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  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 4, Issue 6, November - December (2013), pp. 201-213 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com IJMET ©IAEME DESIGN AND REALISATION OF A COCOA HYBRID DRYER FOR A RURAL ZONE Abraham Kanmognea*, Yves Jannotb, Jean Nganhoua a b Laboratoire d’Energétique, ENSP, BP 8390 Yaoundé, Cameroun LEMTA, Nancy-Université, CNRS, 2, avenue de la Forêt de Haye, BP 160, 54504 Vandoeuvre Cedex, France ABSTRACT We present in this article the study and the realization of a hybrid prototype of drier solar /wood for the agro-alimentary drying of the products in general, and the cocoa in particular. The drier is composed of four essential parts; the room of drying is of dimensions 3 m X 2 m X 1.2 m and is built out of terra cotta briquettes. The two hearths consist of stainless sheet steel of parallel epipedic form covered with ground briquettes. Two galvanized steel tubes with diameter 135 mm crosses the room of drying in the length’s direction and constitute the heat exchanger. The roof of the drier is made out of plexiglass to optimize solar energy in the drying room. The study of the drier was done while following a methodical step and by using tools of the design such as the functional specifications, the technical functional analysis, the diagram APTE, the block functional diagram, the life cycle and the justified choice of the technical solutions of the drier. The construction of the prototype and the test on the prototype made it possible to dry 100 kg of fresh cocoa in 50 hours by using energy coming from wood and 35 kg in 40 hours by using solar energy. Key words: Hybrid Drier, Functional Analysis Technique, Cocoa, Cameroon. 1. INTRODUCTION Cocoa is third in the world ranking of exported agricultural products after coffee and sugar. In the majority of cases, it is produced by small farmers. 90 % of the production in rural zones of world cocoa-plantation results from plantation of a surface area less than 5 hectares [1]. In Cameroun, cocoa alone represents 15 % of total exports [2]. Trade tackles the problem of the quality of cocoa bean through standard references defined in the sales contract. The French standards, a bit different from the American or English standards stipulate that "the delivered goods must be 201
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME reasonably free of foreign broad beans tastes from the cocoa and of defective broad beans [3]. Currently, on the world market, the cocoa coming from Cameroon is of approximate quality because it does not fulfill the standards of quality. This involves a low rating of the cocoa coming from Cameroun. The approximate quality of the Cameroonian cocoa is caused by the drying system, which caused approximately a 10% loss in post-harvest [4, 5]. These losses are caused by: - insufficient drying resulting to molding of the product; - the smell of smoke and tar in beans; - The presence of pebbles in dried beans. The improvement of the activity of drying in the countries of the South passes by the taking into account of the real needs for the users, of the characteristics of the products to be dried and the environment in the design of the driers [6]. There is no universal mechanism in the technological choice of a drier. Various case studies made, it is difficult to have indisputable elements of validation and comparison between the various models of drier [7]. A study of the drying system of cocoa in Cameroon showed that four types of dryers are used by farmers: - the bus dryer; - paved roads and flow concrete platforms; - Samoan ovens; - Soil. Unfortunately, these dryers used are not satisfactory to farmers. The dryer wanted by producers for drying cocoa whose harvest season lies partly in the rainy season is a dual fuel dryer [8]. The objective of this paper is to study and build a dual fuel; solar- wood dryer for drying cocoa in rural areas. To achieve this goal, we assumed that the design and construction of the dryer will take into account the following functions: - ensure drying in any season; - use wood biomass and solar energy; - avoid the taste of smoke and tar in the product; - introduce and easily stir the product into the dryer; - protect the product against rain and insects; - better retain the heat in the dryer; - Less expensive to achieve. 2. MATERIALS AND METHODS 2.1. Material The fireplace is made of stainless steel, covered with cooked soil bricks to better retain heat from the fuel. The frame of the dryer is made of clay briquettes due to the insulating quality and its lower cost. 202
