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1
Senthil, Ramalingam, Aditya Patel, Rohan Rao e Sahil Ganeriwal. "Melting Behavior of Phase Change Material in a Solar Vertical Thermal Energy Storage with Variable Length Fins added on the Heat Transfer Tube Surfaces". International Journal of Renewable Energy Development 9, n. 3 (25 giugno 2020): 361–67. http://dx.doi.org/10.14710/ijred.2020.29879.
Testo completoAbstract (sommario):
This paper investigates the melting behaviour of phase change material (PCM) in a vertical thermal energy storage system with provision of thin rectangular fins of uniform and variable lengths on the heat transfer tube surfaces. The selected PCM and heat transfer fluid (HTF) are paraffin wax and water, respectively. The HTF is passed through the helically coiled copper tube of 10 mm diameter to melt the PCM. The time required to complete the melting of PCM in the system with fins is found to be five hours, whereas for the system without fins it is five hours and forty minutes, for the same conditions of constant water temperature of about 70°C and flow rate of 0.02 kg/s. HTF tube with fins is observed to be more effective with a 13.33% faster rate of melting when compared to that of the HTF tube without fins. Such a fast charging process will be helpful in storing maximum energy within a short period/duration of time shorter duration in for solar thermal and heat recovery applications during lean production times. ©2020. CBIORE-IJRED. All rights reserved
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Senthil, Ramalingam. "Effect of uniform and variable fin height on charging and discharging of phase change material in a horizontal cylindrical thermal storage". Thermal Science 23, n. 3 Part B (2019): 1981–88. http://dx.doi.org/10.2298/tsci170709239s.
Testo completoAbstract (sommario):
The effect of fin profile on melting of phase change material (PCM) is presented. The test section contains an acrylic tube of 50 mm outer diameter and a copper tube of 16 mm outer diameter and a length of 1000 mm each. Both tubes are kept coaxially. The heat transfer fluid (HTF) flows through the copper tube. The PCM is paraffin wax and filled in the annular region. The considered fin profiles are the uniform and variable fin heights of circular, triangular and elliptical profiles. Fins are fixed on the HTF tube and protruded into the PCM. The total fin surface area is maintained same among the fin profiles and the fin arrangements. The one-third of the storage is provided with increasing fin height of 2- 3 mm to melt the settled solid PCM. The hot and cold water is used to charge and discharge the PCM, respectively. Experiments are performed by the hot and cold-water inlet temperatures of 70 ?C and 28 ?C at a flow rate of 0.5 kg per minute. A faster and effective heat transfer from HTF to PCM and vice-versa is investigated. The variable elliptical fins showed faster charging and discharging by 25% and 20%, respectively, than the variable circular fins. The variable elliptical fins showed faster charging and discharging by 11.8% and 11% than the variable triangular fins. The charging and discharging efficiency of 80% and 74% are observed for the elliptical fin profiles.
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Torbarina, Fran, Kristian Lenic e Anica Trp. "Computational Model of Shell and Finned Tube Latent Thermal Energy Storage Developed as a New TRNSYS Type". Energies 15, n. 7 (25 marzo 2022): 2434. http://dx.doi.org/10.3390/en15072434.
Testo completoAbstract (sommario):
This paper presents the development of a computational model of latent thermal energy storage (LTES) in a shell and tube configuration with longitudinal fins. The model describes the physical process of transient heat transfer between the heat transfer fluid (HTF) and the phase change material (PCM) in LTES. For modeling the phase change of the PCM, the enthalpy formulation was used. Based on a one-dimensional computational model, a new Trnsys type was developed and written in Fortran. Validation of the LTES model was performed by comparing numerically and experimentally obtained data for the melting and solidification of paraffin RT 25 as the PCM and water as the HTF. Numerical investigations of the effect of HTF inlet temperature and HTF flow rate on heat transfer in LTES confirmed that significant improvement in heat transfer between the HTF and PCM could be achieved by increasing the HTF inlet temperature during charging or decreasing the HTF inlet temperature during discharging. Increasing the HTF flow rate did not significantly improve the heat transfer between the HTF and PCM, both during charging and discharging. The presented, experimentally validated LTES model could be used to analyze the feasibility of integrating LTES into various thermal systems and ultimately help define the specific benefits of implementing LTES systems.
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Akarsh, A., e Sumer Dirbude. "Effect of HTF flow direction, mass flow rate and fins on melting and solidification in a latent-heat-based thermal energy storage device". Journal of Physics: Conference Series 2054, n. 1 (1 ottobre 2021): 012049. http://dx.doi.org/10.1088/1742-6596/2054/1/012049.
Testo completoAbstract (sommario):
Abstract Latent-heat-based thermal energy systems (LHTES) have commonly been used as a potential energy storage mode over any other mode of thermal energy storage. Many heat transfer enhancement techniques have been proposed over the past years. These techniques reduce the melting and solidification times. Most of these techniques focus on the phase change material (PCM). However, the flow direction of the heat transfer fluid (HTF) can affect the heat transfer performance and pumping power requirement of the system. In this paper, the effect of HTF-flow direction, HTF mass flow rate and addition of the fins on the melting and solidification of the PCM in a shell-and-tube type of energy storage is numerically studied. Two-dimensional transient simulations are performed with ANSYS-Fluent where the phase-change process is modelled using the enthalpy-porosity formulation. The model is verified and validated by comparing with the available experimental data. A reasonable match is observed. The validated model, is used to study the effects of various parameters, such as, mass flow rate of the HTF, and triangular fin (at a fixed fin pitch) for both charging and discharging of the PCM. Finally, an influence of flow direction on the melting and solidification time has been studied. It is found that the contribution of HTF mass flow rate, the addition of the fin and HTF flow directions respectively is 1.3-3.01%, 16.97-17.62%, and 1.3-1.77% of overall heat transfer performance. A major contribution to the enhancement of overall heat transfer of the system is from the addition of fins.
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Yu, Meng, Xiaowei Sun, Wenjuan Su, Defeng Li, Jun Shen, Xuejun Zhang e Long Jiang. "Investigation on the Melting Performance of a Phase Change Material Based on a Shell-and-Tube Thermal Energy Storage Unit with a Rectangular Fin Configuration". Energies 15, n. 21 (3 novembre 2022): 8200. http://dx.doi.org/10.3390/en15218200.
Testo completoAbstract (sommario):
A case study on the melting performance of a shell-and-tube phase change material (PCM) thermal energy storage unit with a novel rectangular fin configuration is conducted in this paper. Paraffin wax and circulated water are employed as the PCM and heat transfer fluid (HTF), respectively. It can be observed that the melting performance could be significantly improved by using rectangular fins. Melting photographs demonstrate that the melting of the PCM is firstly dominated by heat conduction; then, the melting rate is improved further due to natural convection. Moreover, the results illustrate that the influence of the inlet HTF temperature on the melting performance is significantly greater than that of the inlet HTF flow rate. The liquid fraction of paraffin wax in the PCM unit with a higher inlet HTF temperature is always higher than that with a lower inlet HTF temperature at the same time. The total charging time is reduced by 62.38% and the average charging rate is increased by 165.51% when the inlet HTF temperature is increased from 57 °C to 68 °C. As a result, a higher value of the inlet HTF temperature and a lower value of the HTF flow rate are able to improve the energy efficiency of the PCM unit with a rectangular fin configuration.
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Sun, Xinguo, Hayder I. Mohammed, Mohammadreza Ebrahimnataj Tiji, Jasim M. Mahdi, Hasan Sh Majdi, Zixiong Wang, Pouyan Talebizadehsardari e Wahiba Yaïci. "Investigation of Heat Transfer Enhancement in a Triple Tube Latent Heat Storage System Using Circular Fins with Inline and Staggered Arrangements". Nanomaterials 11, n. 10 (9 ottobre 2021): 2647. http://dx.doi.org/10.3390/nano11102647.
