traditional three-stone open fire reported to have efficiency of about 10%

6

ACKNOWLEDGEMENTS

To have come this far is entirely by the grace of God and the support of

His ‘channels of blessings’. A few of such willing vessels of God’s favour are

acknowledged below.

I reserve sincere thanks to the Chairman and members of Federal

Polytechnic, Idah “Staff Development Board” for permitting me to go on

course for 12 months. Equally remembered are my former Heads of

Department, Eng’rs O.A. Adeleye and J.N. Onyejizu, Dr. D.O. Bello, for his

generous and ready counsels and my colleagues who have had to stand in for

me many times when I had to travel to Nsukka.

Fondly remembered is my project supervisor, Prof. S.O. Enibe who has

been a great source of inspiration to me. His consistent display of Christian

virtues in his day-to-day discharge of his official duties has made him a role

model to me. I appreciate my colleagues in the Department of Mechanical

Engineering, Energy and Power Technology option, 2002/2003 set, especially

my bossom friend, late Bro. Ndubuisi Onuoha and Dr & Mrs. Jonathan

Obianuko.

7

Affectionately remembered are the brethren of “Graduate Students

Fellowship”, 2002/2003 set; Rev.-Dr. Daniel Ozioko, senior pastor of

Prevailing Word Assembly, members of the Prevailing Word Assembly,

Nsukka, and Dr. Alhassan Jibrin of Physics and Astronomy Department,

U.N.N., for accommodating me during my first few days in Nsukka.

My sincere love to my wife and children ( Favour, Precious, Destiny and

the little one who died few hours to delivery), for all the lonely days and nights

they spent without “Daddy”, their prayers and other sacrifices they made.

Equally remembered are the loving members of my ministries, “Prayer &

Evangelism Ministries”, for all their prayers that God answered by seeing me

through this long programme, the many services during which they expected

their pastor to minister but could not because of this study and their financial

and material support.

I appreciate my parents for their understanding, prayers and patience.

Finally, I thank all whom I could not name in this report but were used by God

to give me a push in this programme. May the blessings of the Lord rest upon

you all and I pray you do not faint in well-doing, for in due season you will reap

the reward.

8

TABLE OF CONTENTS Content page Certification………………………………………………iii

Dedication……………………………………………….iv

Abstract………………………………………………….v

Acknowledgements…………………………………..….vi

Table of contents…………………………………..…….viii

List of figures……………………………………………xii

List of tables…………………………………………….xiv

Symbols…………………………………………………xv

Greek notations………………………………………….xvii

Subscripts……………………………………………….xviii

Superscripts……………………………………………..xviii

CHAPTER ONE

1.0 INTRODUCTION

1.1 Problem identification……………………..…1

1.2 Objectives of the research…………………....6

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 Stove technology ……………………………7

9

2.2 Gas stoves………………………………….….11

2.3 Electric stoves…………………………………13

2.4 Wood and charcoal stoves……………………..13

2.4.1 Inverted frustum metal stoves…………………14

2.4.2 Channel type stove…………………………….15

2.4.3 Improved charcoal stoves……………………...16

2.5 Kerosene and other stoves……………………..21

CHAPTER THREE

3.0 DESIGN PARAMETERS AND ENERGY BALANCE

CALCULATIONS

3.1.0 Theoretical analysis of charcoal combustion

Characteristics…………………………………..23

3.1.1 Determination of stoichiometric air-fuel ratio…..24

3.1.2 Analysis of the dry products of combustion…….27

3.2.0 Maximum theoretical temperature……………... 30

3.2.1 Determination of adiabatic flame temperature…..30

3.3 Conductive heat transfer…………………………46

3.4 Reducing wall losses……………………………..52

3.5 Convective heat transfer………………………….52

3.6 Determination of convective heat transfer

Coefficient………………………………………..53

10

3.7 Radiative heat transfer…………………………….54

3.8 Energy balance calculations……………………….56

3.9 Energy balance of pot and content………………...64

3.10 Energy balance of stove wall………………………74

3.11 Energy balance across the combustion chamber…...80

3.12 Stove template design………………………………84

3.13 The grate and air holes……………………………..85

3.14 Door………………………………………………..87

3.15 Ash tray…………………………………………….87

CHAPTER FOUR

4.0 STOVE TESTING AND DATA ANALYSIS

4.1 Materials and equipment…………………………94

4.2 Methodology……………………………………..95

4.3 Experimental design……………………………..95

4.4 Method of data analysis…………………………97

4.5 Moisture content determination…………………98

4.6 Locations of thermocouples on the stove

during the tests…………………………………..100

4.7 Data analysis……………………………………..101

4.8 Discussion of results……………………………..113

4.9 Conclusion…………………………………….....115

11

4.10 Recommendations……………………………….115

References………………………………………………117

12

LIST OF FIGURES

FIGURE PAGE

Fig 1 Glass ceramic cook top………………………………..5

Fig. 2.1 Raised kamado stove…………………………………9

Fig. 2.2 Gas stove…………………….……………………….12

Fig. 2.3 Inverted fustrum metal stove………………………..14

Fig. 2.4 Channel type charcoal stove…………………………16

Fig. 2.5 Megan chulha stove…………….……………………..17

Fig. 2.6 Lorena stoves disseminated in Guatemala...………....18

Fig. 2.7 Wood stove developed in Senegal(Ban Ak suff)..……19

Fig. 2.8 Metal jiko stoves…………………...………………….20

Fig. 3.1 Thermal resistance network………………………...…48

Fig. 3.2 Schematic diagram showing pot and content

energy balance…………………………….………….64

Fig. 3.3 Heat conduction through the pot wall……………….64

Fig. 3.4 Schematic diagram of the stove..…………………….74

Fig. 3.5a Stove’s outer wall template……………..………….86

Fig. 3.5b Stove’s inner wall template…………………………86

Fig. 3.6 Door……………………………………….……..…..88

Fig. 3.7 Ash tray………………………………………………88

13

Fig. 3.8 Isometric drawing of the charcoal stove……………89

Fig. 3.9 Orthographic projection of the charcoal stove……..90

Fig. 3.10 Photograph of the constructed stove showing

the grate, chimney, door and air holes……………..91

Fig. 3.11 Stove’s photograph showing the door

closed and air inlets open…………………………92

Fig. 3.12 Photograph of the constructed stove

showing the door opened………………………..…93

Fig. 4 Location of thermocouples on charcoal

stove during the tests……………………………….100

14

LIST OF TABLES

TABLES PAGE

Table 3.1 Composition of charcoal by mass……………….….23

Table 3.2 Analysis of the ultimate composition of charcoal...... 26

Table 3.3 Analysis of products of combustion...……………….27

Table 3.4 Volumetric analysis of the products (1)..……………28

Table 3.5 Volumetric analysis of the products (2)..……………29

Table 3.6 Constants for heat capacity equations….……………58

Table 3.7 Constants for heat capacity equations

shown in matrix format……………………………..59

Table 4.1 Charcoal moisture content…………………….……...98

Table 4.2 Laboratory test data sheet for charcoal stoves……..…101

Table 4.3 Data obtained for stove test 1……………………...….103






Table 4.9 Summary of computed results……………………...…112

15

SYMBOL NUMENCLATURE

∆H Change in enthalpy

∆U Change in internal energy

0C degree Celsius

A area of material

A/F Air-fuel

C length of the pan around at its widest circumference.

C Carbon

CC calorific value of charcoal.

CO2 Carbon dioxide

Cpi mean specific heat at constant pressure of the constituent, i.

cw combustion wall

dT change in temperature

e emissivity

f.p. fire power

G pot-to-wall channel gap

h heat transfer coefficient

H Hydrogen (atom)

Hf enthalpy

K Kelvin

16

K thermal conductivity

Kg Kilogram

KW KiloWatt

M metre

mi mass of constituent, i

mm millimeter

n moles

N Nitrogen (atom)

N2 Nitrogen

O2 Oxygen

p.h.u. percent heat utilized

Q Heat supplied

QF mass of charcoal after boiling has taken place

Qi mass of charcoal before boiling takes place.

R thermal resistance

Ractual Actual air-fuel ratio

Rstoic Stoichiometric air-fuel ratio

S thickness of metal used for producing pot.

S.C. Specific consumption

t temperature

Ta ambient temperature

Tf film temperature

17

Ti inlet temperature

To outlet temperature

Tr reference temperature

U Internal energy

W width of the cylindrical stove template

W Work

X, x, L thickness of material

Xp Percentage excess air

GREEK NOTATIONS

∑ summation

∞ infinity

ᵦ coefficient of thermal expansion

σ Stephan Boltzman’s constant

SUBSCRIPTS

0 reference/initial

1 initial

2 final

P products

R reactants

18

SUPERSCRIPTS

b constant

19

CHAPTER ONE

1.0 INTRODUCTION

1.1 PROBLEM IDENTIFICATION

One of the earliest sources of energy utilized by man was his own

muscle. Food, water and other loads were borne by the arm, head,

shoulder or back. Latter, animals such as dogs, donkeys, oxen and

mules, etc were used as beasts of burden. Next to that was the

discovery of fire, probably obtained by striking rocks together. The fire

was used to cook food, keep warm, clear bush, preserve farm produce,

harden pottery for bowls and produce tools from metals. Subsequently,

other sources of energy such as solar energy, wind energy, electrical

energy, nuclear energy and fossil fuels were discovered (Sutkhame,

1990 ).

