Thermal Engineering

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Design and Experimental Investigation of Solar Cooker with Thermal Energy Storage
(Addis Ababa University, 2018-11) Muluken, Biadgelegn; Abdulkadir, Aman (PhD)
Cooking is the major necessity for people all over the world. It accounts for a major share of energy consumption in developing countries. Therefore, there is a critical need for the development of alternative and affordable methods of cooking. Solar cooking is a novel and eco-friendly method of harnessing sun’s energy. Solar cookers can be of a great use in saving fuel and enabling in eco-friendly cooking of food. Solar energy is available during daytime only and also intermittent. So, thermal storage is important for indoor solar cooking requirements and will ensure continuity of service, reduce the use of conventional energy, and give a reasonable cooking time compared with conventional cooking. The solar cooker designed for this study is1.5 aperture area of compound parabolic dish concentrator integrated with thermal storage media (1.5litter of oil and 0.74kg of rock) as an absorber (area of 0.4 )to increase the duration of the effective energy storage period without tracking and utilize thermal energy for night cooking. The overall system is designed with an assumption to cook 1kg of rice in 45minutes requiring power of 522W which is obtained from the stored energy from the sun. Therefore, the numerical simulation, experimental test, and validation of the two results are done. An absorber with thermal storage is simulated by COMSOL software to show temperature distribution. As it is shown in the simulation section, the temperature of TES could reach365K after 6hours. Where as in the experimental result, due to so many losses the energy reduced in some extent and it reaches 354K. Even if it has low energy, it can cook the required food by placing TES in the insulated tank during discharging. Therefore, there were deviations between experiment and simulation because the model did not account the basic losses and frustration of solar radiation in case of numerical simulation. The model of the TES system was validated with experimental results and a brief reason was found between experiment and simulation for the charging cycle. The discharging of TES is started after it is lifted from solar collector and it is placed on the insulated tank and loaded by pot with water. This is maximum temperature of water reached after 40 minutes is 355K (82℃).
Design and Manufacturing of Solar Injera Dryer
(Addis Ababa University, 2020-10) Senay, Teshome; Abdulkadir, Aman (PhD); Kamil, Dino (PhD)
About two-third of Ethiopian diet consists of injera, which has a strong cultural significance and high nutritional value, as it is rich in fibre, amino acids, calcium, iron and most importantly it is gluten-free. Injera is dried and prepared in times of food scarcity or for commercial and household usage. The objective of this thesis was to design and evaluate a mixed-mode natural convection solar injera dryer with unique vertical air distribution unite with 20 injera drying capacity. Three dimensional simulation of unloaded solar dryer was developed to simulate the performance of the modified mixed mode solar dryer using the computational fluid dynamics (CFD) software ANSYS FLUENT for month of July and April by solving the governing equations describing the unsteady fluid flow. Dual-band discrete ordinates (DO) radiation model, Species transport model and shear stress transport (SST) k-omega (k-ꙍ) turbulence models were employed. The dimensions of the dryer were: 2 m, 2 m , 1.4 m, 2.2 m, 1.5 m and 1 m for collector length, collector area, height of the vertical air distributer channel, the height of the drying chamber, length and width of the drying chamber respectively. 2 C above the ambient throughout the drying period. The overall temperature distribution through the drying trays shows a uniform temperature distribution. The average velocity and mass flow rate through the drying trays were found to be 0.1 m/s and 0.061 kg/s respectively and both were uniformly distributed through the drying trays. There was a pressure gradient through the drying tray, which helps to maintain the airflow through the dryer. The simulation result indicated the collector outlet temperature was 10 o From the experimental result, it was clear that the modified mixed mode drier performance was higher by 19% when compared with other similar mixed mode drier. In addition, the temperatures of the drying air inside the drier was found to be more than 5 C from the ambient temperatures. A uniform temperatures distribution was noticed through the drier, this is the result of the vertical air distributer channel, which was newly developed and integrated through the drying chamber, and the collector and drying efficiency of the drier were found to be 30% and 15.25% respectively. The drying rate of the drier was 2.634*10 o kg/s and the Verma thin layerdrying model fits best for injera drying based on the X -5 . The experimental result was compared with the simulation result and the simulated temperature result showed an average overestimation on drying chamber by -1.5% and underestimation on collector outlet by 1.6 %.