Testo completoAbstract (sommario):
Inherent fluctuations in the availability of energy from renewables, particularly solar, remain a substantial impediment to their widespread deployment worldwide. Employing phase-change materials (PCMs) as media, saving energy for later consumption, offers a promising solution for overcoming the problem. However, the heat conductivities of most PCMs are limited, which severely limits the energy storage potential of these materials. This study suggests employing circular fins with staggered distribution to achieve improved thermal response rates of PCM in a vertical triple-tube heat exchanger involving two opposite flow streams of the heat-transfer fluid (HTF). Since heat diffusion is not the same at various portions of the PCM unit, different fin configurations, fin dimensions and HTF flow boundary conditions were explored using computational studies of melting in the PCM triple-tube system. Staggered configuration of fin distribution resulted in significant increases in the rates of PCM melting. The results indicate that the melting rate and heat charging rate could be increased by 37.2 and 59.1%, respectively, in the case of staggered distribution. Furthermore, the use of lengthy fins with smaller thickness in the vertical direction of the storage unit resulted in a better positive role of natural convection; thus, faster melting rates were achieved. With fin dimensions of 0.666 mm × 15 mm, the melting rate was found to be increased by 23.6%, when compared to the base case of 2 mm × 5 mm. Finally, it was confirmed that the values of the Reynolds number and inlet temperatures of the HTF had a significant impact on melting time savings when circular fins of staggered distribution were included.
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Cieśliński, Janusz T., e Maciej Fabrykiewicz. "Thermal Energy Storage with PCMs in Shell-and-Tube Units: A Review". Energies 16, n. 2 (13 gennaio 2023): 936. http://dx.doi.org/10.3390/en16020936.
Testo completoAbstract (sommario):
The paper presents a survey of the experimental and numerical studies of shell-and-tube systems in which phase change material (PCM) is used. Due to the multitude of design solutions for shell-and-tube systems, the emphasis is placed on double-tube (DT), triplex-tube (TT), and multi-tube (MT) units. Additionally, only single-pass systems are considered. Particular attention is paid to the method of heat transfer intensification. The analysis of the research results begins with the classification of each of the three mentioned systems. The systems are divided according to the angle of inclination, the method of heat transfer enhancement (HTE), the flow direction of heat transfer fluid (HTF), and the arrangement of tubes in the bundle. Moreover, the simplified schemes of the particular research cases are proposed. Then, the works on each of the mentioned systems, i.e., DT, TT, and MT, are discussed chronologically. Finally, in the corresponding tables, details of the discussed cases are presented, such as geometric dimensions, and the type of PCM or HTF used. A novelty in the present work is the precise classification of PCM TESUs as DT, TTH, and MTH. In the literature, there is a lot of discretion in this regard. Second, the methods of heat transfer intensification in the presented PCM TESUs are listed and discussed. Third, unified schemes of design solutions for the discussed PCM TESUs are proposed. The review shows that development directions for shell-and-tube TESUs include systems with high conductivity fins of different shapes, heights, and spacing, several PCMs, and modified shells.
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Pagkalos, Christos, Michalis Gr Vrachopoulos, John Konstantaras e Kostas Lymperis. "Comparing water and paraffin PCM as storage mediums for thermal energy storage applications". E3S Web of Conferences 116 (2019): 00057. http://dx.doi.org/10.1051/e3sconf/201911600057.
Testo completoAbstract (sommario):
A CFD analysis is performed in two different heat storage mediums, water and paraffin phase change material (PCM), in order to evaluate and compare the two mediums for use in heating thermal energy storage (HTES) applications. The two mediums use different heat storing mechanisms, namely water uses Sensible Heat Storage, and the PCM Latent heat storage. The applied computational domain represents a single tube of a heat exchanger (HE), and so it comprises of a copper tube with aluminium fins. The geometric characteristics of the domain are taken in accordance with commercially used HE’s for HTES applications [1]. The characteristics studied are the stored energy of the system, the temperature of the heat transfer fluid (HTF) in the outlet and the temperature of the storage medium. The results of the simulations showed that for the same mass of storage mediums, the PCM can store more energy than water, for the same temperature of the HTF, as expected. Also, the temperature of the medium for the sensible heat storage rises linearly with the energy stored inside it, while in the latent heat storage mechanism, the temperature of the medium rises linearly till the melting (or solidification) of it, then stays almost steady until the melting of the whole volume and then rises again until it reaches the temperature of the HTF.
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Sunden, Bengt Ake, Zan Wu e Dan Huang. "Comparison of heat transfer characteristics of aviation kerosene flowing in smooth and enhanced mini tubes at supercritical pressures". International Journal of Numerical Methods for Heat & Fluid Flow 26, n. 3/4 (3 maggio 2016): 1289–308. http://dx.doi.org/10.1108/hff-12-2015-0538.
Testo completoAbstract (sommario):
Purpose – The purpose of this paper is to numerically investigate the heat transfer performance of aviation kerosene flowing in smooth and enhanced tubes with asymmetric fins at supercritical pressures and to reveal the effects of several key parameters, such as mass flow rate, heat flux, pressure and inlet temperature on the heat transfer. Design/methodology/approach – A CFD approach is taken and the strong variations of the thermo-physical properties as the critical point is passed are taken into account. The RNG k-ε model is applied for simulating turbulent flow conditions. Findings – The numerical results reveal that the heat transfer coefficient increases with increasing mass flow rate and inlet temperature. The effect of heat flux on heat transfer is more complicated, while the effect of pressure on heat transfer is insignificant. The considered asymmetric fins have a small effect on the fluid temperature, but the wall temperature is reduced significantly by the asymmetric fins compared to that of the corresponding smooth tube. As a result, the asymmetric finned tube leads to a significant heat transfer enhancement (an increase in the heat transfer coefficient about 23-41 percent). The enhancement might be caused by the re-development of velocity and temperature boundary layers in the enhanced tubes. With the asymmetric fins, the pressure loss in the enhanced tubes is slightly larger than that in the smooth tube. A thermal performance factor is applied for combined evaluation of heat transfer enhancement and pressure loss. Research limitations/implications – The asymmetric fins also caused an increased pressure loss. A thermal performance factor ? was used for combined evaluation of heat transfer enhancement and pressure loss. Results show that the two enhanced tubes perform better than the smooth tube. The enhanced tube 2 gave better overall heat transfer performance than the enhanced tube 1. It is suggested that the geometric parameters of the asymmetric fins should be optimized to further improve the thermal performance and also various structures need to be investigated. Practical implications – The asymmetric fins increased the pressure loss. The evaluation of heat transfer enhancement and pressure loss Results showed that the two enhanced tubes perform better than the smooth tube. It is suggested that the geometric parameters of the asymmetric fins should be optimized to further improve the thermal performance and also various structures need to be investigated to make the results more engineering useful. Originality/value – The paper presents unique solutions for thermal performance of a fluid at near critical state in smooth and enhanced tubes. The findings are of relevance for design and thermal optimization particularly in aerospace applications.
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Dhaou, Mohamed Houcine, Sofiene Mellouli, Faisal Alresheedi e Yassine El-Ghoul. "Numerical Assessment of an Innovative Design of an Evacuated Tube Solar Collector Incorporated with PCM Embedded Metal Foam/Plate Fins". Sustainability 13, n. 19 (24 settembre 2021): 10632. http://dx.doi.org/10.3390/su131910632.
Testo completoAbstract (sommario):
The objective of this manuscript is to study the possibility of improving the thermal performance of an Evacuated Tube Solar Collector (ETSC) with the integration of a Phase Change Material (PCM) incorporated into metallic foam and fitted with plate fins. A 2D mathematical model has been proposed. Two types of metal foams (copper and nickel) were inserted. In addition, the effect of metal foam pore size of on heat transfer was studied. The results were acquired through numerical simulations of four different cases; namely, Case 1: pure PCM, Case 2: with metal foam, Case 3: with fins and Case 4: with metal foam and fins. The evaluation procedure involved observing the total change in Heat Transfer Fluid (HTF) temperature and melted PCM fraction during a single day. The results proved that the thermal performance of ETSC is improved considerably by inserting metal foam and fins simultaneously. The time required for the whole process is improved by almost 9% compared to the case of pure PCM, and 2% compared to the case of inserting only plate fins. Results revealed that the pore size of the metal foams slightly affects the dynamic process of heat storage/release in the ETSC/PCM system.
