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1
Yanbing, Kang, Zhang Yinping, Jiang Yi e Zhu Yingxin. "A General Model for Analyzing the Thermal Characteristics of a Class of Latent Heat Thermal Energy Storage Systems". Journal of Solar Energy Engineering 121, n. 4 (1 novembre 1999): 185–93. http://dx.doi.org/10.1115/1.2888165.
Testo completoAbstract (sommario):
The present study describes and classifies latent heat thermal energy storage (LHTES) systems according to their structural characteristics. A general model is developed for analyzing the thermal characteristics of the various typical LHTES systems to simulate thermal characteristics such as instantaneous heat transfer rate, instantaneous thermal storage capacity, etc. of the various typical LHTES systems. The model can calculate some important but difficult to measure system parameters for monitoring the charging or discharging processes of the systems. The model is verified using experimental data in the literature. Results from the model can be used to discuss the influence of the characteristic geometric parameters of LHTES units, the physical properties of the phase change material (PCM), the flow type and the velocity of heat transfer fluid (HTF) on the system thermal performance and to identify the key factors influencing the system thermal performance. The general model can be used to select and optimize the system structure and to simulate the thermal behavior of various typical LHTES systems.
2
Oni, Taiwo O., Jacob B. Awopetu, Samson A. Adeleye, Daniel C. Uguru-Okorie, Anthony A. Adeyanju e Niyi E. Olukayode. "Development of a Latent Heat Thermal Energy Storage Material-Based Refrigeration System". International Journal of Heat and Technology 39, n. 2 (30 aprile 2021): 469–76. http://dx.doi.org/10.18280/ijht.390216.
Testo completoAbstract (sommario):
The present research focuses on application of thermal energy storage on a convectional refrigerator to enhance its performance. Salt hydrate was used as latent heat thermal energy storage (LHTES) material to convert the convectional refrigerator to a LHTES material-based refrigerator. The cabinet of the convectional refrigerator was loaded with 10 kg of water at a temperature of 28℃ and experiments were conducted on it to know the time taken for the evaporator temperature (TE) to reach -5℃, and determine the performance characteristics of the convectional refrigerator. The experiments were repeated on the LHTES material-based refrigerator to compare its performance characteristics with those of the convectional refrigerator. The results reveal that the evaporator of the LHTES material-based refrigerator attains the temperature of -5℃ forty minutes before the same temperature (-5℃) was attained in the evaporator of the convectional refrigerator. For the interval of evaporator temperature (−5∘C≤TE≤−1∘C) considered for evaluation of the performance characteristics of the refrigerators in this work, when TE drops from 1℃ to -5℃, the coefficient of performance (COP) for the LHTES material-based refrigerator and convectional refrigerator decreases from 7.36 to 4.62 and 6.44 to 4.15, respectively; the refrigerating effect decreases from 118.41 kJ/kg to 111.80 kJ/kg and 113.37 kJ/kg to 106.69 kJ/kg, respectively; the compressor work increases from 15.10 kJ/kg to 23.18 kJ/kg and 17.60 kJ/kg to 25.68 kJ/kg, respectively. The higher value of the COP and refrigerating effect, and the lower value of the compressor work of the LHTES material-based refrigerator compared with those of the convectional refrigerator imply that there is an improvement in the performance of the refrigerator with the LHTES material. The current work broadens research on the use of a LHTES materials to enhance the performance of a refrigerator.
3
Modi, Nishant, Xiaolin Wang e Michael Negnevitsky. "Solar Hot Water Systems Using Latent Heat Thermal Energy Storage: Perspectives and Challenges". Energies 16, n. 4 (16 febbraio 2023): 1969. http://dx.doi.org/10.3390/en16041969.
Testo completoAbstract (sommario):
Domestic water heating accounts for 15% to 27% of the total energy consumption in buildings in Australia. Over the past two decades, the latent heat thermal energy storage (LHTES) system has been widely investigated as a way to reduce fossil fuel consumption and increase the share of renewable energy in solar water heating. However, the research has concentrated on the geometric optimisation of the LHTES heat exchanger for the past few years, and this might not be sufficient for commercialisation. Moreover, recent review papers mainly discussed the development of a particular heat-transfer improvement technique. This paper presents perspectives on various solar hot water systems using LHTES to shift focus to on-demand performance studies, as well as structure optimisation studies for faster commercialisation. Future challenges are also discussed. Since the topic is an active area of research, this paper focuses on references that showcase the overall performance of LHTES-assisted solar hot water systems and cannot include all published work in the discussion. This perspective paper provides directional insights to researchers for developing an energy-efficient solar hot water system using LHTES.
4
Chocontá Bernal, Daniel, Edmundo Muñoz, Giovanni Manente, Adriano Sciacovelli, Hossein Ameli e Alejandro Gallego-Schmid. "Environmental Assessment of Latent Heat Thermal Energy Storage Technology System with Phase Change Material for Domestic Heating Applications". Sustainability 13, n. 20 (13 ottobre 2021): 11265. http://dx.doi.org/10.3390/su132011265.
Testo completoAbstract (sommario):
The emissions generated by the space and water heating of UK homes need to be reduced to meet the goal of becoming carbon neutral by 2050. The combination of solar (S) collectors with latent heat thermal energy storage (LHTES) technologies with phase change materials (PCM) can potentially help to achieve this goal. However, there is limited understanding of the environmental sustainability of LHTES technologies from a full life cycle perspective. This study assesses for the first time 18 environmental impacts of a full S-LHTES-PCM system from a cradle to grave perspective and compares the results with the most common sources of heat in UK homes. The results show that the system’s main environmental hotspots are the solar collector, the PCM, the PCM tank, and the heat exchanger. The main cause of most of the impacts is the extensive consumption of electricity and heat during the production of raw materials for these components. The comparison with other sources of household heat (biomass, heat pump, and natural gas) indicates that the S-LHTES-PCM system generates the highest environmental impact in 11 of 18 categories. However, a sensitivity analysis based on the lifetime of the S-LHTES-PCM systems shows that, when the lifetime increases to 40 years, almost all the impacts are significantly reduced. In fact, a 40-year S-LHTES-PCM system has a lower global warming potential than natural gas.
5
Chocontá Bernal, Daniel, Edmundo Muñoz, Giovanni Manente, Adriano Sciacovelli, Hossein Ameli e Alejandro Gallego-Schmid. "Environmental Assessment of Latent Heat Thermal Energy Storage Technology System with Phase Change Material for Domestic Heating Applications". Sustainability 13, n. 20 (13 ottobre 2021): 11265. http://dx.doi.org/10.3390/su132011265.
