Latent Heat Thermal Energy Storage Research Articles

Improving the charging performance of latent heat thermal energy storage systems using triply periodic minimal surface (TPMS) structures

The utilization of latent heat thermal energy storage (LHTES) using phase change materials (PCM) has attracted considerable attention due to their high energy density and thermal regulation. However, the inferior thermal conductivity of PCM has hindered their widespread implementation, triply periodic minimal surface (TPMS) structures could considerably ameliorate the energy storage utilization. TPMS structures offer escalated surface area and pore interconnectivity, which can enhance the apparent thermal conductivity and improve the performance of LHTES systems. This study focuses on investigating the performance and storage capabilities of three unique TPMS structures, namely Gyroid, IWP, and Primitive, at different relative densities and charging temperatures. The computational model is developed, verified, and validated with the relevant experiment results. A comparative analysis of the temperature distribution and liquid fraction evolution in TPMS LHTES units is carried out and compared to pure PCM LHTES. At a charging temperature of 80 °C, compared to the complete melting time of 7206 s for the pure PCM LHTES, the results demonstrate that the G10, IWP10, and P10-PCM LHTES achieve complete melting at 344 s, 276 s, and 368 s, respectively. This affirms the superiority of IWP structures in improving the melting rates due to their escalated surface areas and tortuous paths. The use of TPMS structures improves the total heat storage, heat storage rate, and volumetric heat storage density, while reducing the gravimetric heat storage density, compared to the pure PCM LHTES. The G10-PCM LHTES attains total heat storage, heat storage rate, volumetric, and gravimetric heat storage density of 2120 J, 6.16 W, 63.6 kWh/m3, and 227 kJ/kg, compared to 1910 J, 0.27 W, 57.3 kWh/m3, and 250 kJ/kg for pure PCM LHTES, respectively. Moreover, increasing the relative density of TPMS structures adversely reduces the total heat storage, heat storage rate, and volumetric heat storage density, and significantly increases the heat storage rates. As the charging temperature increases, the complete melting time is reduced and the charging performance indicators are improved, for the pure PCM and TPMS-PCM LHTES units.

Optimization of a finned multi-tube latent heat storage system using new structure evaluation indexes

The latent heat thermal energy storage (LHTES) is one of the most promising ways of storing solar thermal energy. Since the thermal conductivity of phase change materials are low, traditional shell and tube heat exchangers tend to develop dead zones. Therefore, structural optimization is essential, and a finned multi-tube design is recommended. In this work, nineteen structures for a heat storage tank are designed to explore the influence of different specifications of heat exchange tubes and fins on heat storage/release performance. After establishing 3D physical models, ANSYS/Fluent simulation and a two-step optimization for charging and discharging processes were conducted. Among these structures, N3-M3-D10.2 emerged as the most efficient during charging process in terms of reducing the complete melting time by 25 % and increasing the 3-h heat storage volume by 2.95 times; however, it shows low performance during discharging process, especially with a 2.24 times non-uniformity factor. In the four preferred structures, the benefit-to-cost ratio of N3-M3-D10.2 is 48 %–86.6 % higher than that of the others. The results also show that the number of tubes and fins are negatively related to the melting rate, and positively related to the solidification rate. Moreover, the influence of fin diameter is greater than that of fin number and tube diameter on heat transfer rate. The novelty of this work is not only lies in both considering the charging and discharging processes, but also in using dimensionless normalized indexes and different weights based on customers’ actual requirements for optimization.