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Najim, Farqad T., Abdullah Bahlekeh, Hayder I. Mohammed, Anmar Dulaimi, Azher M. Abed, Raed Khalid Ibrahem, Fadhil Abbas Al-Qrimli, Mustafa Z. Mahmoud, Jan Awrejcewicz e Witold Pawłowski. "Evaluation of Melting Mechanism and Natural Convection Effect in a Triplex Tube Heat Storage System with a Novel Fin Arrangement". Sustainability 14, n. 17 (2 settembre 2022): 10982. http://dx.doi.org/10.3390/su141710982.
Testo completoAbstract (sommario):
In this research, a numerical analysis is accomplished aiming to investigate the effects of adding a new design fins arrangement to a vertical triplex tube latent heat storage system during the melting mechanism and evaluate the natural convection effect using Ansys Fluent software. In the triplex tube, phase change material (PCM) is included in the middle tube, while the heat transfer fluid (HTF) flows through the interior and exterior pipes. The proposed fins are triangular fins attached to the pipe inside the PCM domain in two different ways: (1) the base of the triangular fins is connected to the pipe, (2) the tip of the triangular fins is attached to the pipe and the base part is directed to the PCM domain. The height of the fins is calculated to have a volume equal to that of the uniform rectangular fins. Three different cases are considered as the final evaluation toward the best case as follows: (1) the uniform fin case (case 3), (2) the reverse triangular fin case with a constant base (case 12), (3) the reverse triangular fin case with a constant height (case 13). The numerical results show that the total melting times for cases 3 and 12 increase by 4.0 and 10.1%, respectively, compared with that for case 13. Since the PCM at the bottom of the heat storage unit melts slower due to the natural convection effect, a flat fin is added to the bottom of the heat storage unit for the best case compared with the uniform fin cases. Furthermore, the heat storage rates for cases 3 and 12 are reduced by 4.5 and 8.5%, respectively, compared with that for case 13, which is selected as the best case due to having the lowest melting time (1978s) and the highest heat storage rate (81.5 W). The general outcome of this research reveals that utilizing the tringle fins enhances the thermal performance and the phase change rate.
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Zaib, Aurang, Abdur Rehman Mazhar, Shahid Aziz, Tariq Talha e Dong-Won Jung. "Heat Transfer Augmentation Using Duplex and Triplex Tube Phase Change Material (PCM) Heat Exchanger Configurations". Energies 16, n. 10 (11 maggio 2023): 4037. http://dx.doi.org/10.3390/en16104037.
Testo completoAbstract (sommario):
The significance of latent heat thermal energy storage is more substantial when compared to sensible energy storage due to its higher energy storage capability. In this paper, heat transfer enhancement techniques for melting (charging) and solidification (discharging) by using external fins and internal–external fins for a phase change material (PCM) in duplex and triplex tube heat exchangers (DTHX and TTHX) are investigated numerically. A two-dimensional analysis is carried out using ANSYS Fluent for various configurations. Moreover, the effect of different critical parameters, number of fins, fin length, fin thickness, and the heat exchanger tube material are evaluated in terms of the total time of complete phase change of the PCM. Four cases are investigated; cases 1 and 2 are based upon a DTHX while cases 3 and 4 are TTHXs. By considering case 1 as a reference case, it is found that case 2 and case 3 reduce the total melting time by 48.76% and 90.12%, respectively. Case 4 achieves the shortest time for complete melting of the PCM, and the total melting time is decreased by 92%. Solidification behaviour for all four cases is also investigated. The novel configurations increase (doubled) the supply of heat transfer fluid (HTF) while at the same time significantly enhance the melting/solidification characteristics for all the cases without disrupting the convectional currents during phase change of the PCM. Tube materials with different thermophysical properties are also investigated with the heat transfer rate and melting time significantly improved with a high thermal diffusivity material. Moreover, the heat transfer is found to increase with fin length and fin thickness.
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Koukou, Maria K., Michail Gr Vrachopoulos, George Dogkas, Christos Pagkalos, Kostas Lymperis, Luis Coelho e Amandio Rebola. "Testing the performance of a prototype thermal energy storage tank working with organic phase change material for space heating application conditions". E3S Web of Conferences 116 (2019): 00038. http://dx.doi.org/10.1051/e3sconf/201911600038.
Testo completoAbstract (sommario):
A prototype Latent Heat Thermal Energy Storage (LHTES) unit has been designed, constructed, and experimentally analysed for its thermal storage performance under different operational conditions considering heating application and exploiting solar and geothermal energy. The system consists of a rectangular tank filled with Phase Change Material (PCM) and a finned tube staggered Heat Exchanger (HE) while water is used as Heat Transfer Fluid (HTF). Different HTF inlet temperatures and flow rates were tested to find out their effects on LHTES performance. Thermal quantities such as HTF outlet temperature, heat transfer rate, stored energy, were evaluated as a function of the conditions studied. Two commercial organic PCMs were tested A44 and A46. Results indicate that A44 is more efficient during the charging period, taking into account the two energy sources, solar and heat pump. During the discharging process, it exhibits higher storage capacity than A46. Concluding, the developed methodology can be applied to study different PCMs and building applications.
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Mohapatra, Kailash, e Dipti Prasad Mishra. "Effect of fin and tube configuration on heat transfer of an internally finned tube". International Journal of Numerical Methods for Heat & Fluid Flow 25, n. 8 (2 novembre 2015): 1978–99. http://dx.doi.org/10.1108/hff-05-2014-0129.
Testo completoAbstract (sommario):
Purpose – The purpose of this paper is to determine the heat transfer and fluid flow characteristics of an internally finned tube for different flow conditions. Design/methodology/approach – Numerical investigation have been performed by solving the conservation equations of mass, momentum, energy with two equation-based k-eps model to determine the wall temperature, outlet temperature and Nusselt number of an internally finned tube. Findings – It has been found from the numerically investigation that there exists an optimum fin height and fin number for maximum heat transfer. It was also found that the heat transfer in T-shaped fin was highest compared to other shape. The saw type fins had a higher heat transfer rate compared to the plane rectangular fins having same surface area and the heat transfer rate was increasing with teeth number. Keeping the surface area constant, the shape of the duct was changed from cylindrical to other shape and it was found that the heat transfer was highest for frustum shape compared to other shape. Practical implications – The present computations could be used to predict the heat transfer and fluid flow characteristics of an internal finned tube specifically used in chemical and power plants. Originality/value – The original contribution of the paper was in the use of the two equation-based k-eps turbulent model to predict the maximum heat transfer through optimum design of fins and duct.
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Hashizume, Kenichi, Takahiro Matsue e Yoshiaki Sueoka. "Effect of fins on forced convection heat transfer around a tube". Heat Transfer?Asian Research 32, n. 5 (12 giugno 2003): 445–54. http://dx.doi.org/10.1002/htj.10098.
Testo completo
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Jalil, Ehsan, e Koorosh Goudarzi. "Heat transfer enhancement of finned‐tube heat exchanger using nozzle‐ and diffuser‐shaped fins instead of straight fins". Heat Transfer 51, n. 2 (13 ottobre 2021): 1336–57. http://dx.doi.org/10.1002/htj.22354.
Testo completo
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Hashizume, Kenichi, e Yoshiaki Sueoka. "Effect of fins on forced convection heat transfer around a tube in an aligned-arranged tube bundle". Heat Transfer—Asian Research 34, n. 8 (dicembre 2005): 555–63. http://dx.doi.org/10.1002/htj.20091.
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Abbood, Sahar A., e Bengt Ake Sunden. "Numerical study of turbulent forced convection in a finned tube with and without CuO nano fluid". International Journal of Numerical Methods for Heat & Fluid Flow 26, n. 7 (5 settembre 2016): 2252–70. http://dx.doi.org/10.1108/hff-04-2015-0146.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to carry out a numerical investigation to study forced convection for a tube with fins on the inner and outer surfaces with water as the base fluid and adding particles of CuO to have a nanofluid. Design/methodology/approach Three geometries are designed by using Solid Works and the number of inside fins is 20 with height 6 mm and thickness 1 mm. The number of outside fins is 20 with height 12 mm and thickness 1 mm. The length of the tube is 1,000 mm and the inner and outer diameter is 26 and 28 mm, respectively. The annular diameter is 60 mm. The geometries are imported to Gambit where the mesh is chosen and the boundary conditions are specified. The commercial software package Fluent version 14.0 has been used to numerically solve the governing equations for the three cases. Findings The temperature contours for the three models at different air velocities, i.e., 5, 7.5 and 10 m/s and water velocities 0.8, 1 and 3 m/s have been investigated. The enhancement of heat transfer by using CuO nanoparticles has been investigated at different nanofluid concentrations. Originality/value In this paper, a numerical study is presented to analyze internal and external longitudinal finned tubes with water inside and air outside, with and without nano CuO particles.
