Thermal Engineering

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http://etd.aau.edu.et/handle/12345678/143

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Browsing Thermal Engineering by Author "Abdulkadir, A. Hassen (PhD)"

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    Design and Development of a Solar Powered Cooling System to Harness Potable Water from Humid Air (A case study in Semi-Arid zones of Ethiopia)
    (Addis Ababa University, 2019-05-14) Gudeta, Wegissa; Abdulkadir, A. Hassen (PhD)
    Water shortage is very noticeable in semi-arid parts of Ethiopia where there is hardly any freshwater source at all. Currently, the most interesting method of getting sustainable alternative potable water by harvesting humid from air is continuously under research around the globe. This study was to quantify water from humid air as one of alternative sources using a solar energy prototype targeting semi-arid zone where predominantly pastoralists are living. This paper presents collection of humid air as sand bed introduced to atmosphere at night and a solar thermal regenerative process during day time then extract water from the system. The main objective of this thesis is to design and manufacture the prototype. The experimental setup consists of composite materials: calcium chloride and river sand as well as the glass box enhancing of capturing moisture from air and facilitate regenerative process. It is obvious that semi-arid has a hot temperature in day time, whereas sand bed is actually cooled at night. Hence, the two windows on the prototype introduce the ambient humid air to pass on the sand bed where the humidity will start adsorb. Whereas the solar glass box is exposed to solar radiation and internal temperature become increase where the evaporation and condensation has begun, the water drops will slide over the inner surface of solar glass and finally collected into the jar through the condensate trough. Due to weather climates similarity of Yabello and Adama, testing was done at Wind Farm Electrical Station -1, Adama. The result of one day experiment showed that moisture was collect on the sand bed during night and evaporation also successfully collected on the inner surface of the glass. Testing has been performed after good preparation at Adama wind farm Electric station-1for day and result shows that promising because water condensation on inner surface noticed. But, the numerical result and experimental result did not agree. Low production rate may be the consequence of air leakage, low of humidity amount in the air and low solar radiation intensity. After observing the test result for the effectiveness of the prototype further modification is recommended.
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    Design and Experimental Investigation of Savonius Wind Turbine with Air Jet mechanism
    (Addis Ababa University, 2021-02) Balcha, Tola; Abdulkadir, A. Hassen (PhD)
    The Savonius wind turbine is a type of wind turbine with a vertical axis that operates on the aerodynamic drag principle. It has potential to be developed as it has great advantages, such as simplicity in design and construction, full-capacity operation and production of energy in areas with low wind potential. However, because of its low performance compared to other turbines, the turbine is rarely used. The low efficiency of the turbine is due to the negative torque generated with this turbine. Several researchers have worked to reduce the negative torque generated by this turbine in a variety of ways. Most of them, however, are achieved by limiting the Omni-directional properties of this turbine, which is its main advantage and feature. In this work, we have developed a new feature called the air jet mechanism to reduce the negative torque of the turbine without omitting its Omni-directional properties. The air jet mechanisms have been developed with the capacity to receive wind from all directions and direct it to the useful area of the turbine blade. Due to its geometrical characteristics, the air jet mechanism also works as a venture to increase the speed of the incoming wind. In order to observe their size influence, three different sizes of air jet mechanisms are developed and labeled as longer air jet mechanism, medium air jet mechanism and shorter air jet mechanism and successively positioned around the conventional two-blade Savonius wind turbine with a diameter of 0.4 m and an aspect ratio of 1.5. The performance test of this specified turbine was performed in the laboratory by adding three different size air jet mechanisms around it and without air jet mechanisms (i.e. the bare turbine alone). The performance of the Savonius wind turbine tested under each air jet mechanism is compared with that of the bare Savonius wind turbine tested under the same conditions. When measured with a longer air jet mechanism at a tip speed ratio of 0.4, the power coefficient of the stated Savonius wind turbine increased from 0.05 to 0.11. The results of the investigation showed that an air jet mechanism could increase the efficiency of the conventional two-blade Savonius wind turbine without omitting the wind reception property from all directions.