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME Heat Diffusers: the two channels are made of galvanized steel pipes 125 mm diameter going through the dryer in the longitudinal direction. They are good conductors of heat and are more resistant to oxidation than the black iron. Drying deck: several materials may be used for the manufacture of the grid and drying deck. We include among other bamboo, synthetic mesh, and stainless steel grille. The synthetic mesh is too loose to temperature. Even with the short life cycle of the bamboo, this material is chosen because it is inexpensive and available in rural areas. The mountings mat are in black iron of profile T, coated with antirust paint. The chimneys are made of two filling pipes of stainless steel. They could also have been built with briquette of cooked clay. The thermal insulation of the base of the dryer can be done with the coconut fiber, wood sawdust, polystyrene, glass wool, cotton or kapok. Among these insulating materials, kapok and coco fibers are less expensive and coco fibers are available in the area of cocoa cultivation. So this material is chosen. Roofing: the dryer can be covered with Plexiglas, glass or special plastic film. The glass was not retained because of its fragility and the special plastic is very rare on the local market. The roof of the dryer will be covered with Plexiglas available on the local market and easier to maintain despite its higher cost. 2.2. Method The survey of producers in the domain of drying and references of dryers permitted us to make a list of the different types of dryers and define the functions that a particular type of dryer should satisfy. The different types of dryers and functions of each part of the dryer are shown in a table constructed as follows: in the first column, we present the list of different types of dryers and on the 2nd line, the list of functions performed by a part or type of dryer. At the intersection of a type of dryer and a function is a note ranging from 1 to 5. Note 5 means that the type of dryer in the 1st column provides great function of the 2nd row. Note 1 means it does the function poorly. The exploitation of the table designed permits us to choose the functions and constraints corresponding to the life cycle of the dryer designed. An internal functional analysis of the dryer is made after the description and afterwards implementation of the various parts of the dryer. 3. RESULTS AND DISCUSSION 3.1. Summary of existing systems The choice of material is often delicate. They are never based solely on mechanical considerations. Consider manufacturing methods, costs and resistance to chemical attack [9]. The technological potential (spare parts and competence) is a major factor to work on driers adapted to our environment [10]. We present in the following table performance of dryer system that takes into account the function of the devices. 203
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME Table 1: Performance of dryer system To admit the air for combustion easily easely To stir up the product product easily To introduce the goes away Increase of moisture from outside To protect the product any season To ensure drying in air Good circulation of Best conservation of heat To use solar energy construction Weak cost of Control limited temperature Not to have the taste of smoke Functions by order of decreasing importance Type of drier (Drier) Lagdo 4 4 3 4 2 4 5 5 3 4 3 4 Tunnel 3 5 2 4 2 5 5 5 3 4 3 / Comité Diocésain 4 4 2 4 2 4 5 5 3 4 3 3 Solaire à V. élect. 3 5 2 4 2 4 2 5 3 4 4 / Autobus 5 5 4 5 2 3 2 4 2 4 4 / ENSIAA C1 3 5 4 5 3 3 2 5 3 4 3 / Mvolyé 3 5 3 5 2 4 2 5 5 3 1 / ENSIAA C2 3 5 4 5 3 3 2 5 3 4 3 / Basculant 3 5 4 5 3 3 2 5 3 4 4 / Brace Institute 3 5 3 5 4 4 2 5 3 4 4 / Samoa 4 5 3 2 1 3 5 5 2 5 4 5 Burareiro 4 4 2 1 5 3 5 5 1 4 4 5 Cameroun 3 4 3 1 3 3 5 5 2 5 4 4 Plate forme CEPEC 5 5 2 1 2 4 4 3 2 5 5 5 Plate forme 4 5 3 1 2 4 4 3 2 5 5 5 Fumoir 2 1 5 1 1 2 5 2 2 3 2 4 Wanson 4 4 2 1 2 3 4 3 2 5 3 5 204
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME 3.2. Selection motivated devices used Choosing a type of dryer with mixed fuel, solar- wood is guided by the advantages and disadvantages of the various systems: the possibility of drying the product in any season, using a reduced drying surface compared to solar drying, drying time reduced compared to solar drying. As regards the supply in solar energy, the dryers may be classified into several categories by considering two characteristics: the transmission mode of the heat and the nature of the airflow in the dryer. The solar supply is direct if the solar radiation reaches the products, and indirect if the products are shielded from sunlight. A dryer is said to be naturally ventilated if the air circulation is provided by the thermal siphon effect, and forced ventilation is ensured by a mechanical action. A dryer is said to be covered if the absorber is protected by a transparent cover and uncovered otherwise. Given the cost of installation, we have eliminated the special solar systems that use photovoltaic solar energy or solar energy by concentration. The area of use (South Cameroon) does not receive very regular sunshine. Our choice will be limited to a covered dryer. Regarding wood combustion heating, systems fall into two groups: direct heating dryer: the products are heated directly by the smoke (drying / smoking) and indirect heating dryer: the smoke is not in contact with product. Table 2 summarizes the characteristics of each system. Table 2: Characteristics of solar-wood mixed drying systems. Solar dryers