Melting Of Phase Change Material Research Articles

Enhancing heat transfer efficiency in solar storage devices using eddy current structures and vibrations

This study introduces a novel phase change material (PCM)-based solar energy storage system integrating Tesla valve-inspired eddy current structures and mechanical vibrations to enhance thermal performance. By systematically optimizing the geometric design and vibration parameters, a 90°shunt angle was identified as the most effective configuration, achieving a significant 59.9% reduction in PCM melting time and completing the melting process in just 178 s. This superior performance was attributed to the generation of strong eddy currents, which disrupted the thermal boundary layer and enhanced heat transfer between the heat transfer fluid (HTF) and PCM. Mechanical vibrations (0.0003 m amplitude and 100 Hz frequency) further improved performance, particularly for shunt angles of 30°and 60°, where melting times were reduced by 13.4% and 13.36%, respectively, demonstrating the synergistic effects of geometry and vibration.The impact of natural convection was evaluated across a range of Rayleigh numbers (11,400 to 1,140,000), revealing that higher Rayleigh numbers enhanced heat transfer, especially for the 90°configuration. In contrast, shunt angles exceeding 90°showed reduced efficiency due to the thickening of boundary layers. Comparative analysis with existing heat transfer enhancement studies demonstrated the superior performance of the proposed system, which achieved greater reductions in melting time compared to designs using fin structures or optimized inclinations. This research provides valuable insights into the development of high-performance, scalable, and sustainable solar energy storage systems, bridging the gap between laboratory innovation and practical application.

Investigation of the influence of the air layer on the phase change material melting process inside a hemicylindrical enclosure: A numerical approach

The rapid growth in energy consumption and the associated difficulties have made thermal energy storage processes using phase change materials (PCMs) a prominent subject of study and development in the last century. The exceptional thermo-dynamic characteristics of this material enable it to accumulate substantial quantities of heat within very limited spaces. The present work involved a numerical investigation of the impact of the air layer on the melting time of paraffin wax RT42 (PCM) within an enclosure with a hemicylinder shape. The enthalpy-porosity relationship is analyzed numerically using ANSYS/FLUENT 16 software. The study included three distinct scenarios that examined the thermal and mass characteristics of paraffin wax within a hemicylindrical enclosure, with the curving wall of the enclosure being thermally insulated. The initial scenario lacked any air layer on the heated vertical wall, whereas the subsequent scenario had an air layer measuring 1 mm thick on the same wall. The third scenario contained an air layer measuring 2 mm within the same wall. The findings indicated that including a 1 mm thick air layer would result in a 125% extended complete melting time of paraffin wax. Similarly, including a 2 mm thick air layer would lead to a 225% rise in the complete melting time of paraffin wax. The presented outcome demonstrates the impact of ambient air on thermal storage units during the charging procedure.

Three-dimensional heat and moisture transfer analysis for thermal protection of firefighters’ gloves with phase change materials

Transient three-dimensional (3D) heat and moisture transfer simulations were conducted to analyze the thermal performances of the entire phase change material (PCM) integrated into firefighters’ gloves. PCM was broken down into several segments to cover the back and palm of the hand but to avoid finger joints to keep hand functions. Parametric studies were performed to explore the effects of PCM melting temperatures, PCM locations in the glove and PCM layer thicknesses on the overall thermal performance improvement of firefighters’ gloves. The study found that PCM segments could extend the time for hand skin surfaces (areas covered or not covered by PCM) to reach second-degree burn injury (60 °C) by 1.5–2 times compared to conventional firefighters’ gloves without PCM. Moreover, PCM segments could help mitigate the temperature increase on hand skin and glove surface after fire exposure.

Structure optimization of U-tube solar collector integrated with phase change materials

Solar collectors are significantly influenced by weather conditions, leading to a mismatch between thermal energy production and demand. To mitigate this issue, U-tube solar collectors integrated with phase change material (PCM) were investigated to store excess solar energy and regulate the temperature of collectors. This study investigates the effects of fin spacing and fin length on the heat transfer performance of these collectors under various conditions. Additionally, the impact of different collector tube lengths was analyzed. The results show that adding fins in solar collectors enhances temperature distribution uniformity and accelerates the PCM melting process. And the addition of fins to the U-tube produces faster temperature increase and significant improvement of temperature uniformity. In configurations featuring with fin length 20 mm and fin spacing 30 mm, the average PCM temperature decreased by 9.4 % and the liquid fraction decreased by 10.2 %, compared with non-finned. Smaller fin spacing or longer fins can improve heat transfer efficiency, and reduce PCM temperatures and liquid fractions. The 2L configuration exhibited optimal performance with an average PCM temperature of 330 K and a liquid fraction of 0.60 and achieved a significant reduction in time to reach 318 K by 47.9 % when compared to the L configuration.

