Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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Author: search.filters.author.Toprak, KasımPublication Index: search.filters.publicationIndex.TR-Dizin

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  • Article
    Non-Equilibrium Molecular Dynamics for Calculating the Thermal Conductivity of Graphene-Coated Aluminum
    (2020) Toprak, Kasım; Yılmaz, Ahmet Berk
    Non-equilibrium Molecular Dynamics (NEMD) simulations have been created in C++ using Message Passing Interface (MPI) library to calculate the phonon thermal conductivity of bare graphene, aluminum, and graphene-coated aluminum. This study focuses on how graphene can alter the thermal conductivity of graphene-coated aluminum. The effect of length, graphene, and the number of graphene layers are analyzed. Even though electrons are dominant on thermal conductivity of aluminum, the effect of graphene coating can be seen in the results. The results show that the thermal conductivity of aluminum increases by up to 149% by graphene coating. When the number of layers increases to two layers, the thermal conductivity increases by up to 261%. Moreover, the results increase with the length of all models.
  • Article
    Citation - WoS: 1
    Performance Analysis of Thermal Storage Assisted Cooling Tower With Night Cooling
    (Gazi Üniversitesi, 2020) Ouedraogo, Kiswendsida Elias; Toprak, Kasım
    As global warming and water scarcity issues continue to grow, it is essential to increase resources efficiency for air conditioners and power plants. In order to increase the efficiency, the systems need to be modified to take the advantages of the low night temperature and thermal storage tanks. In this study, the low night temperature and thermal storage tanks effects on the cooling tower is studied using TRNSYS. Using a chiller operating from 8:00 to 16:00 as a case study, hot water from the condenser is partially stored on daytime and cooled slowly during the night. The storage tank volume is optimized by considering two big tanks and five small tanks. The results show that night cooling reduces cooling water temperature by 5.8 degrees C or 21.8% while the cooling efficiency is increased by 36%. The thermal storage tanks enable to have the low continuous flow rate and help to reduce the fan power by 67.1%. On the storage side, compared to two tanks system, the tanks volume is reduced by 16.5% when 5 tanks are used. In theory this reduction can go up to 50% by increasing the number of tanks and reducing their individual size.