Heat Transfer In Phase Change Material Research Articles

Simulation study on the dynamic characteristics of natural circulation coupled phase change material for equal height difference passive containment cooling system

The passive containment cooling system (PCCS) plays a significant role in ensuring the safety of nuclear power plants. To further reduce peak pressure in the containment during a loss of coolant accident (LOCA), phase change materials (PCMs) are utilized to improve the system’s cooling effectiveness. The dynamic simulation model of PCCS has been developed using Apros software. This article focuses on examining the system’s dynamic characteristics related to various tube startup methods and comparatively analyzing the impact of different PCM thicknesses on heat transfer capacity. The results indicate that post-accident, PCM significantly suppresses peak pressure in the containment. Under the full tube startup method with 4 mm PCM, the peak pressure decreases to 1.75 MPa, whereas under the empty tube startup method, it is reduced to 1.69 MPa. With natural circulation empty tube startup method, PCM can reduce pressure change intensity in the containment but negatively affects natural circulation heat transfer. Although the full tube startup method underperforms the empty tube startup method on suppressing peak pressure, PCM can positively affect natural circulation heat transfer in the early stages of the accident. Empty tube startup offers the advantages of higher heat transfer capacity and lighter weight, making it the optimal choice for ocean nuclear platforms. Additionally, the higher peak power of PCM heat transfer under the empty tube startup method indicates that system can withstand larger thermal shocks.

Enhancing Thermal Energy Storage: Investigating the Use of Graphene Nanoplatelets in Phase Change Materials for Sustainable Applications

The adoption of phase change materials (PCMs) for thermal energy storage in low‐ and medium‐temperature settings is witnessing a notable surge. However, the lesser thermal conductivity (TC) poses a noteworthy challenge to PCM's heat transfer and storage capabilities. One of the noteworthy solutions to augment the TC is incorporating nanoparticles in the PCM. Nevertheless, nanoparticles often clump together after several cycles due to poor compatibility and weak interfacial strength. Functionalization methods have been proposed to address this issue, offering improved performance for energy storage applications. Herein, graphene nanoplatelets (GNP) and functionalized graphene nanoplatelets (FGNP) are dispersed into A70 PCM at mass fractions ranging from 0.1 to 1.0 wt% using two‐step method. Fourier transform infrared analysis confirms the successful integration of FGNP into A70 PCM without altering its chemical characteristics. Adding 1.0 wt% FGNP to A70 PCM increases its TC by 140.88%, with just a 3.02% decrease in latent heat enthalpy. However, incorporating pure GNP (1.0 wt%) improves TC by 48.83%. The engineered nano‐PCMs exhibit robust thermal and chemical stability even after undergoing 1000 thermal cycles, remaining unchanged up to 414.64 °C. This exceptional stability makes the formulated nanoenhanced PCM suitable for sustainable thermal applications.

EFFECT OF METAL FOAM FILLING POSITION AND POROSITY ON HEAT TRANSFER OF PCM: A VISUALIZED EXPERIMENTAL STUDY

The application of phase change material (PCM) in energy storage systems is limited by its low thermal conductivity. One of the effective methods to improve the thermal conductivity of PCM is to embed foam metal within it. To investigate the effects of foam metal infill position and porosity on the melting process and temperature distribution of PCM, a visualized experimental system study is built. Paraffin is employed as the PCM with a melting point of 62°C, while 85%, 90%, and 95% porosity copper foams are chosen in the experiment. The evolution of the liquid-solid phase interface and the temperature distribution in the PCM are recorded. Singlelayer filling schemes show that placing copper foam closer to the bottom accelerates melting, while double-layer schemes further optimize the melting time and temperature distribution. Additionally, decreasing the porosity of copper foam enhances heat transfer, shortening melting times. The study introduces a melting efficiency index, demonstrating that optimizing filling schemes and porosities improves the overall melting performance. When the copper foam with 90% and 85% porosity is arranged in the middle and bottom layers, respectively, the complete melting time is shortened by 38.2% and the maximum and average temperature differences are reduced by 30.0% and 45.2%, respectively, compared with pure paraffin. The findings contribute valuable insights into designing efficient PCM systems for thermal energy storage applications, emphasizing the importance of copper foam arrangement and porosity optimization.