Testo completoAbstract (sommario):
The emissions generated by the space and water heating of UK homes need to be reduced to meet the goal of becoming carbon neutral by 2050. The combination of solar (S) collectors with latent heat thermal energy storage (LHTES) technologies with phase change materials (PCM) can potentially help to achieve this goal. However, there is limited understanding of the environmental sustainability of LHTES technologies from a full life cycle perspective. This study assesses for the first time 18 environmental impacts of a full S-LHTES-PCM system from a cradle to grave perspective and compares the results with the most common sources of heat in UK homes. The results show that the system’s main environmental hotspots are the solar collector, the PCM, the PCM tank, and the heat exchanger. The main cause of most of the impacts is the extensive consumption of electricity and heat during the production of raw materials for these components. The comparison with other sources of household heat (biomass, heat pump, and natural gas) indicates that the S-LHTES-PCM system generates the highest environmental impact in 11 of 18 categories. However, a sensitivity analysis based on the lifetime of the S-LHTES-PCM systems shows that, when the lifetime increases to 40 years, almost all the impacts are significantly reduced. In fact, a 40-year S-LHTES-PCM system has a lower global warming potential than natural gas.
6
Zhang, Yinping, Yan Su, Yingxin Zhu e Xianxu Hu. "A General Model for Analyzing the Thermal Performance of the Heat Charging and Discharging Processes of Latent Heat Thermal Energy Storage Systems*". Journal of Solar Energy Engineering 123, n. 3 (1 gennaio 2001): 232–36. http://dx.doi.org/10.1115/1.1374206.
Testo completoAbstract (sommario):
During melting of phase change materials (PCM) encapsulated in a container, the solid PCM sinks to the bottom or floats to the top of the container according to the gravitational force and buoyancy resulting from the difference between solid and liquid densities. Compared with the solidification process, the melting process has a quite different behavior. Although the heat transfer characteristics of melting processes in various typical kinds of containers have been studied, the general model for analyzing the thermal performance of both melting and solidification processes of latent heat thermal energy storage (LHTES) systems composed of PCM capsules has not been presented in the literature. The present paper describes such a model which can be used to analyze the instantaneous temperature distribution, instantaneous heat transfer rate, and thermal storage capacity of a LHTES system. For solidification, the model is validated with the results in the literature. The thermal performance during melting of a LHTES system composed of PCM spheres is analyzed as an example. The model is not limited to a specific system or a specific PCM, so it can be used to select and optimize system design and to simulate the thermal behavior of various typical LHTES systems.
7
Paroutoglou, Evdoxia, Peter Fojan, Leonid Gurevich, Simon Furbo, Jianhua Fan, Marc Medrano e Alireza Afshari. "A Numerical Parametric Study of a Double-Pipe LHTES Unit with PCM Encapsulated in the Annular Space". Sustainability 14, n. 20 (17 ottobre 2022): 13317. http://dx.doi.org/10.3390/su142013317.
Testo completoAbstract (sommario):
Latent heat thermal energy storage (LHTES) with Phase Change Materials (PCM) represents an interesting option for Thermal Energy Storage (TES) applications in a wide temperature range. A tubular encapsulation model of an LHTES with PCM was developed, and the calculated data were analyzed. In addition, a parametric analysis for the preferable system geometry is presented. Organic paraffin RT18 with a melting point of 18 °C was utilized as PCM for different geometries of LHTES, and the addition of internal and external fins and their influence on LHTES thermal conductivity was investigated. One-step heat exchange from outdoor air to PCM and from PCM to water characterizes the LHTES system in solidification and melting processes, respectively. A 2D axisymmetric model was developed using Comsol Multiphysics 6.0. The LHTES unit performance with PCM organic paraffin RT18 encapsulated in electrospun fiber matrices was analyzed. The study results show that longer internal fins shorten the melting and solidification time. Direct contact of PCM electrospun fiber matrix with 23 °C water showed instant melting, and the phase change process was accelerated by 99.97% in the discharging cycle.
8
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.
9
Paroutoglou, Evdoxia, Alireza Afshari, Niels Chr Bergsøe, Peter Fojan e Göran Hultmark. "A PCM based cooling system for office buildings: a state of the art review". E3S Web of Conferences 111 (2019): 01026. http://dx.doi.org/10.1051/e3sconf/201911101026.
Testo completoAbstract (sommario):
Cooling of air in buildings has a significant effect on thermal comfort and, consequently, productivity of office occupants. This study presents a state of the art review of energy efficient cooling systems that will provide occupants in buildings with satisfying thermal comfort. Using high-temperature cooling systems combined with renewable energy sources increases the energy efficiency in buildings. Latent heat thermal energy storage (LHTES) using Phase Change Materials (PCM) is a renewable energy source implemented in space cooling applications due to its high energy storage density. Since the share of commercial buildings in need of cooling is increasing, there is a need for developing new technical solutions in order to reduce the energy use without compromising thermal comfort. To this end, a proposed ventilation system, preliminarily analyzed in this paper, is expected to reduce further the energy use. The ventilation system is composed of an air handling unit, a 2-pipe active chilled beam system, and a cooling system including a LHTES using PCM. Few researchers have investigated chilled water air-conditioning systems that integrate a LHTES using PCM. In this review, function characteristics, possibilities and limitations of existing systems are discussed.
10
Migla, Lana, Raimonds Bogdanovics e Kristina Lebedeva. "Performance Improvement of a Solar-Assisted Absorption Cooling System Integrated with Latent Heat Thermal Energy Storage". Energies 16, n. 14 (11 luglio 2023): 5307. http://dx.doi.org/10.3390/en16145307.
Testo completoAbstract (sommario):
Phase change materials (PCMs) have emerged as promising solutions for latent heat thermal energy storage (LHTES) systems, offering considerable potential for storing energy derived from renewable sources across various engineering applications. The present study focused on optimization of solar cooling system by integrating LHTES with different PCM tank configurations. TRNSYS simulation software was selected for the study, and the collected experimental data from laboratory system prototype were used for system validation. The results indicate that the use of PCM led to a noteworthy decrease of 6.2% in auxiliary energy consumption. Furthermore, the time during which the heat carrier temperature flow exceeded 90 °C from the storage tank to the auxiliary fluid heater was extended by 27.8% when PCM was utilized compared to that of its absence. The use of PCM in LHTES is more effective under variable weather conditions. On the day when changes in weather conditions were observed, around 98% of the cooling load was provided by produced sun energy. The results of the research can be used to optimize the solar cooling system, which will help reduce the environmental impact of cooling systems running on non-renewable fuels.
11
MacPhee, David W., e Mustafa Erguvan. "Thermodynamic Analysis of a High-Temperature Latent Heat Thermal Energy Storage System". Energies 13, n. 24 (16 dicembre 2020): 6634. http://dx.doi.org/10.3390/en13246634.
Testo completoAbstract (sommario):
Thermal energy storage (TES) technologies are becoming vitally important due to intermittency of renewable energy sources in solar applications. Since high energy density is an important parameter in TES systems, latent heat thermal energy storage (LHTES) system is a common way to store thermal energy. Though there are a great number of experimental studies in the field of LHTES systems, utilizing computational codes can yield relatively quick analyses with relatively small expense. In this study, a numerical investigation of a LHTES system has been studied using ANSYS FLUENT. Results are validated with experiments, using hydroquinone as a phase-change material (PCM), which is external to Therminol VP-1 as a heat transfer fluid (HTF) contained in pipes. Energy efficiency and entropy generation are investigated for different tube/pipe geometries with a constant PCM volume. HTF inlet temperature and flow rate impacts on the thermodynamic efficiencies are examined including viscous dissipation effects. Highest efficiency and lowest entropy generation cases exist when when flow rates are lowest due to low viscous heating effects. A positive relation is found between energy efficiency and volume ratio while it differs for entropy generation for higher and lower velocities. Both efficiency and entropy generation decreased with decreasing HTF inlet temperature. The novelty of this study is the analysis of the effect of volume ratio on system performance and PCM melting time which ultimately proved to be the most dominant factor among those considered herein. However, as PCM solidification and melting time is of primary importance to system designers, simply minimizing entropy generation by decreasing volume ratio in this case does not lead to a practically optimal system, merely to decrease heat transfer entropy generation. Therefore, caution should be taken when applying entropy analyses to any LHTES storage system as entropy minimization methods may not be appropriate for practicality purposes.