Investigating the impact of fin configuration on phase change material melting in square cells: A numerical study

This investigation thoroughly explores the effects of different fin arrangements on the melting behavior of phase change materials (PCMs), specifically paraffin wax (RT42), within a 50 × 50 mm2 square cell. Three distinct cases are considered: Case 1 involves no fins, Case 2 incorporates straight rectangular fins, and Case 3 employs undulated fins. To simulate real-world thermal energy storage conditions, the PCM container is thermally insulated, preventing external heat leakage. The primary objective is to identify the optimal fin arrangement to enhance latent heat storage system efficiency by improving both melting and solidification processes. The novelty of this research lies in the detailed analysis of various undulated fin geometries and their placements, which have not been extensively explored in previous studies. Numerical simulations were conducted using the ANSYS FLUENT solver. The progression of PCM melting was evaluated via the ANSYS design modeler based on the finite volume method, incorporating transient heat conduction and free convection. The results demonstrate that optimized undulated fin configurations can significantly enhance the melting process by promoting uniform temperature distribution and improving heat transfer rates, thereby reducing melting time. This study provides valuable insights for designing efficient latent heat energy storage systems, contributing to advancements in energy management and sustainable technologies.

Bridge-grafted EG/BCN encapsulated PW with effectively improved thermal conductivity and battery thermal management performance

Although phase change materials (PCMs) have been widely utilized in thermal management of batteries, they still confront the challenges of high cost and low thermal conductivity. In this study, low-cost composite PCMs with high energy-storage capacity, thermal conductivity and outstanding thermal management performance were proposed by utilizing the synergetic porous structure of expanded graphite (EG) and boron carbon nitrogen (BCN) nanospheres through bridge-grafting method to encapsulate paraffin wax (PW), which effectively enhanced the anti-leakage and comprehensive performance. The incorporation of BCN nanospheres endowed the composite PCMs with extremely improved thermal conductivity of 1.611 W/(m·K), which was 421 % higher than that of pure PW. And the highly improved melting and crystal latent heat of the composite PCMs reached 184.37 J/g and 185.39 J/g, respectively, which also exhibited excellently thermal-cycling stability. The photo-thermal conversion efficiency of the composite PCMs was enhanced to 92.6 %. When applied to battery thermal management, the maximum temperature of battery wrapped with the composite PCMs was 11.9 °C lower than that of the batteries without PCMs, which confirmed an outstanding battery thermal management effect of the composite PCMs.

Comparative Analysis of Heat Exchanger Models for Phase Change Material Melting Process: Experimental and Numerical Investigation

ABSTRACTThermal energy storage systems using PCM offer promising solutions for efficient thermal applications. This study aims to provide valuable insights into the PCM melting process and compare the thermal performance of different heat exchanger models. The experimental rig is carefully designed to simulate a shell and tube heat exchanger with five longitudinal copper fins at specific conditions. Three distinct models of the heat exchanger, labeled Models A, B, and C, were examined for their heat transfer efficiency during the melting process. Numerical simulations were conducted for the three models and compared with experimental results. Model A represented the benchmark model. It had uniform fin length, location, and angle. Model B was the modified design aimed at enhancing melting progress. These modifications included a longer lower fin, a shorter side fin compared to the reference, and a lower fin angle to optimize heat transfer performance. Model C incorporates further design modifications, with a longer lower fin, a shorter top fin, and different lower fin location. Numerical simulations and experimental observations revealed significant differences in heat transfer performance among the three models. The average heat transfer rates, measured up to the critical decline point, are crucial parameters for practical applications. A comparison among the three models showed that Model B surpassed the average heat transfer rate up to the critical point of Models A and C by 10% and 4%, respectively, demonstrating its superior practical applicability.