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Wu, Feng, Mei Lin, Lin Tian, Qiuwang Wang e Laiqin Luo. "Convective heat transfer and pressure drop of a tube with internal longitudinal fins". Heat Transfer—Asian Research 36, n. 2 (2007): 57–65. http://dx.doi.org/10.1002/htj.20147.
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Shivanian, Elyas, e Antonio Campo. "Exact, analytical heat transfer from longitudinal radiating fins of rectangular profile in a tube/fin ensemble". Heat Transfer 50, n. 5 (26 febbraio 2021): 4843–54. http://dx.doi.org/10.1002/htj.22105.
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Kawaguchi, Kiyoshi, Kenichi Okui e Takaharu Kashi. "The heat transfer and pressure drop characteristics of finned tube banks in forced convection (comparison of the pressure drop characteristics of spiral fins and serrated fins)". Heat Transfer?Asian Research 33, n. 7 (2004): 431–44. http://dx.doi.org/10.1002/htj.20030.
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Mahdavi, Mostafa, e Mahmood Yaghoubi. "Experimental study of natural frost formation over a horizontal tube with annular compact fins under natural convection". Heat Transfer-Asian Research 41, n. 1 (2 dicembre 2011): 84–98. http://dx.doi.org/10.1002/htj.20397.
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Payambarpour, Seyed Abdolkarim, Mohammad Alhuyi Nazari, Mohammad Hossein Ahmadi e Ali J. Chamkha. "Effect of partially wet-surface condition on the performance of fin-tube heat exchanger". International Journal of Numerical Methods for Heat & Fluid Flow 29, n. 10 (7 ottobre 2019): 3938–58. http://dx.doi.org/10.1108/hff-07-2018-0362.
Testo completoAbstract (sommario):
Purpose This study aims to investigate heat and mass transfer in a one-row heat exchanger. The required equations are obtained based on two-dimensional model analysis in a cell of the heat exchanger. By using finite difference approach, the obtained equations are solved to determine distribution of temperature and the efficiency of the heat exchanger in the case of partially wet surface. In this research, Lewis Number as unity and water vapor saturation as parabolic are assumed. Obtained results show that increase in thermal conductivity fin leads to decreasing thermal resistance; therefore, temperature changes in radial from center to out of fin are reduced and efficiency of fin increases. Design/methodology/approach In this regard, fin material plays a significant role in fin efficiency. Changes in airflow also result in an efficiency increase by temperature and relative humidity, and efficiency is decreased by airflow velocity increase, and these changes are almost linear. Moreover, the fins with more wet surface are more sensitive to changes in fin dimensions and air flow characteristics, and it is a result of conjugate heat transfer mechanism, in which latent heat transfer in the fins with more wet surface has a significant role. Findings Thermal property and geometry of the fin under wet conditions play a more important role than the fin under dry conditions. Changes in airflow result in an efficiency increase by temperature and relative humidity, and efficiency is decreased by airflow velocity increase, and these changes are almost linear. Fins with more wet surface are more sensitive to changes in fin dimensions and air flow characteristics. Originality/value Effects of the temperature of water supply and mass flow rate were considered in the study. The results had good agreement with actual data.
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Patel, Jay R., e Manish K. Rathod. "Thermal performance enhancement of melting and solidification process of phase-change material in triplex tube heat exchanger using longitudinal fins". Heat Transfer-Asian Research 48, n. 2 (3 dicembre 2018): 483–501. http://dx.doi.org/10.1002/htj.21372.
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Hosseini, Mohammad M., e Asghar B. Rahimi. "Heat transfer enhancement in solidification process by change of fins arrangements in a heat exchanger containing phase-change materials". International Journal of Numerical Methods for Heat & Fluid Flow 29, n. 5 (7 maggio 2019): 1741–55. http://dx.doi.org/10.1108/hff-06-2018-0333.
Testo completoAbstract (sommario):
Purpose Reducing discrepancy between energy demand and supply has been a controversial issue among researchers. Thermal energy storage is a technique to decrease this difference to increase the thermal efficiency of systems. Latent heat thermal energy storage has interested many researchers over the past few decades because of its high thermal energy density and constant operating temperature. The purpose of this paper is to provide a numerical study of the solidification process in a triplex tube heat exchanger containing phase change material (PCM) RT82. Design/methodology/approach A two-dimensional transient model was generated using finite volume method and regarding enthalpy-porosity technique. After that, a detailed and systematic approach has been presented to modify longitudinal fins’ configuration to enhance heat transfer rate in PCMs and reducing solidification time. The numerical results of this study have been validated by reference experimental results. Findings The ultimate model reduced solidification time up to 21.1 per cent of the Reference model which is a substantial improvement. Moreover, after testing different arrangements of rectangular fins and studying the flow pattern of liquid PCM during solidification, two general criteria was introduced so that engineers can reach the highest rate of heat transfer for a specified value of total surface area of fins. Finally, the effect of considering natural convection during solidification was studied, and the results showed that disregarding natural convection slows down the solidification process remarkably in comparison with experimental results and in fact, this assumption generates non-real estimation of solidification process. Originality/value The arrangement of the fins to have the best possible solidification time is the novelty in this paper.
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Shank, Kyle, Jessica Bernat, Ethan Regal, Joel Leise, Xiaoxu Ji e Saeed Tiari. "Experimental Study of Varying Heat Transfer Fluid Parameters within a Latent Heat Thermal Energy Storage System Enhanced by Fins". Sustainability 14, n. 14 (21 luglio 2022): 8920. http://dx.doi.org/10.3390/su14148920.
Testo completoAbstract (sommario):
Latent heat thermal energy storage (LHTES) systems can be used to combat the limited collection and long-term storage of renewable energy sources. The key component of an LHTES system is its phase change material (PCM), which thermally stores energy. Despite extensive research on thermal conductivity enhancement within PCM, little attention has been paid to the heat transfer fluid (HTF) within the system. This study aimed to observe the impact of variable HTF flow rates and temperatures on the speed of charging and discharging an LHTES system enhanced with annular fins. Two copper fin configurations of 10 and 20 annular fins were tested within an LHTES system with Rubitherm RT-55 PCM. The configurations were tested during charging processes with HTF parameters of 65 °C and 70 °C at 1, 2, and 3 gpm. Discharging processes were tested with HTF parameters of 15 °C and 20 °C at 0.5, 1, and 1.5 gpm. The system energy response and PCM temperature were recorded throughout the tests. The results of the study revealed that a higher flow rate produced a shorter processing time, but furthermore, that a larger temperature gradient between the PCM and HTF caused a more significant decrease in charging and discharging times.
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Motevali, Ali, Mohammadreza Hasandust Rostami, Gholamhassan Najafi e Wei-Mon Yan. "Evaluation and Improvement of PCM Melting in Double Tube Heat Exchangers Using Different Combinations of Nanoparticles and PCM (The Case of Renewable Energy Systems)". Sustainability 13, n. 19 (26 settembre 2021): 10675. http://dx.doi.org/10.3390/su131910675.
Testo completoAbstract (sommario):
In this work, the melting process of phase change material (PCM) in double tube heat exchangers was investigated and evaluated through the use of different combinations (1, 2, 3% Nano-Enhanced PCM and 1, 3, 5% Nano-HTF) of GQD, as well as SWCNT nanoparticles and PCM (RT82). In this study, the effect of three different methods, namely the dispersion of nanoparticles in PCM (nano-enhanced PCM), the dispersion of nanoparticles in HTF (nano-HTF), and the simultaneous dispersion of nanoparticles in PCM and HTF (nano-enhanced PCM, nano-HTF) concerning the nanoparticles participation in the thermal energy storage system in a double tube heat exchanger was evaluated. Other effective factors, such as the inlet fluid temperature, different Reynolds numbers, fin as well as new parameter of pipe, and fin thickness were also evaluated. The results showed that the highest effect of different parameters on the PCM melting process was related to the 1% nano-HTF and 3% nano-enhanced PCM nanoparticles of SWCNT, which decreased the PCM melting rate by about 39%. The evaluation of the effect of pipe and fan thickness also showed that the melting rate improved by 31% through reducing the thickness of the HTF fin and pipe. In general, the current study followed two purposes first, to examine three methods of the dispersion of nanoparticles in the thermal energy storage system; second, to reduce the thickness of the tube and fin. Findings of the study yielded positive results.