Numerical analysis of the combined influence of fin shape and location on constrained melting of phase change materials in a spherical capsule with double fins

AbstractThis study presents a novel approach to investigating the combined influence of fin position and shape on the constrained melting behavior of phase change material (PCM) within a spherical capsule (S.C.) through numerical analysis. Unlike previous research, which predominantly focused on single fin shapes or positions, this work uniquely explores the impact of double, simple, and easily manufacturable fin shapes. A two‐dimensional computational model employing the enthalpy–porosity method assesses melting behavior, temperature distribution, and PCM flow. Numerous fin shapes, namely rectangular, trapezoidal converging, trapezoidal diverging stepped, inverse stepped, and triangular, are considered in the analysis. The study reports the influence of the location of two identically shaped fins on the thermal performance. The fins' cross‐sectional area and base thickness are kept equal in all cases. The thermal performance of an S.C.‐integrated fin system is evaluated by analyzing various attributes such as total saving in the duration of melting, enhancement ratio, and Nusselt number. The results indicate that the position of the fins has a more significant impact on melting performance than the fin shape. The best performance is achieved when fins are placed in the lower half of the capsule, followed by the center and upper halves, regardless of fin shape. For rectangular fins, shifting the position of the fin from the bottom half to the center increases the melting time by 24.7% and the top half by 68.3%. The shortest melting time of 93 min is observed for lower‐half rectangular fins, followed by center‐placed triangular fins (94 min). This study offers a theoretical foundation for optimizing the performance of different technologies using latent heat thermal energy storage systems such as packed‐bed, cascaded thermal energy storage systems.

Influence of the inner tube rotation and translation associated movement on the charging performance for the latent heat thermal energy storage exchangers

Latent heat thermal energy storage technology can reduce energy consumption in buildings and improve economic performance. The inner tube movement improves the charging performance of the horizontal latent heat thermal energy storage exchangers. In order to improve the charging performance, this paper proposed a new inner tube rotation and translation associated movement mode, wrote the user-defined function based on the dynamic mesh technique, and focused on the influence of three movement modes included rotation, translation, rotation and translation associated movement on the charging performance. The results showed that the associated movement further improves the charging performance, compared with static inner tube, the charging time decreases by 53.1 %, the time average charging rate increases by 110.2 % and the average velocity of the phase change material enhances by 132.3 % under the conditions of 0.2 mm/s translation velocity and 0.4 rpm rotation velocity, compared with rotation movement individual under 0.4 rpm, the charging time decreases by 47.8 %, compared with translation movement individual under 0.2 mm/s, the charging time decreases by 21.6 %. The paper can provide a new idea for the joint active and passive optimization study, and improve the energy saving and emission reduction effect in the building energy saving.

Heat transfer enhancement of PCM in the triple-pipe helical-coiled latent heat thermal energy storage unit and complete melting time correlation

Secondary flows induced in helical-coiled pipes significantly enhance the thermal storage performance of latent heat thermal energy storage units. This paper presents a three-dimensional model of a triple-pipe helical-coiled system to investigate the melting characteristics of phase change material within it. A correlation for the complete melting time was developed based on the simulation results. The findings indicate that the thermal-hydraulic fields of the heat transfer fluids and phase change material deflect from the vertical central axis at cross-sections. The secondary flows within the inner pipe are more effective in enhancing melting than those in the outer pipe. Melting performance improves with increasing inner pipe diameter, coil diameter (from 100 mm to 160 mm), inclination angle, or heat transfer fluid temperature, or decreasing helical pitch. The inner pipe diameter, helical pitch and heat transfer fluid temperature exhibit more pronounced influences. An inner pipe diameter of 30 mm, a coil diameter of 160 mm, a helical pitch of 80 mm, an inclination angle of 90°, a heat transfer fluid temperature of 360 K, and a heat transfer fluid Reynolds number of 2000, respectively produce a faster melting process. The developed correlation for the triple-pipe helical-coiled pipe thermal storage unit accurately predicts 96 % of the 45 data within ±11 %.