12
Dugué, Antoine, Saed Raji, Paul Bonnamy e Denis Bruneau. "E2VENT: An Energy Efficient Ventilated Façade Retrofitting System. Presentation of the Embedded LHTES System". Procedia Environmental Sciences 38 (2017): 121–29. http://dx.doi.org/10.1016/j.proenv.2017.03.093.
Testo completo
13
Shank, Kyle, e Saeed Tiari. "A Review on Active Heat Transfer Enhancement Techniques within Latent Heat Thermal Energy Storage Systems". Energies 16, n. 10 (18 maggio 2023): 4165. http://dx.doi.org/10.3390/en16104165.
Testo completoAbstract (sommario):
Renewable energy resources require energy storage techniques to curb problems with intermittency. One potential solution is the use of phase change materials (PCMs) in latent heat thermal energy storage (LHTES) systems. Despite the high energy storage density of PCMs, their thermal response rate is restricted by low thermal conductivity. The topic of heat transfer enhancement techniques for increasing thermal performance of LHTES systems has mainly focused on passive heat transfer enhancement techniques with less attention towards active methods. Active heat transfer enhancement techniques require external power supplied to the system. In this paper, recent advances in active heat transfer enhancement techniques within LHTES systems are reviewed, including mechanical aids, vibration, jet impingement, injection, and external fields. The pertinent findings related to the field are summarized in relation to the charging and discharging processes of PCMs. Suggestions for future research are proposed, and the importance of additional energy input for storage is discussed.
14
Tola, Vittorio, Simone Arena, Mario Cascetta e Giorgio Cau. "Numerical Investigation on a Packed-Bed LHTES System Integrated into a Micro Electrical and Thermal Grid". Energies 13, n. 8 (18 aprile 2020): 2018. http://dx.doi.org/10.3390/en13082018.
Testo completoAbstract (sommario):
Currently, energy storage systems are considered a key solution when mismatch occurs between energy supply and demand, allowing a more efficient energy deployment and use. The present paper is focused on the study of a latent heat thermal energy storage (LHTES) system based on a packed bed of encapsulated phase change material (PCM) of spherical shape, conceived as an auxiliary component of a micro-grid to be built in a Research Center located in southwestern Sardinia (Italy). The main purpose of this work was to perform numerical simulations for predicting the performance of the TES system, designed to store the surplus thermal energy produced during the weekend by a heat pump fed by a photovoltaic (PV) plant. The stored energy would then be utilized during the weekdays to integrate the air-conditioning system supply. The numerical simulations were based on a one-dimensional (1-D) two-equation transient model, able to return the thermocline profile of the water and the PCM separately. The behavior of the LHTES device during charge and discharge phases was reproduced, as well as during the standby periods. Finally, two characteristic indexes of the PV system were evaluated, to investigate the effect of TES on grid interchanges, self-consumption, and self-sufficiency.
15
Pop, Octavian G., Lucian Fechete Tutunaru, Florin Bode e Mugur C. Balan. "Preliminary investigation of thermal behaviour of PCM based latent heat thermal energy storage". E3S Web of Conferences 32 (2018): 01017. http://dx.doi.org/10.1051/e3sconf/20183201017.
Testo completoAbstract (sommario):
Solid-liquid phase change is used to accumulate and release cold in latent heat thermal energy storage (LHTES) in order to reduce energy consumption of air cooling system in buildings. The storing capacity of the LHTES depends greatly on the exterior air temperatures during the summer nights. One approach in intensifying heat transfer is by increasing the air’s velocity. A LHTES was designed to be integrated in the air cooling system of a building located in Bucharest, during the month of July. This study presents a numerical investigation concerning the impact of air inlet temperatures and air velocity on the formation of solid PCM, on the cold storing capacity and energy consumption of the LHTES. The peak amount of accumulated cold is reached at different air velocities depending on air inlet temperature. For inlet temperatures of 14°C and 15°C, an increase of air velocity above 50% will not lead to higher amounts of cold being stored. For Bucharest during the hottest night of the year, a 100 % increase in air velocity will result in 5.02% more cold being stored, at an increase in electrical energy consumption of 25.30%, when compared to the reference values.
16
HOSHI, Akira, Takeo S. SAITOH e David R. Mills. "Application of High-Temperature Latent Heat Thermal Energy Storage (LHTES) System to Solar Thermal Electricity Systems". Proceedings of The Computational Mechanics Conference 2004.17 (2004): 649–50. http://dx.doi.org/10.1299/jsmecmd.2004.17.649.
Testo completo
17
Yusup, Rifki, e Byan Wahyu Riyandwita. "Effects of Flow Rate and Inlet Temperature on Performance of Annulus Type Low-Temperature Latent Heat Thermal Energy Storages". Journal of Emerging Supply Chain, Clean Energy, and Process Engineering 1, n. 1 (6 settembre 2022): 41–54. http://dx.doi.org/10.57102/jescee.v1i1.10.
Testo completoAbstract (sommario):
Solar energy is one of the largest energy potentials that Indonesia has, which can be utilized in solar heater that are integrated with latent heat energy storage (LHTES). This research aims to investigate the effects of the operating conditions of flow rate and inlet temperature on the performance of the annulus type Low-Temperature LHTES using Computational fluid dynamics method in which the enthalpy-porosity is used as the solidification model. The results indicate that the increase of performance can be obtained by increasing the flow rate and inlet temperature. The increase in flow rate will promote higher heat transfer thus produce better performance up to 11.91% and 24.91% during charging and discharging, respectively. Meanwhile, increasing the inlet temperature will increase the performance up to 192.72% during charging and 13.07% during discharging of the Low-Temperature LHTES system.
18
El Mhamdi, Oussama, Soumia Addakiri, ElAlami Semma e Mustapha El Alami. "Study of A Thermal Energy Storage System Using the Lattice Boltzmann Method". E3S Web of Conferences 321 (2021): 04003. http://dx.doi.org/10.1051/e3sconf/202132104003.
Testo completoAbstract (sommario):
Thermal energy storage (TES) systems are much preferred in many engineering applications, which have the ability to overcome the mismatch between energy supply and energy demand. TES can be used to store thermo-chemical, sensible, or latent heat or a combination of these. Among the three forms, latent heat thermal energy storage (LHTES) has grown considerably in importance over recent years as a promising alternative to traditional systems. These systems use phase change materials (PCM), in simple or cascade configuration, and store the latent heat of melting (charging process) and release it during solidification (discharging process). Among different configurations of LHTES systems, tube and shell heat exchangers represent a promising and simple design in high temperature PCM. In this paper, we present a new numerical study involving a tube and shell heat exchanger to evaluate the heat storage phenomena. A case study and numerical results are provided using the Lattice Boltzmann Method.
