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    Effect of hot air inclined jet impingement to container for controlling of energy storage of PCM: experimental and numerical investigation
    (Emerald Group Publishing Ltd, 2024) Oztop, Hakan F.; Kiyak, Burak; Aksoy, Ishak Gokhan
    PurposeThis study aims to focus on understanding how different jet angles and Reynolds numbers influence the phase change materials' (PCMs) melting process and their capacity to store energy. This approach is intended to offer novel insights into enhancing thermal energy storage systems, particularly for applications where heat transfer efficiency and energy storage are critical.Design/methodology/approachThe research involved an experimental and numerical analysis of PCM with a melting temperature range of 22 degrees C-26 degrees C under various conditions. Three different jet angles (45 degrees, 90 degrees and 135 degrees) and two container angles (45 degrees and 90 degrees) were tested. Additionally, two different Reynolds numbers (2,235 and 4,470) were used to explore the effects of jet outlet velocities on PCM melting behaviour. The study used a circular container and analysed the melting process using the hot air inclined jet impingement (HAIJI) method.FindingsThe obtained results showed that the average temperature for the last time step at CYRILLIC CAPITAL LETTER EF = 90 degrees and Re = 4,470 is 6.26% higher for CYRILLIC CAPITAL LETTER EF = 135 degrees and 14.23% higher for CYRILLIC CAPITAL LETTER EF = 90 degrees compared with the 45 degrees jet angle. It is also observed that the jet angle, especially for CYRILLIC CAPITAL LETTER EF = 90 degrees, is a much more important factor in energy storage than the Reynolds number. In other words, the jet angle can be used as a passive control parameter for energy storage.Originality/valueThis study offers a novel perspective on the effective storage of waste heat transferred with air, such as exhaust gases. It provides valuable insights into the role of jet inclination angles and Reynolds numbers in optimizing the melting and energy storage performance of PCMs, which can be crucial for enhancing the efficiency of thermal energy storage systems.
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    Experimental and numerical investigation on melting of phase change material in a disc-shaped container via hot air jet impinging
    (Pergamon-Elsevier Science Ltd, 2024) Kiyak, Burak; Oztop, Hakan F.; Aksoy, I. Gokhan
    Experimental and numerical analyses were performed to investigate the control parameters of a Phase Change Material (PCM) melting by impinging a hot air jet. A novel container was designed to store PCM. The RT25HC was chosen as the PCM, with a 22-26 degrees C melting temperature. Experiments were conducted under a constant air temperature (Tair) of 40 degrees C with two different Reynolds (Re) numbers, 2235 and 4470. The analysis was performed for three jet length-to-container diameter ratios (H/D): 0.4, 0.5, and 0.6. The Finite Volume Method (FVM) was used to solve three-dimensional and time-dependent governing equations. It was found that the optimum melting time was attained when the H/D = 0.5. The measurements, thermal camera images and the numerical results displayed good agreement. The influence of H/D on the melting time decreases as the Reynolds number increases, decreasing the difference between the maximum and minimum melting rates from 23.05 % at Re = 2235 to 7.67 % at Re = 4470. In the experimental comparison, when considering H/D = 0.5, which corresponds to the case with the maximum stored energy at both Reynolds numbers, the energy stored by the H/ D = 0.6 cases is 26.4 % lower at Re = 2235. In contrast, this difference reduces to 5.03 % at Re = 4470.
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    An intelligent approach to investigate the effects of container orientation for PCM melting based on an XGBoost regression model
    (Elsevier Sci Ltd, 2024) Kiyak, Burak; Oztop, Hakan F.; Ertam, Fatih; Aksoy, I. Gokhan
    The orientation of the container filled with phase change material (PCM) is a critical parameter that significantly effects the performance of thermal energy storage systems. In this study, the Computational Fluid Dynamics (CFD) method is utilised to analyse the effects of container position on the melting process of PCM. Unlike conventional methods, the melting process of PCM was conducted using the hot air jet impingement method. The study investigated the impact of two various Reynolds numbers (2235 and 4470) and three different H/D ratio (the ratio of the distance between the jet and the container to the container diameter) which were 0.4, 0.5, and 0.6, on the PCM melting process. In addition, regression analysis was executed using the Extreme Gradient Boosting algorithm (XGBoost). The outcomes unveiled that the artificial intelligence model attained a minimum accuracy of 97.89 % and reached a maximum accuracy of 99.35 % across the 12 datasets for comparing performance metrics. These results serve as a testament to the prowess of the XGBoost algorithm in providing precise predictions of the target variable within a notably extensive range of accuracy for the datasets under consideration.
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    Three dimensional analysis of melting performance of phase change materials in a disk-shaped container with partial circular heating
    (Taylor & Francis Inc, 2023) Kiyak, Burak; Oztop, Hakan F.; Aksoy, I. Gokhan
    Three dimensional analysis of melting performance of phase change materials in a disk-shaped container with partial circular heating has been studied. The phase change materials (PCMs) have succeeded in coming to the fore with their superior features in energy storage. However, the energy storage efficiency of these materials affected by many physical parameters, and determining the appropriate parameters is important for efficient energy storage. This study explores melting and energy storage performance of PCM-RT25 in a disk-shaped container with various partial circular heating cases and aspect ratios (AR). PCM melting analysis was performed with partial heating by selecting equal heating surface area on the disk. The effects of AR on melting performance were analyzed by observing the PCM melting behavior for different disk heights while keeping the disk diameter constant. Governing equations are solved by using finite volume method. Obtained results showed that the PCM melting time decreases as the AR increases in the case of full heating. In partial heating, the increase in AR not only extended the melting time, but also decreased the liquid fraction at the end of the melting. Parameters of AR = 4 and Delta T = 45 degrees C was provided the maximum liquid fraction in partial heating cases. Under these conditions, 90%, 94% and 96% liquid fractions were obtained at the end of melting for the cases that the heater is located in the center of the disk, in the middle near the inner part of the disk and in the middle near the outher part of the disk, respectively.