Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Impact of Cooling Strategies and Cell Housing Materials on Lithium-Ion Battery Thermal Management Performance(Mdpi, 2025) Aydin, Sevgi; Çetkin, Erdal; Samancioglu, Umut Ege; Savci, Ismail Hakki; Yigit, Kadri Suleyman; Cetkin, ErdalThe transition to renewable energy sources from fossil fuels requires that the harvested energy be stored because of the intermittent nature of renewable sources. Thus, lithium-ion batteries have become a widely utilized power source in both daily life and industrial applications due to their high power output and long lifetime. In order to ensure the safe operation of these batteries at their desired power and capacities, it is crucial to implement a thermal management system (TMS) that effectively controls battery temperature. In this study, the thermal performance of a 1S14P lithium-ion battery module composed of cylindrical 18650 cells was compared for distinct cases of natural convection (no cooling), forced air convection, and phase change material (PCM) cooling. During the tests, the greatest temperatures were reached at a 2C discharge rate; the maximum module temperature reached was 55.4 degrees C under the natural convection condition, whereas forced air convection and PCM cooling reduced the maximum module temperature to 46.1 degrees C and 52.3 degrees C, respectively. In addition, contacting the battery module with an aluminum mass without using an active cooling element reduced the temperature to 53.4 degrees C. The polyamide battery housing (holder) used in the module limited the cooling performance. Thus, simulations on alternative materials document how the cooling efficiency can be increased.Article Citation - Scopus: 21Photovoltaic System Efficiency Enhancement With Thermal Management: Phase Changing Materials (pcm) With High Conductivity Inserts(ilhami Colak, 2021) Kyaligonza, S.; Çetkin, Erdal; Cetkin, E.The electrical conversion efficiency of photovoltaic cells from solar radiation heavily depends on the cell temperature. Here we propose a novel thermal management strategy to keep the cell temperature in the same order to attain maximum efficiency. The comparative study presented is based on four solar module configurations: a conventional photovoltaic module (PVT module), a conventional module with PCM layer underneath (PVT/PCM-I), a configuration where fins embedded into PCM (PVT/PCM-II), and configuration where the bottom of the PCM layer in PVT/PCM-II was cooled via convection (PVT/PCM-III). The developed 3D numerical model is solved via ANSYS software involving the solar ray tracing radiation model for incident solar radiations and a transient melting-solidification thermo-fluid model to cater for PCM phase transition. Results from the numerical model were validated via a comparison of experimentally studied results presented in the literature. After 120 minutes, results show that the conversion efficiency of PV cells becomes 16.84%, 18.65%, 18.83%, and 18.98% after 120 minutes for PVT module, PVT/PCM-I, PVT/PCM-II, and PVT/PCM-III with an inlet velocity of 3m/s, respectively. For the respective configurations, the specific electrical power per unit area produced reaches 75.30W/m2, 83.39W/m2, 84.19W/m2, and 89.42W/m2 for solar radiation of 540W/m2 and 26°C ambient temperature. Results reveal that a 5 mm increase in the fin height for PVT/PCM-II results in a 0.22% increase in efficiency while a 0.5m/s increase in the inlet velocity of the cooling air for PVT/PCM-III results in about 0.06% increase in efficiency. © 2021, ilhami Colak. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Computation Time Reduction of Pcm Melting Process by Changing Modeling Parameters(Taylor & Francis, 2022) Demirkıran, İsmail Gürkan; Çetkin, ErdalThis study can be considered as a helpful reference for whom endeavor to boost the computation efficiency of the PCM melting process. Researchers sacrifice accuracy to decrease computation time since computational fluid dynamics (CFD) solutions of PCM melting processes require comparatively very long time, i.e., from hours to days or weeks, depending on the system geometry. The present study compares the approaches recommended in the literature in terms of their influence on computation time reduction and accuracy. A horizontally finned tube LHTES unit is modeled in 2-D space using ANSYS Fluent, the most common commercial CFD software for the considered problem in the literature. The outcomes obtained from the attempts to boost the computation efficiency are as follows: adaptive time step size approach causes 72% enhancement in computation time (from 90 hours to 25 hours), frozen flux algorithm and constant thermophysical properties have almost no influence on computation time. Even though low convergence criteria and neglecting natural convection reduces computation time drastically, the errors in accuracy are not in acceptable level.Article Citation - WoS: 23Citation - Scopus: 26Thermal Management of Electric Vehicle Battery Cells With Homogeneous Coolant and Temperature Distribution(American Institute of Physics, 2020) Göçmen, Sinan; Güngör, Şahin; Çetkin, ErdalElectric vehicles play an integral role in eliminating pollution related