Macro-encapsulated Phase Change Materials Research Articles

Development of Macro-Encapsulated Phase-Change Material Using Composite of NaCl-Al2O3 with Characteristics of Self-Standing

Development of Macro-Encapsulated Phase-Change Material Using Composite of NaCl-Al2O3 with Characteristics of Self-Standing

Energy Storage in Lightweight Aggregate and Pervious Concrete Infused with Phase Change Materials

This study explores the feasibility of utilizing pervious concrete (PC) incorporating diverse lightweight aggregates (LWAs) integrated with phase change materials (PCM) for applications where forced air cooling would be advantageous. The use of such a component provides latent and sensible heat that can cool forced air applications, offsetting ambient temperature increases that occur during the day. Macro- and microencapsulation techniques were used to incorporate inorganic PCM in the PC. The macro-encapsulation technique involved enclosure of PCM within a stable shell prior to addition into the concrete. The microencapsulation technique involved the impregnation of PCM into porous lightweight aggregate. To overcome the PCM reaction with the concrete constituents, an epoxy coating was utilized. The design of the PCM concrete mix and comprehensive laboratory assessment of porosity, water permeability, PCM absorption capacity, compressive strength, and microstructure of the LWAs are detailed. The test results indicate that LWAs have high PCM impregnation rates ranging from 32 % to 57 % by volume. The compressive strengths of PC using LWAs were reduced by 25 % to 65 % when using microencapsulation. The use of microencapsulation was found to reduce the pressure drop under air flow due to the increase in aggregate size as a result of the coating thickness. PCM-PC with a shell thickness of 100 mm, resulted in a pressure drop of less than 100 Pa at a velocity of 0.35 m/s. The use of macro-encapsulated PCM in PC was sensitive to the phase of the PCM, where the liquid phase reduced the compressive strength by 67 %. The failure occurred within the macro-encapsulated PCM at the liquid phase temperatures and at the interface between the encapsulated PCM at solid phase temperatures. The heat transfer provided by the LWA infused PCM when used in a packed aggregate bed or in PC, was shown to match expected latent and sensible heat estimates based on the thermal properties of the materials. This systematic investigation provides valuable insights into LWAs and PCM performance in pervious concrete, offering a comprehensive understanding of their interaction in cooling applications.

مراجعة على التقييم الاقتصادي لدمج المواد المغلفة متغيرة الطور في أغلفة المباني

The worldwide energy crisis has made energy-saving a topic of concern in almost every country. Previous research has explored the use of thermal energy storage materials (TES), such as phase change materials (PCMs), as an effective energy-saving technique. Among various immersion techniques, macro-encapsulation has proven to be efficient, safe, and convenient. However, choosing the right PCM system can be complicated due to the variety of available PCM types, encapsulation materials, and encapsulation shapes. Moreover, while macro-encapsulated PCM systems are efficient, their feasibility depends on several factors, including energy prices, economic situation, and climatic conditions. Therefore, this research aims to provide a comprehensive overview to help create a deeper understanding of the design and application of macro-encapsulated PCM systems. It explains the different types of PCM, encapsulation materials, and encapsulation shapes, guiding the selection for the most appropriate system regarding the surrounding environment. Additionally, it aims to present a guideline for conducting feasibility studies on energy-saving systems such as PCM. A total of 80 research papers covering the intersection between the thermal performance of PCM and the economic assessment have been categorized, studied, and analyzed in order to identify the most accurate method of assessing the system’s feasibility. By providing a base knowledge regarding the various types of each element of the system and the factors that govern the selection of each, this research will help engineers appropriately design the system. In addition, providing a detailed guideline to the assessment of the system shall aid the decision makers in determining the system’s feasibility which encourages its application. Finally, the research investigates and addresses the key issues for future studies.

Thermal performance of an active casing pipe macro-encapsulated PCM wall for space cooling and heating of residential building in hot summer and cold winter region in China

Phase change material (PCM) wall is expected to match the building type and its climate region effectively. In order to meet the space cooling and heating of residential buildings in hot summer and cold winter regions in China, a new active casing pipe macro-encapsulated PCM wall is proposed, in which the cold storage and heat storage PCMs are sealed between the inner pipe and outer pipe with no leakage. To obtain the optimal structure parameters and better thermal performance of the PCM wall, the mathematical model of the PCM wall is established and validated by experiment, and the effects of PCM filling pattern, structural parameter of casing pipe, water temperature in inner pipe and indoor setting temperature are simulated and analyzed. The results show that the optimal PCM filling pattern is to fill the cold storage PCM and heat storage PCM in the gap between the inner pipe and outer pipe separately; the optimal PCM filling thickness is 13 mm; the optimal structural parameters are inner pipe diameter of 20 mm and casing pipe centre spacing of 61 mm. The water temperature in the inner pipe and PCM energy storage/release time reasonably match the indoor setting temperature. Under the optimal operating conditions, the average PCM wall surface temperatures of 20.5 and 26.8 ℃ and the PCM wall surface heat fluxes of 45.9 and 57.2 W/m2 can be obtained in summer and winter conditions, respectively. The research provides an optimized casing pipe macro-encapsulated PCM wall system that can reliably and efficiently meet both the space heating and cooling demands of residential buildings in hot summer and cold winter regions in China.