Benefits of zeotropic mixture for heat pump water heater with phase change material thermal energy storage

Integrating heat pump water heater (HPWH) into latent heat thermal energy storage (LHTES) with phase change material (PCM) has been recognized as a promising way to mitigate the energy use for heating water in the building sector. This paper uses zeotropic mixture R1234yf/R1234ze(Z) in HPWH and spherical PCM encapsulations in LHTES. The mathematical model is established and validated. Effects of zeotropic mixture composition, working fluid flow rate and heat transfer fluid (HTF) flow rate are discussed to reveal the instantaneous behaviors and overall performance of the integrated system. The results indicate that as the charging process progresses, the condensing pressure of the system steadily increases, leading to a decline in COP. By employing zeotropic mixtures, the system performance can be effectively improved, with the highest COP of 2.68 when the mass fraction of R1234ze(Z) is 70 %, which represents an 18.1 % and 6.8 % improved COP compared to R1234yf and R1234ze(Z), respectively. A smaller refrigerant flow rate or a larger HTF flow rate contributes to a higher COP. For heat storage capacity in LHTES, a higher mass fraction of R1234ze(Z) and a larger refrigerant flow rate are preferable, while a smaller HTF flow rate is beneficial. Finally, a multi-objective optimization is carried out. Results suggest that the best overall performance is achieved with a COP of 2.70 and a heat storage capacity of 629.24MJ, under conditions of the mass fraction of R1234ze(Z) at 70 %, a refrigerant flow rate of 0.28 kg/s, and an HTF flow rate of 0.46 kg/s.

Enhancing Heat Storage Capacity: Nanoparticle and Shape Optimization for PCM Systems

ABSTRACTPhase change material (PCM)‐based heat storage systems utilize the absorption or release of latent heat during a phase change of the storage material to store thermal energy. Nevertheless, the effectiveness of these systems is restricted by the shape and structure of their confinement, as well as the heat conductivity of the storage material. This work investigates a novel method to enhance the effectiveness of PCM systems by concurrently utilizing two techniques: the inclusion of nanoparticles and the alteration of the system's geometry. Introducing nanoparticles enhances the thermal conductivity of the storage medium while altering the shape, which improves heat transfer efficiency by adjusting the surface area available for heat exchange. RT‐35 was tested for use in latent heat thermal energy storage systems for space heating and cooling. With a melting point of 35°C, RT‐35 was chosen to moderate building temperatures by storing and releasing thermal energy for space heating and cooling. The results indicate that using nanoparticles and adjusting shape can greatly enhance the effectiveness of PCM systems. By incorporating Al2O3 nanoparticles, the melting time of the PCM was reduced by 20% compared to the pure PCM, and it is more efficient than the best case of shape modification. These findings indicate that including nanoparticles and modifying the shape are effective methods to improve the performance of heat storage devices. This technology's potential surpasses this study's limits and can be utilized in diverse applications, including solar thermal energy storage, district heating and cooling, and industrial process heat.

Improving a shell-tube latent heat thermal energy storage unit for building hot water demand using metal foam inserts at a constant pumping power

The phase transition heat transfer during the melting and solidification processes of phase change materials (PCMs) was modeled in a shell-tube thermal energy storage unit. For the first time, special attention was dedicated to the heat transfer enhancement on the heat transfer fluid (HTF) side by placing metal foam (MF) inserts in the HTF tube. The MF inserts on the HTF side were placed next to the fin bases to produce the maximum heat transfer enhancement. A two-temperature local thermal non-equilibrium model was applied to accurately model the transient heat transfer in the MF domains. To perform a fair heat transfer analysis and consider the hydrodynamic aspects of heat transfer, the pumping power for driving the HTF fluid was kept fixed. The finite element method with automatic time-step control was used to integrate the model equations. Results show that the insertion of the MF in the HTF tube enhances conduction heat transfer but reduces flow for a constant pump power. Using a small amount of MF provides a good flow rate and a convective heat transfer while using a large amount of MF provides good conduction heat transfer but a poor flow rate and convection. A moderate amount of MF inserts results in poor conduction and a poor flow rate, notably increasing the phase transition time. A 5 % MF insert could provide about a 13 % shorter solidification time compared to a 25 % MF insert. Thus, a well-designed and engineered MF insert configuration on the HTF side can reduce the phase transition time and improve the energy storage power.

