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AbstractIn this study, experimental investigations and exergy analysis on shell and helically coiled tube heat exchanger are carried out forfree convection heat transfer. The measured data are totally optimised utilizing thermodynamics rules in which exergy study isperformed to investigate the thermal performance of the helical system under different operating conditions. The experimentalset-up of apparatus are designed and made for cold water and hot water as a working fluid of both the shell side and helical coilside, respectively. The effects of several parameters such as geometry and operational conditions on the exergy destruction anddimensionless exergy destruction are investigated. The counter flow direction is considered under the steady state flow condition,and the critical Reynolds number was more than 4000 in this study. The main objective of this work was to clarify the effect of thevolume flow rates and inlet temperatures of hot water and cold water in the shell and helical coil on exergy efficiency and pressuredrop. Results showed that the exergy destruction and dimensionless exergy destruction decrease with the increase of coil pitchand Dean number. In contrast, the exergy destruction and dimensionless exergy destruction are obviously increased with the hotwater flow rates or cold water flow rates. These exergy characteristics are also augmented with the values of hot water inlettemperatures and cold water inlet temperatures. The pressure drop is considerably increased with the increase of Dean numberand reduced with the increase of coil diameter. While, the exergy efficiency steadily increases with the decrease of the cold waterflow rates and with the increase of Dean number (2) (PDF) Exergy analysis of Shell and helical coil heat exchanger and design optimization. Available from: https://www.researchgate.net/publication/346515986_Exergy_analysis_of_Shell_and_helical_coil_heat_exchanger_and_design_optimization [accessed Mar 29 2023].

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The present study outlines a mathematical framework for evaluating the energy and exergy efficiency of charging operations involving two distinct phase change materials (PCMs) denoted as PCM1 and PCM2, as well as various heat transfer fluids (HTF) and thermal energy storage (TES) systems. Using a phase change material (paraffin wax RT55 and lauric acid) in a concentric thermal storage system is investigated experimentally herein using a triple pipe heat exchanger (TPHX). As part of a three-pipe (TPHX) system, the innermost pipe transports water (hot water). The inside pipe of the exchanger is coated with paraffin wax, while the outer pipe is constructed of lauric acid. To this end, experiments were conducted to examine how changes in flow rates, input temperatures, and Stefan numbers (selected in response to charge situations) affect PCM's energy and exergy calculations. Energy-exergy efficiency and entropy generation were both found to be enhanced by increasing the intake flow rate and temperature. As the intake flow rate is increased from 11 L/min to 52 L/min, the complete melting time isreduced by 12%, 15.7%, and 19.09% for PCM1, while reduce by 23.25%, 24.5%, and 25% for PCM2, while as the input temperature is increased from 316 K to 328 K, the melting time is reduced by 36.2%. Also, the results show that the energy stored, energy efficiency and exergy efficiency at PCM1 is bigger than PCM2 at same flow rate. Where energy storge increase by 15% at minimum flow rate and 12.85% at maximum flow rate, the energy efficiency of PCM1 increase by 47% then PCM2 at maximum flow rate, while increase by 43% at minimum flow rate, while exergy efficiency of PCM1 increase by 9.45% then PCM2 at maximum flow rate, while increase by 8.47% minimum flow rate. Evaluating the Nusselt number and the entropy generation number can also help boost the efficiency of a thermal storage system.

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A heat exchanger’s performance depends heavily on the operating fluid’s transfer of heat capacity and thermal conductivity. Adding nanoparticles of high thermal conductivity materials is a significant way to enhance the heat transfer fluid's thermal conductivity. This research used engine oil containing alumina (Al2O3) nanoparticles and copper oxide (CuO) to test whether or not the heat exchanger’s efficiency could be improved. To establish the most effective elements for heat transfer enhancement, the heat exchangers thermal performance was tested at 0.05% and 0.1% concentrations for Al2O3 and CuO nanoparticles. The simulation results showed that the percentage increase in Nusselt number (Nu) for nanofluid at 0.05% particle concentration compared to pure oil was 9.71% for CuO nanofluids and 6.7% for Al2O3 nanofluids. At 0.1% concentration, the enhancement percentage in Nu was approximately 23% for CuO and 18.67% for Al2O3 nanofluids, respectively. At a concentration of 0.1%, CuO nanofluid increased the LMTD and overall heat transfer coefficient (U) by 7.24 and 5.91% respectively. Both the overall heat transfer coefficient (U) and the heat transfer coefficient (hn) for CuO nanofluid at a concentration of 0.1% increased by 5.91% and 10.68%, respectively. The effectiveness (εn) of a heat exchanger was increased by roughly 4.09% with the use of CuO nanofluid in comparison to Al2O3 at a concentration of 0.1%. The amount of exergy destruction in DTHX goes down as Re and volume fractions go up. Moreover, at 0.05% and 0.1% nanoparticle concentrations, the percentage increase in dimensionless exergy is 10.55% and 13.08%, respectively. Finally, adding the CuO and Al2O3 nanoparticles improved the thermal conductivity of the main fluid (oil), resulting in a considerable increase in the thermal performance and rate of heat transfer of a heat exchanger.

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Three models of latent heat storage with circular fins were studied numerically and experimentally in this paper. The models were shell‐and‐tube, shell‐and‐nozzle, and shell‐and‐reducer. These models were investigated for two different inlets of heat transfer fluid (HTF), from the bottom and top of the models, so the number of studied cases was six. The results of the comparison between the cases showed that the different HTF inlet with a fixed mass flow rate greatly affects the completion time of the melting process; the bottom inlet of HTF accelerates the melting compared to the top inlet because it enhances the role of natural convection. Compared with shell‐and‐tube with bottom HTF inlet, the shell‐and‐nozzle with bottom inlet reduces the melting time by 11.2%, while the shell‐and‐reducer with bottom inlet delays the melting by 24%. The results of the top HTF inlet cases showed that shell‐and‐nozzle delays the melting by 16% compared with shell‐and‐tube, while the melting is not completed in shell‐and‐reducer. Shell‐and‐nozzle with a bottom HTF inlet shows the shortest melting time and the best thermal performance among all the other cases due to the geometric design of the model. On comparing the numerical and experimental results, good agreement was found between them.