Direct à ventilation naturelle Indirect à ventilation naturelle Indirect heating using a natural ventilated heat exchanger advantages : Fast drying, simple construction, reduced cost inconveniences: degradation products with U.V, non-uniform temperature Advantage: average cost, fairly uniform temperature, products are free from U.V rays inconveniences : Heat loss , drying slower than in direct : Indirect heating using forced ventilated heat exchangers advantage : uniform temperature inconveniences: high cost Indirect heating without using forced ventilated heat exchangers Direct heating without using natural ventillated heat exchanger inconvenience : Product contaminated with smoke inconvenience : Product contaminated with smoke Wood dryer Indirect à ventilation forcée Direct à ventilation forcée advantage : Products are free from U.V rays inconvénients : High cost, Construction is complex advantage : Fast drying, average cost inconvénient : Degradation of the product by the U.V rays advantage : Product free from U.V rays, uniform temperature inconvénients : drying is less rapid,, construction is complex advantage : fairly uniform temperature, protection from rain inconvénients : limited temperature, high cost, necessity of electrical energy, construction is complex advantage : fairly uniform temperature inconvénients : high cost, degradation of the product by the rays U.V necessity of electrical energy inconvenience : - Product contaminated with smoke inconvenience : Product contaminated with smoke inconvenience : Product contaminated with smoke inconvenience : Product contaminated with smoke inconvenience : Product contaminated with smoke 205 inconvenience : Product contaminated with smoke
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME Choice between the direct and indirect solar dryer Cocoa is not very sensitive to UV rays. Traditional dried cocoa direct under sunlight (when time permits) is of very good quality. Direct drying permitting faster drying seems to be preferable. Choice of mode of ventilation The dryer is often aimed at non-electrified rural areas; our choice was directed to natural ventilation. Choice of heating mode Product contamination by smoke is the main drawback of drying using a direct wood heating system, hence the choice of indirect heating. The circulation of the drying air around the heating surface will be by natural convection due to non electrification of areas for which the dryer is destined. Conclusion on the choice of dryer The dryer that caught our attention was the mixed dryer that uses solar energy with natural ventilation and indirect heating with wood using natural ventilated heat exchanger because despite some drawbacks, it remained the most suitable in the production area [11]. 3.3. Functional specifications The functional analysis is divided into two parts: the outer functional analysis that lead to Functional Specification (FS) and internal functional analysis permits us to have a Table of Functional Analysis (TAF). The functional specification is a legal agreement between the giver of finance and the subcontractor. The purpose and implications of the FS are many knowing that it helps to clarify and formalize the responsibilities of the applicant, the design and realization of the director. In the case of our study, the FS presents the system (dryer) abstraction of solutions. This is a model that other researchers can take to develop alternative dryers. The FS is also a way of comparing solutions proposed to the drier with existing alternatives or future ones. There are several methods of functional analysis (FA) for the design in general: FIT, FAST, SADT etc. In mechanics the following functional analysis methods are used: the Intuitive method that identifies functions thus come to mind, systematic method (FIT), which consists of writing the expression of specific functions and the SADT (Structural Analysis Design Technic) method, adapted to the processing of data is useful for maintenance [12]. FAST (Functional Analysis and System Technic) method that prioritizes technical functions is particularly suited to the redesign. Intuitive method involves a significant risk of omission when the functions are enumerated. The SADT and FAST methods are cumbersome and ill-suited to the first design [13]. We used the systematic method given its precision to the functions used in the design of the dryer. The functional specification relates to a dryer for small cocoa producer. The dryer can be used to dry other agricultural products (groundnuts, maize, cassava, coffee, etc.). The principle of operation of the dryer is as follows: air heated by natural convection in contact with two channels circulates around the products placed in a thick layer on drying deck. Products also heat up by absorbing some of the heat flux radiated by the sun, the atmosphere and the transparent cover. This dryer can be implemented in many regions in Cameroon and some countries in Central and West Africa. Its adaptation requires a careful choice of materials used in manufacturing. The life cycle of a product is the set of actions that the product undergoes during the period of construction and use. The choice of materials of construction is very important. The life cycle of the dryer includes two phases. The normal usage phase which corresponds to the period of production of cocoa (OctoberJanuary) and the intermediate phase during which the dryer can be used to dry other products such as mango (March-September), corn (June-August) or peanuts. 206