Dynamic performance optimization of two-stage thermoelectric generator: Impact of different geometric leg shapes in each stage

This study presents a single-stage and two-stage thermoelectric generator (TEG) with different geometric shapes of the legs (rectangular, trapezoidal, inverted trapezoidal, rhomboid, and hourglass shapes). The various geometric shapes of the legs are combined between the two stages using phase change material (PCM) to cool the generator. The study's objective is to determine the optimal dynamic behavior of the TEG through the geometric design of the legs. The results show the behavior of the efficiency, the generated voltage, and the time it takes for the PCM to melt. The legs of the optimal two-stage system, Rhomboid-Rhomboid (G) and Trapezoidal-Inverted Trapezoidal (B), with a relationship γT=4, reach the best efficiency of 3.88% and 3.9% for the first and second stages, respectively, applying a heat flow of Qh=0.1W. On the other hand, the single-stage rhomboid system achieves the same maximum efficiency as the two-stage rhomboid system (G system), which is 3.9%. The temperature difference of each module is almost the same as that of the single-stage system. However, the voltage generated by the two-stage TEG is higher, and the efficiency remains practically constant compared to the single-stage system, which decreases with time. The effect of PCM's phase change process on TEG performance is analyzed, considering the characteristic heat transfer of PCM.

Analyzing competing effects between heat transfer area and natural convection to enhance heat transfer in latent heat storage

Phase change materials (PCMs) are effective means of storing thermal energy and to balance temporal supply-demand mismatch. To enhance heat transfer within the PCM, internal fins are often employed to increase the heat exchange area, but they usually suppress simultaneously natural convection reducing the performance of the PCM storage. To better understand these two conflicting effects and to find a better trade-off between the different heat transfer means, a comprehensive numerical study of PCM storage with different fin shapes (straight and sinusoidal wavy fins) and surface areas, but with equivalent volume fraction, was accomplished. The results show that increasing the surface area of sinusoidal fins improves only marginally the heat transfer, mainly because the flow velocity of natural convection along the normal direction of the solid interface is inhibited. The velocity normal to the solid interface was found to be the most critical factors to the overall heat transfer efficiency of the system and to the time needed to complete the phase change in the PCM container. The study clearly shows that to enhance the heat transfer in PCM, the effects from natural convection (direction and strength) play a more important role than the heat exchange surface area. To improve the thermal performance and efficiency of PCM storage systems both factors need to be combined in an optimal way.

Experimental heat transfer study of an enhanced storage medium

Phase change materials (PCMs) are suitable for storing solar energy due to their high-density energy storage and ability to operate in a wide range of temperatures. However, the lower thermophysical properties of PCMs limit their use in solar energy storage applications. Therefore, the incorporation of nanoparticles has emerged as a promising technique to enhance the storage density of PCMs.Extensive studies have been conducted on the measurement of thermophysical properties of both PCMs and nano-PCMs (PCMs with nanoparticles dispersed in them). However, there has been no comprehensive study covering the following aspects: (a) the measurement of thermophysical properties of NaNO3 (PCM) and nano-NaNO3 (nano-PCM), (b) solar energy storage of NaNO3 involving both sensible heat and latent heat in the same study, (c) the construction and implementation of an experimental rig capable of studying heat transfer in PCM and nano-PCM for solar energy storage applications (with a maximum temperature of up to 350 °C), and (d) investigating the effect of nanoparticles on large-scale solar energy storage systems. Therefore, the aim of this study is to experimentally investigate all of the aforementioned points. In order to develop and test these solar storage mediums, an experimental setup has been designed and manufactured, as mentioned earlier.Furthermore, limited studies have considered sodium nitrate salt (NaNO3) as a PCM. In this study, NaNO3 is used as the base material, and two types of materials are considered: PCM1, which consists of sodium nitrate salt (NaNO3), and PCM2, which consists of sodium nitrate salt (NaNO3) with 0.75 wt% iron oxide nanoparticles (Fe2O3) added. The experiments conducted involved both steady-state and transient conditions. The results showed that the addition of nanoparticles improved the charging and discharging by 25.6 % and 23.929 %, respectively. Moreover, the specific heat capacity and latent heat of the developed PCMs increased by 17.857 % and 9.97 %, respectively. These findings suggest that PCM2, with the presence of nanoparticles, melts and discharges energy faster compared to PCM1. Overall, this study contributes to the understanding of solar energy storage using PCMs and nano-PCMs, highlighting the potential benefits of nanoparticle incorporation in enhancing their performance.