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Ju, Yongfeng, Roohollah Babaei-Mahani, Raed Khalid Ibrahem, Shoira Khakberdieva, Yasir Salam Karim, Ahmed N. Abdalla, Abdullah Mohamed, Mustafa Z. Mahmoud e Hafiz Muhammad Ali. "Discharge Enhancement in a Triple-Pipe Heat Exchanger Filled with Phase Change Material". Nanomaterials 12, n. 9 (9 maggio 2022): 1605. http://dx.doi.org/10.3390/nano12091605.
Testo completoAbstract (sommario):
This study aims to study the discharging process to verify the influence of geometry modifications and heat transfer flow (HTF) patterns on the performance of a vertical triplex-tube latent heat container. The phase change material (PCM) is included in the middle tube, where the geometry is modified using single or multi-internal frustum tubes instead of straight tubes to enhance the discharging rate. The effects of the HTF flow direction, which is considered by the gravity and opposite-gravity directions, are also examined in four different cases. For the optimal geometry, three scenarios are proposed, i.e., employing a frustum tube for the middle tube, for the inner tube, and at last for both the inner and middle tubes. The effects of various gap widths in the modified geometries are investigated. The results show the advantages of using frustum tubes in increasing the discharging rate and reducing the solidification time compared with that of the straight tube unit due to the higher natural convection effect by proper utilization of frustum tubes. The study of the HTF pattern shows that where the HTF direction in both the inner and outer tubes are in the gravity direction, the maximum discharging rate can be achieved. For the best configuration, the discharge time is reduced negligibly compared with that for the system with straight tubes which depends on the dimensions of the PCM domain.
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Havaldar, Sanjay N., Harsh V. Malapur, Kaustubh G. Kulkarni e Gary A. Anderson. "Numerical Investigation of Concentrated Solar Central Billboard with Hexagonal Tubes." IOP Conference Series: Earth and Environmental Science 1084, n. 1 (1 ottobre 2022): 012021. http://dx.doi.org/10.1088/1755-1315/1084/1/012021.
Testo completoAbstract (sommario):
Abstract The solar receiver is the most important component of any central solar tower power plant (CSP) system. A numerical analysis of four billboard geometry designs of the central tower receiver was undertaken in this study. On the receiver, the surface area, heat transfer fluid (HTF), and intensity of beam radiation were all constant. The mass flow rate of HTF was modified, and the temperature gain was used as a metric to determine the most efficient design based on the analytical results. Four different models of vertical tube receivers were designed and analyzed. In the analysis, the surface area of the receivers was the same. When compared to the vertical variable circular tube receiver design, the vertical variable hexagonal tube receiver design achieved a marginally higher temperature for the HTF fluid at lower mass flow rates.
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Li, Min, Jasim M. Mahdi, Hayder I. Mohammed, Dmitry Olegovich Bokov, Mustafa Z. Mahmoud, Ali Naghizadeh, Pouyan Talebizadehsardari e Wahiba Yaïci. "Solidification Enhancement in a Multi-Tube Latent Heat Storage System for Efficient and Economical Production: Effect of Number, Position and Temperature of the Tubes". Nanomaterials 11, n. 12 (26 novembre 2021): 3211. http://dx.doi.org/10.3390/nano11123211.
Testo completoAbstract (sommario):
Thermal energy storage is an important component in energy units to decrease the gap between energy supply and demand. Free convection and the locations of the tubes carrying the heat-transfer fluid (HTF) have a significant influence on both the energy discharging potential and the buoyancy effect during the solidification mode. In the present study, the impact of the tube position was examined during the discharging process. Liquid-fraction evolution and energy removal rate with thermo-fluid contour profiles were used to examine the performance of the unit. Heat exchanger tubes are proposed with different numbers and positions in the unit for various cases including uniform and non-uniform tubes distribution. The results show that moving the HTF tubes to medium positions along the vertical direction is relatively better for enhancing the solidification of PCM with multiple HTF tubes. Repositioning of the HTF tubes on the left side of the unit can slightly improve the heat removal rate by about 0.2 in the case of p5-u-1 and decreases by 1.6% in the case of p5-u-2. It was found also that increasing the distance between the tubes in the vertical direction has a detrimental effect on the PCM solidification mode. Replacing the HTF tubes on the left side of the unit negatively reduces the heat removal rate by about 1.2 and 4.4%, respectively. Further, decreasing the HTF temperature from 15 °C to 10 and 5 °C can increase the heat removal rate by around 7 and 16%, respectively. This paper indicates that the specific concern to the HTF tube arrangement should be made to improve the discharging process attending free convection impact in phase change heat storage.
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Bouali, Belkacem, e Hanane-Maria Regue. "Contribution to the Parametric Study of the Performance of A Parabolic Trough Collector". E3S Web of Conferences 321 (2021): 02016. http://dx.doi.org/10.1051/e3sconf/202132102016.
Testo completoAbstract (sommario):
This paper presents an analysis of the performance of a parabolic trough collector (PTC) according to some key operating parameters. The effects of the secondary reflector, the length and thickness of the absorber tube (receiver tube) and the flow rate of the heat transfer fluid (HTF) are investigated. The main objective is to determine an optimal operation, which improves the performance of a traditional PTC. The target variables are the temperature at the outlet of the tube, the amount of energy collected by the HTF and the efficiency of the system. The solar flux data concern the city of LAGHOUAT located in the south of Algeria. Four days in different seasons are considered. The optical analysis of the system is performed by using the open source SolTrace code. The output of this analysis is used as a boundary condition for the CFD solver. The conjugate heat transfer and the fluid flow through the absorber tube are simulated by using ANSYS-CFX solver. Water is considered as heat transfer fluids. The obtained results show that the use of a curved secondary reflector significantly improves the performance of the traditional PTC. As the thickness of the tube increases, the heat storage in the material increases, which increases the temperature at the exit of the tube and therefore the efficiency of the system. However, the length of the tube depends on the mass flow of the HTF and vice versa. To keep the efficiency constant by choosing another length, it is necessary to choose a mass flow rate proportional to the flow rate corresponding to the initial length.
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Kis Agustin, Helena Carolina, Ika Dewi Wijayanti e Rakhmat Satrio Wibowo. "Morphology of Crown Tube Austenitic Stainless Steel TP316 HTF Failure". Applied Mechanics and Materials 836 (giugno 2016): 67–71. http://dx.doi.org/10.4028/www.scientific.net/amm.836.67.
Testo completoAbstract (sommario):
High temperature operations of flares often give the serious problems to its crown tube. Especially the materials that used are stainless steel. The locations of disposal gas combustion at the crown become the primary aspect of flare operation. The macro structure of failed crown tube was found to have the fissure on its edge, which has the variation of appearances. The chance of materials to react with high temperature combustion contributes to the differences of tube crown color that failed. The former and the later appearances indicated the mode of failure. This paper observes the locations effect of disposal gas combustion to the failure of crown tube color and fissure mode. Visual examination was implemented to figure out the effect of the environment to the crown tube. SEM data also should be considered to convince the phases that came out from the interaction between crown tube and high temperature combustion. The difference of temper color of failure crown was found on the inner and outer surface. Unevenly heat source from the inner surface caused the ignition force from the inner surface of crown tube that led the initial deformation for the crown.
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Fadl, Mohamed, e Philip Eames. "Thermal Performance Analysis of the Charging/Discharging Process of a Shell and Horizontally Oriented Multi-Tube Latent Heat Storage System". Energies 13, n. 23 (25 novembre 2020): 6193. http://dx.doi.org/10.3390/en13236193.