Enhanced Efficiency of Latent Heat Energy Storage by Inclination

Latent heat storage (LHS) has emerged as a promising solution for addressing the challenges of large-scale and long-term energy storage, offering a clean and reusable system. Being in the developmental stage, and with only limited theoretical predictions being available, there is a need to enhance the efficiency of LHS systems. In this study, we use numerical simulations to study the melting process of a phase-change material (PCM) in a rectangular domain. A significant enhancement in the melt rate of the PCM is found by a simple inclination of the domain, with a 60% increase in melt rate compared to a standard square unit without inclination through enhanced heat transfer. We establish a theoretical relation for the optimal PCM melt rate, based on the inclination angle and the domain aspect ratio, outlining the optimal conditions for the PCM melt rate, which is solely dependent on the domain geometry. We further propose a heat-transfer model that predicts the optimal aspect ratio for achieving the maximum melt rate as a function of the Rayleigh and Prandtl numbers. Published by the American Physical Society 2024

Enhancing Solar Water Heater Performance Using Phase Change Materials and Modified Encapsulation Geometry

ABSTRACTSolar energy's abundant availability in India makes it a potential solution to meet increasing energy needs without harming environment. Solar water heating (SWH) systems are effective in converting solar radiation into heat for domestic and industrial applications. However, their inability to provide hot water during nighttime or off‐sunshine hours due to the intermittent nature of solar energy presents a challenge. Thermal energy storage, particularly using phase change materials (PCMs), has emerged as a solution. In this study, spherical ball‐type encapsulated PCM, specifically RT60, was incorporated into a solar water heater tank under variable atmospheric conditions. The PCM stores excess energy during daylight and releases it when the water temperature drops below the PCM's melting point. The results reveal a significant reduction in the temperature drop of water from 4.5°C to 1.4°C when utilizing PCM compared to conventional storage water tanks without PCM. Additionally, energy storage capacity is enhanced by 5.13% with PCM incorporation. Furthermore, modifying the encapsulation geometry to a rectangular shape enhances heat transfer and reduces temperature drop even further to 0.9°C, making it a promising approach to improving SWH system performance. This study highlights the possibility of enhancing encapsulation shape and applying PCM to enhance SWH system performance. The results highlight the possibility of increasing solar thermal systems' energy efficiency and usefulness, which will support sustainable energy sources.

Role of two isothermal cylinders towards three-dimensional flow and melting of phase-change materials

Recently, investigators focused on examining the melting of phase change materials (PCM) in regular two-dimensional or three-dimensional flow domains. At the same time, this topic still needs more study to get a better understanding of it. Also, such problems should be reported using the local thermal non-equilibrium (LTNE) model because the latent heat substances and the included porous elements have different temperatures. Therefore, this study examines the three-dimensional flow and melting process of phase change materials (PCM) within cubic enclosures filled with copper foam, using a local thermal non-equilibrium model (LTNE). The system includes two isothermal cylinders with different temperature conditions, varying distances, and radii, placed within the flow domain. The enthalpy-porosity approach is applied to model the PCM behavior, while the Brinkman-extended non-Darcy model accounts for high-velocity flow situations. A magnetic field is introduced to control the flow, with the Lorentz force acting opposite to gravity. The governing equations are solved using a home-developed code based on the finite volume method with the SIMPLE algorithm. Key parameters investigated include cylinder radii, Fourier number, Hartmann number, horizontal and vertical distances between cylinders, and Darcy number. The results are presented through streamlines, temperature distributions for fluid and solid phases, and profiles of the Nusselt number and average liquid fraction.

Study on the thermal storage properties of a spiral tube heat storage tank based on numerical analysis

IntroductionThe spiral tube heat storage tank is a highly efficient device designed for storing and releasing heat, utilizing a spiral tube structure. Its key advantages include efficiency, reliability, and flexibility, making it suitable for a wide range of conditions, from high temperatures and pressures to low temperatures and high vacuums.MethodsThis study aims to analyze phase change heat storage in spiral tube heat storage tanks using numerical simulation.ResultsIt explores the impact of varying water supply temperatures on heat transfer efficiency and the melting behavior of phase change materials within the tanks. Proposed enhancements, informed by numerical simulation results, seek to improve heat transfer efficiency. Simulation findings indicate that charging efficiency rises with increased temperature differentials, akin to sleeve-type heat exchangers.DiscussionCalculations suggest faster melting of phase change materials at the central position of the tank’s spiral tube, with slower melting near the vessel wall. Consequently, reducing the number of spiral tubes in the middle is suggested for future structural optimization.