Heat-dissipation performance of photovoltaic panels with a phase-change-material fin structure

Photovoltaic (PV) power generation can directly convert solar radiation photons into electrical energy, but PV panels produce a large amount of waste heat during absorption of solar radiation, significantly increasing the working temperature and reducing the photoelectric conversion efficiency of the panels. In this study, a phase-change material (PCM) is used to cool the PV panels, and fins are added to enhance PCM heat transfer. Using numerical simulation, the effects of fin spacing, fin height, solar radiation intensity, and ambient temperature on the heat-dissipation performance of the PV/PCM system were then studied. The fin–PV/PCM structure showed a good cooling effect. With decreasing fin spacing, the increase in the panel temperature gradually decreased. Fin spacing of 6 mm exhibited the best cooling effect, with the battery plate temperature reduced by 31.9 °C compared with that of the natural convection condition without fins. The increase in the panel temperature gradually decreased with increasing fin height, and the cooling effect of the panel improved significantly when the fin height was increased from 30 to 70 mm. The heat-dissipation effect of the fin–PV/PCM system was better with higher solar radiation intensity and higher ambient temperature. The results of this study will have important reference value for performance improvement of PV panels.

Employing perforated copper foam to improve the thermal performance of latent thermal energy storage units

The performance of latent thermal energy storage units (LTESU) is limited by the low thermal conductivity of phase change materials (PCM). Copper foam can enhance PCM's heat conduction, but its structure inhibits the internal natural convection. Based on this, the perforated copper foam was proposed to enhance the natural convection of PCM. The contrast experiment built three LTESUs (Namely, the LTESU only with the copper tube (LTESU-CT), the LTESU with full copper foam (LTESU-FCF) and the LTESU with perforated copper foam (LTESU-PCF). The melting and solidifying state, temperature distribution, and thermal efficiency were compared in three LTESUs during thermal charging and discharging processes. Results showed using copper foam could enhance the thermal performance of LTESU obviously and the perforated copper foam could generate the convective heat exchange, which had a time-average Nusselt number 34.1 % higher in LTESU-PCF than that in LTESU-FCF. Due to the reduced heat transfer area, LTESU-PCF had the lower thermal efficiency than LTESU-FCF, but its thermal storage capacity and release capacity were 6.4 % and 1.4 % higher than that in LTESU-FCF, respectively. It was confirmed that employing perforated copper foam could s enhance the natural convection and heat transfer of PCM significantly, but the perforation parameter still needs to be further explored to achieve higher thermal performance.

Evaluation of the solidification process in a double‐tube latent heat storage unit equipped with circular fins with optimum fin spacing

AbstractIn this study, the effect of fin number and size on the solidification output of a double‐tube container filled with phase change material (PCM) was analyzed numerically. By altering the fins' dimensions, the PCM's heat transfer performance is examined and compared to finless scenarios. To attain optimal performance, multiple inline configurations are explored. In addition, the initial conditions of the heat transfer fluid (HTF), including temperature and Reynolds number, are considered in the analysis. The research results show a significant impact of longer fins with higher numbers on improving the solidification rate of PCM. The solidification rate increases by 67%, 170%, 308%, and 370% for cases with 4, 9, 15, and 19 fins, respectively, all with the same fin length and initial HTF boundary condition. The best case results in a solidification time that is 4.45 times shorter compared to other fin number and dimension scenarios. The study also found that moving from Reynolds numbers 500 to 1000 and 2000 reduced discharging times by 12.9% and 22%, respectively, and increased heat recovery rates by 14.4% and 27.9%. When the HTF entrance temperature was 10°C and 15°C, the coolant temperature showed that the entire discharging time decreased by 37.5% and 23.1% relative to the solidification time when the initial temperature was 20°C. Generally, this work highlights that increasing the length and number of fins enhances thermal efficiency and the phase change process.

Effect of enhancement in metal foam pore density on heat transfer of phase-change materials

To explore the effect of metal foam(MF)pore density on the melting and heat transfer of phase-change materials(PCMs), a semi-cylindrical visualization experimental setup was established to experimentally study copper MFs with different pore densities coupled with paraffin wax. The results showed that as pore density increases, the melting time of the composite PCMs decreases compared to that of pure paraffin wax by 11.5%, 16.2% and 18.1% for pore densities of 5, 20, and 30 PPI, respectively. Composite PCMs with a pore density of 30 PPI exhibited fastest melting and lowest maximum temperature difference during melting. Considering the relative thermal energy storage(TES) capacity and relative TES rate, composite PCMs with a pore density of 30 PPI exhibited optimal overall thermal storage performance. Furthermore, heat conduction was the primary means of thermal transmission during the melting of the bottom paraffin. However, the melting of the upper paraffin was nevertheless influenced by natural convection, Hence, as pore size decreased, the influence on the weakening of natural convection became more significant. The results of the study provide guidance for the optimal design of latent heat storage devices for semi-cylinders.