Macroencapsulated Al-Si phase change materials for high temperature latent thermal energy storage

This research investigated the encapsulation of Al-Si alloy phase change materials (PCMs) for efficient thermal storage at high temperature. Two strategies, the direct powder formation route and in situ powder alloying formation route, were employed successfully. In the direct powder formation route, Al-Si alloy powders were spheroidized into spheres and encapsulated within Al2O3 powder shells with the help of organic binder, which were finally sintered at high temperature, forming Al-Si@Al2O3 capsules with cavities. Isostatic pressing at 50 MPa and 200 MPa were applied to the Al-Si cores, in order to optimize the cavity size. In the in situ powder alloying formation route, Al and Si powders were used as raw materials, which could be in situ transferred to Al-Si alloy inside the capsule during the sintering formation process. With the powders as the raw materials, the final capsules obtained after sintering could provide a buffer cavity inside the capsules, which could accommodate the volumetric expansion of the PCMs during melting, thereby mitigating the potential leakage and rupture of the capsules. Investigations into the melting-solidification cycles revealed the remarkable durability of the Al-Si phase change capsules. Isostatic pressure treatment decreased internal ineffective cavities, improving the heat storage density of the capsules. The Al-12Si(Ar)-200 MPa capsule exhibited superior thermal storage performance, enduring up to 1300 cycles. The Al-12Si core had a melting enthalpy of 479 J/g, while the thermal storage density of the phase change capsule within the temperature range of 500 °C–700 °C reached 496 J/g. The results underscore the significant potential of macroencapsulated Al-Si PCM, positioning it as a promising candidate for high-temperature thermal storage applications.

Multiscale Finite Element Modeling of the Effect of Macro-Encapsulated Phase-Change Materials on the Thermal Performance of Hydronic Floor Heating Systems

Phase-change materials (PCMs) are commonly employed in building service equipment to regulate indoor temperatures and reduce energy consumption. This study conducted multi-scale finite element modeling to analyze the steady-state and dynamic thermal behavior of a hydronic radiant floor heating system integrated with macro-encapsulated PCMs. It predicted performance values for hydronic floor heating with and without macro-encapsulated PCMs. The study assessed the impact of the PCM volume fraction, heating water temperature, capsule thermal conductivity, and shape on the thermal performance of hydronic floor heating through various finite element models. The predictive capability of the finite element model was validated using experimental data, showing good agreement. Although the inclusion of PCMs lowered the floor temperature, it improved temperature distribution and retained heat when the system was inactive. The PCM volume fraction significantly influenced the performance of the hydronic floor. However, the shape of the macro-encapsulated PCM and thermal conductivity of the shell had minimal effects in the studied case. For instance, increasing the thermal conductivity of the shell of the PCM capsule fifty times from 0.3 to 15 W m−1 K−1 resulted in an increase in surface temperature by 1.2 °C.

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

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

Effect of internal channels on energy storage in macro-encapsulated phase change material

Effect of internal channels on energy storage in macro-encapsulated phase change material

Numerical investigation and optimization of macro-encapsulated phase change material capsules in building roof slab

Globally, rising temperatures, together with the growing population, urbanization, and improved living standards, are driving a sharp increase in energy demand in the building sector. Space cooling and heating are the major areas of energy consumption. The building's roof slab thermal performance significantly impacts the heating and cooling requirements. Various studies investigated incorporating phase change material (PCM) to enhance the thermal characteristics of roof slabs. In this paper, the effective utilization of macro-encapsulated PCM in reinforced cement concrete (RCC) roof slab is investigated numerically. This research explored the effect of shape, heat transfer area, and thermal shading with the same amount of PCM on the impact of the reduction of inner roof temperature. Validation of the model with the experimental results is done for the current study. A total of 12 different cases, along with a reference case, were examined. In addition, the structural performance of the RCC conventional slab and slab with PCM capsules is also examined. Findings of the study include: cuboid with less thickness was found as the best shape. The increment in heat transfer area leads to better thermal performance while also providing the best case, with 3.2 °C and 1.2 °C peak and average temperature reduction. The thermal shading phenomenon was found to have positive results for the winter solstice. The deflection of all the slab cases was observed to be within the limits.