Data-driven multi-fidelity topology design of fin structures for latent heat thermal energy storage

This work develops a data-driven multi-fidelity topology design (MFTD) method for designing fins in a latent heat thermal energy storage tube. The high-fidelity simulation resolves the actual solid-liquid phase change process using the enthalpy method, while the low-fidelity topology optimization (TO) simply considers the natural convection with Darcy flow. The above MFTD method is integrated into the framework of evolutional algorithm, and the variational autoencoder is introduced to generate new offspring. Fins for accelerating the melting and solidification processes at different Grashof number (Gr) are designed. It is found that when the fin volume fraction is low, the melt designs exhibit strong heterogeneity due to the strong convection, while the solidification designs are almost isotropic. Along with the increase of the fin volume fraction, the fins are first getting longer, then having more branches or sub-branches and finally becoming thicker. The superiority of the present data-driven MFTD method to the gradient-based direct TO method for solving optimization problems with strong multimodality has been demonstrated in this work. Results find that compared with the designs from direct TO, the MFTD melt design can further reduce the melting time by at least 27 % and 20 % at Gr = 3.3 × 103 and Gr = 3.3 × 104 respectively, and the MFTD solidification design can further shorten the solidification time by at least 9 %.

Vat photopolymerization for thermal energy storage applications using encapsulated phase change material suspended in photocurable resin

A novel approach to additively manufacture latent heat thermal energy storage heat exchangers through the development of microencapsulated phase change material (MEPCM) suspensions in photocurable resin for vat photopolymerization (VPP) 3D printing is presented. Using MEPCM addresses the leakage risks that have typically been associated with PCMs and subsequently makes the particulates a suitable additive for VPP 3D printing. In the current study, VPP was employed to fabricate functional composites with varying MEPCM mass fractions for thermal, rheological, microstructure, and chemical characterization. Microstructure visualization was conducted to assess the overall distribution of MEPCM within the 3D printed samples and to confirm the structural integrity of the encapsulated particles after printing. The influence of the base resin viscosity was explored by investigating two photocurable resins with different viscosities—a high-tensile UV photopolymer and an ABS-like resin—during the printing process. Thermal properties, such as latent heat of fusion, phase-change temperature, thermal conductivity, and decomposition temperature of the 3D printed samples were determined. Rheology was used to observe the effect of varying shear rates on the MEPCM-resin mixtures to identify the optimal viscoelastic properties for VPP 3D printing. It was determined that the ABS-like resin was able to contain a larger amount of PCM (40 wt%) while maintaining printability due to the lower viscosity of the corresponding pure resin. The 40 wt% MEPCM composite exhibited an average viscosity of 18,817 cPs, a maximum latent heat of fusion of 54.12 kJ/kg, and a 12.4 % reduction in thermal conductivity compared to the pure polymer.

Optimization of the annular fin arrangement in phase change heat storage units based on response surface methodology

Latent heat thermal energy storage (LHTES) technology is of increasing industrial interest due to its advantages such as high heat storage density and near-constant temperature during the phase change process. However, the latent heat storage technology is impacted by the low thermal conductivity of the phase change material (PCM), leading to delays and heat loss in the heat transfer process within LHTES. This limitation reduces the efficiency of heat transfer and diminishes the performance of the heat storage unit. To address this issue, this paper employs numerical simulation and response surface methodology to investigate different types of annular fin phase change heat storage units, aiming to derive the optimal configuration for enhancing unit performance. Therefore, the effect of fin type and number on the melting and solidification process is analyzed in detail. The research results indicate that among the five different types of fins studied, the total time required for the unit to complete melting and solidification is the least with type “e” fins, only 51.78 h, demonstrating that type “e” fins have the best effect on improving unit performance. For type “e” fins, when the number of fins n is 15, it can most effectively shorten the melting and solidification time of the phase change heat storage unit, reducing it to only 47.81 h. In addition, the response surface methodology was utilized to derive the optimal fitting formulas for different types of annular fins and to validate these formulas, and the error between the validation analysis and the numerical simulations was within 5%, which confirms the reliability of the fitting formulas developed in this study. This approach facilitates the selection of various annular fin models for subsequent experimental and simulation studies, thereby reducing the time and cost associated with model selection.