Testo completoAbstract (sommario):
In this study, the thermal performance of latent heat thermal energy storage system (LHTESS) prototype to be used in a range of thermal systems (e.g., solar water heating systems, space heating/domestic hot water applications) is designed, fabricated, and experimentally investigated. The thermal store comprised a novel horizontally oriented multitube heat exchanger in a rectangular tank (forming the shell) filled with 37.8 kg of phase change material (PCM) RT62HC with water as the working fluid. The assessment of thermal performance during charging (melting) and discharging (solidification) was conducted under controlled several operational conditions comprising the heat transfer fluid (HTF) volume flow rates and inlet temperatures. The experimental investigations reported are focused on evaluating the transient PCM average temperature distribution at different heights within the storage unit, charging/discharging time, instantaneous transient charging/discharging power, and the total cumulative thermal energy stored/released. From the experimental results, it is noticed that both melting/solidification time significantly decreased with increase HTF volume flow rate and that changing the HTF inlet temperature shows large impacts on charging time compared to changing the HTF volume flow rate. During the discharging process, the maximum power output was initially 4.48 kW for HTF volume flow rate of 1.7 L/min, decreasing to 1.0 kW after 52.3 min with 2.67 kWh of heat delivered. Based on application heat demand characteristics, required power levels and heat demand can be fulfilled by employing several stores in parallel or series.
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Stanciu, Dorin, Camelia Stanciu, Valentin Apostol e Horatiu Pop. "Numerical simulation of a phase change material melting process". E3S Web of Conferences 112 (2019): 01010. http://dx.doi.org/10.1051/e3sconf/201911201010.
Testo completoAbstract (sommario):
Storage processes are usually integrated in solar energy systems applications due to daily variation of this energy source availability. Among different thermal storage solutions, phase change materials (PCM) lately became more extensively used covering a wide range of operating temperatures. In this regard, a numerical simulation of a PCM melting process is performed under ANSYS CFD environment. A particular configuration is considered consisting in a 2m length annular tube having a 5.48 cm external diameter. The tube is filled with paraffin chosen as PCM. A concentric interior tube of 2.54 cm diameter is used for transporting the heat transfer fluid (HTF) from the solar collector. Heat is transferred through the 1 mm thick pipe wall to the PCM placed all around the HTF tube. The numerical results reveal the melting process of the PCM at different instances and tube sections. The time variation of the PCM liquid fraction is emphasized. The results describe the dynamic behavior of a PCM melting process and might be further integrated in any solar power plant storage charging process simulation.
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Pakalka, Saulius, Kęstutis Valančius e Matas Damonskis. "ŠILUMNEŠIO DEBITO ĮTAKOS FAZINIO VIRSMO MEDŽIAGOS VEIKIMUI TYRIMAS / INVESTIGATION OF THE INFLUENCE OF MASS FLOW RATE ON PHASE CHANGE MATERIAL BEHAVIOUR". Mokslas - Lietuvos ateitis 11 (10 ottobre 2019): 1–5. http://dx.doi.org/10.3846/mla.2019.10578.
Testo completoAbstract (sommario):
The paper presents an experimental study of the influence of heat transfer fluid (HTF) mass flow rate on phase change materials (PCM) behaviour. The experimental study was performed on a specially designed test bench. Research object – PCM based thermal energy storage unit which consists of a stainless steel tank with dual circuit tube-fin copper heat exchanger. The tank (storage volume) was filled with phase change material RT82. The experiment was carried out using three different mass flow rates of HTF: high – 0.25 kg/s, medium – 0.125 kg/s, low – 0.05 kg/s. The analysis showed that in the case of high and medium mass flow rates the melting/solidification process highly depends on the temperature of inlet HTF. Influence of mass flow rate is higher in the case of low mass flow rate.
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Nagappan, Beemkumar, Karthikeyan Alagu, Yuvarajan Devarajan e Dinesh Babu Munuswamy. "Energy and Exergy Analysis of Multi-Temperature PCMs Employed in a Latent Heat Storage System and Parabolic Trough Collector". Journal of Non-Equilibrium Thermodynamics 43, n. 3 (26 luglio 2018): 211–20. http://dx.doi.org/10.1515/jnet-2017-0066.
Testo completoAbstract (sommario):
AbstractThis study represents the exergy analysis of the evacuated tube parabolic trough collector and the cascaded latent heat storage system using multi-temperature phase change material (PCMs) during the charging process. The objective of the work is to control the losses and increase the efficiency of the system. The exergy analysis has been conducted on the basis of the first and second laws of thermodynamics in a parabolic trough collector with various mass flow rates of the heat transfer fluid (HTF). The overall variation of exergy efficiency of the collector with varying mass flow rate of the HTF is 5.9 %. The thermodynamic analysis of the cascaded latent heat storage system has been done during the charging process in which the PCM absorbs energy from the HTF and undergoes a phase transformation from the solid to the liquid state. The exergy analysis is conducted by varying the mass flow rate of the HTF in the storage system for both insulated and non-insulated systems. It is noticed that the variation of exergy stored for 5 and 10 liters per minute is 24.609 kW and 40.48 kW, respectively. It is concluded that the high range of energy and exergy stored in the system is achieved by the high flow rate of the HTF.
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Anggara, Fajar, Henry Carles e Pathur Razi Ansyah. "STUDI NUMERIK: PENGARUH DEBIT INLET TERHADAP KARAKTERISTIK PELELEHAN PARAFFIN WAX PADA TABUNG SILINDER". Scientific Journal of Mechanical Engineering Kinematika 4, n. 1 (13 giugno 2019): 15–26. http://dx.doi.org/10.20527/sjmekinematika.v4i1.48.
Testo completoAbstract (sommario):
Latent Heat Thermal Energy Storage (LHTES) is the method to store thermal energy by changing the phase of Phase Change Material (PCM). This method is being developed to store heat loss for increasing energy efficiency. In this paper, the effect of variation flow rate on the melting characteristics PCM was investigated by three-dimensional numerical simulation using ANSYS FLUENT 17. The set-up of this research was carried out on concentrically two cylindrical tubes with diameter outer tube 10 cm and length 60 cm while diameter inner tube 5 cm and length 50 cm. The inner tube is used as a PCM container and the outer tube which has bottom and top hole is used as Heat Transfer Fluid (HTF) circulation. Variation HTF or hot water flowrate was carried out by 4L / min, 8L / min and 12 L / min while the temperature is kept at 75oC, then flowed through bottom hole and out to top hole. From this study it was found that the variation flow rate did not have significant effect on the melting pattern, only the greater flow rate, the smaller melting time. Natural convection is the main role of heat transfer when melting.
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Pitambar Subhash Gadhave, Chandrakant Laxman Prabhune, Hanumant Pandurang Jagtap e Parmeshwar Pandurang Ritapure. "Investigative Study of Solidification and Melting of Stearic Acid in Triplex Pipe with Perforated Fin Surface". Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 98, n. 1 (19 settembre 2022): 125–36. http://dx.doi.org/10.37934/arfmts.98.1.125136.
Testo completoAbstract (sommario):
The energy storage capacity of latent heat thermal energy storage systems is high therefore these systems are efficient among all other thermal heat storage. This study experimentally investigates the charging and solidification of stearic acid (C18H36O2) in the finned triplex pipe heat exchanger with holes on the fin surface. The melting and discharging of stearic acid are carried out at steady inlet heat transfer fluid (HTF) i.e., water temperature. This study also investigates the result of the change in HTF flow rate on solidification and melting of phase change material. Finally, the study focuses on the comparison of average effectiveness for finned triplex tube heat exchanger and finned triplex tube with cylindrical holes on fin surface with rates of 0.33 and 0.43 Kg/s. The results showed that the average effectiveness with a finned triplex tube with a perforated fin surface is 4% more than that of a finned triplex tube at 0.33 Kg/s whereas it is 5 % more at 0.43 Kg/s during the charging process. On the other side during discharging process average effectiveness is 14 % more at 0.33 Kg/s and 11 % at 0.43 Kg/s.
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Shehab, Saad Najeeb. "Natural-Convection Phenomenon from a Finned Heated Vertical Tube: Experimental Analysis". Al-Khwarizmi Engineering Journal 13, n. 4 (20 marzo 2019): 30–40. http://dx.doi.org/10.22153/kej.2017.05.004.