19
Metin, Cagri, Servet Giray Hacipasaoglu, Ersin Alptekin e Mehmet Akif Ezan. "Implementation of enhanced thermal conductivity approach to an LHTES system with in‐line spherical capsules". Energy Storage 1, n. 1 (febbraio 2019): e39. http://dx.doi.org/10.1002/est2.39.
Testo completo
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Yang, Jialin, Zhenlan Dou, Pengxiang Zhao, Xichao Zhou, Lin Cong, Na Li e Chunyan Zhang. "Numerical studies on storage process of phase change material with metal foam for prefabricated cabin energy system". Journal of Physics: Conference Series 2474, n. 1 (1 aprile 2023): 012084. http://dx.doi.org/10.1088/1742-6596/2474/1/012084.
Testo completoAbstract (sommario):
Abstract Latent heat thermal energy storage (LHTES) is a promising technology in prefabricated cabin energy system. This paper proposed a new thermal energy storage (TES) system with phase-change material (PCM) embedded in metal foam and heating source is steam or hot water. The mathematical formulas and numerical models of representative units are studied. The effect of natural convection is considered in the simulation of melting process. Finite volume method is used to discretize the governing equation The Forchheimer-Darcy law is used to model the porous resistance and a local thermal equilibrium model is developed. The model is firstly validated against low temperature experiments from the literature and then used to simulate the charging behaviour of LHTES system proposed by this paper. Foamed metal and fin are effective means to improve the heat transfer performance and shorten the melting time of heat storage system. In this paper, the effects of pore density, porosity, wall temperature and fin spacing on temperature change and melting rate are discussed.
21
Algarni, Mohammed, Mashhour A. Alazwari e Mohammad Reza Safaei. "Optimization of Nano-Additive Characteristics to Improve the Efficiency of a Shell and Tube Thermal Energy Storage System Using a Hybrid Procedure: DOE, ANN, MCDM, MOO, and CFD Modeling". Mathematics 9, n. 24 (14 dicembre 2021): 3235. http://dx.doi.org/10.3390/math9243235.
Testo completoAbstract (sommario):
Using nano-enhanced phase change material (NePCM) rather than pure PCM significantly affects the melting/solidification duration and the stored energy, which are two critical design parameters for latent heat thermal energy storage (LHTES) systems. The present article employs a hybrid procedure based on the design of experiments (DOE), computational fluid dynamics (CFD), artificial neural networks (ANNs), multi-objective optimization (MOO), and multi-criteria decision making (MCDM) to optimize the properties of nano-additives dispersed in a shell and tube LHTES system containing paraffin wax as a phase change material (PCM). Four important properties of nano-additives were considered as optimization variables: volume fraction and thermophysical properties, precisely, specific heat, density, and thermal conductivity. The primary objective was to simultaneously reduce the melting duration and increase the total stored energy. To this end, a five-step hybrid optimization process is presented in this paper. In the first step, the DOE technique is used to design the required simulations for the optimal search of the design space. The second step simulates the melting process through a CFD approach. The third step, which utilizes ANNs, presents polynomial models for objective functions in terms of optimization variables. MOO is used in the fourth step to generate a set of optimal Pareto points. Finally, in the fifth step, selected optimal points with various features are provided using various MCDM methods. The results indicate that nearly 97% of the Pareto points in the considered shell and tube LHTES system had a nano-additive thermal conductivity greater than 180 Wm−1K−1. Furthermore, the density of nano-additives was observed to be greater than 9950 kgm−3 for approximately 86% of the optimal solutions. Additionally, approximately 95% of optimal points had a nano-additive specific heat of greater than 795 Jkg−1K−1.
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Antony Aroul Raj, V., C. Hariharan, R. Velraj e R. V. Seeniraj. "Numerical Investigations of Outward Solidification in Cylindrical PCM Storage Unit". Applied Mechanics and Materials 787 (agosto 2015): 177–81. http://dx.doi.org/10.4028/www.scientific.net/amm.787.177.
Testo completoAbstract (sommario):
In the present work a transient numerical model is developed to investigate and predict the performance of a paraffin phase change material (PCM) in the annular portion of the cylindrical container during its solidification and melting processes. Enthalpy method of modeling is adopted and the discretised non-dimensional form of governing equations and boundary conditions are solved by implicit finite difference method by using MATLAB software. The temperature variation of PCM along two axes of the polar co-ordinates (r, z) and the time required for solidification are analyzed and presented. The effect of system variables on the performance of the Latent Heat Thermal Energy system ( LHTES) is studied. The model tested finds application in the concept of free cooling which is the process of storing the coldness of the night time ambient air in the LHTES in order to cool the building during the daytime by retrieving the stored cold energy.
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Ma, Fei, Tianji Zhu, Yalin Zhang, Xinli Lu, Wei Zhang e Feng Ma. "A Review on Heat Transfer Enhancement of Phase Change Materials Using Fin Tubes". Energies 16, n. 1 (3 gennaio 2023): 545. http://dx.doi.org/10.3390/en16010545.
Testo completoAbstract (sommario):
Latent heat thermal energy storage (LHTES) has received more and more attention in the thermal energy storage field due to the large heat storage density and nearly constant temperature during phase change process. However, the low thermal conductivity of phase change material (PCM) leads to poor performance of the LHTES system. In this paper, the research about heat transfer enhancement of PCM using fin tubes is summarized. Different kinds of fins, such as rectangular fin, annular fin, spiral fin, etc., are discussed and compared based on the shape of the fins. It is found that the longitudinal rectangular fins have excellent heat transfer performance and are easy to manufacture. The effect of fins on heat transfer enhancement is closely related to the number of fins and its geometric parameters.
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Pise, A. T., A. V. Waghmare e V. G. Talandage. "Heat Transfer Enhancement by Using Nanomaterial in Phase Change Material for Latent Heat Thermal Energy Storage System". Asian Journal of Engineering and Applied Technology 2, n. 2 (5 novembre 2013): 52–57. http://dx.doi.org/10.51983/ajeat-2013.2.2.667.
Testo completoAbstract (sommario):
Latent heat energy storage systems using paraffin wax could have lower heat transfer rates during melting / freezing processes due to its inherent low thermal conductivity. The thermal conductivity of paraffin wax can be enhanced by employing high conductivity materials such as alumina (Al2O3) nanopowder. In this paper the experimental investigation has been carried out to study the performance enhancement of paraffin wax with nanoalumina (Al2O3) particles in mass fraction of 1, 3, and 5% in a Latent Heat Thermal Energy Storage (LHTES) System at constant flow rate and variable temperature of heat transfer fluid (HTF). The effect of alumina nanoparticle on total cyclic time of LHTES for different mass fraction has been studied. Commercially available paraffin wax is used as a phase change material (PCM). The present results illustrate that the suspended nanoparticles substantially increase the heat transfer rate and also the nanofluid heat transfer rate increased with an increased in the nanoparticles mass fraction. The comparative results with and without nanoalumina (Al2O3) enhancement indicate that the charging rate of thermal energy can be greatly enhanced using paraffin wax with alumina as compared with a simple paraffin wax as PCM. The increase of the heat release rate of the nanoparticle-enhanced phase change materials shows its great potential for diverse thermal energy storage application.