Design and Techno-economic Evaluation of Solar PV power Supply for Off-Grid Communities in Ethiopia: The Case of Indode Village
(Addis Ababa University, 2020-09) Genanaw, Embiale; Abdulkadir, Aman (PhD)
Now a day, alternative energy supply has become compulsory to improve the life standard and increase the development of rural areas which are living without modern electricity and still dependent on traditional fuels. Usage of these traditional fuels is hazardous to human health and the environment. Solar energy is one of the alternative energy sources to overcome this problem. This thesis study has presented off-grid solar PV system to power Indode village which has 322 households and 1,171 people. Based on the village’s load demand and metrological data, the system components are sized and simulation was done using PVsyst software to optimize the system technically and assure its economic viability. The total numbers of common kitchens to serve Indode’s community are 10 which consume the major part of the solar power produced. In addition to powering the kitchens, the system is designed to power the health center, the schools, the administration offices and other business shops. The total installation cost of the project is 21,328,100.00 Birr with total number of 1028 batteries, 1812 solar modules, and 63 inverters are required for the system. The Net Present Value, the Return on Investment and the Payback period of the project are determined to be 84,730,997.18 Birr, 397.3%, 9.3 years, respectively. Considering a 25-year project life span, the economic indicators show that the solar PV system is a viable source of electricity in Indode’s village and can be considered as applicable to other off-grid communities in the country.
Design, Construction and Testing of Solar Egg Incubator with Thermal Storage System
(Addis Ababa University, 2020-12) Sintayehu, Bekele; Abdulkadir, Aman (PhD)
Incubation is a process by which birds hatch their eggs and develop the embryo within their egg in to young off-spring. In Ethiopia where most of the population live in rural areas where there is no access to grid provided electricity, the method of hatching used were restricted to natural incubation in which the mother hen or broody hen provide the necessary condition for the development of embryo to fully developed offspring. But this is inefficient technique in terms’ of production number, since the mother hen can produce limited amount of young offspring (from 10-12 per cycle). So to solve the problem associated poultry industry hatching method, in this research design, construction and testing of solar poultry egg incubator for hatching chicken egg which can be used in rural areas of the country is discussed. The system has solar thermal collector integrated with low power photovoltaic panel. It uses solar thermal energy to heat air inside solar collector. Air is pressurized from the environment to the solar collector by the inlet fan and gain heat inside the air chamber. The heated air from the collector flow to the incubation chamber due to pressure difference created between them by the inlet fan. Heat exchange process takes place inside the incubation chamber from the hot air to the egg maintaining the egg at 37.80c and 60% the optimum temperature and relative humidity required for incubation respectively. The machine has incubation capacity of 80 egg per on incubation cycle (21 days). The amount of heat energy needed for the incubation of the specified amount of egg is 185w. Total collector area of is used for utilization of the required amount of energy. Thermal energy storage system using paraffin wax as a thermal mass. It is used to store thermal energy needed for the time direct solar radiation is not available. 20kg of paraffin wax is used as a thermal storage material and the volume of thermal storage container is to replace the amount of 80w lost energy in the form of heat from the incubator box during the time direct solar radiation is not available.
Design, Manufacture and Experimental Investigation of Biogas Injera Baking Pan
(Addis Ababa University, 2019-12) Dessie, Gashay; Abdulkadir, Aman (PhD)
Energy is a primary and basic question for living things of peoples to lead their life. Energy is a key factor for the development of one country. Energy demand increases with respect to the population size. Energy is utilized from different sources for conducting day to day activities of human beings. Even though there exist so many sources of energy developing and under developing countries relays on biomass energy sources for cooking purposes. Biogas is a fuel which can be obtained from different sources like animal manure, animal slaughter, plants, sewage, ruminant, etc. biogas encompasses different gases depending on the sources such as, methane, carbon dioxide major constituent while hydrogen sulfide, hydrogen, nitrogen may include. By doing so we human being faces a number of problems such as shortage of cooking fuel, health problem due to emission of firewood, air pollution, acid rain formation depending on the content of emissions and ozone layer depletion those are the typical challenging problems which encounters our surrounding. The main aim or goal of this research paper minimizing or overcoming previously mentioned problems that come due open fire stoves most commonly. In order to implement this paper we were used the following methodology data collection of biogas thermal property and baking clay pan thermal property; input fuel content; knowing biogas properties its composition as well as flow rate; chemical kinetics of biogas, determined dimension of ,3D burner assembly using CATIA, design of flame port geometry,3D flame port assembly by CATIA, design of insulation layer were have been done finally we manufacture the optimized burner geometry and carried out the experimental investigation hence we obtain the result of 22.1% thermal efficiency the prototype somewhat portable and can be movable able to bake by transporting somewhere we desired, the burner ables to drive biofuel uniformly to the beanth of clay mitad because of flame port geometry orientation and distribution over the circular flame port surface. Here we can deduce that this stove ables to distribute heat to mitad uniformly as can be observed from the experimental investigation Biogas used for power generation, thermal heating upon with modification of utilizing equipment‟s. Biogas generates heat energy up on combustion reaction with in the combustion chamber.