Testo completoAbstract (sommario):
In this work, an experimental analysis is made to predict the thermal performance of the natural-convection phenomenon from a heated vertical externally finned-tube to surrounding air through an open-ended enclosure. Two different configurations of longitudinal rectangular fin namely, continuous and interrupted are utilized with constant thickness, different numbers, and different heights are extended radially on the outer surface of a heated tube. The tube is heated electrically from inner surface with five varied power input magnitudes. The effect of fins configuration, fins number, fins height, and heat flux of the inner tube surface on the thermal performance of natural convection have been studied and analyzed experimentally. Obtained results show that the tube with twelve interrupted longitudinal fins gives the best natural-convection thermal performance in terms of average Nusselt number, about 20% greater than that for the tube with continuous fins. Experimental correlations to predict the average Nusselt number for the heated tubes with continuous and interrupted longitudinal fins are proposed. The present data are compared to previous study and good convergence is noticed.
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Ramachandran, S. "Experimental Analysis of Storage of Solar Energy in Phase Change Materials Encapsulated in Copper Cylinders". Applied Mechanics and Materials 766-767 (giugno 2015): 445–50. http://dx.doi.org/10.4028/www.scientific.net/amm.766-767.445.
Testo completoAbstract (sommario):
The Demand and increase in the cost of fossil fuels have made the entire world to turn towards the renewable energy resources. There are various renewable energy out of which solar energy is the efficient energy and available in abundant. The main disadvantage of solar energy is that it is not continuous and it is available only in the day time and so the storage of solar thermal energy is considered as an important one. In this study, thermal energy is transmitted through the therminol-55 oil which is the Heat Transfer Fluid (HTF). D-Mannitol-a white, crystalline solid with the chemical formula C6H8(OH)6 is taken as the Phase Change Material (PCM) and stored inside the copper cylindrical encapsulations. The D-mannitol PCM was stored in the copper cylinder encapsulations with and without fins. These encapsulations were immersed in a cylindrical mild steel tank containing HTF. The therminol-55 oil was allowed to flow through the solar parabolic trough collector to transfer heat. Along with this, an additional heater was provided for heating HTF up to the temperature 300oC. This hot oil was allowed to flow in to the PCM tank where the PCM copper cylinders were immersed. The experiments were conducted in two stages one with finned encapsulations and another without finned encapsulations. Here the experiments were done in two modes one is charging mode and another one is discharging mode. In charging mode the temperature of the HTF was raised to 300oC and was allowed to cool during its discharging mode to 120 oC. The time taken for the charging and discharging of heat was measured to analyse the heat transfer study of thermal storage system.
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Mao, Qianjun, Ning Liu e Li Peng. "Numerical Investigations on Charging/Discharging Performance of a Novel Truncated Cone Thermal Energy Storage Tank on a Concentrated Solar Power System". International Journal of Photoenergy 2019 (27 gennaio 2019): 1–17. http://dx.doi.org/10.1155/2019/1609234.
Testo completoAbstract (sommario):
Developing a concentrated solar power (CSP) technology is one of the most effective methods to solve energy shortage and environmental pollution all over the world. Thermal energy storage (TES) system coupling with phase change materials (PCM) is one of the most significant methods to mitigate the intermittence of solar energy. In this paper, firstly, a 2D physical and mathematical model of a novel truncated cone shell-and-tube TES tank has been proposed based on enthalpy method. Secondly, the performance during the charging/discharging process of the truncated cone tank has been compared with the traditional cylindrical tank. Finally, the effects of inlet conditions of heat transfer fluid (HTF), and thickness of tube on the charging/discharging process, stored/released energy capacity; energy storage/release rate and heat storage efficiency have been investigated. The results show that the performance of truncated cone tank is better, and the charging/discharging time reduces 32.08% and 21.59%, respectively, compared with the cylindrical tank. The effect of wall thickness on the truncated cone TES tank can be ignored. And the inlet temperature and velocity of HTF have the significant influence on the charging/discharging performance of TES tank. And the maximum heat storage efficiency of the truncated cone TES tank can reach 93%. However, some appropriate methods should be taken for improving the thermal energy utilization rate of HTF in the future. This research will provide insights and significant reference towards geometric design and operating conditions in TES system.
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Kumar, Kamuju Naveen, Akanksha Maurya e Deepak Sharma. "Performance Investigation of Cylindrical Cavity Receiver Using Roughened Surfaces". IOP Conference Series: Materials Science and Engineering 1259, n. 1 (1 ottobre 2022): 012028. http://dx.doi.org/10.1088/1757-899x/1259/1/012028.
Testo completoAbstract (sommario):
Abstract Solar cavity receiver is an integral part of the solar parabolic dish collectors used for absorbing concentrated solar irradiation. The performance of the receivers can be enhanced utilizing different types of heat transfer fluids (HTF) and modified geometries. The thermal performance of a redesigned cavity receiver with solid semi-circular tube attached to its surface was investigated using CFD three-dimensional simulation. The influence of operating and geometric parameters (i.e., inlet mass flow rate and inlet temperature) were investigated. The results obtained shows that, redesigned solar cavity receiver has thermal efficiency of 8.49-10.27% higher than a normal cavity receiver with an inlet flow rate of 0.01-0.04 kg/s under the same environmental and operating conditions. The temperature of outlet of HTF increases with increases in inlet temperature for Therminol66 oil. The comparison of thermal performance using different HTF (i.e., Therminol66, Ethylene Glycol, Water) is also conducted and it is found that Therminol66 oil gives 9% and 17% higher outlet temperature than ethylene glycol and water respectively at intake flow rate of 0.02 kg/s.
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Guo, Zhanjun, Wu Zhou, Sen Liu, Zhangyang Kang e Rufei Tan. "Effects of Geometric Parameters and Heat-Transfer Fluid Injection Direction on Enhanced Phase-Change Energy Storage in Vertical Shell-and-Tube System". Sustainability 15, n. 17 (30 agosto 2023): 13062. http://dx.doi.org/10.3390/su151713062.
Testo completoAbstract (sommario):
Internationally, energy-storage technologies have facilitated the large-scale utilization of renewable energy, reducing reliance on conventional power generation and enhancing energy efficiency. In the pursuit of strengthening the efficiency of phase-change energy-storage systems, the focus lies on further enhancing the efficiency of vertical shell-and-tube energy-storage systems. This study investigates the influence of two different heat-transfer fluid (HTF) injection directions on the melting of phase-change materials (PCM) in a vertical shell-and-tube latent heat storage (LHS) system. The melting behavior of PCM is analyzed under both pure conduction and natural convection conditions. The research findings reveal that during the initial melting stage, both HTF injection methods primarily rely on thermal conduction, resulting in no significant changes in PCM melting. However, in the later stages of natural convection, bottom HTF injection exhibits superior heat-transfer efficiency compared to top injection. Under a constant volume of phase-change material, both pipe length and pipe thickness affect the PCM melting process. As the pipe length increases within the range of 1.6 m to 0.2 m, the PCM melting time also increases. The results show that the melting time of the PCM is reduced by almost 15,000 s when the tube length H exceeds 800 mm, regardless of whether the heat-transfer fluid is injected at the top or bottom. In this paper, we also obtained results that the three composites containing 10% expanded graphite save 5.3%, 10.2%, and 14.3% of melting time, respectively, compared to pure paraffin when H = 200 mm and top injection are considered. For bottom injection, the three composites saved 7.7%, 12.5%, and 17.2% of melting time, respectively. This further emphasizes the more significant effect of priming in improving melting time.
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Gnanavel, C., R. Saravanan e M. Chandrasekaran. "Numerical Exploration of Influence of Phase Changing Material in Heat Transfer Augmentation in the Double Tube Heat Exchanger". International Journal of Engineering & Technology 7, n. 3.27 (15 agosto 2018): 162. http://dx.doi.org/10.14419/ijet.v7i3.27.17751.
Testo completoAbstract (sommario):
The double tube heat exchanger is a device in which the inner tube carries the hot fluid. Phase Changing Material is the energy storage device is used for Solar heater applications to maintain the constant temperature, in the present study of this work is CFD Analysis of plain tube heat exchanger with Phase Changing Material (PCM) and without Phase Changing Material (PCM), Charging time, liquid volume fraction with the various Heat Transfer Fluid (HTF) inlet temperature 70, 75, 80 deg Celsius and various flow conditions of laminar flow of 2000 Re, Transition flow of 4000 Re and Turbulent flow of 10,000 Re
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Bošnjaković, Mladen, e Simon Muhič. "Numerical Analysis of Tube Heat Exchanger with Perforated Star-Shaped Fins". Fluids 5, n. 4 (13 dicembre 2020): 242. http://dx.doi.org/10.3390/fluids5040242.