Maximizing thermal management of photovoltaic-thermal systems with proper configuration of porous fins and phase change materials

Effective thermal management is crucial to enhance the performance and longevity of photovoltaic-thermal (PVT) systems. Phase change materials (PCMs) offer a promising solution for absorbing excess heat from PV modules; however, their poor thermal conductivity limits their effectiveness. This work explores the incorporation of porous fins within PCMs to improve heat absorption and thermal regulation in PVT systems. A detailed mathematical model is developed to analyze the effects of varying fin porosity (0.85–0.95), fin thickness (7–21 mm), fin height (7–21 mm), and fin inclination (−15°–30°) on PCM melting and PVT cooling performance. Results show that optimally configured porous fins significantly enhance PCM melting rates and heat extraction from PV cells. Incorporating optimal fins reduces peak PV temperatures by up to 5 °C compared to PCM alone at irradiation rate of 1000 W/m2. Meanwhile, reducing the fin thickness from 21 to 7 mm accelerates the overall PCM melting rate by 14 %. The cooling performance also shows a nonlinear increase with fin tilt angle, with maximum enhancement occurring at 15° downward tilt for the studied configuration. The optimized fin-enhanced PVT design achieves 3.1 % higher electrical efficiency and 15 % increase in thermal efficiency compared to conventional PCM-PVT systems without fins. Findings provide design guidance to harness porous fins for maximized PCM-based cooling of PVT systems.

Numerical analysis on phase change material melting process of a conical spiral tube energy storage tank

Numerical analysis on phase change material melting process of a conical spiral tube energy storage tank

Techno-economic optimization and feasibility of PCM-based seasonal thermal energy storage systems for district heating and cooling

Phase change materials (PCM) are an attractive seasonal thermal energy storage solution for load shifting due to relatively high energy density. Nevertheless, the choice of the right design parameters, such as storage size and phase-change temperature, is nontrivial, as these are tightly linked to the expected seasonal operation of the storage. This paper presents a combined design and operation optimization framework for sizing PCM-based seasonal thermal storage, which can capture dynamic behaviour of the storage in sensible and latent phases, and its impact on the efficiency of connected heat pumps and chillers. The proposed method, formulated as a mixed integer quadratically-constrained programming problem, was applied to a case study of heating-dominated district. It was found that the optimal PCM melting temperature equals to the heating demand supply temperature, thus removing the need of a heat pump to discharge the storage. The optimal operation of storage requires a full charging and discharging cycle of both latent and liquid phase. Higher CO2 emission price does not lead to a significant reduction of CO2 emissions, but the storage size does, leading to a higher heating coverage ratio of the storage, and consequently CO2 emissions and cost savings, which can be further enhanced with PV integration. The economic analysis indicates that, unless other benefits such as storage volume reduction are accounted for, PCM cost should drop by a factor 4 to make this solution economically viable for seasonal storage.

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.

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.

Optimization of thermal energy storage in phase change Material/Nano additive heat exchangers utilizing elliptical and circular tubes with and without fins

This study numerically investigates the enhancement of thermal energy storage systems using phase change materials (PCMs) combined with nano additives and finned tubes. The analysis compares elliptical and circular tubes with configurations of two or four fins to improve heat transfer efficiency. Finned elliptical tubes demonstrate a reduction in PCM melting time by up to 19 % at 50 °C, achieving faster melting compared to unfinned designs. Circular tubes with fins also exhibit a 12.6 % reduction in melting time, showing slightly higher thermal performance than elliptical tubes in certain conditions. The study considers different nano additives—graphene nanoplatelets (GnP), copper (Cu), copper oxide (CuO), and aluminum oxide (Al2O3)—to evaluate their impact on PCM heat transfer rates. Among these, GnP achieves the most effective thermal enhancement. The findings indicate that fin configuration, tube geometry, and nano additives significantly affect PCM melting and heat transfer dynamics. This research optimizes the design of PCM-based heat exchangers, contributing to more efficient and sustainable thermal energy storage solutions for various applications.