Electrochemistry of Phase-Change Materials in Thermal Energy Storage Systems: A Critical Review of Green Transitions in Built Environments

This article reviews recent research on phase-change materials (PCMs) used in thermal energy storage systems with the aim of enhancing their performance. The study explores various methods to improve heat transfer in PCMs, such as microencapsulation, infill materials, fins and nanofluids. Additionally, it evaluates techniques to boost heat transfer in latent heat thermal energy storage (LHTES) systems and investigates ways to increase thermal conductivity using porous and low-density materials. PCMs store thermal energy, making them suitable for use in solar energy systems when solar energy is not available. The need for eco-friendly alternatives to conventional heating and cooling in global construction and the significant energy consumption of buildings has driven research on this topic. As such, this study additionally examines current advancements in free cooling systems with latent heat storage to identify the key factors affecting their effectiveness. The findings show that using PCMs for overnight cooling maintains the room temperature within the comfort zone and reduces the cooling loads in various climates. Using machine learning methods, this study also compares recent advancements in the use of PCMs in various solar energy systems, including solar thermal power plants, solar air purifiers, solar water heaters and solar appliances. Results derived feature key factors crucial for the optimal selection of PCMs and the challenges associated with sustainable green transitions in built environments. HIGHLIGHTS This review provides an in-depth examination of PCM thermal energy storage systems. This study investigates the use of fillers, nanofluids, and nanoparticles for enhanced heat transfer. Analytical methods for boosting the PCM thermal conductivity are briefly outlined. Geometric design and thermal conductivity enhancement affect the Latent Heat Thermal Energy Storage (LHTES). The assessment also evaluates advanced free-cooling systems using the LHTES. PCMs help to store heat energy in solar systems and bridge supply gaps. GRAPHICAL ABSTRACT

Impact of key parameters on the numerical modelling of Phase-Changing phenomena in horizontal latent heat thermal energy storage

Numerous studies have focused on numerical investigations of the performance of the shell-and-tube Latent Heat Thermal Energy Storage (LHTES). However, many studies have often overlooked rigorous assessment of key parameters’ impact on the numerical simulation accuracy relative to experimental results. Therefore, this paper aims to develop a numerical model to track the solid–liquid interface during phase-changing phenomena in a horizontal LHTES system and investigate the effects of key parameters on the simulation accuracy. For this purpose, an experimental facility was built, and the numerical model was developed in ANSYS using the enthalpy-porosity method. During the simulation of the computational model, consideration was given to thermophysical properties (constant versus variable) of phase change material, contact resistance (zero versus nonzero), and the mushy zone constant (105, 5 × 105, and 106). The simulation results were compared with experimental data obtained from the in-house studies. The results showed that, compared to using constant thermophysical properties, employing variable thermophysical properties more accurately tracked the solid–liquid interface during melting. It substantially improved the simulation accuracy with a Root Mean Square (RMS) error less than 5 % for most of the temperature-measuring locations. Conversely, variable properties did not make a significant difference in the solidification process. The contact resistance due to the air gap was determined to be 0.035 m2·K/W for the current study. Furthermore, incorporating this resistance resulted in a more accurate approximation of the solid–liquid interface during melting, with RMS errors below 5 % across all locations. The study comparing different mushy zone constants recommended utilizing a slightly higher value of 106 for melting, whereas its impact on solidification was found to be insignificant.