The energy available to us can be divided into two main groups

based on their sources. These are renewable and non-renewable

sources. Renewable energy is obtained from animals and plants in the

form of food, wood, and alcohol. These can be replaced when more is

20

needed and are in the form of solar energy, wind energy, tidal or

geothermal energy. Non renewable energy belongs to that group of

energy that cannot be replaced once utilized. Examples are coal, oil and

natural gas. These are known as fossils (Wikipedia, 2006).

The energy at man’s disposal is limited in supply. It is now an

indisputable fact that our energy consumption habit which has been with

us for many years cannot be treated with levity as our fossil fuel

resources are being depleted at a fast rate. This consumption pattern

has sky-rocketed the cost of conventional sources of energy with its

observable side effects on our industries, domestic lives, agricultural

production and commerce.

It is a well-known fact that more than half of the people in third

world countries depend heavily on bio-fuels such as charcoal, fuel wood,

crop residues and dung to meet their energy requirement for cooking.

Going by the persistent low level of poverty and under-developments in

these countries, it is unlikely that a major transformation to the use of

petroleum fuels and electricity would be effected in the near future.

21

Due to poor storage facilities and inefficient transportation system,

much of farmers’ produce are wasted after harvest even in the face of

bumper harvests. In view of the Nigerian government’s recent “Cassava

for Export Programme”, it is hoped that production of cassava will

witness a boom and that calls for prudent handling of the fruits of the

programme for it to yield the expected results.

Garri frying is a means of processing and preserving cassava. First

the cassava tuber is harvested, peeled, washed and grated using a

cassava grating machine. The grated cassava is then stored in a sack or

other containers that will allow the fluid to drain for days depending on

the quality of the garri to be produced. Sometimes a screw jack is

employed to facilitate the squeezing of the sack containing the grated

cassava. In the rural areas, the sacks containing the grated cassava are

placed on logs of wood or stones and heavier logs of wood or stones are

placed on them. Around the third day, the dried and fermented cassava

is brought out of the sacks, sieved and dried in a frying pan.

The use of fuel wood has a tendency to aggravate the current

state of deforestation. In the attempt to combat deforestation which

leads to loss of forest cover and environmental degradation, many

programmes have been put in place to conserve the supply and

production of fuel-wood. Such measures include planting of fast growing

22

trees, better land management and fuel importation. These programmes

have not produced the anticipated magic.

The United Nations Food and Agricultural Organization (UNFAO)

cited four causes of global deforestation which are: Shifting agriculture,

opening pasture land to grow beef for export, commercial timber

operation including timber access roads and uncontrolled bush burning.

(Baldwin,1987). The foregoing shows that the use of charcoal for

cooking is not a primary cause of deforestation on the global scale.

Undoubtedly, the effect may become significant in urban areas and in

arid regions where demand for fuel wood is high and the biomass

productivity of the land is small.

A restrained use of charcoal as fuel is a way of limiting energy

losses due to the utilization of fuel woods. The petroleum fuels are non-

renewable and scarce in supply. Prudent domestic use of charcoal as

fuel helps in making more petroleum fuels available for industrial and

heavy duty purposes.

A stove can be defined as a heat-producing device. The word

describes an appliance employed either for cooking or for generating

warmth. In British English, however, the term cooker is normally used for

23

cooking appliance and stoves for wood- or coal-burning units in room-

heating devices. According to Wikipedia (2006), another American

English word for a cooking stove is range.

There are many kinds of stoves. A kitchen stove is used to cook

food, and refers to a device that has both burners on the top (also known

as the cook top or range or, in British English, the hob) and, often, an

oven. A cook top just has burners on the top and is usually installed into

a counter top as shown in fig. 1.1.

Fig. 1.1 Glass-Ceramic cook-top

(Source: Stove-Wikipedia, the free encyclopedia)

A drop-in range has both burners on the top and an oven and hangs

from a cutout in the counter top (that is, it cannot be installed free-

standing in its own). In industrial usage, stove may refer to the place

24

where fuel is burnt before the heat is fed to a large heat consumer such

as an open hearth furnace.

A stove generates heat by one or more of the following means:

A) Burning of natural gas, liquefied gases (e.g. Propane, butane),

heating oil, bio-fuel (such as wood, coal, corn) or synthetic heating

pellets.

B) Electrically, by either electrical resistance (by way of a heating

element) or induction (Wikipedia, 2006).

1.2 OBJECTIVES OF THE RESEARCH

1) To design and construct a channel type, metallic charcoal

stove.

2) To lag the combustion chamber with the view to reducing

excessive heat loss and health discomfort associated with un-

lagged single-wall metallic stoves.

3) To evaluate the performance of the constructed stove in terms

of fire power, specific fuel consumption and percent thermal

efficiency.

25

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 STOVE TECHNOLOGY DEVELOPMENT

The history of kitchen stove in Europe began in earnest in the 18th

century. People cooked in open fires fuelled by wood prior to that time, on the

ground or on low masonry constructions. Waist-high brick-and-mortar hearths

and the first chimneys appeared in the middle ages, so that cooks no longer had

to kneel or sit to attend to foods on the fire. Cooking was effected principally on

cauldrons hung above the fire or placed on trivets. The heat control was effected

by placing the caldrons higher or lower above the fire. (Wikipedia, 2006).

Three major disadvantages of open fire that prompted inventors as far

back as 16th century to device improvements are: it is dangerous; it produces

much smoke and has poor thermal efficiency. Attempts were made to enclose

the fire to make better use of the heat that is generated and thus reduce the wood

consumption. A first step was the fire chamber, the fire was enclosed on three

sides by bricks-and-mortar walls and covered by an iron plate.

This technique also caused a change in the kitchen ware used for cooking, for it

required flat-bottomed pots instead of caldrons. Only in the year 1735 did the

first design that completely enclosed the fire appear; the castrol/stove of the

26

French architect Francois Cuvillies was a masonry construction with several fire

holes covered by perforated iron plates. It is also called stew stove. Near the end

of the 18th century, the design was refined by hanging the pots in holes through

the top iron plate, thus improving heat efficiency even more (Wikipedia, 2006).

Chinese and Japanese Civilization had, much earlier, discovered the

principle of closed stove. Clay stoves that enclosed the fire completely were

already known from the Chinese Qin Dynasty, (221BC - 206/207 BC), Kamado,

similar in design to the Qin, appeared in the Kofun period (3rd – 6th century BC)

in Japan (Wikipedia, 2006). These stoves employed wood or charcoal as fuel.

The stoves were fired through a hole in the front. In the two designs, pots were

hung into or placed over the holes at the top of the knee-high stove. During the

Edo period (1603 – 1867 BC), raised Kamados, fig. 2.1, were developed in

Japan. (Wikipedia, 2006).

27

Fig. 2.1: Raised Kamado stove

(Source: Stove-Wikipedia, the free encyclopedia)

After the discovery of fire by man, open fireplace served as a veritable

source of light before lamps were discovered. The open fireplace is inefficient

on two counts. One, a large updraft pulling air (and consequently heat) out of

the chimney is required in order to prevent air and smoke from spilling back

into the room. That is to prevent the discomfort such fire users are exposed to.

The updraft both draws heat away and draw air from the entire house through

the chimney.

28

Two, in an open fire, some of the combustible gas coming off the wood escapes

and thus is lost not being ignited. The resolution of these problems led to the

development of masonry heaters, and then metal stoves came into use in the 18th

century (Wikipedia, 2006).

The Franklin stove believed to have been invented by Benjamin Franklin

in 1742, is an early and famous example of wood burning metal stove. The

stove was not designed for cooking but house heating. In the 19th century,

Benjamin Thompson was among the first to present a working useful kitchen

stove. His Rumford stove used one fire to heat several pots that were also hung

into holes so that they could be heated from the sides too. Each hole had heat

regulator. Rumford stove was designed to serve large canteen or castle kitchens.

The stove was not suitable for domestic use until after another 30 years

following reduction in the size of the iron stove and subjecting the technology

to thorough improvement.

The regulation of air in-flow into the metal stove to allow only the

amount required for complete combustion, results in reduction of air flow.

Modern wood and charcoal stoves also increase the completeness of

combustion. Catalytic converters which aid the gas and smoke particles not

really burned to combust are used in more expensive stoves. Other models

29

designed to produce complete combustion and hence improve efficiency use

designs such as firebox insulation ( as in this project), a large baffle to produce

longer, hotter gas flow path, pre-heating the air prior to its entering the

combustion chamber, and the use of radiation shields under the combustion

chamber.

A window is incorporated in the design of modern enclosed stoves to let

out some light and to aid the user assess the progress of the fire. The window is

usually constructed using glass or semi-translucent manufactured mica.