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME Technical functions and constraints The functions of a system are of two types: the service functions which are the answers to the need of the owner of the system and the technical functions that are internal to the system and the result from the designer's choice. A function is characterized by its assessment criteria, its level (tolerance compared to another criteria), its flexibility is the degree of importance of the assessment criteria in the system (essential (0) important (1), negotiable (2), for guidance (3)) and its control that can be measured on the prototype, testing or simulation. Table 3 summarizes the functions corresponding to the life cycle of the mixed dryer and allows better monitoring during construction of the dryer ensuring that all functions are applied. Table 3: Functions corresponding to the life cycle of the dryer Function AssessmentCriteria Characterization Flexibility Control F1 :Insert the product into the dryer amount of product Load time Know how hardship m < 200 kg < 30 min Worker’s level achievable by a woman 1 3 3 3 Prototype testing temperature temperature variation < 60°C room temperature< 30°C 0 2 cycle time no mechanical or chemical reaction with the support < 90 heures 0 Intake and exit air flow Opening of air extraction traps F2 : Heat air F3 : Keep the product in the dryer F4 : Circulate the air F5 : The user controls the quality of the product F6 : Extract the product F7 : Protect product in the dryer outside F8: Conserve heat F9 : Esthetic F10 : Clean after several cycles color, touch 1 Opening of air renewal traps 90% product good measurement (providing a control) prototype testing 1 1 3 water content weight at the end of drying quantity of product discharge time know how hardship < 7% m < 107 kg m < 107 kg < 30 min worker level achievable by a woman 0 0 0 3 3 3 insect, , flies, smoke dust Return of moisture ban prototype testing expert during prototype testing 0 1 1 heat loss form ease of cleaning cycles number before cleaning minimum energy loss Rectangular 20 min/grid 5 cycles 207 1 2 2 prototype testing prototype testing modeling on prototype on prototype
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME 3.4 Description of the elements of the dryer The base of the dryer The dryer is based on a concrete of 3.5 m x 2.5 m at least 5 cm thick. A polyethylene film of the same surface area as the base layer is incorporated into the concrete thereby preventing rising of moisture. Above the layer of concrete is found a 5 cm layer of coconut fiber which is for thermal insulation (fig. 1) Polyethene film Coconutfiber concrete Figure 1: Cut of the base of the dryer Heat exchanger The heat exchanger consists of two tubes of galvanized 134 mm in outer diameter and 125 mm in inner diameter each steel. Each tube measure 3 m in length. One end of the tube opens into the fireplace and the other end closed, allows the pipe smoke in the drawing chimney. Fireplace It consists of a parallelepiped block of steel 50 cm wide, 75 cm high and 50 cm deep. The block is welded to the end of the exchanger. A circular opening 134 mm in diameter on one side of the fireplace provides the passage of smoke to the heat exchanger (fig. 2). In the lower part of the furnace a metal screen placed 15 cm from the floor serves to support pieces of firewood, and also delimits the height of the ashtray. The lower part of the face opposite to the heat exchanger is small with perforated holes of 6 mm in diameter across the width allowing the supply of air for combustion in the fireplace. A door with metallic flap is fitted on the upper part of the opposite junction so that the fireplace can be supplied with wood. Clay briquette walls provide thermal insulation around the fireplace. Chimneys for drawing off smoke 260 cm long, the drawing chimneys are welded each 5 cm from the sealed end of the heat exchanger tubes. They are made of stainless steel and have an outer diameter of 82 mm and an inner diameter of 78 mm. At the upper end of each pipe is welded a cone with a diameter slightly greater than the external diameter of the chimney. At the other end of the chimney (welded junction between the tube and the chimney exchanger), a circular hole of diameter equal to the inner diameter of the chimney is arranged on the heat exchanger tube for the evacuation of smoke from the exchanger to chimney (fig. 2). 208