Performance enhancement of a horizontal latent thermal energy storage unit with elliptical fins

The practical use of latent thermal energy storage (LTES) system is limited by the low thermal conductivity of the available Phase Change Materials (PCMs). In this study, the elliptical fin is proposed and applied to Horizontal Double Tube LTES Unit (HDT-LTESU) for improving the performance of thermal storage. Paraffin wax is used as PCM that is placed in the annulus between tube and shell. Three-dimensional numerical simulation based on enthalpy porosity method is performed to study the characteristics of the PCM melting/solidification and the performance of charging/discharging thermal energy of HDT-LTESU with different aspect ratios elliptical fins. The mechanism of enhanced thermal energy storage is also verified and analyzed by the entransy theory. It was found that the addition of elliptical fins can effectively improve convection heat transfer of PCM at the top and bottom of the annulus. Further, the high aspect ratio fins are more favorable for improving the comprehensive performance enhancement, and enhancement ratio can reach up to maximum 16.9% and 13.8% for melting and solidification, respectively. The entransy dissipation is reduced, and the phase change process of heat transfer is improved.

Thermodynamic responses of adaptive mechanisms in BiPV façade systems coupled with latent thermal energy storage

Ventilated building-integrated photovoltaic (BiPV)/phase-change material (PCM) façades have been applied and validated in building energy simulations; however, the dynamic thermal response of these façades has not been investigated. Notably, performance predictions and simulations for systems featuring natural airflows in the façade cavity are important for guiding the decision-making for energy-efficient buildings. To address this challenge in literature, in this work, numerical analyses were conducted, focusing on the climate adaptive reactions of a BiPV façade system coupled with a latent thermal energy storage system, based on a PCM. Numerical methods for determining the PCM heat transfer were evaluated, including their limitations. The thermodynamic reactions of two BiPV façade concepts were comparatively studied using two simulation domains: building energy simulations and computational fluid dynamics. The reliability of the theoretical methods was also evaluated. Good agreement between the simulation results and experimental data was noted through dynamic outdoor tests, empirically validating the study; standard statistical indicators were calculated and employed to assess the consistency between the experimental and simulation results. The used numerical approach can reliably predict the thermo-responsive capabilities of PCM-based BiPV façades with respect to the overall tendencies. The parameter variation techniques revealed modifications in the overall thermal and energy performance of the façade system. The most undesirable instance of overheating was predicted when using RT27; therefore, the PCM is considered inappropriate in this case.

Experimental and Numerical Study of Photo Voltaic Thermal Phase Change Material Heat Transfer Augmentation with Encapsulation of Embedded Material/Fins

Experimental and Numerical Study of Photo Voltaic Thermal Phase Change Material Heat Transfer Augmentation with Encapsulation of Embedded Material/Fins

Numerical investigation on non-Newtonian melting heat transfer of phase change material composited with nanoparticles and metal foam in an inner heated cubic cavity

In this paper, the non-Newtonian melting heat transfer of a latent heat thermal energy storage (LHTES) system composited with phase change material (PCM), nanoparticles and metal foam is numerically investigated inside an internal heated cubic cavity. The enthalpy-porosity method and power-law fluid model are adopted to model melting process for nano-enhanced PCM, and the Darcy-Forchheimer law and local thermal non-equilibrium model are assumed for metal foam. The effects of Rayleigh number (Ra), nanoparticle fraction (Φ), metal foam porosity (ε) and heater size on evolvement of solid-liquid interface, temperature of liquid PCM (θnf) and metal foam (θs), and full melting are addressed. The results reveal that with the increase of Ra, the convective heat transfer of PCM dominates the melting characteristic of the composite LHTES unit and accelerates the melting rate. With the increase in Φ, the non-Newtonian rheological behavior of liquid PCM is more pronounced with erratic convection flow due to increase of consistency parameter. Moreover, the convective heat transfer enhancement of θnf with addition of nanoparticles compensates for the conductive heat transfer enhancement of θs with increased ε. The internal heater size also plays an important role in the melting performance of composited PCM.

