Latent Heat Thermal Energy Storage System Research Articles

Thermal storage performance of a novel shell-and-tube latent heat storage system: Active role of inner tube improvement and fin distribution optimization

This study presents a numerical analysis of the melting process in a shell-and-tube latent heat thermal energy storage (LHTES) system, featuring a twisted elliptical inner tube with annular fins. Utilizing paraffin as the phase change material (PCM) and water as the heat transfer fluid (HTF), this research examines the impact of varying twist degrees, fin quantity and fin distribution on the system's thermal performance during melting process. The analysis of the melting process includes complete melting time, temperature, and the contour of the solid-liquid interface. Notably, the study identifies that both fin quantity and distribution play a significant role in the melting process. The findings indicate that an optimal configuration, comprising a 720° twisted degree, 11 fins, and a base number a of 0.80, enhances the melting efficiency of the LHTES system by 156.44 % and reduces ineffective heat loss by 41.36 %. These results highlight the potential advantages of the twisted elliptical inner tube structure and propose an innovative approach with an exponentially non-uniform fin distribution, marking an advancement in the field of thermal energy storage.

Super‐liquid‐repellent thin film materials for low temperature latent heat thermal energy storage: A comprehensive review of materials for dip‐coating

AbstractWhen discharging latent heat thermal energy storage (LHTES) systems, performance is influenced by the formation and adherence of a solid layer of phase change material (PCM) on heat eXchange (HX) surfaces. Super‐liquid‐repellent thin films (STFs) may be able to reduce solidifying PCM adhesion on HX surfaces during discharging, delay PCM solidification to lower temperatures, and by modifying nucleation sites potentially enable long‐term seasonal thermal storage. Techniques employed previously to fabricate sintered polymeric STF coatings include chemical vapour deposition, dip‐coating, spray‐coating, spin‐coating, layer‐by‐layer (LbL) assembly, sol‐gel, anodizing, electrodeposition, electrospinning, so on. Dip‐coating is considered attractive for fabricating thin films on simple and complex surface geometries due to process maturity, scalability, flexibility and cost‐effectiveness. To identify suitable materials for preparing STFs on metal HX surfaces using the dip‐coating process, more than 200 journal articles published in English during the period 2010 to 2022 were reviewed and the potential role of STFs in LHTES applications was assessed. The review identified key areas and applications stimulating STF material developments and formulations. The dip‐coating of potential STF materials was classified under three major themes driving current research and development (R&D) activities, that is, high performance thin films, eco‐friendly thin films and fundamental research formulations. This review provides a platform from which to develop coatings and HX systems to enable the cost‐effective implementation of STFs for improved heat transfer in future mobile/stationery LHTES systems.

Lattice Boltzmann simulation of effects of realistic boundary conditions on volumetric radiation‐conduction melting of a novel cylindrical enclosure filled with phase change materials

AbstractIn this research, a novel solar latent heat thermal energy storage (LHTES) system, including the cylindrical enclosures filled with a phase change material (PCM), is proposed, which can be installed on the building windows to alleviate the drawbacks of traditional PCM‐filled double‐glazed windows, such as daylight hindrance and leakage. The lattice Boltzmann method (LBM) is used to simulate the volumetric radiation‐conduction melting of the PCM within a single cylinder of the proposed LHTES system with considering more realistic conditions such as convective boundary condition, shadow effect, and variable solar radiation angle compared with the available works in the literature. As such, several boundary conditions are assessed, and parameters such as cylinder diameter, extinction coefficient, scattering albedo, solar angle, shadow effect, and natural convection heat transfer coefficient are studied on the time history of the melting fraction and charging time. The results revealed that considering the applied conditions, such as convection heat loss to the environment and shadow, significantly affects the charging time of the system. It is shown that the charging time for convective boundary condition with , , and increases, respectively, by 11%, 30%, and 50% relative to a case with the insulated boundary condition without the shadow effect and 38%, 91%, and 175% compared with the insulated case with a 90° shadow.

