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Author: search.filters.author.Gnanasekaran, N.Subject: search.filters.subject.3D modeling

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    Thermohydraulic Efficiency of a Solar Air Heater in the Presence of Graded Aluminium Wire Mesh—A Combined Experimental–Numerical Study
    (Multidisciplinary Digital Publishing Institute (MDPI), 2023) Diganjit, R.; Gnanasekaran, N.; Mobedi, M.
    In this work, aluminium wire mesh (WM) samples with 3, 9, and 18 pores per inch (PPI) and porosities of 0.894, 0.812, and 0.917, respectively, were combined together to form graded structures including 3-9-18, 9-18-3, and 18-3-9 PPIs. A 5 mm thickness for each WM was considered for a length of 2 m and inserted into a single-pass solar air heater (SAH) in which the height of the SAH was 120 mm. For the numerical analysis, a 3D numerical model was considered in ANSYS fluent software, and the Rosseland radiation model renormalization group (RNG) k-ε enhanced wall function was incorporated to account for solar radiation. The local thermal equilibrium (LTE) model was considered to obtain the heat-transfer characteristics of the WM. The numerical results of the thermohydraulic performance parameter (THPP) of the 9-18-3 PPI WM were 13.04% and 11.92% higher than the 3-9-18 and 18-3-9 PPI samples, respectively. Later, 25% of the 9-18-3 graded wire mesh (GWM) was considered at four different locations, i.e., 0, 0.5, 1, and 1.5 m away from the inlet, and analysed to obtain the best location for efficient heat transfer. The computational results show that 1.5 m away from the inlet is the best location among the different locations considered. The experimental results of the GWM at 1.5 m away from the inlet demonstrated a 20.91% and 23.32% increase in thermal efficiency compared to the empty channel for the 0.027 kg/s and 0.058 kg/s mass flow rates, respectively. From numerical-cum-experimental analysis, it was found that inserting 25% length of GWM of the entire length of the test section at a distance of 1.5 m from the inlet in single pass SAH improves the overall performance of the empty channel of single-pass SAH. © 2023 by the authors.
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    Extensive analysis of PCM-based heat sink with different fin arrangements under varying load conditions and variable aspect ratio
    (Elsevier Ltd, 2023) Nedumaran, M.S.; Gnanasekaran, N.; Hooman, K.
    The present study compares a modified variable height fin heat sink with the conventional constant height fin heat sink. The two heat sinks are filled with an equal volume of PCM (n-eicosane) and a fin volume fraction of 8 %. The experiments are performed for constant loads and also different power surge conditions. The pulsed heat loads are applied for two scenarios: 1. Constant load 4 W - power surge and constant load 4 W - power surge - 1800 s no-load condition, and 2. Power surge (50 s, 100 s, and 150 s) - no-load conditions of 1800 s. During experiments, the proposed variable height fin heat sinks possess better thermal performance for all load scenarios. Further, a 3D computational model is developed using ANSYS Fluent 19 to assess not only the effect of fin arrangement for different aspect ratios but also the impact of fin shape. The enclosure aspect ratio employed for the given study ranges from 0.3 to 0.8 for both the heat sinks. Regarding the fin structure in a heat sink, four types of fin shapes are adopted: square, circular, diamond, and triangular. The contour images of temperature and the liquid fraction are shown for the charging process. For the discharging process, the time required for the heat sinks to completely solidify the PCM is discussed. From the outcomes, variable height fin heat sinks provide enhanced melting/solidification for all the aspect ratios and fin shapes considered. As the aspect ratio increases, the time difference between the heat sink for the completion of the discharging cycle is reduced. Moreover, the triangular shaped fin shows a higher enhancement percentage of 2.29 % and 1.43 % during melting and 6.25 % and 12.5 % during solidification for both the heat sinks, respectively. © 2023 The Author(s)