Heat transfer augmentation of triplex type latent heat thermal energy storage using combined eccentricity and longitudinal fin

The universe has shifted its focus from non-renewable to renewable energy sources from the last decade. The limited availability of fossil fuels and pollution is the reason behind the utilization of renewable sources. A major renewable energy source, solar energy, requires efficient thermal energy storage due to its intermittent nature. Phase change material (PCM) can store a large amount of heat by changing its phases. However, the low thermal conductivity of PCM makes its usage very limited. Hence, PCM's heat transfer augmentation technique using eccentricity and fin is studied in the present research. First of all, positive (lower displacement of the inner tube) and negative eccentricity (upper displacement of the inner tube) are studied in triplex type latent heat thermal energy storage (TTLHTES). Among the eccentricities of -15 mm to +15 mm, the eccentricity of +10 mm is found most effective in melting with a 27.63% reduction in melting time, while -3 mm eccentricity is found most effective in solidification with a 12.82% reduction in solidification time. The combination of fins with eccentricity is examined for melting and solidification enhancement. The combination of fin and eccentricity efficiently reduces melting time, with a maximum decrement of 67.37% with +3 mm eccentric TTLHTES with four fins. However, the only fin without any eccentricity is found more effective in solidification enhancement. The solidification time is reduced maximum by 46.15% using four longitudinal fins and no eccentricity. It can be concluded that fin and eccentricity must be coupled when melting time is required to enhance. However, only fin must be utilized when solidification is more critical.

Theoretical analysis of phase change heat transfer and energy storage in a spherical phase change material with encapsulation

Encapsulation of a phase change material (PCM) is a commonly used technique for providing mechanical and chemical stability, and enabling the manufacturing of PCM composites. However, thermal impedance of the encapsulating layer may adversely affect phase change heat transfer in the PCM. Experimental measurement of heat transfer and phase change in an encapsulated PCM is difficult, particularly for the case of micro/nano-encapsulation. As a result, development of robust theoretical phase change heat transfer models in presence of encapsulation is critical. This paper presents theoretical analysis of the problem of phase change heat transfer in a spherical PCM with an encapsulant layer. Temperature distribution in the newly formed phase and the encapsulant layer is determined by solving a spherical two-layer thermal conduction problem in non-dimensional form. The rate of phase change propagation is then determined from the temperature distribution. The effect of thermal contact resistance at the PCM-encapsulant interface is accounted for. Results are shown to be consistent with past work for the special case of no encapsulation. Results are also shown to agree well with numerical simulations. The use of only a few eigenvalues is shown to result in good accuracy. The effect of encapsulant thickness, thermal properties and PCM-encapsulant thermal contact resistance as well as external boundary condition on phase change propagation is analyzed. The non-dimensional model is used to address practical problems in phase change energy storage with typical materials and conditions. This work contributes an important theoretical analysis tool for a problem of much practical importance. Results from this work may help optimize and improve the performance of encapsulated PCMs for energy storage and thermal management.

Thermal management analysis of PCM integration in building using a novel performance parameter - PCM effectiveness index

Integration of phase change material (PCM) in walls and roof of a building is done to augment human comfort at places where variation of local diurnal temperature of ambient air is extensive. An exhaustive tool to study on year-round thermal effect due to solar radiation falling on a building is generally required to identify the correct PCM and the portion of a year that warrants better thermal management. The transient behavior associated with PCM heat transfer through building roof and walls vary in accordance with location and orientation of the building and the prevailing seasons. Hence, it becomes necessary to carry out a detailed analysis with the integration of PCM layers and to collect information with suitable theoretical approach as experimental study on energy performance of a building is time-consuming and expensive. In this paper, a 3-D building model has been developed and analyzed using ANSYS FLUENT for performing CFD analysis for comparing two identical buildings with and without PCM located at Chennai. The PCM was integrated in roof and walls of the building and analysis was carried out for different days of the year. A novel concept of PCM effectiveness index is introduced to measure the thermal performance due to PCM integration in building. This novel concept is useful for building engineers to measure the effectiveness of PCM integration and to select the correct PCM for thermal management in buildings at any location and time of the year.