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Tascioni, Roberto, Alessia Arteconi, Luca Del Zotto e Luca Cioccolanti. "Fuzzy Logic Energy Management Strategy of a Multiple Latent Heat Thermal Storage in a Small-Scale Concentrated Solar Power Plant". Energies 13, n. 11 (29 maggio 2020): 2733. http://dx.doi.org/10.3390/en13112733.
Testo completoAbstract (sommario):
Latent heat thermal energy storage (LHTES) systems allow us to effectively store and release the collected thermal energy from solar thermodynamic plants; however, room for improvements exists to increase their efficiency when in operation. For this reason, in this work, a smart management strategy of an innovative LHTES in a micro-scale concentrated solar combined heat and power plant is proposed and numerically investigated. The novel thermal storage system, as designed and built by the partners within the EU funded Innova MicroSolar project, is subdivided into six modules and consists of 3.8 tons of nitrate solar salt kNO3/NaNO3, whose melting temperature is in the range 216 ÷ 223 °C. In this study, the partitioning of the storage system on the performance of the integrated plant is evaluated by applying a smart energy management strategy based on a fuzzy logic approach. Compared to the single thermal energy storage (TES) configuration, the proposed strategy allows a reduction in storage thermal losses and improving of the plant’s overall efficiency especially in periods with limited solar irradiance. The yearly dynamic simulations carried out show that the electricity produced by the combined heat and power plant is increased by about 5%, while the defocus thermal losses in the solar plant are reduced by 30%.
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Singh, Dileep, Taeil Kim, Weihuan Zhao, Wenhua Yu e David M. France. "Development of graphite foam infiltrated with MgCl2 for a latent heat based thermal energy storage (LHTES) system". Renewable Energy 94 (agosto 2016): 660–67. http://dx.doi.org/10.1016/j.renene.2016.03.090.
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Wang, Peilun, Pengxiang Song, Yun Huang, Zhijian Peng e Yulong Ding. "Numerical Simulation of the Heat Transfer Behavior of a Zigzag Plate Containing a Phase Change Material for Combustion Heat Recovery and Power Generation". Journal of Combustion 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/3092508.
Testo completoAbstract (sommario):
This study presents a numerical analysis of the melting process of phase change materials (PCMs) within a latent heat thermal energy storage (LHTES) system employing zigzag plate. The numerical model used NaCl-MgCl2 mixture as PCMs and hot air as heat transfer fluid (HTF). An experimental system was built to validate the model, and the experimental data agrees reasonably well with the simulation results. The simulation results revealed the effects of the Reynolds and Stefan numbers and the surface topography of the zigzag plate on the charging process. Besides, the effect of the relationship between Reynolds and Stefan numbers on the charging process under a new boundary condition employing a fixed input power was studied. It is found that by modifying the shape of the zigzag plate surface it is feasible to enhance the heat transfer of the LHTES unit remarkably. The melting rate of PCMs increases with the value of Ste or Re numbers with only one of them changing; however, the melting rate of PCMs decreases with the increasing Ste (or decreasing Re) in a fixed input power condition.
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Ghalambaz, Mohammad, Hassan Shirivand, Kasra Ayoubi Ayoubloo, S. A. M. Mehryan, Obai Younis, Pouyan Talebizadehsardari e Wahiba Yaïci. "The Thermal Charging Performance of Finned Conical Thermal Storage System Filled with Nano-Enhanced Phase Change Material". Molecules 26, n. 6 (14 marzo 2021): 1605. http://dx.doi.org/10.3390/molecules26061605.
Testo completoAbstract (sommario):
A latent heat thermal energy storage (LHTES) unit can store a notable amount of heat in a compact volume. However, the charging time could be tediously long due to weak heat transfer. Thus, an improvement of heat transfer and a reduction in charging time is an essential task. The present research aims to improve the thermal charging of a conical shell-tube LHTES unit by optimizing the shell-shape and fin-inclination angle in the presence of nanoadditives. The governing equations for the natural convection heat transfer and phase change heat transfer are written as partial differential equations. The finite element method is applied to solve the equations numerically. The Taguchi optimization approach is then invoked to optimize the fin-inclination angle, shell aspect ratio, and the type and volume fraction of nanoparticles. The results showed that the shell-aspect ratio and fin inclination angle are the most important design parameters influencing the charging time. The charging time could be changed by 40% by variation of design parameters. Interestingly a conical shell with a small radius at the bottom and a large radius at the top (small aspect ratio) is the best shell design. However, a too-small aspect ratio could entrap the liquid-PCM between fins and increase the charging time. An optimum volume fraction of 4% is found for nanoparticle concentration.
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Tofani, Kassianne, e Saeed Tiari. "Nano-Enhanced Phase Change Materials in Latent Heat Thermal Energy Storage Systems: A Review". Energies 14, n. 13 (25 giugno 2021): 3821. http://dx.doi.org/10.3390/en14133821.
Testo completoAbstract (sommario):
Latent heat thermal energy storage systems (LHTES) are useful for solar energy storage and many other applications, but there is an issue with phase change materials (PCMs) having low thermal conductivity. This can be enhanced with fins, metal foam, heat pipes, multiple PCMs, and nanoparticles (NPs). This paper reviews nano-enhanced PCM (NePCM) alone and with additional enhancements. Low, middle, and high temperature PCM are classified, and the achievements and limitations of works are assessed. The review is categorized based upon enhancements: solely NPs, NPs and fins, NPs and heat pipes, NPs with highly conductive porous materials, NPs and multiple PCMs, and nano-encapsulated PCMs. Both experimental and numerical methods are considered, focusing on how well NPs enhanced the system. Generally, NPs have been proven to enhance PCM, with some types more effective than others. Middle and high temperatures are lacking compared to low temperature, as well as combined enhancement studies. Al2O3, copper, and carbon are some of the most studied NP materials, and paraffin PCM is the most common by far. Some studies found NPs to be insignificant in comparison to other enhancements, but many others found them to be beneficial. This article also suggests future work for NePCM and LHTES systems.
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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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Soudian, Shahrzad, e Umberto Berardi. "Assessing the effect of night ventilation on PCM performance in high-rise residential buildings". Journal of Building Physics 43, n. 3 (13 maggio 2019): 229–49. http://dx.doi.org/10.1177/1744259119848128.