2.2 Gas stoves

Other types of stoves are fuelled by gas and electricity. The first gas

stoves were developed already in the 1820s but these were not widely used

(James Sharp in Northampton, England, patented a gas stove in 1826 and

opened a gas stove factory in 1836). At the World Fair in London in 1851, a gas

stove was shown but only in 1880s did this technology start to become a

commercial success. The main reason for this delay was the slow growth of the

gas pipe network. The gas stove technology underwent further development

until the invention in 1922 of a high-end gas stove called the AGA cooker by

Swedish Nobel prize winner Gustaf Dalen. This stove is considered to be the

30

most efficient design and is a much sought after kitchen “must have” in certain

circles-despite the hefty price tag. In the Third World countries, domestic gas

stove application is hunted by high cost and inadequate supply of gas

(www.en.wikipedia.org/wiki/stove, 2006. A typical gas stove is shown in fig.

2.2.

Fig.2.2: Gas stove

(Source:www.en.wikipedia.org/wiki/stove)

31

2.3 Electric stoves

In 1892, Thomas Ahearn invented the electric cooking range, one of

which was installed in the Windsor Hotel in Montreal. This electric stove was

shown at the Chicago World’s Fair in 1893, where an electrified model kitchen

was showcased. The electrical stove technology has developed in several

successive generations resulting in the emergence of resistor heating coils

(which heated iron hotplates), glass ceramic cook tops and induction stoves.

The spread of electric stove in underdeveloped countries is slow because many

towns and villages are not electrified. Also many in the underdeveloped

countries are living below the poverty line so they cannot afford this improved

efficient stove.

2.4 WOOD AND CHARCOAL STOVES

This research work is a practical contribution to the global effort to

reduce the burden borne by rural poor in their bid to meet the energy

requirement for daily cooking, processing and preservation of farm produce.

The use of fire has been with man for a long time now. Early discoverers of fire

used it for hunting, clearing of land for agriculture, cooking, among other uses.

Charcoal stoves have been constructed using materials such as metal, clay and

ceramic. The stoves could be single pot or multi-pot.

32

2.4.1 INVERTED FRUSTUM METAL STOVE

This stove is made up of metal and the shape is that of an inverted

frustum of a square pyramid as shown in figure 2.3. A square or rectangular

base having an air hole cut in it serves as the stand. The common defects of this

design are poor draft, blocking of air holes and poor efficiencies resulting from

excessive heat loss. Appropriate sizing of the air holes and careful insulation

will improve the stove performance (Baldwin, 1987).

Fig. 2.3: Inverted frustum charcoal stove

Air hole

33

2.4.2 CHANNEL TYPE STOVE

The channel type stoves are stoves whose combustion chambers are

cylindrical (fig. 2.4). That implies uniform cross-sectional area along the length

of the combustion chamber. The material for the combustion chamber could be

clay or metallic depending on design considerations and purpose. The clay type

is usually fired after moulding to improve its hardness while the metallic type is

normally painted to discourage rust. They clay type is susceptible to breakage

either at the point of application or in the course of transportation. The stove

body has a tendency to store a lot of heat and that affects the amount of heat that

is made available to the pot. A very outstanding advantage of the clay type is

that the stove wall serves as heat shield to the user.

The metal type obviously is lighter and conducts heat faster than the clay

type. The higher heat conduction rate exposes the user to danger of being burnt,

unless properly lagged. The metallic type is more portable and durable, hence

the choice for this work.

34

Fig. 2.4: Channel type charcoal stove

2.4.3 IMPROVED CHARCOAL STOVES

The apparent ineffectiveness of several of government’s measures and

other sectors in stemming the pain the rural poor bear, stirred some Non-

Governmental Organizations (NGOs) involved in basic needs programmes and

rural development at household level to develop and disseminate relevant

energy alternatives by focusing on stoves. Their efforts are yielding results in

Africa, India and other third world countries. An example is the Megan Chulha,

fig. 2.5, which was developed in 1947 by the AU – India Village Industries

association,(SCNCER).

35

Fig. 2.5: Magan chulha stove

(Source: ASEAN SUB COMMITTEE ON NON-CONVENTIONAL ENERGY RESEARCH, (SCNCER))

In SriLanka, improved woodstove were developed by Sarvodaya Meluib,

Horena, Tunaku. In Senegal, the Centre of Studies and Research on Renewable

Energy (CERER) at the University of Dakar, started an energy saving

programme initiated by a French and Senegalese Engineer, and further assisted

by three American consultants from the Approvecho Institute. This effort

yielded the Lorenas, fig. 2.6, “Ban Ak Sunf” (BAS), fig.2.7, a Wolof Word for

clayey sand, “Lauga”, “Coumba gueye” and “Kaya” evolved. Others were

Kenyan “JIKO” of various sizes, fig. 2.8, which were essentially portable metal

charcoal stoves produced by local artisans from recycled sheet steel. Countries

36

such as Ethiopia, Mali, Niger among other Sahelian countries have one form of

improved stove production and dissemination programme or the other

(SCNCER).

Fig. 2.6: Lorena stoves disseminated in Guatemala


37

(i) (ii)

(iii) (iv)

Fig.2.7: Wood stoves developed in Senegal (Ban Ak suff)


38

Fig. 2.8: Metal Jikos Stoves


39

2.5 KEROSENE AND OTHER STOVES

These are stoves which use petroleum fuels as energy source. Kerosene

is the main source of power. A required amount of kerosene is poured into the

stove and the oil moves through the wick by capillary action. The stoves vary

depending on the size, height, position of kerosene tank, number of pots and the

material used in fabricating them. The general problems confronting wide

spread use of kerosene are scarcity of kerosene and adulteration of kerosene

(where they are available). Scarcity heightens the price beyond the reach of the

common man. Several lives have been lost and others deformed or defaced on

account of burns resulting from kerosene adulteration

Other stoves use saw dust as fuel. Saw dusts are obtained from saw mills

or carpentry shops. The saw dusts may be made into briquettes, or poured into

the stove and compacted very well, leaving a hole at the centre. The hole

enhances draft. Saw dust stoves produces a lot of soot and smoke which

blackens the cooking vessels, and cause discomfort to the stove user.

In order to enhance convective heat transfer in stoves, three generic forms

of stove have been developed over the years. They are multi-pot stoves, channel

stoves and nozzle stoves. The channel stove, used in this project, offer better

40

performance than multi-pot stoves and they, generally, are more developed and

tested than nozzle stoves.

41

CHAPTER THREE

3.0 DESIGN PARAMETERS AND ENERGY BALANCE

CALCULATIONS

Charcoal is used as fuel in this channel type of stove being studied. Fuel

is defined simply, as a combustible material that may come as solid, liquid or

gas. The burning of charcoal, a solid fuel, liberates energy which could be used

for cooking or processing of food.

3.1.0 THEORETICAL ANALYSIS OF CHARCOAL COMBUSTION

CHARACTERISTICS

According to Baldwin (1987), charcoal has the following composition by mass:

TABLE 3.1 Composition of Charcoal by mass

ELEMENT C H O N Ash S

% BY

MASS

82.0 3.1 11.3 0.2 3.4 0.0

42

3.1.1 DETERMINATION OF STOICHIOMETRIC AIR-FUEL RATIO

Stoichiometric (or chemically correct) mixture of air and fuel is one that

contains the quantity of oxygen required for complete combustion of one unit of

the fuel. In this work a mass balance of the reactants is shown below, using the

values in table 3.1, in order to obtain the stoichiometric air-fuel ratio.

1282 C +

11.3 H +

163.11 O +

142.0 N + 3.4 Ashes + a (0.21O2 + 0.79N2)

→ bCO2 + dH2O + (28

2.0 + 0.79a) N2 + 3.4 Ash………………….(3.1)

Carbon balance:

1282 = b, hence b = 6.83.

Hydrogen balance:

11.3 = 2d, hence d = 1.55

Oxygen balance:

163.11 + 0.42a = 2b + d = 2 x 6.83 + 1.55

163.11 + 0.42a = 15.22,

43

From which a = 34.55.

(i) Carbon

C + O2 CO2 …………………………………..……… 3.2

12 kg of Carbon + 32 kg of oxygen 44 Kg of CO2

1 kg of carbon + 32/12 kg of oxygen 44/12 kg of CO2

0.82 of carbon + 32/12 x 0.82kg of oxygen 44/12 x 0.82 kg of CO2

Oxygen required = 2.19kg 02/kg charcoal

CO2 produced = 44 0.82( )

12 = 3.01 kg of CO2/Kg charcoal.

HYDROGEN

H2 + ½O2 H2 ………………….………… 3.3

2 Kg of hydrogen + 16kg oxygen 18kg water vapour

1kg of H2 + 8kg O2 9kg water vapour

0.031kg H2 + 8 x 0.031kg O2 9 X 0.031kg water vapour

O2 required = 8 x 0.031kg O2 / kg charcoal

= 0.248kg 02/kg charcoal

44

H2O produced = 0.279kg H2O/ kg charcoal

These results are tabulated in the table given below; the oxygen in the fuel is

shown as a negative quantity in the column oxygen required.

Table 3.2: Analysis of the ultimate (gravimetric) composition of charcoal

Constituent Mass fraction oxygen required product mass (Kg/kg charcoal) (Kg/kg charcoal) CO2 H2O

C 0.82 2.19 3.01 - O 0.113 - 0.113 - - H 0.0031 0.248 0.279 N 0.002 - - - Ash 0.034 - - - S 0.00 - - - Total = 2.325 3.01 0.279

Since air contains 23.3% of O2 by mass,

Stoichiometric A/F ratio = x O2 required

= x 2.325 = 9.98:1

45

Nitrogen associated with this A/F ratio,

= 9.98 x 0.767

= 7.65.