Investigation of Factors Affecting Corrosion Mechanisms in Latent Heat Thermal Energy Storage Systems

Concentrated Solar Power (CSP) plants integrated with Latent Heat Thermal Energy Storage (LHTES) systems offer a promising solution for dispatchability, reliability, and economic concerns generally associated with renewable energy technologies. These systems, however, require an operational life of up to 30 years to compete with power plant systems operating on fossil fuels. This is a significant challenge due to the high temperatures and corrosive eutectic salts utilised in LHTES systems. Additionally, these systems and its subcomponents are expected to be under varying degrees of stress due to the diurnal cyclic temperature variations inherent in the plant’s operational cycle. Hence, it is crucial to understand the various factors that can affect the operational life of materials used in such applications and conduct thorough material compatibility studies to assess the combined impact of these operating conditions on corrosion mechanisms. This study presents a novel static immersion test approach using modified Compact Tension (CT) specimens manufactured from 316L to investigate the effects of Na2CO3:NaCl (59.45:40.55 wt.%) salt, elevated temperatures (700 ℃ for up to 1000 hours), and stress on corrosion induced in the alloy. The post-exposure results are characterised with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) shows that corrosion mechanisms are significantly affected by factors such as high operating temperatures leading to changes in both corrosion morphology and rate, high stresses causing localised preferential corrosion, as well as corrosive salt and oxygen availability affecting the type of corrosion induced.

Partitions influence on rectangular latent heat thermal energy storage unit performance during melting and solidification

The growing use of renewable energy sources demands efficient storage solutions due to their variability. Thermal energy storage systems utilising phase change materials are emerging as viable options to address this challenge. This study evaluates the impact of various partition types on phase change duration in thermal energy storage systems. The well-known and validated enthalpy-porosity algorithm implemented in the Fluent 2021R2 software was used. The shortest melting time was observed in the case with four vertical tubes and three horizontal partitions, which was 82 % shorter than in the reference case. The highest change in specific enthalpy of phase change material (252.5 kJ/kg) during melting was also noted for this system. The shortest solidification time was observed for the case with four tubes and two diagonal partitions, which was 72 % shorter than in the reference case. The greatest increase in the specific enthalpy of phase change material (240.4 kJ/kg) during the solidification process was also observed in this system. In conclusion, due to the thermal conductivity of the partitions, the temperature distribution throughout the domain becomes more homogeonous, thus contributing to more uniform heat flux extraction and supply throughout the process.

Conditions for economic efficiency of latent heat thermal energy storage systems at nuclear power plants

In conditions of uneven schedules of electricity consumption and construction of power plants using renewable energy sources, nuclear power plants will participate in regulating the unevenness of daily energy consumption. At the same time, nuclear power plants have high economic feasibility of operating with a maximum installed capacity utilization factor due to significant capital investments at a relatively low fuel price. The use of nuclear power plants to cover uneven energy consumption will reduce the possibility of a return on investment, which will only be realized with greatly inflated capacity charges. At the same time, the annual operating costs will increase significantly. A possible decrease in the economic efficiency of a nuclear power plant is due to the fact that, at the request of the system operator of the energy system, the NPP will be to reduce electricity generation during off-peak hours or sell electricity on the market at significantly lower prices. In this regard, the problem of increasing economic efficiency of nuclear power plants under conditions of uneven daily energy consumption becomes particularly relevant. The solution to the problem could be the accumulation of excess energy and its subsequent use. Previously, the authors developed a method of additional redundancy of auxiliary needs of nuclear power plants based on the use of low-power steam turbines. In the present paper, schemes for increasing efficiency of using low-power steam turbines at nuclear power plants when regulating the load unevenness in the power system using thermal energy storage systems based on the latent heat thermal energy storage are developed. The design characteristics of the accumulator as part of a nuclear power plant are determined to ensure operation of the heat storage system throughout the entire period of energy consumption. In this research, the lithium nitrate was considered as a phase change material. The technical and system conditions under which the maximum economic effect is achieved have been determined. The boundary conditions under which a return on investment is achieved are shown.

