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    CFD-based multi-objective optimization of indoor air quality and thermal comfort in a classroom
    (Sage Publications Ltd, 2023) Aydin, Kadir; Yilmaz, Berrin
    Comfort conditions and air quality in educational buildings can affect students' performance, achievement and productivity, but they can also threaten their health. In this study, a sample classroom in Trakya University, Edirne, which lacks a ventilation system, is discussed. Depending on the determined parameters, an optimization study was performed using computational fluid dynamics. Predicted mean vote (PMV) for general thermal comfort, draught rate (DR) for local thermal comfort and the carbon dioxide (CO2) level for indoor air quality are selected as target functions. Outdoor air temperature, heating/ventilation system, insulation thickness, number of people in the classroom and clothing factor were identified as parameters that could affect the target functions. According to the numerical results, the rank of importance of the parameters affecting the target functions was calculated using the Taguchi method. The effect percentages of the parameters were determined using the analysis of variance. Then, all target functions were optimized with the grey relational analysis. The best case obtained as a result of the optimization has PMV, CO2 and DR values of -0.12, 511 ppm and 5.37%, respectively. When the general results are evaluated, a comfortable and healthy environment is provided in the classroom with the underfloor air distribution system operating at 100% fresh air and a reduced number of occupants.
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    Hydrogen production and storage analysis of a system by using TRNSYS
    (Pergamon-Elsevier Science Ltd, 2020) Karacavus, Berrin; Aydin, Kadir
    In this study, hydrogen production and storage were investigated. The Transient System Simulation Program (TRNSYS) and Generic Optimization Program (GenOpt) packages were combined for the design and optimization of a system that produces hydrogen from water and stores the hydrogen it produced in the compressed gas tank. The system design is based on the electricity grid. Electrical energy produced in photovoltaic (PV) panels was used to electrolyze water. The systems for Izmir, Istanbul and Ankara provinces which are in different climate zones of Turkey were optimized and the annual system performances based on the optimum angles were analyzed. For the mentioned provinces, the PV tilt angles which minimize electricity drawn from the grid at the electrolyzer are also investigated. The electrical energy produced in the photovoltaic panels, the hydrogen and oxygen amounts produced, the efficiency of the electrolyzer, the gas and pressure levels in the hydrogen tank were compared. According to the results of the analysis, the annual total power produced in photovoltaic panels is 42803.66 kW in Izmir, 42573.74 kW in Istanbul and 44613.95 kW in Ankara. Hydrogen levels produced in the system are calculated as 10488.39 m(3) year(-1) in Izmir, 9824.70 m(3) year(-1) in Istanbul, and 10368.65 m(3) year(-1) in Ankara. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Numerical investigation of general and local thermal comfort of an office equipped with radiant panels
    (Sage Publications Ltd, 2019) Karacavus, Berrin; Aydin, Kadir
    Thermal comfort of an office environment is one of the most important factors affecting the performance of employees. One of the systems used in heating and cooling of offices is the radiant system which can create a thermal environment at acceptable levels. In this study, general and local thermal comfort of an office with a dimension of 3 m x 6 m x 3.5 m, where two manikins are positioned next to each other, are numerically studied with the help of computational fluid dynamics. Two different models were created for analyses. In the first model, the panel was placed below a window whereas in the second it was positioned on the ceiling. For each model, analyses were carried out at different temperatures and with different panel heat fluxes. The compliance of the office's general and local comfort levels with ISO 7730 was evaluated taking into account results of analyses. The calculation revealed that general and local comfort levels for these models were not in compliance with ISO 7730 when the outside temperature was -10 degrees C. However, when the outside temperature was 3.3 degrees C and 10 degrees C, the general and local thermal values of both models were within acceptable limits.