Since air contains 76.7% nitrogen by mass.

Total nitrogen = 7.65 + 0.2 = 7.85 kg N2.

3.1.2 ANALYSIS OF THE PRODUCTS OF COMBUSTION The results of the analysis of the products of combustion by mass are as shown

in the table below:

Table 3.3 : Analysis of products of combustion PRODUCT MASS

Kg % dry % wt

CO2 3.01 27.72 27.02 H20 0.279 - 2.50 N2 7.85 72.28 70.48 Total dry = 10.86 Total wet = 11.14

46

Table 3.4: VOLUMETRIC ANALYSIS OF THE PRODUCTS(1) Product Mass, kg M n = moles % dry

volume % wet volume

CO2 3.01 44 0.0684 19.61 18.78 H20 0.279 18 0.0155 - 4.25 N2 7.85 28 0.2804 80.39 76.97 Total dry = 0.3488 Total wet = 0.3643

For 20% excess air supply, with stoichiometric A/F ratio = 9.98:1, the

actual A/F ratio is obtained from the relation,

Percentage excess air

= actual A/F ratio – stoichiometric A/F ratio Stoichiometric A/F ratio

Or actual A/F ratio = 0.2 x 9.98 + 9.98

= 11.98:1

N2 associated with this actual A/F ratio = 11.98 x 0.767 = 9.19 Total nitrogen = 9.19 + 0.2 – 9.39 kg

47

Oxygen associated with this A/F ratio = 11.98 x 0.233

= 2.79 kg

Excess Oxygen = 2.79 – 2.33 = 0.46 kg.

Mixture strength is obtained from the relation,

Mixture strength = stoichiometric A/F ratio

Actual A/F ratio

= = 0.83

Table 3.5: VOLUMETRIC ANALYSIS OF THE PRODUCTS(2) Product Mass, kg M V = Dry % vol. Wet % vol. CO2 3.01 44 0.0684 16.36 15.77 H20 0.279 18 0.0155 - 3.57 O2 0.46 32 0.0144 3.44 3.32 N2 9.39 28 0.3354 80.20 77.34 Total dry = 0.4182 Total wet = 0.4337

48

3.2.0 MAXIMUM THEORETICAL TEMPERATURE OR ADIABATIC

FLAME TEMPERATURE

It is an experimental fact that the energy released on the complete

combustion of unit mass of a fuel depends on the temperature at which the

process is carried out. The following steps would be used to determine the

attainable maximum theoretical temperature.

3.2.1 DETERMINATION OF ADIABATIC FLAME TEMPERATURE

ASSUMPTIONS:

(1) A system with an 20% excess air is assumed due to the fact that most

solids do not burn completely on account of sufficient air molecules

required not getting to the combustion chamber, resulting in some un-

burnt carbon, and carbon monoxide in the combustion product.

Inadequate combustion, as well, lowers fuel efficiency and produces

soot (TSI Incorporated). Charcoal fuel has an inherent disadvantage of

releasing so much carbon monoxide.

49

(2) Though at temperatures in excess of 1300K, carbon dioxide dissociates

into carbon monoxide and oxygen, an endothermic reaction which lowers the

adiabatic flame temperature, it is theoretically assumed that no dissociation of

the product ensues.

(3) An initial air fuel temperature of 320C, corresponding to the ambient

temperature, is assumed.

(4) Air and the combustion products are assumed to be perfect gases with

specific heats which vary only linearly with temperature.

The combustion process is defined as taking place from reactants at a

state identified by the reference temperature To and another property, either

pressure or volume, to products at the same state. If the process is carried out at

constant volume, the non-flow energy equation

Q + W = ∆U, or Q + W = (U2 – U1) ……………. (3.5)

can be applied to give,

Q = UP2 - UR1 …………………………………… (3.6a)

= (UP2 – UPO) + (UPO – URO) + (URO – UR1)… (3.6b)

50

= (UP2 – UPO) + ∆UO + (URO – UR1)…………. (3.6c)

Or -Q = UR1 – UP2 …………………………………… (3.7)

Where W =0 for constant volume combustion, U1 = UR1, the internal energy of

the reactants which is a mixture of fuel and air at T1 and U2 = UP2, the internal

energy of the products of combustion at T2.

The change in internal energy does not depend on the path between the two

states but on the initial and final values and is given by the quantity, -Q, the heat

transferred to the surroundings during the process (Eastop T.D., McConkey A.)

The heat supplied Q, is called internal energy of reaction at T0 and is

denoted by ∆UO. That is, Q = ∆UO = UPO - URO. Now, a similar analysis for a

steady flow or constant pressure combustion process between states 1 and 2, (H2

– H1), can be written more explicitly as (HP2 – HR1), and this can be further

expanded for analytical purposes.

Q = (H2 – H1) = HP2 – HR1

= (HP2 – HPO) + (HPO – HRO) + (HRO – HR1)

= (HP2 – HPO) +∆HO + (HRO – HR1) ……………………………… (3.8)

51

According to Rogers and Mayhew, the first and last terms on the right-hand side

of equation 3.8 can be obtained from,

(HP2 – HPO) = pip

icm (T2 – T0) …………………… (3.9)

(HRO – HR1) = piR

icm (T2 – T1

Where cp is the mean specific heat at constant pressure of the constituent i. The

term ∆HO is called the enthalpy of combustion at T0, or the constant pressure

heat of combustion at T0.

For an adiabatic process ∆Q =0, so the steady flow energy equation reduces to

HP1 – HR1 = 0. ……………………………………………. (3.10)

Here, (HPt – H32) = 0, and the subscript ‘pt’ refers to the products temperature.

Expanding this equation yields,

(HP1 – HR32) + ∆H25 + (HR25 + HR32) = 0

The evaluation of this equation involves a method of successive

approximation because the appropriate mean specific heat data for the

52

first term (and subsequent terms) depends upon the unknown temperature. In

the course of the experiment, the recorded average ambient temperature was

320C so; the first mean temperature is,

2))27332()27325(( =

2603 = 301.5 ≈ 302 K.

Since the values of parameters at 302 K were not directly reflected in the

table, interpolation between 300 K and 325 K would be carried out. The heat

capacity of the air at 302 K is determined by interpolating between 300 K and

350 K from the table of properties of gases at atmospheric temperature.

From literature charcoal has a specific heat of 1 KJ/Kg K

Interpolating for Hydrogen yields,

302325300302

=

232 =

XX

38.14

31.14

23X – 329.13 = 28.76 – 2X

25X = 357.89

X =14.32KJ/Kg K

53

For Oxygen, interpolation gives,

232 =

XX

923.0918.0

23X – 21.114 = 1.864 – 2X

25X = 22.96

X = 0.9184KJ/Kg K

Interpolation for Nitrogen yields,

232 =

XX

040.1040.1

23X – 23.93 = 2.080 – 2X

From which, 25X = 26.01

Or X = 1.0404KJ/Kg K

For Carbon dioxide, this gives

232 =

XX

871.0846.0

23X -19.458 = 1.742 – 2X

54


X = 0.848KJ/Kg K

For water vapour, interpolation yields,

232 =

XX

871.1864.1

23X – 42.872 = 3.742 – 2X


X = 1.865 KJ/Kg K

Still using the above specific heat as first iteration, and using the values in

tables 3.4 and 3.5 respectively by applying the relation,

(Hp25 – HR32) = 3225 piR

icm

= -7[(0.82 x 1) + (0.031 x 14.32) +

(2.8989872 x 0.9184) + (9.1725412 x 1.0404)]

= -94.26 KJ/Kg.

55

From literature, ∆H25 = -29, 288 KJ/Kg.

(Hpt – Hp25) = p

micpi(t – 25)

= t - 25[(3.006652 x 0.848) + (0.279 x 1.865) +

(0.4643312 x 0.9184) + (9.1725412. x 1.0404)]

= 13.04(t – 25)

From, (Hpt. – HR25) + ∆H25 + (HR25 – HR32) = 0

Or, p

micpi(t – 25) + ∆H25 + 3225 piR

icm = 0

Which yields,

13.04(t1-25) – 29,288 – 94.2 = 0

Or t1 = 2278 0C

The second iteration is between TO = 250C and 2278 0C. The specific heats will

be determined at the mean temperature of 2

))2732278()27325(( = 2

2849 =

1425 K.

For hydrogen, the interpolation yields,

1425150014001425

=

7525 =

xx

02.16

77.15

56

From which x = 15.83 KJ/Kg K

Interpolating for oxygen yields,

7525 =

xx

143.1

134.1 .

From which, x =1.136 KJ/Kg K

For Nitrogen, interpolation gives,

7525 =

xx

244.1

232.1 .

From which, x = 1.235 KJ/Kg K

Interpolating for carbon dioxide yields,

7525 =

xx

326.1

313.1 .

From which x = 1.316 KJ/Kg K.


7525 =

xx

609.2

.552.2 .

57

From which x = 2.566 KJ/Kg K.