to transportation, especially if the electricity is generated via renewable sources. However, storing electricity onboard requires many battery cells. If the temperature of the cells is not strictly regulated, their capacity decreases in time, and they may burn or explode due to thermal runaway. Battery thermal management systems emerged for safe operations by keeping the battery cell temperatures under limit values. However, the current solutions do not yield uniform temperature distribution for all the cells in a pack. Here, we document that constant temperature distribution can be achieved with uniform coolant distribution to the channels located between batteries. The design process of the developed battery pack begins with a design used in current packs. Later, how the shape of the distributor channel affects flow uniformity is documented. Then, the design complexity was increased to satisfy the flow uniformity condition, which is essential for temperature uniformity. The design was altered based on a constructal design methodology with an iterative exhaustive search approach. The uncovered constructal design yields a uniform coolant distribution with a maximum of 0.81% flow rate deviation along channels. The developed design is palpable and easy to manufacture relative to the tapered manifold designs. The results also document that the peak temperature difference between the cells decreases from a maximum of 12K to 0.4K. Furthermore, homogenous distribution of air is one of the limiting factors of the development of metal-air batteries. This paper also documents how air can be distributed uniformly to metal-air battery cells in a battery pack.Article Citation - WoS: 35Citation - Scopus: 38Heat Transfer Enhancement in a Microchannel Heat Sink: Nanofluids And/Or Micro Pin Fins(Taylor & Francis, 2020) Coşkun, Turgay; Çetkin, ErdalHere, we show that overall thermal conductance in a rectangular microchannel heat sink can be maximized with the combination of nanofluids and micro pin fins. We uncover the effect of micro pin fins and nanofluids both separately and simultaneously in order to uncover their effect on the thermal conductance (i.e., thermal resistance). Both nanofluids and micro pin fins decrease the overall thermal resistance due to increase in the average thermal conductivity of the flow system. In addition, they increase the heat transfer surface area of the solid interacting with the fluid. However, the pumping power (pressure drop) increases in both methods due to the increase in the resistances to the fluid flow. The results document what should be the nanoparticle volume fraction mixed into the base fluid and the micro pin fin volume in order to minimize thermal resistance. If the thermal conductivity of the nanoparticles and micro pin fins are the same, the thermal conductance becomes the maximum with 4% and 0.14% volume fractions for the nanofluid and micro pin fins, respectively. This result shows that inserting micro pin fins and using nanofluids with a given volume fraction ratio maximize the overall thermal conductance. © 2019, © 2019 Taylor & Francis Group, LLC.Article Citation - WoS: 36Citation - Scopus: 39The Natural Emergence of Asymmetric Tree-Shaped Pathways for Cooling of a Non-Uniformly Heated Domain(American Institute of Physics, 2015) Çetkin, Erdal; Oliani, AlessandroHere, we show that the peak temperature on a non-uniformly heated domain can be decreased by embedding a high-conductivity insert in it. The trunk of the high-conductivity insert is in contact with a heat sink. The heat is generated non-uniformly throughout the domain or concentrated in a square spot of length scale 0.1 L0, where L0 is the length scale of the non-uniformly heated domain. Peak and average temperatures are affected by the volume fraction of the high-conductivity material and by the shape of the high-conductivity pathways. This paper uncovers how varying the shape of the symmetric and asymmetric high-conductivity trees affects the overall thermal conductance of the heat generating domain. The tree-shaped high-conductivity inserts tend to grow toward where the heat generation is concentrated in order to minimize the peak temperature, i.e., in order to minimize the resistances to the heat flow. This behaviour of high-conductivity trees is alike with the root growth of the plants and trees. They also tend to grow towards sunlight, and their roots tend to grow towards water and nutrients. This paper uncovers the similarity between biological trees and high-conductivity trees, which is that trees should grow asymmetrically when the boundary conditions are non-uniform. We show here even though all the trees have the same objectives (minimum flow resistance), their shape should not be the same because of the variation in boundary conditions. To sum up, this paper shows that there is a high-conductivity tree design corresponding to minimum peak temperature with fixed constraints and conditions. This result is in accord with the constructal law which states that there should be an optimal design for a given set of conditions and constraints, and this design should be morphed in order to ensure minimum flow resistances as conditions and constraints change.