Analysis and comparative assessment of charging dynamics in vertical multi-channel latent heat storage system with corrugated wavy channels

Latent heat thermal energy storage (LHTES) is a promising technology, but thermal response limitations caused by the relatively poor thermal conductivity of phase change materials (PCMs) remains an issue. In recent years, computational fluid dynamics (CFD) has proven to be a powerful and reliable tool in design optimization of different systems and problems in the energy sector. Building on that, the present work will use CFD to investigate the thermal performance enhancements achieved using vertical double-tube LHTES systems with multi-channel sinusoidal wavy geometries. The main parameters investigated here are the wavy channel height (H), pitch (P) and the number of channels (N) and the results are assessed in terms of melting rates and heat transfer coefficients. The analysis found that increasing the height from 1 mm to 3 mm, accelerated the phase change by 21 %, while reducing the pitch from 12.5 mm to 5 mm, enhanced the heat storage rates by 28 %. In addition, increasing the number of channels from 3 to 7 improved the charging rate by 64 %. Compared to a conventional straight channel, the enhanced wavy channel (N = 7, H = 3 mm, P = 5 mm) achieved 80 % higher thermal storage rate and 42 % faster charging time. The above findings provide new insight into the potential of utilizing compact vertical LHTES systems via customized wavy channels, with significant impact towards enhancing the existing thermal energy storage systems.

Performance evaluation and optimization of compact tube-fin latent heat storage system in phase change nanoemulsion discharge mode

The low thermal conductivity of phase change materials (PCMs) and the reduced heat transfer temperature difference along a tube both limit the thermal performance of latent heat thermal energy storage (LHTES). Herein, a compact tube-fin LHTES system based on phase change nanoemulsions was developed and the heat transfer process of nanoemulsion and PCM was numerically investigated. The effects of the heat transfer structure of the heat exchanger and the thermophysical parameters of the heat transfer fluid (HTF) on the cold energy discharge performance of the system were quantified. The optimized model reduced the discharge time by 24.4 % in nanoemulsion mode relative to water. Heat transfer improvement on the PCM side could be achieved by decreasing the fin spacing and tube spacing and by increasing the fin thickness. Such improvement reinforced the heat transfer enhancement of the nanoemulsion. The heat transfer mechanism was explained by the temperature distributions of the HTF and PCM along the tube. The phase-change thermostatic properties of the nanoemulsion and PCM contributed to the formation of dual-phase-change coupled heat transfer (i.e., the heat transfer process when the fluid inside the tube and the PCM filled outside the tube undergo a simultaneous phase change) within the LHTES, increasing the heat transfer temperature difference and the magnitude of the driving force. Increasing the phase change temperature difference accelerated the onset of dual-phase-change heat transfer, while increasing the PCM content prolonged the process. Briefly, this study provided operational and design assistance for LHTES systems in nanoemulsion mode with the intention to accelerate heat transfer rates.

Solar photothermal utilization of coupled latent heat storage: A numerical and optimization study

The combination of Organic Rankine Cycle (ORC) and Latent Heat Thermal Energy Storage (LHTES) is a novel approach for effectively utilizing solar energy. However, the influence of solar energy fluctuations on the heat transfer process of LHTES systems is not yet clear. In this study, a sinusoidal heat source is applied to a rotating triple-tube LHTES system, and numerical analysis and model verification are conducted. The parameters of the sinusoidal heat source are optimized using the response surface method. The effects of heat source amplitude, half period, and rotation speed on the heat release time and heat release rate of LHTES are investigated, and corresponding quadratic regression equations are fitted. The optimized structure (rotation speed = 0.5 rpm, amplitude = 7.5 K, half-cycle = 100) obtained through the response surface method reduced the solidification time by 12.45% compared to the initial structure (rotation speed = 0.3 rpm, amplitude = 7.5 K, half-cycle = 100). The average temperature response and heat release rate increased by 28.34% and 16.25%, respectively. The sensible heat and total heat release within one solidification cycle increased by 12.17% and 1.87%, respectively. This study lays the foundation for the optimization design of LHTES systems and the integrated application of Organic Rankine Cycle.