  9. 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME Figure 2: Diagram showing layout of the fireplace, heat exchanger, chimney The frame of the dryer The frame of the dryer of dimension 3m x 2m x 1.2m is made up of briquette from cooked soil 22cm x 11cm x 6.5cm. Three rectangular holes of 12.5cm x 30cm are arranged 12.5 cm below the heat exchanger wall on each side to permit the renewal of air in the dryer. The intake airflow rate into the dryer can be regulated depending on the opening or closing of these orifices. Platform drying The drying platform has dimension 3m x 2m consists of iron with T profile painted with rust proofing material going through the drying chamber in the direction of the width. The ends of the chains are embedded in the two sidewalls. The spacing between the irons is 25 cm. A grid of 3 m x 2 m in woven bamboo mat is placed on the irons. The drying platform is 37.5 cm above the heat exchangers. Roofing It is made of plexiglas of 4 mm thickness divided into four modules of 1.5 m x 1.5 m. It is removable allowing access on the drying platform. Eight circular holes 80 mm in diameter are arranged on the roof and are used for extracting humid air from the dryer. The exhaust air flow may be controlled by closing or opening of the orifices through the shutters designed for this purpose. 3.5. Internal Functional Analysis dryer The objectives of the internal functional analysis are: the improvement of the dryer with respect to the needs and justification of the cost of the dryer. It is to define the purpose of the dryer, namely services rendered, by identifying the relationship it has with its environment [12] .The block diagram below reflects these relationships Function Block Diagram (FBD) of the dryer The functional block diagram permits us locate the dryer in its operating environment, identifies the relationships established by the dryer and the surrounding environment and expresses the purpose of each of these relationships. Two types of relationships are expressed: the relationship through the product or feature usage and relationships that bind the product directly to an exterior element or adaptation function. Figure 3 shows the different relationships between the dryer and its surroundings. 209
  10. 10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME Figure 3: APTE diagram of the dryer The diagram of the dryer with the surrounding environment does not show the various internal components of the dryer, or the connections between its elements. Relations between the components can be internal or external contacts to the dryer. The contact between the two components is materialized in a FBD by a route connecting these components (fig. 4) shows the functional block diagram of the dryer. Figure 4: Function block diagram of the dryer Array of functional analysis (AFA) dryer The functional analysis array is a complementary tool of the functional block diagram. This is a representation of table describing: the list of components of the dryer; the elementary functions associated with each component and the cost of each component of the dryer. Two types of functions are useful for AFA: the design function FK and the service function JN. The design function is an internal function of the dryer not directly involved in the service to be rendered. It corresponds to the technical functions that the designer adds just necessary to perform the service. It is represented by the material, labor force and energy, which are not directly useful to the user. The service function is 210
  11. 11. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME that expected for a product to meet the needs of a user. AFA can analyze the distribution of costs before deducing design performance (RC) which is an indicator for positioning the actual product compared to its optimum corresponding to that exactly necessary. The design performance in % is defined by the expression: RC = 100 C J C J +C F N N [14] K CJN is necessary cost and CPK is just the cost of the design function. The performance of the joint design of the dryer is 90% and the cost is 2 000 000 FCFA. 3.6. Implementation and operation of the dryer The Joint dryer measures 3 m x 2 m x 1.2 m. It offers the possibility of drying various products (cocoa, fruits, vegetables, cassava etc. ...) throughout the year. The frame of the dryer is built of clay bricks. The roof consists of a transparent cover, which is removable to allow access to the product to be dried. The drying platform 5.8 m² of useful surface is made of woven bamboo mat plated on T-shaped metallic tile-gutters that traverse the drying chamber in the direction of the width and the ends of which are sealed in the walls briquette earth. The heat transfer in the drying chamber takes place by natural ventilation around two steel pipes placed below the drying platform and through the drying chamber in the direction of the length. The hot flue gases from the fireplace pass through the steel pipes, which serves as heat exchanger between the hot flue gases and the surrounding air, before being discharged to the outside through two chimneys mounted to the opposite side of the fireplace. The admission of air into the drying chamber is equipped with openings on both walls 3 m below the smoke pipes. The extraction of humid air takes place through eight small chimneys arranged on the roof of the dryer (fig.5). 7 6 4 5 1 Air 2 3 8 1: Fire place (2), 2: Heat exchanger (2), 3: air admission orifices (3), 4: decanting chimney (2), 5: drying platform, 6: roof made of plexiglas, 7: air extraction orifices (3), 8: base of dryer Figure 5: diagrammatic representation of the dryer 211