Numerical phase change model considering crystal growth under supercooling

The supercooling of phase change material (PCM) significantly affects the heat release characteristics of heat storage systems. Therefore, accurate numerical modeling of the solidification process is key for studying heat storage. Few models considering the crystal growth of supercooling PCMs have been established; however, their accuracy under slight supercooling conditions is unsatisfactory. In this study, the implicit finite difference method was used to establish a two-dimensional PCM heat transfer model that considers the crystal growth process in detail. The growth rate of the crystallization front was used to control the crystallization start time at each node, and the solidification speed was used to manage the heating process once the crystallization was triggered. The accuracy of the model was verified by the experimental results obtained by melting, cooling, and triggering crystallization in a stable supercooled state and during cooling. Based on the simulations of a concentric tube PCM heat exchanger, the effects of several parameters on the heat release rate were investigated, such as the supercooling degree, the PCM initial temperature, and the inlet temperature of Heat transfer fluid (HTF). The results show that a large supercooling degree will accelerate the heat release rate of the PCM heat exchanger after the crystallization is triggered. An increase in the initial PCM temperature reduces the sharp increase in HTF outlet temperature caused by crystallization; a decrease in HTF inlet temperature also has the same effect. A comparison of various models demonstrated that the use of the crystallization front to calculate the PCM temperature directly causes up to 3% of the heat to be released earlier or later. Moreover, ignoring the crystal growth process causes up to 9% of the heat to be released in advance, and ignoring the supercooling causes an even greater error.

Unconstrained melting of phase change material in cylindrical containers inside hot water tanks: Numerical investigation and effect of aspect ratios

In this study, a numerical model with variable mushy zone constants was developed based on the enthalpy-porosity method for the unconstrained melting of phase change material (PCM) encapsulated in cylindrical containers inside hot water tanks. In particular, a method for dynamically determining mushy zone constants was established. Mushy zone constants were explicitly calculated for each element in the solid region and updated at each iteration in the solution procedure of the model. The model showed satisfactory performance, with a mean absolute relative error of 5.2% between experimental measurements and numerical results. Based on this model, the unconstrained melting process of PCM and the influence of the aspect ratio of the cylindrical container were investigated. Results showed that contact melting accelerated the heat transfer of PCM at the bottom region and further enhanced the natural convection of liquid PCM at the side region. Moreover, the aspect ratio exerted little influence on the heat transfer coefficient at side wall surfaces. The correlation between the total melting time and aspect ratio was also calculated. The peak total melting time occurred for an aspect ratio of 5.49, and the smallest total surface area corresponded to an aspect ratio of 2. Clearly, larger total surface areas do not necessarily result in shorter total melting time. Further analysis indicated that flatter containers likely to be preferable to slenderer containers in practical designs. In addition, increasing the percentage of the bottom surface area to the total surface area can increase the average heat transfer coefficient of latent heat storage units.

Nature-inspired triply periodic minimal surface-based structures in sheet and solid configurations for performance enhancement of a low-thermal-conductivity phase-change material for latent-heat thermal-energy-storage applications

Low-thermal-conductivity phase-change materials (PCMs) are often hybridized with high-thermal-conductivity metal matrices to achieve improved heat-transfer performance in latent-heat thermal-energy-storage (LHTES) applications. Owing to recent developments in additive-manufacturing technology that allow any complicated topology to be manufactured with ease, triply periodic minimal surfaces (TPMS) have gained considerable attention. These nature-inspired TPMS structures have already shown promising results in a variety of applications. TPMS structures can be developed in either sheet or solid configurations, both of which exhibit distinct architectures. Herein, a numerical study is presented whereby an organic PCM (docosane) is hybridized with two TPMS structures, namely, gyroids and I-graph-and-wrapped-packages (IWPs) in both sheet and solid configurations. The effective thermal conductivity of each resulting TPMS-PCM composite was calculated using steady-state simulations. Moreover, transient simulations were conducted under isothermal and isoflux conditions to assess the structures' heat-transfer performance. The obtained results were compared with those obtained using PCM only, and the incorporation of gyroid and IWP structures in both sheet and solid configurations was found to significantly improve the PCM's heat-transfer performance. For isothermal case under pure conduction, sheet-based configurations outperformed the solid-based ones with IWP sheet configuration being the best configuration with a PCM melting time of 118 s. However, upon taking buoyancy into account, IWP solid showed best performance with a PCM melting time of 108 s. Furthermore, the performance of each TPMS-PCM composite was found to depend on the type of structure incorporated into it and the value of the applied boundary condition. For isoflux case, IWP sheet showed the best performance in terms of temperature homogeneity in PCM domain as compared to the rest of the TPMS structures under both pure conduction case and the case with buoyancy effects. The PCM melting time in isoflux case was not found to have a strong dependence on TPMS structure type. In both isothermal and isoflux cases, Gyroid solid based TPMS-PCM composite showed the least performance. Moreover, the effects of PCM buoyancy are more pronounced in solid configurations than the sheet ones. Therefore, this study may serve as a design guideline to select appropriate TPMS configuration based on the applied boundary conditions/application.