Stacked ensemble learning approach for PCM-based double-pipe latent heat thermal energy storage prediction towards flexible building energy

Dynamic performance prediction of the PCM-based double-pipe latent heat thermal energy storage (LHTES) system plays an important role for building peak load shifting. This study presents a stacked ensemble learning framework for the phase change performance prediction of LHTES systems. The proposed model has a two-layer structure involving base and meta models: Regression Tree, Support Vector Regression and Linear Regression. Sensitivity analysis has been utilized for the feature extraction considering possible geometrical and physical parameters of LHTES systems with a fixed PCM volume that can store 0.94 kWh of energy within 255 min. Case studies show that the proposed model outperforms the base models in terms of both prediction accuracy and robustness. Compared with base models, the proposed model has a maximum 7.82% (charging) enhancement in Mean Absolute Percentage Error (MAPE) over all-range data sets and a maximum 16.43% enhancement in MAPE for the initial discharging stage, and has more stable predictive results within the high accuracy zone (accuracy > 95%) with a maximum 7.3% (charging) increase in the distribution density over all-range data sets and a maximum interquartile range reduction of 25.6% (middle discharging stage) in Mean Absolute Error. Application of the proposed model achieved more building peak load reduction.

Thermal performance enhancement of multiple tubes latent heat thermal energy storage system using sinusoidal wavy fins and tubes geometry modification

In this paper, performance enhancement of a shell and multiple tube latent heat thermal energy storage system (LHTESS) is numerically investigated by implementing sinusoidal wavy fins and different geometrical designs of heat transfer tubes. The annular space of the shell is filled with the paraffin wax RT35 as phase change material (PCM) and absorbs heat from hot water through the multiple tubes. With the constant total cross-section area of all tubes and fins as the constraint condition, the effect of tube number and tube shape incorporated with the proposed fins on the heat transfer properties of PCM during the melting process is evaluated. The computational results demonstrate that the sinusoidal wavy fins can improve the phase change efficiency compared to the conventional straight fins. The double-pitch sinusoidal wavy fins decrease the total melting time by 9.5% compared to the straight fins for the single-tube case. As the number of HTF tubes increased from one to four, the complete PCM melting time decreased by 38.3%. Geometrical design alterations of heat transfer tubes from circular to petal-shaped are proposed to further improve the thermal performance of multiple tubes LHTESS. The melting rate of PCM is accelerated with an increase in the number of petals. The petal tubes with nine petals can save the charging time up to 24 % in comparison with the circular tubes in a four-tube case with double-pitch sinusoidal wavy fins, and up to 57% compared to the base case with a single circular HTF tube and straight fins.

Experimental investigation of thermal performance of vertical multitube cylindrical latent heat thermal energy storage systems.

The multitube design in the shell-and-tube type latent heat thermal energy storage (LHTES) system has received intensive attention due to its promising benefits in enhancing heat storage efficiency. In this paper, single and multi-tube shell LHTES systems were experimentally investigated. First, this study experimentally compared the thermal characteristics between a multiple-tube heat exchanger (MTHX) and a single-tube heat exchanger (STHX). The STHX's geometrical parameters coincided with a virtual cylindrical domain in the MTHX, being similar to the single-tube model formulated by simplifying the numerical solution to investigate the MTHX. The experimental data was then used to validate the simplified numerical model commonly used in the literature that converted the multi-tube problem to a single-tube model by formulating a virtual cylindrical domain for each tube in the MTHX system. The results showed that there was a noticeable difference in the thermal characteristics between the actual STHX and the virtual cylindrical STHX domain in the MTHX system. The comparison indicated that the simplified numerical model could not accurately reflect the thermal performance of the MTHX system. An experimental study or three-dimensional numerical modelling was required for the thermal analysis of the multi-tube problems. Second, the effect of tube number in the MTHX was experimentally investigated. It was found that an increase in tube number boosted both charging and discharging rates without inhibiting the natural convection. The five-tube configuration decreased the total charging and discharging duration by 50% compared to the two-tube one. Finally, the effect of heat transfer fluid (HTF) operating parameters on the system performance was evaluated on the five-tube MTHX system. The results revealed that the adoption of higher HTF temperature considerably improved the charging performance. The charging time decreased by up to 41% with the HTF temperature increasing from 70 to 80°C. Meanwhile, a variation in the HTF flow rate from 5 to 20 L/min showed a more pronounced influence on charging than on discharging due to the different dominant heat transfer mechanisms.