Testo completoAbstract (sommario):
This article investigates the possibility to enhance the use of latent heat thermal energy storage (LHTES) as an energy retrofit measure by night ventilation strategies. For this scope, phase change materials (PCMs) are integrated into wall and ceiling surfaces of high-rise residential buildings with highly glazed facades that experience high indoor diurnal temperatures. In particular, this article investigates the effect of night ventilation on the performance of the PCMs, namely, the daily discharge of the thermal energy stored by PCMs. Following previous experimental tests that have shown the efficacy of LHTES in temperate climates, a system comprising two PCM layers with melting temperatures selected for a year-around LHTES was considered. To quantify the effectiveness of different night ventilation strategies to enhance the potential of this composite PCM system, simulations in EnergyPlusTM were performed. The ventilation flow rate, set point temperature, and operation period were the main tested parameters. The performance of the PCMs in relation to the variables was evaluated based on indoor operative temperature and cooling energy use variations in Toronto and New York in the summer. The solidification of the PCMs was analyzed based on the amount of night ventilation needed in each climate condition. The results quantify the positive impact of combining PCMs with night ventilation on cooling energy reductions and operative temperature regulation of the following days. In particular, the results indicate higher benefits obtainable with PCMs coupled with night ventilation in the context of Toronto, since this city experiences higher daily temperature fluctuations. The impact of night ventilation design variables on the solidification rate of the PCMs varied based on each parameter leading to different compromises based on the PCM and climate characteristics.
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Wang, Huiru, Zhenyu Liu e Huiying Wu. "Entransy dissipation-based thermal resistance optimization of slab LHTES system with multiple PCMs arranged in a 2D array". Energy 138 (novembre 2017): 739–51. http://dx.doi.org/10.1016/j.energy.2017.07.089.
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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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Arena, Simone, Efisio Casti, Jaume Gasia, Luisa F. Cabeza e Giorgio Cau. "Numerical simulation of a finned-tube LHTES system: influence of the mushy zone constant on the phase change behaviour". Energy Procedia 126 (settembre 2017): 517–24. http://dx.doi.org/10.1016/j.egypro.2017.08.237.
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Peng, Li, Hongjun Wu, Wenlong Cao e Qianjun Mao. "Exergy Analysis of a Shell and Tube Energy Storage Unit with Different Inclination Angles". Energies 16, n. 11 (24 maggio 2023): 4297. http://dx.doi.org/10.3390/en16114297.
Testo completoAbstract (sommario):
To optimize the utilization of solar energy in the latent heat thermal energy storage (LHTES) system, this study conducts exergy analysis on a paraffin-solar water shell and tube unit established in the literature to evaluate the effects of different inclination angles, inlet temperatures, original temperatures, and fluid flow rates on the exergy and exergy efficiency. Firstly, the thermodynamic characteristics of the water and the natural convection effects of the paraffin change with different inclination angles. When the inclination angle of the heat storage tank is less than 30°, the maximum exergy inlet rate rises from 0 to 144.6 W in a very short time, but it decreases to 65.7 W for an inclination angle of 60°. When the inclination angle is increased from 0° to 30°, the exergy efficiency rises from 86% to 89.7%, but it decreases from 94% to 89.9% with the inclination angle from 60° to 90°. Secondly, under the condition that the inclination angle of the energy storage unit is 60°, although increasing the inlet temperature of the solar water enhances the exergy inlet and storage and reduces the charging time, it increases the heat transfer temperature difference and the irreversible loss of the system, thus reducing the exergy efficiency. As the inlet water temperature is increased from 83 to 98 °C, the exergy efficiency decreases from 94.7% to 93.6%. Moreover, increasing the original temperature of the LHTES unit not only reduces the exergy inlet and storage rates but also decreases the available work capacity and exergy efficiency. Finally, increasing the inlet water flow rate increases the exergy inlet and storage rates slightly. The exergy efficiency decreases from 95.6% to 93.3% as the unit original temperature is increased from 15 to 30 °C, and it is enhanced from 94% to 94.6% as the inlet flow rate is increased from 0.085 to 0.34 kg/s with the unit inclination angle of 60°. It is found that arranging the shell and tube unit at an inclination angle is useful for improving the LHTES system’s thermal performance, and the exergy analysis conducted aims to reduce available energy dissipation and exergy loss in the thermal storage system. This study provides instructions for solar energy utilization and energy storage.
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Mao, Qianjun, Ning Liu e Li Peng. "Recent Investigations of Phase Change Materials Use in Solar Thermal Energy Storage System". Advances in Materials Science and Engineering 2018 (12 dicembre 2018): 1–13. http://dx.doi.org/10.1155/2018/9410560.
Testo completoAbstract (sommario):
Solar thermal energy storage (TES) is an efficient way to solve the conflict between unsteady input energy and steady output energy in concentrating solar power plant. The latent heat thermal energy storage (LHTES) system is a main method of storing thermal energy using phase change materials (PCMs). Thermal properties, that is, melting points and latent heat, are the key parameters of PCMs for the TES system. In this paper, the PCMs are classified into inorganic and organic by the chemical composition, and according to the melting point, the inorganic PCMs can be divided into three contributions: low-temperature heat storage (less than 120°C), medium-temperature heat storage (120–300°C), and high-temperature heat storage (more than 300°C). The present article focuses mainly on the recent investigations on the melting point and latent heat of PCMs via DSC setup in the solar TES systems. The results can provide a good reference for the selection and utilization of PCMs in the solar TES systems.
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Shaghaghi, Aidin, Reza Eskandarpanah, Siavash Gitifar, Rahim Zahedi, Hossein Pourrahmani, Mansour Keshavarzzade e Abolfazl Ahmadi. "Energy consumption reduction in a building by free cooling using phase change material (PCM)". Future Energy 3, n. 2 (15 maggio 2024): 31–36. http://dx.doi.org/10.55670/fpll.fuen.3.2.4.
Testo completoAbstract (sommario):
It is significantly important to implement energy storage systems nowadays. Latent heat thermal energy storage (LHTES) systems contain numerous advantages as a result of their small temperature variation and higher energy storage densities during storage. The present paper deals with the cooling load of a room in Zanjan, Iran using Carrier software. Then, a free cooling system using commercial paraffin RT25 was numerically analyzed as phase change material (PCM) while investigating the effects of the flow rate of the storage tank and inlet air temperature overcharging and discharging procedures. Based on cold energy storage simulation, by airflow with the temperature of 20°C at night, the paraffin is solidified in 4 h. Stored cold energy of 1.4 kW in PCM releases energy through a free cooling system within 2.1 h of July afternoon in the room.
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Behi, Hamidreza, Mohammadreza Behi, Ali Ghanbarpour, Danial Karimi, Aryan Azad, Morteza Ghanbarpour e Masud Behnia. "Enhancement of the Thermal Energy Storage Using Heat-Pipe-Assisted Phase Change Material". Energies 14, n. 19 (28 settembre 2021): 6176. http://dx.doi.org/10.3390/en14196176.
Testo completoAbstract (sommario):
Usage of phase change materials’ (PCMs) latent heat has been investigated as a promising method for thermal energy storage applications. However, one of the most common disadvantages of using latent heat thermal energy storage (LHTES) is the low thermal conductivity of PCMs. This issue affects the rate of energy storage (charging/discharging) in PCMs. Many researchers have proposed different methods to cope with this problem in thermal energy storage. In this paper, a tubular heat pipe as a super heat conductor to increase the charging/discharging rate was investigated. The temperature of PCM, liquid fraction observations, and charging and discharging rates are reported. Heat pipe effectiveness was defined and used to quantify the relative performance of heat pipe-assisted PCM storage systems. Both experimental and numerical investigations were performed to determine the efficiency of the system in thermal storage enhancement. The proposed system in the charging/discharging process significantly improved the energy transfer between a water bath and the PCM in the working temperature range of 50 °C to 70 °C.