Self-growing bionic leaf-vein fins for high-power-density and high-efficiency latent heat thermal energy storage

Latent heat storage (LHS) has found extensive applications across various fields. However, large-scale deployment is still restricted due to the worse thermal charging performance of traditional LHS systems. In this research, the self-growing fins of the tube-shell LHS system are designed via the bionic topology optimized method to improve thermal storage performances, inspired by the structures and functions of leaf veins. Notably, the system installed with topology-optimized self-growing fins (T-FIN) demonstrates the shortest melting time, largest specific power density (SPD), and highest efficiency simultaneously. At the inlet conditions of 0.5 L min−1 and 358.15 K, the thermal charging time decreases by 46.4 % and 57.1 % compared with the systems equipped with traditional long-fins (L-FIN) and short-fins (S-FIN), while increasing the SPD by 80.6 % and 125.7 %, respectively. Moreover, the efficiency of exergy and entransy storage is 2.49 and 2.42 times, respectively, as large as those of the S-FIN. The intrinsic mechanism is attributed to enhanced synergy between the liquid-PCM temperature field and the flow field. Furthermore, outer tube shapes are optimized by the Genetic Algorithm for the first time, leading to a further decrease in charging time by 21.57 % compared with its original counterpart. These findings provide a valuable idea for designing efficient bionic LHS systems.

Numerical investigation of performance enhancement in a PCM-based thermal energy storage system using stair-shaped fins and nanoparticles

This study numerically investigates the melting performance enhancement of phase change material (PCM) in a latent heat thermal energy storage (LHTES) unit using a novel stair-shaped fin and nano-enhanced PCM. Different fin configurations are designed and their thermal performance is compared to traditional straight fins, while the total mass of fins is kept constant. Nano-enhanced PCM is prepared by the inclusion of CuO nanoparticles into RT82 as PCM. The simulation results reveal that the stair-shaped fins can notably enhance the efficiency of phase change compared to the traditional straight fins. The configuration with more extended fin close to the lower zone of the latent heat thermal energy storage unit had the best thermal performance. The full PCM melting time for the most efficient stair-shaped fin configuration is reduced by 52% compared to the straight fins. The combined impacts of the most effective stair-shaped fin design and nanoparticles on the phase change melting performance are evaluated. The inclusion of nanoparticles with volume concentrations of 2% and 5% into the pure PCM leads to 61% and 65% reduction in charge rate, respectively, as compared to the straight fin with pure PCM.

Research and optimization of heat transfer characteristics of heat pipe-coupled phase change energy storage system

Abstract Heat pipe coupled Latent Heat Thermal Energy Storage (LHTES) is a commonly used technique for improving heat storage, due to its advantages such as heat conduction, isothermal, and uniform temperature. Adding fins to the heat pipe can enhance energy storage efficiency and system performance. Although previous research has looked into how heat pipe layouts affect LHTES, there is still a dearth of research on fin geometry optimization for boosted heat transfer. In this work, we used ANSYS Fluent to simulate the consequence of fin placement upon the heating capacity of a Phase Change Material (PCM) based LHTES system. Through an in-depth analysis of the heat transfer mechanisms, in an effort to quicken the PCM’s solidification process, we adjusted the fins’ length and spacing. The LHTES system’s overall solidification time was greatly shortened by the optimized model, going from 18800 seconds to 8500 seconds, achieving a 54.79% enhancement in thermal transfer efficiency.

A shell-tube latent heat thermal energy storage: Influence of metal foam inserts in both shell and tube sides

Enhancing heat transfer in latent heat thermal energy storage systems is of utmost importance to facilitate the efficient absorption and release of thermal energy. The primary objective of the current study is to investigate the influence of a metal foam layer on heat transfer enhancement in both the heat transfer fluid side and the shell side. The research explores the incorporation of a fixed 30 % foam layer, which can either extend along the tube wall or penetrate deeper into the shell, moving away from the heat transfer fluid tube. A local thermal non-equilibrium two-temperature heat equation model is utilized to mathematically model the interactions within the metal foam embedded in the heat transfer fluid tube and the phase change material domain. The governing equations are solved using the finite element method. The results indicate that adjustments to the inlet pressure and the metal foam shape parameter (FL) can significantly reduce the melting time, with a variation of approximately 40 %. Specifically, at a constant inlet pressure of 750 Pa, the energy storage power at a 90 % charging increases from 32.2 W (FL = 0.75) to 48.7 W (FL = 1.37). A modification of FL shape parameter increased the power output by 34 %.