Design, Manufacturing and Experimental Investigation of Pico-Power Hydrokinetic Turbine
(Addis Ababa University, 2021-09) Teklemariam, Tadesse; Abdulkadir, Aman (PhD)
Ethiopia has plenty of rivers and groundwater sources in the countryside which have the potential to generate electricity from Pico up to Mega power. There is a hydrokinetic turbine technology to generate green energy using river flow water. The gap is to interact with this technology and energy resource of water. The cost of imported equipment for this technology is expensive as well as the available equipment is mostly for large-scale hydropower energy conversion technology projects. This study aims to design, manufacture locally available material and experimental investigation of Pico power hydrokinetic turbine to grasp energy from the river water resource. The hydrokinetic turbine is the systems class of “zero-head” hydropower whereby energy is extracted from the kinetic energy of flowing water, similar to wind turbines, rather than the potential energy of falling water. The method to do this research includes optimizing the geometry of the turbine blade and force analysis of the blade using Ansys software. The blade was manufactured with a 3D printer and the mechanical components were manufactured in the workshop of the school of mechanical and industrial engineering. The test was conducted in four setups at different water velocities. The results are AC RMS value of 11.33Amp and RMS value of voltage 6.89volt respectively with the motor revolution of 486.75 rpm. The power coming from the experiment showed that it is sensitive to current and they have the same sinusoidal pattern plotting the results within each interval of seconds. The net power can be obtained from the turbine was 128.37 watts. The efficiency of the turbine is 51.48%.
Design, Numerical Optimization and Experimental Investigation of Waste - Heat Recovery System Coupled To Electric Injera Baking Pans (MITADS)
(Addis Ababa University, 2018-06) Ashebir, Dingeto; Abdulkadir, Aman (PhD)
Electric Injera baking pans (Mitads) are the most prevalent and energy-intensive appliances used in Ethiopia and encounters bulk amounts of heat loss in the systems. However, only few and rarely published research and development were made to improve the thermal efficiency and reduce the heat loss encountered in the system. Therefore, this study aims to make design; numerical optimization and experimental investigation of waste heat recovery system coupled to electric injera baking pans to improve the efficiency of baking pan and reduce the wastage of energy in the baking process. Thus, to verify (quantify) the amount of heat loss accounted in the baking process intensive experimental investigation was made, and data obtained was analytically analyzed and electric Injera baking process was encountered 46.15% heat loss in which bottom insulation encountered 70% of total loss accounted in the process. Therefore, to reduce the major loss accounted in the bottom insulation analytical design and numerical optimization of waste heat recovery system was carried out by using comsol multiphysics software and 6.5mm thick ash insulation at the top and bottom of oil pan and 1.5mm oil pan thickness was obtained as the optimum dimension of heat recovery system. Then, the waste heat recovery system was manufactured as per optimization result and some of the insulation was replaced by simple heat recovery oil pan, with the diameter of 540mm and thickness of 19mm` and coupled to heat recovery tank, to discharge the energy recovered to make coffee and water heating. The performance evaluation of the system was carried out by experimental investigation and the system was recovered 60.66kJ (which account 9.63%) of heat energy at each baking and tested experimentally by boiling water. This study also quantifies the loss accounted in the new system and the system encountered 34.57% heat loss and bottom insulation accounted 22.57%. Compared to the ordinary baking pan the electric injera baking pan coupled with waste heat recovery system will improves the efficiency of baking process by 11.53%. The heat energy recovered by the system is utilized for water heating purpose and for making coffee.
Experimental and Numerical Study of Heat Transfer Characteristics in Traditional and Modern Cook-pot. (A Case Study on Ethiopian Cookware)
(Addis Ababa University, 2018-10) Achamyeleh, Muche; Abdulkadir, Aman (PhD)
The development in the design of cooktops and cookware with an increasing energy cost needs a research. This study was taken up to research the heat transfer characteristics of different cookpots on electric coil and identify the most appropriate pots. Experimental analysis and numerical simulations on different cookpots apply for determination of cookpot’s thermal behavior. Clay and metal made cookpots have been considered for the analysis. Both experimental and numerical study made separately for a clay pot and metal pot, those contains water as cooking material (water boiling test). In this paper, a methodology for evaluating the thermal efﬁciency of a pot on an electric stove using experimental methods and numerical simulations in Ansys transient thermal were presented. The numerical simulations and experimental tests corresponded well with one another. The experimental data were collected using commercial Ethiopian cookpots (metallic and clay made ‘shekla’). From the experimental work, the cookpot’s actual heating property and thermal efficiency had been determined. for the case study, the experiments were done using only an electrical stove, and all the tests were carried out at a power input level of 1500 W. The corresponding constant heat flux is applied directly through the bottom surface of the pot. By modeling similar cookpots with the experimental one, transient thermal simulation gives the result, that shows the existing heat transfer properties, like; heat transfer pattern, heat flux distribution, temperature gradient and overall efficiency of the cookpot throughout the pot surface, graphically and numerically. The numerical results then compared with experimental measurements to set the difference. From this result, the convection and radiation losses are less in case of optimum height to diameter ratio so thermal efficiency is highest among the cooking pots hence the large amount of heat energy has to be saved during cooking process. The effects of the parameters like stove to pot contact area, bottom flatness, body shape, filling amount, thickness, handle and ratios of diameter vs depth also addressed. Then after, the study extended to recommend the cookpot that have relatively good heat transfer behavior than the existing one.

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