ABSTRACT

This project is designed to make the students utilize as many theoretical and practical concept as have been instructed in Alston to mechanical engineering workshop technology. Students are expected to learn and apply concepts, principles about energy specially the conversions of electrical energy to thermal energy, conduction and conventional heat transfer etc. Also the determination of the properties of various ferrous and non-ferrous materials, electrical installation occults. The application of engineering measurement and quality control. Also to build an intellectual ability in interpretation of working drawing in designing and development before and after working process. Students will get an opportunity to appreciate safety, and the use of both machine and hand tools in the course of working.

CHAPTER ONE

INTRODUCTION

1.1     BACKGROUND OF STUDY

An Oven is a thermally insulated chamber use for the heating, baking or drying of a substance (www.Oven.Merriam-webster.com). The earliest ovens were found in Central Europe and dated to 29,000 BC, it was used as roasting and boiling pits located within yurt structures. They were used to cook mammoth (Jennifer, 2009) In Ukraine from 20,000 BC they used pit with hot covered in ashes. The food was wrapped in leaves and set on top then covered with earth (Peter et al) In camps found in Mezhirich, each mammoth bone house had a hearth used for heating and cooking. ( www.Mezhirich. Donsmaps.com) Ovens have been used since prehistoric times by cultures that lived in the Indus Valley and pre-dynastic Egypt. Settlements across the Indus Valley had an oven within each mud-brick house by 3200 BC (Dales and George, 1974) Hence, before the intervention of modern baking oven, people have alternative means of cooking and baking but the alternative they have chosen led to loss of lives and properties. The different types of baking oven are Earth oven, Ceramic oven, Gas oven, Mansonry oven and Electric oven. An electric baking oven is a heating chamber or  an enclosed box- like space which is meant for baking foods. In science and Engineering laboratories, it is in form of a small furnace which is used in the removal of moisture from some Engineering materials in order to improve their physical properties such as ductility and hardness. It can also be used for the purpose of heat treatment of engineering materials such as steel and it’s alloy. An Electric baking oven has several advantages over other baking ovens. It is easy to install, moreso relatively damp, portable and has a very easy mode of operation. It is also easy to maintain and has high durability. It is highly preferred to all other types of oven due to the availability of electricity over a wide range of places throughout the countries.  Having considered the advantages that can be derived from the use of electric oven, it is relatively cheap when compared with other means of baking.

As a result of vast advancement in technology, the invention of an electric baking over was brought about by an American self- taught engineer called Dr. Percy Spancer. In the spring of 1946, Percy Spencer and an associate P.R. Hauson (Roly Hauson), were working on a secret they called “The Speedy Weenie” which means ‘a quick hot dog’. Engineers went to work on Spencer’s hot new idea, developing and refining it for practical use. By late 1946, the Ray theon company had filed a patent proposing that baking ovens are used to cook food, baked bread and pre heat food. 

In 1947, Ray them demonstrated the world’s first baking oven and called it a “Rad arange” the winning name in an employee contest Housed in refrigerator sized cabinets. These primitive units were gigantic and enormously expensive, standing 5 ½ feet tall, weighting over 750 pounds and costing about 5000 pounds each. The Margie iron tube had to be water-cooled, so plumbing installations were also required. In 1965, Ray theom acquire Amana Refrigeration two year later, the first counter top, domestic oven was introduced. It was a 100-volt baking oven which cost just under 500 pounds and was smaller, safer and more reliable than previous   models this introduced the first popular home model.  

As the food industry of electric baking oven began to recognize the potential and versatility of the baking oven, its usefulness was put to new tests. Technology advanced and further developments led to a baking oven that was polished and priced for the consumer kitchen. However, there were many myths and fears surrounding these mysterious new electronic “radar ranges” By the seventies, more and more people were finding the benefits of baking oven to outweigh the possible risks and none of the them were dying of radiation poisoning, going blind, sterile or becoming impotent. As fears faded, a swelling wave of acceptance began filtering into the kitchens of American and other countries. Myths were melting away and doubt was turning into demand. By 1975, sales of baking ovens would for the first live exceed that of Gas ranges.  

An expanding market has produced a style to suit every taste; a size, shape and colour to fit any kitchen and a price to please almost every pocket book. Options and features, such as the addition of convention heat, probe and sensor cooking meet the needs of virtually every cooking, heating or drying application. Over the years, improvements have been made in electric baking ovens and this trend still continues. This has led to the incorporation of features like a thermostat which turns the oven on and off and also helps in regulating the temperature of the electric baking Oven, insulator or lagging materials e.g. thermoses thing plastic which help in preventing heat loss from the oven and timber may allow the baking oven to be turned ON and OFF automatically at Pre-set times and it can also used to shut the baking oven off when the food is completely cooked or when the bread is completely baked to the desired degree. Some ovens provide various ands to cleaning. Continuous clearing ovens have the oven chamber coated with a catalytic surface that helps break down (oxidize) food splatters and spills overtime. 

Baking is the oldest and most popular food processing techniques that uses the prolonged dry heat by convection  rather that the thermal radiation normally in an oven, but also in  ashes or on hot stones. It is a complex simultaneous heat and mass transfer process commonly applied in food industries.

A baking oven is the most widely used appliance in food service industry. An oven can be simply described as a fully enclosed thermally insulated chamber use for the heating, baking or drying of a substance. In a baking oven, the hot air flows over the baking material either by natural convection or forced by a fan, the convection heat transfer from the air, the radiation heat transfer from the oven heating surfaces, and the conduction heat transfer across contact area between product and metal surface. The moisture in the food material simultaneously diffuses toward the surfaces, then, it transfers from the surface by convection, and the product loses moisture with continuous movement of the oven ambient air. These are the simultaneous momentum, heat and moisture transfer mechanisms within a baking product (Tong and Lund 1990; Ozilgen and Heil 1994) and between the product and its environment (Carvalho and Martins 1993), which theoretically are well known. Commercially, ovens are available in the various configurations like electric ovens, micro oven and wood oven etc.