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El ouali, Abdelmajid, Hajar Zennouhi, Wafaa Benomar, Najma Laaroussi, Tarik El rhafik e Tarik Kousksou. "Energetic Analysis of Packed Bed Latent Heat Storage Systems". ITM Web of Conferences 46 (2022): 01001. http://dx.doi.org/10.1051/itmconf/20224601001.
Testo completoAbstract (sommario):
Nowadays, with the rapid growths in world population and economy, the world energy demand and consumption have increased enormously which led to a wide variety of harsh environmental impacts [1]. As a potential solution for energy conservation storing the excess energy to fill the gap between energy supply and demand, using phase change materials (PCMs) has received much attention. Thermal energy storage with PCM is a promising technology based on the principle of latent heat thermal energy storage (LHTES)[2], where PCM absorbs or releases large amounts of energy at a certain temperature during the phase change transition period (charging and discharging process), with a high heat of fusion around its phase change temperature range [3]. Thermal energy storage in packed beds is receiving increased attention as a necessary component for efficient implementation of concentrated solar power plants. In this study, the thermal characteristics, during a single charge period, of a packed bed made of PCM filled spherical capsules is presented. It was found that the energy efficiency of the system proved to be very sensitive to the choice of the PCM melting temperature.
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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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Koukou, Maria K., George Dogkas, Michail Gr Vrachopoulos, John Konstantaras, Christos Pagkalos, Kostas Lymperis, Vassilis Stathopoulos et al. "Performance Evaluation of a Small-Scale Latent Heat Thermal Energy Storage Unit for Heating Applications Based on a Nanocomposite Organic PCM". ChemEngineering 3, n. 4 (1 novembre 2019): 88. http://dx.doi.org/10.3390/chemengineering3040088.
Testo completoAbstract (sommario):
A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to the PCM, and a water pump to circulate water as a heat transfer fluid (HTF). The performance of the unit using the commercial organic paraffin A44 was studied in order to understand the thermal behavior of the system and the main parameters that influence heat transfer during the PCM melting and solidification processes. The latter will assist the design of a large-scale unit. The effect of flow rate was studied given that it significantly affects charging (melting) and discharging (solidification) processes. In addition, as organic PCMs have low thermal conductivity, the possible improvement of the PCM’s thermal behavior by means of nanoparticle addition was investigated. The obtained results were promising and showed that the use of graphite-based nanoplatelets improves the PCM thermal behavior. Charging was clearly faster and more efficient, while with the appropriate tuning of the HTF flow rate, an efficient discharging was accomplished.
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Demchenko, V. G., e V. Yu Falco. "EXPERIMENTAL RESEARCH OF THERMAL STABILITY OF SUBSTANCES FOR THERMAL ENERGY STORAGE". Thermophysics and Thermal Power Engineering 41, n. 2 (26 aprile 2019): 64–71. http://dx.doi.org/10.31472/ttpe.2.2019.9.
Testo completoAbstract (sommario):
Optimizing the storage methods for excess heat energy and associated technical and technological solutions has a significant impact on the development of LHTES systems. New technologies for storing thermal energy are increasingly an alternative to the classic methods of providing thermal infrastructure facilities. In this paper we analyze the results of experimental studies of heat-storage materials for their further integration into the Smart Grid heating system of infrastructure objects and use in the M-TES. The conducted literary review showed that the thermophysical parameters of the investigated substances for the conservation of heat from different authors are very different. We conclude that this is due to the quality of the materials being studied and the errors of laboratory measurements. This negatively affects the design of LHTES systems and greatly complicates the calculation and modeling of heat transfer processes. It is especially important to correctly determine the amount of heat that can be obtained during the charging and discharge cycles of TES, as well as the lifetime of the material that accumulates heat. Therefore, the purpose of this work is to identify the appropriate material for energy storage applications between 0 0C and 115 0C and evaluate it, depending on the thermophysical properties and the time of stable operation. Taking into account the economic aspects, only the available technical materials are considered within the framework of this study, since the choice of material is aimed at the use of M-TES in real conditions of operation. Figure 1 summarizes the results of research on heating and cooling cycles of heats of heat storage substances. High thermal power and, hence, high thermal conductivity are important for the storage efficiency of PCM, especially in the process of solidification, because in a heat transfer predominant solid layer that grows continuously. However, both PCMs are not suitable for mobile thermal storage systems in this form. The huge disadvantages are the emergence of different values of the melting point, the high retention time of both candidates, as well as their prices. Therefore, further research should be directed to eliminate these negative effects. Despite the relatively low density of heat storage with aqueous solutions of antifreeze, they are beneficial candidates for waste heat transfer systems within the framework of this study. Addition of NaCl salt practically does not affect the speed of heating and cooling of the coolant. The addition of bischofite worsens the thermophysical properties of water and shows a small density of heat accumulation. It has been experimentally established that after 3 ... 4 cycles of heating and cooling from a solution of technical bischofite, a dark yellow, insoluble precipitate forms, which creates problems during the operation. Significant increase in TES discharge time was obtained when testing ozokerite. All of the above substances have shown a stable state after 30 cycles of heating / cooling and indicate overcooling below the melting point by about 30 °C. Trihydrate sodium acetate shows no stable results. Subsequently, after 20 cycles of heating and cooling, it loses its properties.
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Colangelo, Alessandro, Elisa Guelpa, Andrea Lanzini, Giulia Mancò e Vittorio Verda. "Compact Model of Latent Heat Thermal Storage for Its Integration in Multi-Energy Systems". Applied Sciences 10, n. 24 (16 dicembre 2020): 8970. http://dx.doi.org/10.3390/app10248970.
Testo completoAbstract (sommario):
Nowadays, flexibility through energy storage constitutes a key feature for the optimal management of energy systems. Concerning thermal energy, Latent Heat Thermal Storage (LHTS) units are characterized by a significantly higher energy density with respect to sensible storage systems. For this reason, they represent an interesting solution where limited space is available. Nevertheless, their market development is limited by engineering issues and, most importantly, by scarce knowledge about LHTS integration in existing energy systems. This study presents a new modeling approach to quickly characterize the dynamic behavior of an LHTS unit. The thermal power released or absorbed by a LHTS module is expressed only as a function of the current and the initial state of charge. The proposed model allows simulating even partial charge and discharge processes. Results are fairly accurate when compared to a 2D finite volume model, although the computational effort is considerably lower. Summarizing, the proposed model could be used to investigate optimal LHTS control strategies at the system level. In this paper, two relevant case studies are presented: (a) the reduction of the morning thermal power peak in District Heating systems; and (b) the optimal energy supply schedule in multi-energy systems.
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Czerwiński, Grzegorz, e Jerzy Wołoszyn. "Influence of the Longitudinal and Tree-Shaped Fin Parameters on the Shell-and-Tube LHTES Energy Efficiency". Energies 16, n. 1 (26 dicembre 2022): 268. http://dx.doi.org/10.3390/en16010268.