Design improvement of latent heat thermal energy storage in wavy channel enclosures using neural networks

This study conducts an in-depth analysis of latent heat thermal energy storage (LHTES) in a uniquely designed wavy enclosure filled with anisotropic copper metal foam saturated by paraffin wax. It is subjected to a high-temperature fluid stream on its top and bottom wavy walls, with its side walls well-insulated. The enclosure serves as a test bed to scrutinize the melting dynamics of paraffin wax as a Phase Change Material (PCM). The primary relations for conservation of mass, momentum, and energy were written as partial differential equations and solved using the finite element method. Among the novel aspects of this work is the exploration of wavy wall topographies defined by wave amplitude and wave number. The investigation reveals that an increase in wave amplitude generally boosts key parameters like melt volume fraction, stored thermal energy, and average temperature in the LHTES system, albeit at the slight expense of reduced heat flux at the top wavy wall. Furthermore, the study investigates the impact of anisotropic angles in the copper foam and uncovers that a 90° anisotropic angle remarkably elevates all performance indicators without requiring additional material or weight. Increasing the anisotropic angle from 0° to 90° reduces the melting duration from 3750 s to 2500 s, representing a 33 % decrease in melting time. Leveraging high-accuracy neural network (NN) models, the research also offers insights into the system's response to variations in control variables like wave amplitude, wave number, and porosity. This approach significantly reduces computational time, allowing for a comprehensive analysis of many design configurations that would otherwise be computationally prohibitive.

Improving heat storage performance of shell-and-tube unit by using structural-optimized spiral fins

Spiral fins have been widely used to enhance the heat transfer of latent heat thermal energy storage (LHTES) systems. However, owing to the inhomogeneous melting of solid-liquid phase change materials (PCMs) driven by convective heat transfer, the uniform spiral fins always have poor enhancing performance. In the present work, we proposed structural-optimized spiral fins, including optimized fin thickness, optimized fin height, and optimized fin pitch, to uniformly and efficiently transfer the heat from fins to PCM. By comparing their melting results with the original-uniform model, we found that negative models with larger fin volume at the bottom are more efficient in accelerating the melting process, and they can maximally reduce the complete melting time of PCM by 15.01% compared with the original one. On the contrary, the positive model with a smaller fin volume at the bottom slows down the melting of the LHTES unit. The heat transfer mechanism along the whole melting process is analyzed by comparing the thermal parameters (including liquid fraction, average temperature, average liquid velocity, and heat flux) of the original and optimized models. The enhancements of the negative models are owing to their benefits to the developments of convective heat transfer in the top region and conductive heat transfer at the bottom. According to the results of this paper, researchers can design novel high-performance LHTES systems using optimized spiral fins.