Now,

HR25 – HR32) =

-7((0.82X1)+(0.031X15.38)+(2.8989872X1.136)+(9.1725412X1.235))

= -111.5 KJ/Kg K.

So also,

p

micpi(t – 25) =

((3.006652*1.316)+(0.279*2.566)+(0.4643312*1.136)+(9.1725412*1.235)) = 16.53(t2-25) Now, 16.53*(t_2 - 25) - 29288 - 111.5 = 0 Or t_2 = 18040C The third iteration is between 250C and 18040C.

The specific heats are obtained at mean temperature of

2

2375 = 1187.5 ≈ 1188 K

58

For hydrogen, interpolation yields,

11881200

115001188 =

1238 =

XX

34.15

25.15 →X = 15.32 KJ/Kg K

Interpolation for oxygen yields,

1238 =

XX

115.1.109.1 →X = 1.114 KJ/Kg K

For Nitrogen, interpolation gives,

1238 =

XX

204.1.196.1 →X = 1.202 KJ/Kg K

Interpolation for carbon dioxide, yields,

1238 =

XX

280.1.270.1 →X = 1.278 KJ/Kg K

For water vapour, interpolation gives,

1238 =

XX

425.2

.392.2 →X = 2.417 KJ/Kg K

59

Inserting these new values in equation.3.9 yields,

HR25 – HR32) = -7*((0.82*1) + (0.031*15.32) + (2.8989872*1.114) + (9.1725412*1.202)) = -108.8

So also,

p

micpi(t – 25) =

((3.006652*1.278) +(0.279*2.417)+(0.4643312*1.114)+(9.1725412*1.202))(t3 – 25) = 16.06(t -3 – 25) Hence, 16.06*(t_3 - 25) - 29288 - 108.8 = 0

Or t -3 = 18550C

The fourth iteration is between 250C and 18550C. The mean temperature is

22426 = 1213 K

For hydrogen, interpolation yields,

1213125012001213

=

3713 =

XX

44.15

34.15 →X = 15.37 KJ/Kg K

Interpolation for oxygen gives,

3713 =

XX

120.1115.1 →X = 1.116 KJ/Kg K

60

For Nitrogen, interpolation yields,

3713 =

XX

212.1.204.1 →X = 1.206 KJ/Kg K

Interpolating for carbon dioxide gives,

3713 =

XX

290.1.280.1 →X = 1.283 KJ/Kg K


3713 =

XX

458.2

.425.2 →X = 2.434 KJ/Kg K

Inserting these new values in equation 3.9 yields,

HR25 – HR32) = -7*((0.82*1)+(0.031*15.37)+(2.8989872*1.116)+(9.1725412*1.206)) = -109.2 So also,

p

micpi(t – 25) =

((3.006652*1.283) +(0.279*2.434)+(0.4643312*1.116)+(9.1725412*1.206)) (t -4 – 25) = 16.12(t -4 – 25).

61

Hence,

16.12*(t -4 - 25) - 29288 - 109.2 = 0 Or t -4 = 18490C The fifth iteration is between 250C and 18490C. The mean temperature is

22420 = 1210 K.

Interpolation for hydrogen gives,

1210125012001210

=

4010 =

XX

44.15

34.15 →X = 15.36 KJ/Kg K

For oxygen interpolation yields,

4010 =

XX

120.1115.1 →X = 1.116 KJ/Kg K

Interpolation for Nitrogen gives,

4010 =

XX

212.1.204.1 →X = 1.206 KJ/Kg K

Interpolating for carbon dioxide yields,

4010 =

XX

290.1.280.1 →X = 1.282 KJ/Kg K

62

For water vapour, interpolation gives,

4010 =

XX

458.2

.425.2 →X = 2.432 KJ/Kg K


HR25 – HR32) =

-7*((0.82*1) + (0.031*15.36) + (2.8989872*1.116) + (9.1725412*1.206)) = -109.2

So also,

p

micpi( t -5 - 25) =

((3.006652*1.282) + (0.279*2.432) + (0.4643312*1.116) + (9.1725412*1.206)) (t -5 - 25) =16.11( t -5 - 25) Hence, 16.11*( t -5 - 25) - 29288 - 109.2 = 0 Or t -5 = 18500C. The sixth iteration is between 250C and 18500C. The mean temperature is

22421 = 1210.5 ≈ 1211 K.

For hydrogen,

1211125012001211

=

3911 =

XX

44.15

34.15 →X = 15.36 KJ/Kg K

63

For oxygen,

3911 =

XX

120.1115.1 →X = 1.116 KJ/Kg K

For Nitrogen interpolation yields,

3911 =

XX

212.1.204.1 →X = 1.206 KJ/Kg K

Interpolating for carbon dioxide gives ,

3911 =

XX

290.1.280.1 →X = 1.282 KJ/Kg K


3911 =

XX

458.2

.425.2 →X = 2.432 KJ/Kg K


HR25 – HR32) = -7*((0.82*1)+(0.031*15.36)+(2.8989872*1.116)+(9.1725412*1.206)) = -109.2.

p

micpi(t – 25) =

((3.006652*1.282)+(0.279*2.432)+(0.4643312*1.116)+(9.1725412*1.206)) ( t -

6 - 25) =16.11( t -6 - 25). Hence, 16.11*(t_6 - 25) - 29288 - 109.2 = 0 Or t -6 = 18500C

64

Since the results of the 5th and 6th iterations did not differ significantly, the

resulting temperature, 18500C (or 2123 K) is taken as the theoretical maximum

temperature.

3.3 CONDUCTIVE HEAT TRANSFER

Two principal areas through which conductive heat transfers should be expected

in the stove are:

i) Heat conduction through the pan to the product to be fried, baked

or boiled

ii) Heat conduction through the stove wall

Fourier’s relation, Q

KA T TX

1 2 ………………………… (3.11)

gives the thermal conductivity, k, of an object, where

From the above equation,

Given Ax

65

For A > > X, Q will be large

For A << X, Q will be small.

The heat transfer area varies with thermal conductivity and temperature

difference.

From the work of Baldwin (1987), it was noted that the use of this

equation for the examination of heat transfer across a stove wall generates

values that are many times too large. This is because the heat transferred into

and out of an object depend not only on the conductivities, to and from the

surface, but also on the conductivity within the object itself, dirt or oxide layers

and air at the surface of the material itself. With respect to this, equation (3.11)

can be rearranged using thermal resistance concept as,

Q =

21

21

11)(

hkx

h

TTA

……………… (3.12)

It would be observed that the thermal resistance of a medium depends on the

geometry and the thermal properties of the medium.

QT T

R

1 2 .......................................... (3.13)

66

Sample or design calculations will here be made using the equation

(3.13) above

Here Q =2.1.

21

CONVSteelCONV RRRTT

RCONV = 1/hA

RSteel = l/kA

T2

T2

T1 T1

T2 T1

Fig. 3.1 Thermal resistance network

T1 T2

Q Rconv.1 Rconv.2 Rwall

T0

67

So, Q = h1A (T∞1 – T1) = KAL

TT 21 = h2A (T2 - T∞2) ……………… (3.14)

Equation 3.14 can be re-arranged, on the basis of fig. 3.1, as

Q

T T

h A

T TL

KA

T T

h AT TR

T TR

T TRconv steel conv

1 1

1

1 2 2 2

2

1 1

1

1 2 2 2

2

1 1` ` `

. .

Adding the numerators and denominators yields

QT T

Rtotal

1 2 W,

Where, Rtotal = Rconv .1 + Rsteel + Rconv.2

=1/h1A + L/KA + 1/h2A

Data;

Height of stove = 460 m

Diameter of stove = 570 mm

Distance between fuel bed and pan = 230 mm

Hence, surface area of stove, A = 2rh + r2 because it has base but no top in

which, A = 2rh + r2

68

= r (2h + r)

= 3.14 x 285 (2 x 230 + 285)

= 666,700.5 mm2

= 0.67 m2

Mild steel is the material for the stove body. Thermal conductivity of mild steel,

= 42.9 (W/m K).

For the air

K = 38.0 (W/m K)

Here, h = 14.51 w/m2k as determined from the section on determination of

convective heat transfer co-efficient.

Rh A

LKA h ATotal

1 1

1 2……………………………………………. (3.15)

RTotal = + +

= 0.102862668 + 1.178318932 x 10-4 + 0.102862668

≈ 0.206

From the relation given below, the heat transferred through the stove wall was

determined.

69

Q = =

= 1818 0.206

8.825 k W

Also from,

Q =

T1 = T -

= 1818 – 187

= 1631 K or 1444 0C

Similarly from

T2 = + T

= + 305

= 187 + 305 = 492 K or 219 0C

70

3.4 REDUCING WALL LOSSES

The large heat loss by light weight single wall (metal) charcoal stove can be

greatly reduced by chemically or mechanically polishing or coating the exterior

surface to provide a bright metallic finish. In order to sustain the effectiveness

of such a finish, the surface be kept clean and free of soot and rust. Paints

should not be used as they have a tendency to increase radiant heat loss. The

outside wall of this charcoal stove, which can be quite hot during can be made

of double-wall. To reduce stove wall heat losses, use can be made of light

weight insulates such as fiberglass, glass wool or vermiculite.