Assessment of Thermal Management Using a Phase-Change Material Heat Sink under Cyclic Thermal Loads

Phase-change materials (PCMs) are widely used in the thermal management of electronic devices by effectively lowering the hot end temperature and increasing the energy conversion efficiency. In this article, numerical studies were performed to understand how temperature instability during the periodic utilization of electronic devices affects the heat-dissipation effectiveness of a phase-change material heat sink embedded in an electronic device. Firstly, three amplitudes of 10 °C, 15 °C, and 20 °C for fixed periods of time, namely, 10 min, 20 min, and 40 min, respectively, were performed to investigate the specific effect of amplitude on the PCM melting rate. Next, the amplitude was fixed, and the impact of the period on heat sink performance was evaluated. The results indicate that under the 40 min time period, the averaged melting rate of PCMs with amplitudes of 20 °C, 15 °C, and 10 °C reaches the highest at 19 min, which saves 14 min, 10 min, and 8 min, respectively, compared with the constant input of the same melting rate. At a fixed amplitude of 20 °C, the PCM with a period of 40 min, 20 min, and 10 min has the highest averaged melting rate at 6 min, 11 min, and 19 min, saving the heat dissipation time of 3 min, 8 min, and 14 min, respectively. Overall, it was observed that under identical amplitude conditions, the peak melting rate remains consistent, with longer periods resulting in a longer promotion of melting. On the other hand, under similar conditions, larger amplitude values result in faster melting rates. This is attributed to the fact that the period increases the heat flux output by extending the temperature rise, while the amplitude affects the heat flux by adjusting the temperature.

Comprehensive effective thermal conductivity correlation and fast model for the melting of a phase change material inside a horizontal shell-and-tube unit

The effective thermal conductivity is a robust alternative to include the effect of natural convection during the melting of a phase-change material, while solving only the energy equation. With this approach, significant time savings may be obtained, maintaining satisfactory accuracy. However, it remains unclear how well the existing equations predict the enhanced conductivity for horizontal shell-and-tube heat exchangers, particularly in terms of accurately estimating the liquid fraction. In this paper, a simplified model for the melting of a phase-change material is developed based on the pure conduction formulation while considering natural convection. The model was solved using the finite volume method and implemented in Python. A previously validated computational fluid dynamics (CFD) model was used to calculate the enhanced conductivity, which was then applied to the simplified model. The simplified model was found to be 3500 times faster than the CFD model, with a maximum deviation of only 8.2%. Subsequently, existing correlations to predict the effective thermal conductivity were assessed. The results for the liquid fraction predictions indicated maximum deviations ranging from 33.6% to 144.8%, for predictors developed under melting conditions, and from 35.6% to 231.1%, for equations developed without considering phase-change. Further, new correlations, spanning all melting regimes, were proposed, revealing maximum deviations of 17.73% and 10.24% for the different scenarios evaluated. Therefore, the new correlations demonstrated to be the preferred choice to obtain more accurate models for the melting of phase-change materials inside horizontal shell-and-tube units.

Structural optimization and battery temperature prediction of battery thermal management system based on machine learning

Lithium-ion batteries significantly extend the driving range for electric motorcycles. The battery thermal management system (BTMS) is critical for achieving optimal battery performance. Moreover, precise battery temperature prediction is essential for efficient thermal management. Therefore, a battery thermal management system integrating air and phase change material (PCM) cooling is proposed. Initially, the impact of PCM height, PCM thickness, and air velocity on battery temperature is analyzed. Subsequently, with cost minimization as the objective and ensuring that the maximum battery temperature remains below a threshold, the Black Kite Algorithm (BKA) is employed to optimize the BTMS structure. Finally, a BKA-Convolutional Neural Network (CNN)-Self Attention (SA) model is introduced for battery temperature prediction. The results indicate that increasing the thickness of the PCM and air velocity facilitates battery heat dissipation but with diminishing marginal effects. An increase in PCM height enhances battery cooling at low air velocities but becomes detrimental at high air velocities. The optimized PCM height is 35 mm, resulting in a cost of 0.073 USD for the BTMS per battery. Additionally, the BKA-CNN-SA model achieved a maximum error of 0.45 °C on the validation set and accurately predicted battery temperature changes before and after PCM melting.