Incorporating Copper and Carbon Nanotube Nanoparticles into Phase Change Materials for Enhanced Thermal Management in Batteries

The primary objective of this study was to explore the impact of integrating nano-additives on heat transfer enhancement within an LHTES (Latent Heat Thermal Energy Storage) system. Our findings revealed that introducing a minimal amount of nano-materials (less than 5.0 vol%) into the Phase Change Material (PCM) led to a remarkable alignment between experimental correlations and mixture models. Furthermore, employing the mixing model allowed for the accurate prediction of outcomes. In the current context of scientific research, there is a strong endorsement for the widespread adoption of Electric Vehicles (EVs) as a sustainable alternative to Internal Combustion Engines (ICEs), crucial for advancing decarbonization and mitigating climate-related crises. Lithium-ion batteries are the predominant choice for EVs and various electrical devices. However, the operational challenges posed by high temperatures, impacting their lifespan, charge/discharge cycles, and the risk of thermal runaway, necessitate effective thermal management systems. Given this background, our study focuses on simulating the heat dissipation of a single cylindrical Li-ion battery cell employing a Nano-enhanced Phase Change Material (NePCM)-based cooling system. We also introduce a novel fin design in this work. Through comprehensive analysis, we examine the performance of battery modules utilizing PCM and NePCM at different discharge rates, both with and without the newly proposed fin design. Our research demonstrates that the incorporation of fins and nanoparticles into PCM significantly enhances heat transfer and reduces the charging time compared to the base PCM. Notably, carbon-based nanoparticles outshine their metal-based counterparts in terms of melting rate and maintaining a uniform temperature profile within the battery.

Trends in research on latent heat storage using PCM, a bibliometric analysis

Latent heat thermal energy storage (LHTES) is a particularly noteworthy thermal energy storage (TES) technology due to its high energy storage density. LHTES involves the use of phase change materials to store thermal energy, which can subsequently be used for heating and cooling applications as well as power generation. This paper outlines the techniques and tools employed to analyse the existing literature on TES and LHTES systems research. Bibliometric, a statistical approach to analysing written publications in specific fields of research, is used to identify significant findings and determine the course of scientific output. A strategic analysis of knowledge development is crucial for detecting opportunities and advancements within the field. This research offers valuable insights into the publication trends within the fields of TES and LHTES over the last three decades. Additionally, the study conducts a thorough examination of the geometric configurations of LHTES systems and their potential impacts on ongoing and future research. By tracking publication rates over 30 years, this study provides a comprehensive overview of how research in TES and LHTES has evolved. Understanding these trends helps researchers and policy makers gauge the growth and relevance of these fields in the context of energy storage and thermal management.

Numerical study on the discharging performance of a latent heat thermal energy storage system with fractal tree-shaped convergent fins

In this paper, an innovative fractal tree-shaped convergent fin (FTSCF) is embedded into a latent heat thermal energy storage system (LHTESS) to numerically investigate the parametric influences of FTSCF including FTSCF number N, maximum branching level m, length ratio α, branch convergence β, level convergence γ, rotation angle δ of the branch at the outermost level and branching angle θu on the discharging performance of the LHTESS under the fixed total fin volume. The results imply that increasing N, m, and α significantly reduces the complete solidification time τ of the phase change material (PCM). Further, the τ of the PCM demonstrates a pattern of initial decrease followed by an increase under the influences of β, γ, and δ, indicating the presence of an optimal FTSCF structure maximizing the discharging efficiency of LHTESS. Compared to the fins without branch convergence, the minimum τ of PCM within the LHTESS reduces by 4.33 %, 5.03 %, and 12.42 % by the branch convergence β when γ = 0.5, 0.707, and 1. In addition, the minimum τ of PCM monotonically decreases when θ1 = θ2 increases from 50° to 90°. The present work provides a technique to improve the discharging performance of the LHTESS by using fin convergence.

