Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/9145

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Browsing by Institution Author "MENGÜÇ, Mustafa Pınar"

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    Airflow characteristics and thermal comfort of air diffusers
    (ASME, 2023) Eraslan, Tolga Arda; Keskin, Cem; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Eraslan, Tolga Arda; Keskin, Cem
    Indoor environment quality control is very important for building operations as occupant of buildings spend up to 90% of their time indoors. After Covid-19 pandemic break out, indoor environment quality has become even more crucial to the society because of health concerns. Indoor Environmental Quality (IEQ) covers conditions such as air quality, lighting, thermal conditions, ergonomics inside a building and their effects on the occupant or occupants of the building. Thermal conditions and air quality are usually achieved with the mechanical or natural ventilation systems or by HVAC equipment. As buildings became more complex structures, different airflow distribution systems to be developed to fulfill such requirements. For this purpose, not only the airflow distribution systems need to be modified but also diffusers that provide which supplies/draws air to/from systems are to be improved. Detailed analysis of these subcomponents is needed to assure that such devices provide high levels of comfort effectiveness and energy efficiency. The objective of this study is to develop a comprehensive analysis for air characterization and indoor air regime of different diffusers (square diffuser, operable flap diffuser) and their effect on comfort level of occupants Fanger’s model of thermal comfort is used with CFD simulations and a tool is considered for the validation experiments. Using more than 16 thermal sensors including one on a mannequin head, on a table and at foot level, the readings were correlated by using anemometers to measure air flow at supply diffuser and at different operating levels. CFD simulations were according to different scenarios which are to provide a comparison between diffusers and understand indoor airflow regimes. The results considering the flow interaction between diffusers and surroundings showed a detailed visual illustration in CFD simulations and their relation to perceived comfort levels.
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    Design methodology of a concentrating solar volumetric receiver
    (ASME, 2023) Akba, Tufan; Baker, D.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Akba, Tufan
    A volumetric receiver design process is proposed to respond wide range of power, outlet temperature, or mass flow rate needs. In the receiver model, concentrated solar radiation hits the inner surface cavity and heats the gaseous fluid passing through the porous media assembled between the cavity and the insulator. Porous media properties and receiver geometry are coupled in the design process to determine the best possible option. A two-step process starts with a parameter sweep to create a surrogate model. Then, gradient-based design optimization is performed using two different surrogate models to maximize the outlet air temperature for bounded design variables in receiver volume and outer surface temperature constraints. The proposed design process has the advantage of exploring more design options faster using the surrogate model and more accurate results using the base model in the plant-level simulations. The methodology is discussed by comparing the surrogate models and the model validation shows that over 95% accuracy is obtained using both surrogate models. Surrogate-based design optimization is compared as in solution time and the final results are compared with respect to the base receiver model.
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    Numerical analysis of solar radiation effects at indoors with internal partitions and external solar shades
    (International Solar Energy Society, 2020) Yelekci, Ali Can; Keskin, Cem; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Yelekci, Ali Can; Keskin, Cem
    A numerical study is conducted to couple natural convection in an office space with thermal radiation due to solar radiation. The study specifically investigates the effect of partitions located between desks of the office space to develop a tool-box to determine the effect of windows on thermal and visual comfort of occupants. Three different partition cases (according to the aspect ratio of the partition to the ceiling height, which are 0.3, 0.5 and 1.0) were studied. Moreover, the effects of different designs of solar shades in front of windows were investigated. All walls other than the facade of the enclosure are assumed adiabatic, and the enclosure has a single window, which acts as a thermal radiative heat source. All surfaces are assumed to be gray-diffuse surfaces for calculation of thermal radiation. The solar radiation is analyzed for a perfect sunny day with both diffuse and direct sunlight, and for an overcast day with only diffuse sunlight. Based on the choice of partitions geometry, solar shade aspect ratios and the weather conditions, variations on the surface temperature distribution inside the office are analyzed.