  12. 12. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME 3.7. Test of the dryer Having designed, studied and built the dryer, we proceeded to dry the cocoa. The test on the prototype made it possible to dry 100 kg of fresh cocoa in 50 hours by using energy coming from wood and 35 kg in 40 hours by using solar energy. 4. CONCLUSION We have designed and built a mixed solar / wood dryer after first defining the terms of reference (working document) which was prepared to fulfill the primary function which is to dry. The functional specifications fixed all the main features of the dryer and operating conditions to be satisfied. Then, a block diagram of the dryer is designed with different functions to be performed by each system clearly stated. The overall design is decomposed into subsystems which are all subject to the study of variants in order to choose the best technological solutions. This phase was completed by a detailed description and drawings of the entire dryer. The dryer was built and field test of the dryer presented a satisfactory result. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Solar drier mixed wood: application to drying of cocoa. National Seminar on "raw materials, equipment and quality agro-industry", 2006, from 5 to 7 April 2006. A. Kanmogne, 2003, Contribution à l’étude du séchage du cacao au Cameroun : conception, réalisation et modélisation d’un séchoir adapté aux conditions locales. Thèse de Doctorat/PhD, Université de Yaoundé I, 142 p. D. Despraux, A. Leblond, 1996. Summary of meetings cocoa. The various aspects of quality. Plantation, research, development, March-April. A. Kanmogne, Y. Jannot, B. Lips and J. Nganhou, 1997, System analysis in Cameroon used for drying agricultural products, paper presented at the 5th Conference in Yaoundé, Cameroon from 10 to 12 December 1997, 15 p. A. Kanmogne, Y. Jannot, B. Lips and J. Nganhou, 2012. Sorption isotherms and drying characteristic curve of fermented cocoa. International Journal of Science and Technology, ISSN: 2250-141 pp 19-31. T.T.E. Boroze, 2011. Outils d’aide à la Conception des séchoirs pour les produits agricoles tropicaux. Thèse de Doctorat en Physique appliqué, Université de Lomé (Togo), 440 p. A. Boulemtafes et D. Semmar, 1999. Conception et realization d’un séchoir solaire indirect, Revue Energie Renouvelable PP 97-100. A. Kanmogne, Y. Jannot and J. Nganhou, 2012, concise description and analysis of systems in the southern region of Cameroon for drying cocoa.Tropicultura 2012, 30, 2, 94-102. George Skinner, 1998. Machine design, principles and application, Volumes 3 and Presses PolytechniqueUniversitaireRomande, CH-1015 Lausanne. Mame Abdou Diagne, 2003. Conception d’un séchoir à cylindre rotatif pour les produits granulés à base de cereals (application au “arraw”). Projet de fin d’étude d’ingénieur de conception, Ecole Supérieure Polytechnique, Université Cheikh Anta Diop de Dakar (Sénégal), 79 p. Y. JANNOT. Coûts compares des différentes sources d’énergie au Nord Cameroun en vued’ application domestique en zone rurale, Rapport d’étude, 10 p. O. GARRO, 1997 Training in System Design:Application to drying. FICU seminar, Ecole Nationale Polytechnique Yaoundé (Cameroon) 24-28 November. A. Kanmogne, 2010, Appui au développement des pays tropicaux, livre, ISBN : 978-613-155816-0, Editions Universitaires Européennes, 140 p. 212
  13. 13. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 6, November - December (2013) © IAEME [14] J.Favier and all, 2000, Dictionary of Engineering Sciences, Design, Production, Management, Maintenance (Concepts and Approaches) Foucher 2nd edition, 414 pages. [15] Qasim Murtaza, “Simulation of Spray Dryer Chamber by the Standard K-Є, Reliable K-Є and Reynolds Stress Models used in the Production of Thermal Spray Powders”, International Journal of Design and Manufacturing Technology (IJDMT), Volume 1, Issue 1, 2010, pp. 24 - 44, ISSN Print: 0976 – 6995, ISSN Online: 0976 – 7002. [16] Ajeet Kumar Rai, Shahbaz Ahmad and Sarfaraj Ahamad Idrisi, “Design, Fabrication and Heat Transfer Study of Green House Dryer”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 4, 2013, pp. 1 - 7, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [17] Singh, L.P., Choudhry V. and Upadhyay, R. K., “Drying Characteristics of a Hygroscopic Material in a Fabricated Natural Convective Solar Cabinet Drier”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 3, 2013, pp. 299 - 305, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [18] Phairoach Chunkaew, Aree Achariyaviriya, Siva Achariyaviriya, James C. Moran and Sujinda Sriwattana, “Operating Parameters Effects on Drying Kinetics and Salted Sunflower Seed Quality Utilizing a Fluidized Bed”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 6, 2013, pp. 256 - 268, ISSN Print: 0976-6480, ISSN Online: 0976-6499. 213