Experimental study on the thermal characteristics of a visualized shell-and-tube LHTES system at different endothermic and exothermic temperatures

This research developed a novel medium-temperature (up to 300 °C) latent heat thermal energy storage (LHTES) system, utilizing a compact shell-and-tube thermal exchange system containing spiral finned tubes, 220 kg of phase change material (PCM) was employed, enabling 44.52 MJ of heat storage, a visible window allowed to observe the phase change process and investigate the temperature variations in conjunction with thermocouples. The study analyzed the thermal traits and explored the impact of charging and discharging temperatures on the system's thermal performance.The outcomes indicated that natural convection gradually supplants heat conduction in the charging process as the primary heat transfer mechanism and a temperature stratification phenomenon emerges within the TES; during the discharging process, a contrasting behavior is observed. Employing charging-discharging temperature configurations of 290-170, 280-160, and 270-150 °C, the cumulative energy input to complete the cycle process is 63.59, 56.43, and 54.87 MJ, correspondingly, the released energy is 33.64, 33.41, and 33.57 MJ, yielding cycle efficiencies of 52.90, 59.20, and 61.20 %, respectively, with the charging temperature rising from 270 to 290 °C, storage time decreased 25.6 %, but lead to an 8.49 % decrease in heat storage efficiency, while the discharging temperature has a relatively minor influence on the system.

A CFD results-based reduced-order model for latent heat thermal energy storage systems with macro-encapsulated PCM

Macro-encapsulation of phase change material (PCM) is a promising approach to overcome a serious drawback of many latent heat thermal energy storage systems (LHTESSs): their low thermal power. Simulations are often used to support the design of these storage systems, but the simulation of the charging process of such an LHTESS with detailed CFD models is too computationally expensive. To obtain information about the behavior of a complete LHTESS, highly simplified system simulation models are usually applied. A new approach to create a reduced-order model is herein presented that aims to increase the accuracy of these system simulation models. The first step consists of performing a set of detailed CFD simulations of one capsule with different boundary conditions. The results are written into look-up tables that contain the charging power of one capsule as a function of the enthalpy stored and the boundary conditions. These look-up tables are then implemented into the reduced-order model. The temporal mean deviation of the energy content in the storage unit between experiments and the reduced-order model is only 5 % and the simulation time of the fastest reduced-order model was 5 s, while the CFD simulations took up to about two weeks on a workstation. Finally, for the conditions tested, the heat transfer fluid (HTF) does not have to be included in the CFD simulation, but can be replaced by a properly defined convective boundary condition. The capsule wall, however, needs to be included in the CFD model (especially for capsule wall materials with a distinctively higher thermal conductivity than the PCM) to account for the heat flow towards the bottom of the capsule supporting close contact melting.

The Effect of Different Configurations of Copper Structures on the Melting Flow in a Latent Heat Thermal Energy Semi-Cylindrical Unit

Utilizing latent heat thermal energy storage (LHTES) units shows promise as a potential solution for bridging the gap between energy supply and demand. While an LHTES unit benefits from the latent heat of the high-capacity phase change material (PCM) and experiences only minor temperature variations, the low thermal conductivity of PCMs hinders the rapid adoption of LHTES units by the market. In this regard, the current work aims to investigate the thermal behavior of a semi-cylindrical LHTES unit with various copper fin configurations (including horizontal, inclined, and vertical fins) on the melting flow. The novelty of this research lies in the fact that no prior studies have delved into the impact of various fin structures on the thermal performance of a semi-cylindrical LHTES system. The nano-enhanced phase change material (NePCM) fills the void within the unit. The warm water enters the semicircular channel and transfers a portion of its thermal energy to the solid NePCM through the copper separators. It is found that the system experiences the highest charging capability when the fins are mounted horizontally and close to the adiabatic upper wall. Moreover, the presence of dispersed graphite nanoplatelets (GNPs) inside the pure PCM increases the charging power and temperature of the LHTES unit.