3.5 CONVECTIVE HEAT TRANSFER.

It is by convective heat transfer that the hot gases from the fire heat the frying

pan, or that wind cools a hot stove. Convective heat transfer in charcoal stove is

by natural convection process. Fluid velocities associated with natural

convection are low, usually under 1m/s (Baldwin, 1987)

In natural convection, the case of interest for charcoal stoves, the driving

force of the hot gas is its higher temperature and resulting lower density

71

compared to its surrounding. As the hot air rises, it gives up some of its energy

to its surroundings such as the frying pan or stove wall. As its temperature thus

decreases, it loses the force propelling it upward. As its velocity thus decreases,

so does the rate at which it gives up heat to its surroundings and so on.

The convective heat transfer rate is given by

Q hA T T 1 2 …………………………………….. (3.16a)

3.6 DETERMINATION OF CONVECTIVE HEAT TRANSFER

COEFFICIENT.

The parameter h is determined in two ways: either experimentally or

theoretically. The relation to be used here is

NU = hg/K ……………………………………………………. (3.16b

According to Welty (1978), the above relation and others relating to convective

heat transfer have been modified to apply specifically to air and a simplified

expression, for the heat transfer co-efficient written in the form

h ADTL

b

………………………………………………. (3.16c)

Where, A and b are constants, depending on the geometry and flow conditions,

and L is the significant length, also a function of geometry and flow.

72

For vertical cylinders

hh W m k

131135814 51

13

2

..

for DT = 1358K

L = 1

Lagging the stove assists in minimizing heat transfer from the combustion

chamber through the stove walls, thereby increasing heat transfer efficiency and

lowering the convective transfer coefficient, h.

3.7 RADIATIVE HEAT TRANSFER

In charcoal stoves, radiative heat transfer play key role in heat transfer:

-From the fire bed and flames to the frying pan;

- From the hot gases to the charcoal to sustain combustion;

- From the flames and fire bed to the stove wall;

- From the stove body to the pot;

- From the stove body to the surrounding

The fire bed temperature and the view factor are the two factors required

in order to calculate the radiative energy transfer from the charcoal bed to pan.

73

In order to do this calculation, it is assumed that the gases and flames between

the charcoal bed and the pan do not absorb or emit any radiation. The view

factor is the fraction of the energy emitted by one surface that is intercepted by

a second and is dependent on the relative geometry of the two surfaces. In this

study the view factor between fire/bed and pan is equal to the view factor of two

concentric parallel discs.

To check the expected temperatures of the fuel bed and thus the radiative

heat transfer to the pan, a thermocouple was placed above the charcoal fire.

Details are presented in chapter four.

Radiative heat transfer to the pan can be increased by moving the pan

closer to the charcoal bed. So, also, closing the firebox and regulating the

supply of air (lean mixture) enhances the average fire bed temperature.

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

amount of heat lost, etc. These parameters are of importance when

considering further improvement on the stove’s performance. They also

form the bulk of criteria used by consumers to decide on their choice of

stove design.

3.12 STOVE TEMPLATE DESIGN

The width of the cylindrical stove template (fig. 3.5a & 3.5b) as

given by Baldwin (1987) for stoves welded together, end to end is,

W C G s 2 …………………………………………… (3.95)

In this instance

W x x x

m

056 2 0 008 0 014

186. . .

.

The stove template height, H, is given as

H = A + P + L …………………………………………….. (3.96)

P is given as,

P = 0.4D

103

= 0.4 x 0.56

= 0.224m

L already has been determined as 0.26m and 4 = 0.1m

Hence, H = 0.1 + 0.22 + 0.26 = 0.58m

3.13 THE GRATE AND AIR HOLES

The grate is circular in shape and made from sheet metal. It is welded to

the finished cylinder. The functions of the air holes punched in the grate

are:

(i)The presence of holes facilitate primary air supply

ii) They provide means of passages of ash to ash collecting tray,

after combustion.

iii) They accommodate burning charcoal.

In this stove a total of 44 holes were punched on the grate. The holes

are each 12mm diameter.

104

105

3.14 DOOR

The door, fig.3.6, was attached to the combustion chamber. The bottom

of the door was placed at the top of the air holes while the top is below

the bottom of the pot so that hot gases do not exit through the door but

are directed up around the door. The door was used for feeding the

charcoal before frying operations and also employed in removing used

charcoal after frying. Locks were provided on the door to keep the

charcoal from discharging and to help regulate air flow rate.

3.15 ASH TRAY

The ash tray (fig.3.7) is circular in shape and was placed under the stove

for collecting and disposing of ash during and after frying. The ash tray

helps in keeping clean the environment where the stove is being used.

106

107

108

109

Fig. 3.10: Photograph of the constructed stove showing the grate, chimney, door

and the air holes.

110

Fig. 3.11 Stove photograph showing the door closed and air inlets open.

111

Fig. 3.12: Photograph of the constructed stove showing the door opened.

112

CHAPTER FOUR

4.0 STOVE TESTING AND DATA ANALYSIS

4.1 MATERIALS AND EQUIPMENT

The followings were the equipment used for carrying out all the

tests necessary in the stove under consideration.

1) Thermocouples and digital thermometers: they were used to

measure temperature of the combustion chamber (hot gas). They

were five in number.

2) Weighing balance: used to measure all the weights required.

3) Thermometers: used to measure the temperatures of water. A dry

bulb thermometer was used.

4) Flexible metal tape. This was used to measure template, stove,

grate, door, ash tray and pot dimensions.

5) Stop watch: used to measure time – required for boiling of water

and combustion of charcoal

6) 6- channel data switch, fabricated in UNN Mechanical Engineering

laboratory.

113

4.2 METHODOLOGY

A charcoal burning stove was designed and constructed as

shown in chapter three. Water boiling test (WBT) was carried

out in order to generate the data required for assessing the

stove’s performance.

4.3 EXPERIMENTAL DESIGN

In order to carry out the water boiling tests, the following steps

were taken:

1) 1.30 Kg – 1.45 Kg of charcoal was weighed separately and the

moisture content determined.

2) The pot was cleaned and dried. The pot was filled with water to 2/3

(two-third) of its capacity. The pot with water was then weighed

and the weight was recorded.

3) The ash tray, pot support and charcoal grate were positioned so

that the required quantity of charcoal is loaded into the stove.

4) The charcoal was sprinkled with some quantity of kerosene and lit.

114

5) The pot was then put on the stove after the kerosene was seen to

have burnt out and temperatures at key locations in the water,

combustion chamber wall, grate and chimney were recorded with

the aid of dry bulb thermometer every five minutes interval of time

till the desired cooking or boiling time was reached. This time was

measured using a stop watch. The temperatures below the grate,

combustion chamber, pot, stove’s outer surface and exhaust gas

were also recorded every five minutes using a six - channel data

switch with the aid of thermocouples connected to the stove as

shown in fig. 4.1. The test data obtained are shown in table 4.2

6) At the end of the boiling tests, the charcoal and pot with water

were once again weighed.

7) The stove and pan were then allowed to cool before being

removed.

115

4.4 METHOD OF DATA ANALYSIS

The results recorded were used to compute the following universally

accepted indices of stove performance:

Fire power, P = IQQ FI

60_ CC, (Kilowatts)………………….. (4.1a)

The relation can be expressed as

PQ Q

ti F CC, ………………… (4.1b)

The specific fuel consumption, SC, for a stove given by Kris-Spit is the

ratio of total quantity of charcoal used in the cooking process to the amount of

water used in cooking. According to Baldwin, S.F., “for convenience, the

specific fuel consumption defined here can be expressed in terms of grams of

charcoal consumed per kilogram of water ‘cooked’”. This computation provides

a fuel-consumption figure which invariably has positive influence on the

decision of intended users of the stove.

For a stove, the percent heat utilized may be defined as the percentage of heat

released by the fire that is absorbed by the water in the pot.

PHUX Mw T T X Ww Ww

M Cf i l

c c

4186 10 2260 1031

32.

… (4.2)

4.186 KJ/kg K = specific heat of water

2260KJ/kg = latent heat of vaporization of water at atmospheric

pressure and 100OC

116

4.5 MOISTURE CONTENT DETERMINATION

Four samples of charcoal each weighing 1.5kg were obtained and taken to

the Soil Science Laboratory, University of Nigeria, Nsukka on 28th, November,

2006. They were each kept in an oven spread on white cardboard papers to keep

the charcoal particles from defacing the oven. The oven’s temperature was set at

105 0C and the samples were kept there between 11.15am and 3.15pm. The

charcoals, after they were retrieved from the oven, were weighed even while

they were warm to be sure no moisture was re-absorbed.

The weights of the various charcoals after they were oven dried are

shown below in table 4.1.

Table 4.1 Charcoal moisture content

SAMPLE INITIAL WEIGHT, Kg FINAL WEIGHT, Kg TEST NO.

A 1.5 1.30 3

B 1.5 1.35 4

C 1.5 1.45 5

D 1.5 1.35 6

117

The oven used was marked, oven BS, size three, model OV-168 and

was manufactured by Gallenhamp.