Testo completoAbstract (sommario):
This article discusses the possibility of further reducing the mass of the heat exchanger with stainless steel star-shaped fins while achieving good heat transfer performance. For this purpose, we perforated the fins with holes Ø2, Ø3, and Ø4 mm. Applying computational fluid dynamics (CFD) numerical analysis, we determined the influence of each perforation on the characteristics of the flow field in the liquid–gas type of heat exchanger and the heat transfer for the range of Re numbers from 2300 to 16,000. With a reduction in the mass of the fins to 17.65% (by Ø4 mm), perforated fins had greater heat transfer from 5.5% to 11.3% than fins without perforation. A comparison of perforated star-shaped fins with annular fins was also performed. Perforated fins had 51.8% less mass than annular fins, with an increase in heat transfer up to 26.5% in terms of Nusselt number.
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Long, Jian You. "Simulation Investigation for Heat Transfer in Fin-Tube Thermal Storage Unit with Phase Change Material". Advanced Materials Research 168-170 (dicembre 2010): 895–99. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.895.
Testo completoAbstract (sommario):
This paper addresses a simulation investigation of a fin-tube thermal storage unit involving phase change process dominated by heat conduction. The heat transfer of fin-tube thermal storage unit with phase change material (PCM) was simulated by Fluent. Graphical results including outlet temperature of heat transfer fluid (HTF), average temperature of PCM and phase front interface of solid and liquid phase of PCM versus time and fin distance were presented and discussed. According to simulation results, it was concluded that only the fin-tube thermal storage unit with fin distance of 12fin/inch could satisfied the request of heat release performance of household heat pump water heater for shower.
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Hussien, Kamil Abdul. "Experimental Investigation of Heat Transfer Enhancement by Using Different Number of Fins in Circular Tube". Wasit Journal of Engineering Sciences 6, n. 3 (10 dicembre 2018): 1–12. http://dx.doi.org/10.31185/ejuow.vol6.iss3.99.
Testo completoAbstract (sommario):
Abstract-The present work investigates the enhancement of heat transfer by using different number of circular fins (8, 10, 12, 16, and 20) in double tube counter flow heat exchanger experimentally. The fins are made of copper with dimensions 66 mm OD, 22 mm ID and 1 mm thickness. Each fin has three of 14 mm diameter perforations located at 120o from each to another. The fins are fixed on a straight smooth copper tube of 1 m length, 19.9 mm ID and 22.2 mm OD. The tube is inserted inside the insulated PVC tube of 100 mm ID. The cold water is pumped around the finned copper tube, inside the PVC, at mass flow rates range (0.01019 - 0.0219) kg/s. The Reynold's number of hot water ranges (640 - 1921). The experiment results are obtained using six double tube heat exchanger (1 smooth tube and the other 5 are finned one). The results, illustrated that the heat transfer coefficient proportionally with the number of fin. The results also showed that the enhancement ratio of heat transfer for finned tube is higher than for smooth tube with (9.2, 10.2, 11.1, 12.1 13.1) times for number of fins (8, 10, 12, 16 and 20) respectively.
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Guerraiche, D., K. Guerraiche, Z. Driss, A. Chibani, S. Merouani e C. Bougriou. "Heat Transfer Enhancement in a Receiver Tube of Solar Collector Using Various Materials and Nanofluids". Engineering, Technology & Applied Science Research 12, n. 5 (2 ottobre 2022): 9282–94. http://dx.doi.org/10.48084/etasr.5214.
Testo completoAbstract (sommario):
The solar flux distribution on the Parabolic Trough Collector (PTC) absorber tube is extremely non-uniform, which causes non-uniform temperature distribution outside the absorber tube. Therefore, it generates high thermal stress which causes creep and fatigue damage. This presents a challenge to the efficiency and reliability of parabolic trough receivers. To override this problem, we have to homogenize the heat flux distribution and enhance the heat transfer in the receiver’s absorber tube to improve the performance of the PTC. In this work, 3D thermal and thermal stress analyses of PTC receiver performance were investigated with a combination of Monte Carlo Ray-Trace (MCRT), Computational Fluid Dynamics (CFD) analysis, and thermal stress analysis using the static structural module of ANSYS. At first, we studied the effect of the receiver tube material (aluminium, copper, and stainless steel) on heat transfer. The temperature gradients and the thermal stresses were compared. Second, we studied the effect of the addition of nanoparticles on the working Heat Transfer Fluid (HTF), employing an Al2O3-H2O based nanofluid at various volume concentrations. To improve the thermal performance of the PTC, a nanoparticle volume concentration ratio of 1%–6% is required. The results show that the temperature gradients and thermal stresses of stainless steel are significantly higher than those of aluminium and copper. From the standpoint of thermal stress, copper is recommended as the tube receiver material. Using Al2O3 in water as an HTF increases the average output temperature by 2%, 6%, and 10% under volume concentrations of 0%, 2%, and 6% respectively. The study concluded that the thermal efficiency increases from 3% to 14% for nanoparticle volume fractions ranging from 2% to 6%.
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Sun, Xinguo, Jasim M. Mahdi, Hayder I. Mohammed, Hasan Sh Majdi, Wang Zixiong e Pouyan Talebizadehsardari. "Solidification Enhancement in a Triple-Tube Latent Heat Energy Storage System Using Twisted Fins". Energies 14, n. 21 (1 novembre 2021): 7179. http://dx.doi.org/10.3390/en14217179.
Testo completoAbstract (sommario):
This work evaluates the influence of combining twisted fins in a triple-tube heat exchanger utilised for latent heat thermal energy storage (LHTES) in three-dimensional numerical simulation and comparing the outcome with the cases of the straight fins and no fins. The phase change material (PCM) is in the annulus between the inner and the outer tube, these tubes include a cold fluid that flows in the counter current path, to solidify the PCM and release the heat storage energy. The performance of the unit was assessed based on the liquid fraction and temperature profiles as well as solidification and the energy storage rate. This study aims to find suitable and efficient fins number and the optimum values of the Re and the inlet temperature of the heat transfer fluid. The outcomes stated the benefits of using twisted fins related to those cases of straight fins and the no-fins. The impact of multi-twisted fins was also considered to detect their influences on the solidification process. The outcomes reveal that the operation of four twisted fins decreased the solidification time by 12.7% and 22.9% compared with four straight fins and the no-fins cases, respectively. Four twisted fins improved the discharging rate by 12.4% and 22.8% compared with the cases of four straight fins and no-fins, respectively. Besides, by reducing the fins’ number from six to four and two, the solidification time reduces by 11.9% and 25.6%, respectively. The current work shows the impacts of innovative designs of fins in the LHTES to produce novel inventions for commercialisation, besides saving the power grid.
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Bošnjaković, Mladen, e Simon Muhič. "Numerical Analysis of Tube Heat Exchanger with Trimmed Star-Shaped Fins". Applied Sciences 12, n. 10 (11 maggio 2022): 4857. http://dx.doi.org/10.3390/app12104857.
Testo completoAbstract (sommario):
In some engineering applications, it is very desirable that the heat exchanger is as light as possible while maintaining the heat transfer rate at an acceptable level. In this context, the possibility of reducing the weight of the heat exchanger with the star-shaped fins by cutting off the thermally least efficient part of the fin was investigated. For this purpose, the rear part of the fins was trimmed to Ø28, Ø31 and Ø34 mm. Numerical analysis was used to determine the influence of each variant on the flow characteristics in the air–water heat exchanger and on heat transfer for the range of 2300 < Re < 16,000. The best results were obtained by trimming the rear part of the fin to Ø28 mm. With a 5.53% reduction in fin weight, heat transfer can be increased by up to 8.12% compared to the star-shaped fins without trimming. The pressure drop can be reduced by up to 0.92%. The trimmed fins were also compared with perforated star-shaped fins (perforation Ø2). At approximately the same weight, the trimmed fins increase the heat transfer coefficient by up to 5.75% with a reduction in pressure drop of up to 0.76% compared to the perforated fins.