A novel design of heating system using phase change material for passenger car cabin in cold starting conditions

In this paper, the use of exhaust waste heat energy stored in a latent heat thermal energy storage (LHTES) system for cabin heating of a passenger car at cold climate conditions was investigated by experimental and computational fluid dynamics (CFD). A liquid circulation system was installed for this purpose, consisting of two heat exchangers, one in the passenger car's rear compartment and the other in which the phase change material (PCM) in the LHTES system was stored. Commercial RT55 paraffin wax was used as PCM, and tap water was used as heat transfer fluid (HTF). Experimental and CFD analysis studies, which started at 283 K cabin interior temperature, were continued for 1500 sec (25 min). Before the experiments, the cabin interior of the passenger car was cooled up to 283 K with the air conditioning system, and the air conditioning system was kept on at a setting where the cabin interior temperature would remain constant at 283 K during the experiments. Thus, real cold climate conditions were provided for the experimental study. As a result, it has been observed that with the new cabin heating system, thermal comfort conditions for people are provided after the first five minutes, and this temperature can be maintained throughout the experiment. So much so that the cabin temperature increased from 283 K to 295 K in five minutes and reached approximately 297 K at the end of the experiment with a slow rate of increase. Furthermore, the difference in RT55 temperatures between the experimental and CFD analysis results is less than 3% during the cabin interior heating period.

Latent heat thermal energy storage in a shell-tube design: Impact of metal foam inserts in the heat transfer fluid side

The improvement of heat transfer in latent heat thermal energy storage (LHTES) system is a crucial task. In the current study, the impact of diverse metal foam (MF) layer arrangements on heat transfer fluid (HTF) within a shell-tube LHTES is explored. Six distinct cases (A-F) with varied MF coverage percentages and layer dimensions were assessed. The local thermal non-equilibrium model was utilized to take into account the PCM and MF temperatures. The finite element method was used for solving the partial differential equations. The impact of MF configurations and inlet pressures (250 Pa, 500 Pa, and 750 Pa) on the thermal energy storage/release was addressed. Cases A-C, featuring a 50 % MF concentration, exhibit shorter melting times than Cases DF, with decreasing MF concentrations. A higher MF concentration improves the melting process due to increased thermal conductivity and lower thermal resistance on the HTF side. Cases DF, with a centralized MF layer and decreasing concentrations from 25 % to 6.25 %, display progressively shorter melting times, suggesting that a lower MF concentration leads to more efficient melting. Solidification times also decrease with increasing inlet pressures across all cases. Reynolds numbers, influenced by average HTF tube outlet velocity, vary substantially across cases and inlet pressure differences. Cases A-C demonstrate similar Reynolds numbers for each inlet pressure difference, while Cases DF show a more pronounced increase in Reynolds numbers as the MF layer is reduced and flow resistance drops. Cases A (50 % MF layer) and F (6.5 % MF layer) provide the quickest charging and discharging times due to their unique combination of MF layer properties and inlet pressures. The study highlights the need to consider MF layer composition and inlet pressure when designing optimal LHTES systems for efficient energy storage/release.

Exploration of phase change material melt front during latent heat thermal energy storage charging

Latent Heat Thermal Energy Storage (LHTES) is a technology that utilises the phase change energy of a material to store energy and is used in multiple engineering disciplines. The use of this technology at high temperatures presents new material challenges that need to be considered. The exploration of Phase Change Material (PCMs) melting phenomena was completed with finite volume methods to model advection-diffusion interactions of different PCM classes undergoing pure substance melting. This study modelled a two-dimensional system with heat flux elicited by an isothermal wall – producing a melt front in the PCM. The investigation focussed on retention of a Solid Salt Barrier (SSB) between the liquid PCM and the storage tank wall. The importance of such a barrier is to mitigate the corrosion between the liquid PCM and the containment vessel. Results reveal the possibility of SSB retention through the adaptation of a LHTES system aspect ratio. A thermal storage inefficiency via unmelted PCM has been demonstrated and quantified when an SSB is maintained. Through varying geometry and PCM choice (carbonate, fluoride, and chloride eutectics), it was also shown that SSB retention is possible; however, when optimising the rate of internal enthalpy change, the corresponding aspect causes the SSB protected wall to be insignificant compared to exposed surfaces at the top and base. This paper provides insight into the implications of aspect ratio choice for thermal energy storage tank designs; as well, suggestions are made regarding exploration of divergent geometries to greater utilise the PCM energy storage capacity available in SSB systems.