The charcoals were picked from the open field and so could contain

moisture. It was expedient to remove the moisture in the charcoal before

being loaded into the stove because the presence of moisture results in

higher thermal inertia value with the attendant effect of lowering the

thermal efficiency of the system. It does occur that at the onset of

combustion, carbon monoxide reacts with the moisture to form carbon

dioxide thus requiring large energy to warm the stove and bring the

stove to burning.

118

4.6 LOCATIONS OF THERMOCOUPLES ON THE STOVE

DURING THE TESTS

Fig: 4.1 Location of thermocouples on Charcoal Stove during the tests.

Below a charcoal grate T1

Combustion chamber, T2

Stove’s outer surface, T4

Channel gap, T3

Chimney, T5

119

4.7 DATA ANALYSIS

A total of six tests were carried out on the constructed stove in the Department of

Mechanical Engineering, University of Nigeria, Nsukka, Nigeria between 27th and 29th

November, 2006. The laboratory test data sheet reflecting the general requirement for

each test is shown in table 4.2. Tables 4.3 to 4.8 shows the data generated for each test

while table 4.9 is a representation of the results of the analysis of tests 3 to 4.

TABLE 4.2 LABORATORY TEST DATA SHEET FOR CHARCOAL

STOVES

Parameter Test 1 Test 2 Test 3 Test 4 Test 5 Testt 6

Date 27/11/2006 27/11/2006 28/11/2006 28/11/2006 29/11/2006 29/11/2006

Tester Ojonimi Y.

Usman

Ojonimi Y.

Usman

Ojonimi Y.

Usman

Ojonimi Y.

Usman

Ojonimi Y.

Usman

Ojonimi Y. Usman

Weather

Type of pot Aluminium Aluminium Aluminium Aluminium Aluminium Aluminium

Time

duration

2.52pm –

3.57pm

5.33pm –

5.54pm

4.37pm –

5.01pm

5.34pm –

5.57pm

7.34pm – 8.0am 9.11am – 9.44am

Fuel Charcoal Charcoal Charcoal Charcoal Charcoal Charcoal

Moisture

content

Not

measured

Not

measured

0.20Kg 0.25Kg 0.05Kg 0.15Kg

Calorific

value

31MJ/Kg 31MJ/Kg 31MJ/Kg 31MJ/Kg 31MJ/Kg 31MJ/Kg

120

Type of

stove

Metal Metal Metal Metal Metal Metal

Pot to wall

dim

5mm 5mm 5mm 5mm 5mm 5mm

Channel

height

120mm 120mm 120mm 120mm 120mm

Insulation

and location

Glass

wool/combus

tion chamber

Glass

wool/combus

tion chamber

Glass

wool/combus

tion chamber

Glass

wool/combus

tion chamber

Glass

wool/combustion

chamber

Glass wool/combustion

chamber

Grate type Metal Metal Metal Metal Metal

Number of

holes

44 44 44 44 44 44

Combustion

chamber

type

Lagged

metal type

Lagged

metal type

Lagged

metal type

Lagged

metal type

Lagged metal

type

Lagged metal type

Weight of

empty pan

0.70Kg 0.70Kg 0.70Kg 0.70Kg 0.70Kg 0.70Kg

Weight of

stove and

pan

18Kg 18Kg 18Kg 18Kg 18Kg 18Kg

121

Table 4.3: Data obtained for stove test 1.

Time T1OC T2

OC T3OC T4

OC T5OC T6

OC

2.52 33 33 32 33 33 29

2.57 157 143 108 36 44 36

3.02 141 177 148 55 89 37

3.07 168 302 210 67 92 38

3.12 199 383 217 70 100 55

3.17 202 437 231 75 115 66

3.22 210 462 253 76 116 79

3.27 220 482 278 84 119 86

3.36 213 474 301 105 79 92

3.37 195 463 310 104 121 95

3.42 191 435 304 107 137 95

3.47 179 402 287 100 131 94

3.52 152 360 262 98 109 91

3.57 139 313 236 84 106 90

The moment the water in the pot begins to boil vigorously, the time is recorded.

The above data was not used to evaluate the indices of stove performance since water was

not boiled.

122

TABLE 4.4: DATA OBTAINED FOR STOVE TEST 2

Time T1OC T2

OC T3OC T4

OC T5OC T6

OC

05.33 32 32 33 32 32 29

05.38 317 420 158 51 148 35

05.43 411 716 255 80 193 50

05.48 441 795 341 99 222 69

05.53 454 861 393 117 256 90

05.54 455 879 409 122 263 98

The moment the water in the pot begins to boil vigorously, the time is

recorded in addition to other readings already taken.

DATA ANALYSIS

The data shown in table 4.4 was used in the following analysis

WATER

Mass of pot =0.70kg

Initial mass of pot + water = 4.75kg

Final mass of pot + water = 4.45kg

123

Initial mass of water, mi = (4.75 – 0.70) kg

= 4.05kg

Final mass of water, mf = (4.45 – 0.70)kg

= 3.75kg

Mass of water evaporated = (4.05 – 3.75)kg

= 0.30kg.

CHARCOAL

Initial mass of charcoal = 2.0kg

Final mass of charcoal = 1.35kg

Mass of charcoal burnt = (2.0 – 1.35)

= 0.65kg

TIME

Time taken to bring to boil = 16 minutes

(1) Fire power, P m cI

KWc c

60

0 65 31 1060 16

20 989 5820 99

6.

, ..

x xx

KW

MW

124

I = The time elapsed in minutes.

(2) The percent heat utilized, PHU, is given as

PHUx Mw T T X Ww Ww

M Cx

f i l

c c

4186 10 2260 10100%

31

32.

Substituting values,

PHU

x x x X xx x

x 4186 10 4 05 98 29 2260 10 0 30

0 65 31 10100%

3 3

6

. . ..

1169 777 70 678 00020 150 000 00

100%, , . ,

, , .

x

1847 777 7020 150 000 00

100%, , ., , .

x

0 09170 100%917%

..

x

(3) The specific fuel consumption, sc, as given by Krist-Spit, is.

scmw

c

i

125

Inserting values in the above equation yields,

sc

0 654 05

01605

.

..


Time T1OC T2

OC T3OC T4

OC T5OC T6

OC

04.37 31 33 32 30 31 31

04.42 55 135 166 37 81 38

04.47 73 232 234 43 125 50

04.52 187 377 286 50 191 68

04.57 292 564 375 69 235 85

05.01 341 666 445 91 247 98

DATA ANALYSIS

TIME

Total time taken to boil = 29 minutes

(1) Fire power, scm c

Ic c

60

126

0 30 31 1060 29

534

6.

.

x xx

MW

The parameters are as defined above.

(2) The percent heat utilized, PHU, is

PHU

X w T T x w wM x C

xf i i f

c c

4186 10 2260 10100%

31

3.

4186 10 360 98 31 2260 10 0 30

0 30 31 10100%

3 3

6

. . ..

X x x x xx x

x

1 009 663 2 678 0009 300 000 00

01815 100%1815%

, , . ,, , .

..

x

Parameters are as defined earlier.

(3) Specific consumption,

sc 0 30360..

0 0833.

127


Time T1OC T2

OC T3OC T4

OC T5OC T6

OC

5.34 31 33 32 30 31 31

5.39 39 137 168 39 142 40

5.44 103 212 188 43 176 53

5.49 276 388 243 53 222 70

5.54 404 582 341 79 257 90

5.57 431 664 381 97 280 98

The analysis of the data obtained in this test is, as well, shown in table

4.9 .

128


Time T1OC T2

OC T3OC T4

OC T5OC T6

OC

7.34 25 25 25 25 25 26

7.39 42 54 92 28 66 28

7.44 64 65 123 30 98 35

7.49 131 165 172 39 125 50

7.54 219 311 263 54 160 71

7.59 297 579 356 82 204 96

8.00 291 627 378 83 178 96

The analysis of the data obtained in this test is, as well, shown in table

4.9 .

129


Time T1OC T2

OC T3OC T4

OC T5OC T6

OC

9.11 29 30 29 29 29 25

9.16 37 103 111 36 63 30

9.21 47 93 119 40 66 34

9.26 85 138 138 40 93 38

9.31 151 313 196 42 159 50

9.36 230 494 273 62 215 71

9.41 289 586 348 79 193 88

9.44 318 633 379 82 190 98

The analysis of the data obtained in test 6 is recorded in table 4.9.

130

TABLE 4.9: SUMMARY OF COMPUTED RESULTS

TEST NO 3 4 5 6

Mass of pot, kg 0.70 0.70 0.70 0.70

Initial mass of water,

wi , kg

3.60 3.60 3.60 3.60

Initial mass of pot and

water, kg

4.30 4.30 4.30 4.30

Final mass of pot and

water, kg

3.95 4.00 4.20 4.10

Mass of water

evaporated, kg.

0.35 0.30 0.10 0.20

Time taken to boil,

minutes.

29 28 26 30

Mass of charcoal

burnt, kg.