Electric ovens are the direct fired oven, which effectively distribute heat while being powered by electricity, although this can often result in a higher heating cost for the consumer. Many prefer this type of oven because they tend to use dry heat, which helps prevent the buildup of rust. Electric ovens also feature a thermostat that controls the oven’s temperature electronically, and many have top, bottom, or rear grill elements. Electric ovens can take longer to heat, but they are relatively inexpensive in cost compared to other types of ovens. 

Wood-fired ovens are indirectly fired ovens that use wood fuel for cooking. While the traditional wood-fired oven is like a masonry oven (mud oven), such ovens can also be built out of cob or iron. Wood-fired ovens are distinct from wood-fired stoves that have a hot cooking surface for pots and pans like electric stove. A wood stove may also have an oven separate from the fire chamber. Regardless of material they all have an oven chamber consisting of a floor (or hearth), a dome and an entry (oven opening). The wood fired oven has an advantage of the less capital requirement, ease of construction and similarly the wood fired has the disadvantage of longer baking time, the product has not baked uniformly and has the problem of the changing the original flavor of the product.

Gas oven one of the first recorded uses of a gas stove and oven referenced a dinner party in 1802 hosted by Zachaus Winzler, where all the food was prepared either on a gas stove or in its oven compartment. In 1834, British inventor James Sharp began to commercially produce gas ovens after installing one in his own house. In 1851, the Bower's Registered Gas Stove was displayed at the Great Exhibition. This stove would set the standard and basis for the modern gas oven. Notable improvements to the gas stove since include the addition of the thermostat which assisted in temperature regulation; also an enamel coating was added to the production of gas stoves and ovens in order to help with easier cleaning.

Gas oven is one which works by the liquefied petroleum gas for the baking of the bread, cake and biscuit.The major operational principle of the gas oven is the process of heat transfer. Heat transfer tends to occur whenever there is a temperature difference, and the ways in which heat may be transferred in the gas oven that is convection.

Convection is the transfer of energy from one place to another by the motion of a mass of materials between the two points. In a natural convection, the motion of the fluid is entirely as a result of differences in density resulting from temperature differences. Naturally, convection occurs when a solid surface is in contact with a fluid of different temperature from a surface. Density differences provide the force required to move the fluid (moisture) in the food.

In the oven, the fluid involved is the enclosed air and the burner surface, which provides the solid surface, while the oven walls serve as the solid surfaces. The rate at which heat is transferred across an enclosed oven is calculated from a coefficient based upon the temperature differences of the surfaces.

Study of baking oven is important because it could lead to a more efficient process of baking favorable to energy efficiency and better product quality (Fellows, 2000). The baking process usually requires significant energy consumption as relatively high temperature is applied in order to remove moisture in bakery products and create desired texture. Analysis and optimization of baking process and equipment have been conducted for minimizing energy consumption (Therdthai et al., 2003).

1.2     OBJECTIVES

This project is undertaken to

(1) Compare the various ways used in the production of an electric and gas oven.

(2) Disclose the different types of process in the manufacturing of an electric oven and also a gas oven in the past in comparison to the morden days method.

(3) Exploit the local facilities available in the construction of the oven as against imported ovens.

(4) To exhibit the usefulness of a dual-purpose oven in the economy and technology growth of the nation.

(5) To know the convenience in the use of alternate power source for operation of ovens.

(6) Discover the basic principle involved in the design and maintenance of a dual purpose oven.

1.3     IMPORTANCE OF OVENS

In actual analytical enunciation an oven is an enclosed chamber in which things are heated or cooked with various sources of power.

Its importance borders around its function, which are as follows;

(i) It is used to meet the everyday basic need of cooking, (baking, toasting, gritting, toasting) of food materials for human consumption.

(ii) Ovens are used for heat treatment of substance in laboratories and industries.

(iii) Also as a means of preservation by heat application to perishable materials (organic and inorganic) in general.

(iv) Sterilization of instruments and equipment for industrial use is done by heat application using oven.

(v) Expelling of moisture content to a required measure in some substance is also done using oven.

(vi) Early manufactured ovens where used as a source of room heaters during cold weathers in cold climates.

Other importance boarding around its energy source is that the use an alternative source of energy when either fossil fuel or electricity is not available. This can be relatively save cost when necessitated.

1.4     LIMITATIONS

Disadvantages in the use of ovens:

(i) Cleaning and repair is a difficult and time- consuming endeavor.

(ii) Expect for mass production singular construction is relatively expensive to produce.

(iii) If precautions are not well carried out, it can result in fire hazard, which is dangerous to life and properties.

(iv) Because ovens provides heat for one or more areas, the temperature may vary in different areas of the oven.

(v) Oils and moisture collected on metal surface can end up trying to rust the metal coating if not clean regularly.

(vi) It is expensive to operate in high volume operations.

(vii) Speed seem to be the key factor and time taken to get to required constant temperature can be wastage of time.

(viii) Access to internal component n case of adjustment and maintenance is tasking as it requires an entire disassembling.

(ix) In case of mechanical faults resulting from shut down, an entire disassembling and requires is required.

(x) Due to its function by heating, there is always a premature wear or mechanical failure of some of the internal component.

1.5      JUSTIFICATION OF STUDY

The research work is justified for the following reasons: 

(i)      It has simple operational method and serves as a medium of exposure to the intricacies of design and fabrication. 

(ii)    It could be designed and fabricated locally, instead of waiting and longing for it’s importation. 

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