Testo completoAbstract (sommario):
Changes in the energy sector, associated with the move away from fossil fuels, pose a challenge for appropriate thermal energy management in residential buildings. The important element to deal with the variability of renewable energy in thermal systems is latent heat thermal energy storage. Due to the low thermal conductivity of phase change materials, a number of techniques are proposed to enhance the heat transfer process. In this research, the global sensitivity of fin geometrical parameters on the melting and solidification times and energy efficiency of these processes was investigated. The computational model of the phase change was developed using the finite volume method with the enthalpy-porosity model and Boussinesq approximation. Numerical simulations were carried out according to the design of experiments technique. The multi-dimensional response surface was developed, and the multi-objective optimisation was done. The research shows that the melting process is most influenced by the position of the top fin (α angle) and the solidification process by the position of the bottom fin (γ angle). The angle of the tree fin (β) has a different effect on both processes, with the energy efficiency decreasing during melting and increasing during solidification. Maximum values for the energy efficiencies of melting (ηm=0.973) and solidification (ηs=0.988) were obtained for α=18.2∘, β=89.0∘, L=10.7mm and γ=21.0∘.
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Seeniraj, R. V., R. Velraj e N. Lakshmi Narasimhan. "Thermal analysis of a finned-tube LHTS module for a solar dynamic power system". Heat and Mass Transfer 38, n. 4-5 (1 aprile 2002): 409–17. http://dx.doi.org/10.1007/s002310100268.
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Khatri, Rahul, Rahul Goyal e Ravi Kumar Sharma. "Analysis of energy storage materials for developments in solar cookers". F1000Research 11 (11 novembre 2022): 1292. http://dx.doi.org/10.12688/f1000research.126864.1.
Testo completoAbstract (sommario):
Solar energy is accessible freely and can be utilized for many household and industrial applications. The consumption of solar energy for cooking applications has found significant success. Various innovations have been employed in facilitating cooking during off-sunshine hours. Thermal energy storage helps in overcoming the fluctuations in the supply of energy required for cooking during different time periods of the day. This study focuses on the different types of thermal energy storage mediums that are currently utilized in solar cooking. Primarily, oils and pebbles are most commonly used as sensible heat storage (SHS) while organic phase change materials (PCMs) are used as latent heat thermal energy storage materials (LHTES). The properties and performances of various SHS and latent heat storage (LHS) mediums have been compared for their suitable utilization. SHS materials are cost-effective but have lower thermal gradient compared to LHTES materials. The energy storage capability of LHTES is high while degradation with the increasing number of charging and discharging cycles is also considerable. The melting point should be close to the utilization temperature for being used as LHTES as thermal diffusivity of the materials greatly influences the performance of solar cookers. The cooking time is lower for solar cooking systems equipped with energy storage compared to non-equipped cooking systems. It is recognized that the use of energy storage has been proved as a huge advantage to solar cooking systems, however, the design, and heat transfer characteristics of the cooking vessel along with the storage material type and volume must be optimized in order to make this technology more influential.
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Khatri, Rahul, Rahul Goyal e Ravi Kumar Sharma. "Analysis of energy storage materials for developments in solar cookers". F1000Research 11 (21 febbraio 2023): 1292. http://dx.doi.org/10.12688/f1000research.126864.2.
Testo completoAbstract (sommario):
Solar energy is accessible freely and can be utilized for many household and industrial applications. The consumption of solar energy for cooking applications has found significant success. Various innovations have been employed in facilitating cooking during off-sunshine hours. Thermal energy storage helps in overcoming the fluctuations in the supply of energy required for cooking during different time periods of the day. This study focuses on the different types of thermal energy storage mediums that are currently utilized in solar cooking. Primarily, oils and pebbles are most commonly used as sensible heat storage (SHS) while organic phase change materials (PCMs) are used as latent heat thermal energy storage materials (LHTES). The properties and performances of various SHS and latent heat storage (LHS) mediums have been compared for their suitable utilization. SHS materials are cost-effective but have lower thermal gradient compared to LHTES materials. The energy storage capability of LHTES is high while degradation with the increasing number of charging and discharging cycles is also considerable. The melting point should be close to the utilization temperature for being used as LHTES as thermal diffusivity of the materials greatly influences the performance of solar cookers. The cooking time is lower for solar cooking systems equipped with energy storage compared to non-equipped cooking systems. It is recognized that the use of energy storage has been proved as a huge advantage to solar cooking systems, however, the design, and heat transfer characteristics of the cooking vessel along with the storage material type and volume must be optimized in order to make this technology more influential.
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Wallwork, Vince, Zhenghe Xu e Jacob Masliyah. "Processibility of Athabasca Oil Sand Using a Laboratory Hyd ro t ransport Extraction System (LHES)". Canadian Journal of Chemical Engineering 82, n. 4 (19 maggio 2008): 687–95. http://dx.doi.org/10.1002/cjce.5450820407.
Testo completo
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Seeniraj, R. V., R. Velraj e N. Lakshmi Narasimhan. "Heat Transfer Enhancement Study of a LHTS Unit Containing Dispersed High Conductivity Particles". Journal of Solar Energy Engineering 124, n. 3 (1 agosto 2002): 243–49. http://dx.doi.org/10.1115/1.1488669.
Testo completoAbstract (sommario):
A theoretical analysis is presented for the performance study of a Latent Heat Thermal Storage (LHTS) system that contains a phase change material (PCM) dispersed with high conductivity particles. The effect of fraction of dispersed particles in the PCM on energy storage time and heat flux is presented for laminar and turbulent flows, and also analytical expressions are presented for various quantities of interest to study the energy storage capabilities. The combined effect of thermal and flow properties of both the heat transfer fluid (HTF) and the PCM-mixture is also included in the study. It is observed that there exists an optimum fraction of particles to be dispersed in the PCM for maximum energy storage/extraction.
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Krastev, Vesselin Krassimirov, e Giacomo Falcucci. "Comparison of enthalpy-porosity and lattice Boltzmann-phase field techniques for the simulation of the heat transfer and melting processes in LHTES devices". E3S Web of Conferences 312 (2021): 01002. http://dx.doi.org/10.1051/e3sconf/202131201002.
Testo completoAbstract (sommario):
Thermal energy torage (TES) is a key enabling technology for the efficient exploitation of distributed generation systems based on renewable energy sources. Among the available options, research on latent heat TES (LHTES) solutions has been particularly active in the last decade, due to their ability to store and release high amounts of thermal energy in a very narrow temperature range. LHTES devices are based on phase change materials (PCMs), which act as thermal sinks or sources during their solid-to-liquid transition and vice-versa. As such, the development of reliable numerical tools for the prediction of the heat transfer and phase change characteristics of PCMs is of foremost importance, to help designing innovative and efficiently integrated LHTES implementations. In the present paper, the consolidated enthalpy-porosity (EP) method is compared to a novel lattice Boltzmann-phase field (LB-PF) algorithm in the simulation of a standard numerical benchmark for paraffin-like PCM melting problems. Performances and limitations of the two approaches are discussed, including the influence of model-related and purely numerical parameters. Outcomes from this study are used to confirm general guidelines for the application of well established methodologies, as well as to suggest new pathways for out-of-standard modeling techniques.