0.30 0.35 0.36 0.50

Fire power, (MW) 5.34 6.46 9.94 8.61

Percent heat utilized,

PHU, %

18.15 15.55 15.80 9.04

Specific consumption,

%

0.08 0.08 0.14 0.14

131

4.8 DISCUSSION OF RESULTS

Six tests were conducted on the constructed stove principally to

assess the thermal efficiency. The tests took place in an uncompleted

building beside Civil Engineering Department’s workshop, University of

Nigeria, Nsukka. The tests were carried out in a building in order to ward-

off the effects of wind. One of the tests was not reported on because it

failed to cause the water to boil, resulting from the quantity of fuel that was

used. However, it served as ‘guide post’ in determining the quantity of fuel

needed in subsequent tests.

The five recorded tests were conducted at different times of the

day -morning and evening. The two that were conducted in the morning

generally took longer times before water started boiling, that is twenty-six

and thirty-three minutes respectively (see experimental test results 5 and

6). The duration resulted from the fact that air was calm mostly in the

morning and the draft was by natural convection.

The three tests conducted in the evening when the wind was

blowing strongly took twenty-one (21) minutes (see experimental test

result 2); twenty-four minutes (see experimental test result 3); and twenty-

three (23) (see experimental test result 4), respectively to bring the water

132

to boil. That shows that the tests conducted in the evenings witnessed

higher temperatures than the ones conducted in the mornings. It also

proves the fact that with this stove it is much easier to attain the high

power phase in the afternoon than in the morning.

From the test results, water began to boil vigorously at an average

temperature of 98 0C whether in the morning or evening. So also, in each

test result, it would be seen that the maximum temperature on the outer-

surface of the stove was about 1000C (on the average) even when the

temperature in the combustion chamber (T2) in most cases read above

6000C. That shows that the insulation actually prevented heat

transmission from the inner surface of the combustion chamber wall to the

outer surface. This makes the stove user-friendly.

The channel-type of metallic stove was chosen as stated in the

literature review because it has been reported to offer better performance

than multiport stoves and the nozzle stoves. In this stove under

evaluation, the temperature of the channel gap (T3) gives an idea of the

temperature of the flue gas in contact with the pot. And when it is again

compared with the chimney exit temperature, an understanding of the

heat lost to the pot wall in the process is obtained. From the test results,

the temperature of the flue gas was always about 4000C which was about

133

of combustion chamber temperature in each case. This record shows

impressive heat transfer efficiency, partly due to the small size of the

channel gap and adequate pot-to-grate height.

4.9 CONCLUSION

Table 4.9 represents the result of the evaluation of the indices of

performance of the charcoal stove. From the result it was revealed that an

average amount of 0.43 kg of charcoal would be required to be burnt for

an average period of 29 minutes to bring 3.6 kg of water to boil.

The experiment yielded a thermal efficiency of 15%. Based on the

results of the study, it can be seen that the performance of the charcoal

stove was better than the traditional three-stone open fire reported to have

efficiency of about 10%.

4.10 RECOMMENDATIONS

It is a well known fact that there are some levels of imperfections

associated with everything made by man. So, there is always room for

improvement. With respect to this stove, such areas are:

i) The quality and thickness of the insulating material need a review

with a view to using a cheaper and more efficient insulator.

134

ii) Better thermocouples such as copper constantan should be

employed for further tests, as that is the recommended thermocouple for

evaluating the performance of charcoal stoves. Such thermocouples are

more stable at temperature range of between 8000C and 12000C, as

stated in literature. It was not used in this work because of the difficulty

encountered in the efforts to lay hands on the material.

iii) Heat shields should be used below the charcoal grate so as to

increase the heat transfer efficiency, if the air preheating effect would not

be sacrificed.

iv) The distance between the charcoal bed and the bottom of the pot

should be reduced in such a way that the combustion efficiency and heat

transfer efficiency can be maximized

v) The channel gap can further be reduced to enhance more heat

transfer to the pot

The stove is recommended for small and medium scale agro-

based enterprises whose business entails cassava processing both for

local consumption and export, as well as other processing jobs and

cooking.

135

REFERENCES

Air flow and Velocities due to Natural draft.

www.Engineeringcoolbox.com. Baldwin, S.F,(1987). Biomass Stoves: Engineering Design, Development, and

Denomination. VITA, USA. David M Himmelblau, (2005). Basic Principles and Calculations in Chemical

Engineering. Pearson Education (Singapore) Pte. Ltd, Indian Branch,6th edition.

Duffie, J.A. and Beckman, W.A. (1980) Solar Engineering of Thermal

Processes, Wiley, New York, N.Y. Eastop, T.D. and McConkey A. (1999 ) “Applied Thermodynamics”,

Addition Wesley Longman, Inc. 5th edition, Enibe, S.O. (2003) Thermal Analysis of a natural circulation solar air heater

with phase change material energy storage, Renewable Energy 28 (2003), (2269 – 2299).

EPRI & U.S. Department of Energy (1997). Renewable Energy Technology

Characterization. A topical Report: Prepared by Office of Utility Technologies, Energy Efficiency and Renewable Energy, U.S. Department of Energy 1000 Independence Avenue, Washington, D.C. 20585 and EPRI, 3412 Hillview Avenue, Palo Alto, California.

Gengel Y.A. & Turner R.H. (2001), Fundamentals of Thermal Fluid Sciences,

McGrawHill Holman, J.P (2002). “Heat Transfer” McGraw-Hill Book Company, Inc. Joseph G.M. & Micheal W. (2006), Development and Testing of Ovens using

136

Sawdust as Fuel, Department of Mechanical Engineering, Internatonal Development Research Centre, Fourah Bay College, University of Sierra Leone, Dakar, Senegal.

Krist-Spit, C.E. “The combustion quality of the charcoal stoves - Sakkanal and

Malgache” in From Design To Cooking, eds. C.E. Krist-Spit and D.J. Vander Headen, Wood burning stove group, Eindhoven University of Technology; and Division of Technology of Society, Apeldoorn, The Netherlands. January 1985.

Nag, P.K. (2005) Power Plant Engineering, Tata McGraw-Hill Publishing

Company Limited, New Delhi, 2nd edition. Ndirika, V.I.O, (2002). Development and Performance evaluation of

charcoal- fired cooking Stoves. Nigerian Journal of Renewable Energy, Vol.10, Nos. 1 & 1, pp. 71-77,

Ngwu Ernest I. Performance evaluation of a portable charcoal stove for

Garri frying, Unpublished B.ENG student’s project, University of Nigeria, Nsukka

Nwori, Amgeze P. Performance Analysis of Energy efficient charcoal

Stove. Unpublished B.ENG student’s project, University of Nigeria, Nsukka .

Obi, A.I., Yawas D.S and Dauda M. (2002 “Development and Test Performance

of a three-burner wood fired stove”. Nigerian Journal of renewable energy vol. 10, Nos.1&2, pp. 63 – 70.

Odigboh E.U. & Osuagwu (2003) Effective Communication of Technical Ideas

In Science and Engineering, University of Nigeria Press Ltd. Okafor, Obinna O. (2003). Design, Construction and performance evaluation of

a Natural Circulation solar Air-heating system with phase change material energy Storage and an automatic temperature regulating device. Unpublished B.ENG. student’s project report, University of Nigeria, Nsukka.

Oparaku, N.F., Unachukwu, G.O.,& Okeke, C.E. (2003) Design, Construction

and Performance Evaluation of solar cabinet drier with an auxiliary heater, Nigerian Journal of Solar energy, vol. 14, (pp 41 – 50)

137

Osagie, O.P, (2002). Performance Evaluation of a solar egg incubator with Paraffin PCM energy storage system. Unpublished B.ENG Project Report. University of Nigeria, Nsukka .

Performance estimation of stoves

www.Cookstove.net (2005) R.C. Sachdeva, (2008). Fundamentals of Engineering Heat and Mass Transfer

(SI Units), New Age International Publishers, 3rd edition, Rajput, R.K (2004). Heat and Mass Transfer, S. Chand &

Company Ltd, New Delhi Wesley Longman, Inc., 2nd edition,

Sukhatme, S.P.(1990). Solar Energy: Principles of Thermal Collection and Storage, Tata McGraw-Hill Publishing Company Limited, New Delhi. TSI Incorporated (2004). Combustion Analysis Basics: An overview of measurements, methods, and calculations used in combustion analysis www.tsi.com Usoh, Charles O.E’. (1992). Design and construction of a portable energy

Saving coal stove. Unpublished M.ENG Project Report, University of Nigeria, Nsukka

Usman, O.Y. (1997). Design of heated air drier, an unpublished B.Eng. project

report, University of Agriculture, Makurdi. Welty, James R. (1978). Engineering Heat Transfer, John Willey & sons. Welty, James R; Wilson R.E; Wicks C.E; (1976). Fundamentals of momentum,

heat and mass transfer, John Wiley & Sons, 2nd edition,. Wikipedia, (2006)

http://en.wikipidia.org/wikistoves. Designing stoves with Baldwin & Winiarski. “Design Principles for wood burning cook stoves.

Zubair A.M. & Onyishi B.U. (2007). Energy Conversion and Heat Transfer,

138

Jireh Publishers Ltd, 2nd edition.

Documents

EXPERIMENTAL PERFOMANCE EVALUATION OF CHARCOAL … · 2015. 9. 16. · 3 CERTIFICATION This is to certify that this work “Experimental Performance Evaluation Of Charcoal Stove”