A Review of Recent Improvements, Developments, Effects, and Challenges on Using Phase-Change Materials in Concrete for Thermal Energy Storage and Release

Most concrete employs organic phase change materials (PCMs), although there are different types available for more specialised use. Organic PCMs are the material of choice for concrete due to their greater heat of fusion and lower cost in comparison to other PCMs. Phase transition materials are an example of latent heat storage materials (LHSMs) that may store or release thermal energy at certain temperatures. A phase transition occurs when a solid material changes from a solid state to a liquid state and back again when heat is added or removed. It is common knowledge that adding anything to concrete, including PCMs, will affect its performance. The goal of this review is to detail the ways in which PCMs affect certain concrete features. This overview also looks into the current challenges connected with employing PCMs in concrete. The review demonstrates a number of important findings along with the possible benefits that may pave the way for more research and broader applications of PCMs in construction. More importantly, it has been elucidated that the optimum PCM integrated percentage of 40% has doubled the quantity of thermal energy stored and released in concrete. Compared to conventional concrete, the macro-encapsulated PCMs showed thermal dependability, chemical compatibility, and thermal stability due to delaying temperature peaks. Furthermore, the maximum indoor temperature decreases by 1.85 °C and 3.76 °C in the test room due to the addition of 15% and 30% PCM composite, respectively. Last but not least, incorporating microencapsulated PCM has shown a positive effect on preventing freeze-thaw damage to concrete roads.

Influence of tank-to-particle diameter ratio on thermal storage performance of random packed-bed with spherical macro-encapsulated phase change materials

Thermal energy storage material is always filled in the packed bed system in a random accumulation manner, and there is an interrelationship between the tank-to-particle diameter ratio (TPDR) and the porosity. Therefore, in this paper, the packed bed latent heat storage system is constructed based on spherical macro-encapsulated phase change materials (PCM). To study the influence of TPDR on the thermal performance of a randomly packed bed, a transient two-dimensional axisymmetric symmetry continuous solid phase model is developed. The experimental and numerical results are compared to verify the accuracy of the model. The heat transfer and pressure drop characteristics between air and PCM capsules are analyzed in detail. The results indicate that the average porosity reaches the maximum at around TPDR≈1.7 position, which is about 0.7. In the same packed bed, when the TPDR is larger, the pressure drop is more affected. The diameter of the heat storage ball changes from 25 mm to 75 mm, the TPDR is reduced by 66.7%, the heat storage of the PCM is almost unchanged, and the heat storage capacity of the stainless-steel spherical shell is reduced by 72%, and the heat storage capacity of the entire heat storage ball is reduced by 12%.

Innovative wall package made of macro-encapsulated phase change material and geopolymer concrete: in-field thermal analysis for a Mediterranean climate

The paper proposes the experimental characterization of a wall package made of geopolymer concrete and phase change materials (PCMs) in the climate of south Italy. Data collected from May to July 2021 were presented by elaborating surface temperatures and heat fluxes with the introduction of several new indices as the thermal stress reduction amplitude, the percentage of time in melting range and the extreme surface solicitations. The results indicate that the PCMs reduce the thermal solicitation and preserve the geopolymer blocks. The indoor surface temperature can be lowered also of 3°C during the hours with maximum sol-air temperatures and this could contribute to reduce the local discomfort phenomenon. Globally, the heat flux monitored on the geopolymer layer behind the PCM is attenuated and its trend is more regular; this reduction implies a reduction of heat gains through the opaque building envelope and finally a reduction of the energy demand.

Experimental and numerical investigations on radiant floor heating system integrated with macro-encapsulated phase change material

Macro-encapsulated phase change material (PCM) with PCM as core and polymer as shell is reported an extremely stable energy storage medium in radiant floor heating system (RFHS). Herein, RFHS-based rooms with and without macro-encapsulated PCM are built, and the comfort and economy of the corresponding rooms are evaluated. Experimental results show that the room with macro-encapsulated PCM has longer thermal comfort time and slighter temperature deviation than without, according to the comfort standard. Then, a 3D unsteady heat transfer model is established and corrected by experimental data. Results show that macro-encapsulated PCM as temperature buffer layer regulates the heating-cooling rate of room and forms a semi-elliptic air radiant temperature zone. The room with macro-encapsulated PCM has lower daily electricity cost (c‾) of 0.2595 CNY/day and higher comfort time ratio of inside air (t‾) of 80.88%, decreased by 36.71% and increased by 15.43% than without, respectively. The thermal conductivities of shell and core of macro-encapsulated PCM are orthogonally optimized to be respectively 0.25 and 1.00 W/(m·K), with lowest c‾ (0.2480 CNY/day) and higher t‾ (85.47%), decreased by 4.43% and increased by 5.67% than pre-optimization. When the ambient temperature changes within −10∼10 °C, the input power of the room with macro-encapsulated PCM is orthogonally optimized to save c‾ by 35.91%∼39.39% than without.

Phase change materials incorporation into 3D printed geopolymer cement: A sustainable approach to enhance the comfort and energy efficiency of buildings

The advent of 3D printing has revolutionized conventional construction, offering cost-effective and fast construction of complex structures. Nevertheless, there remain challenges to be addressed regarding the effective integration of functional additives into 3D printing construction materials. Herein, we present a straightforward and environmentally friendly approach to promote sustainable buildings while reducing energy consumption. This is achieved by integrating Macroencapsulated Phase Change Materials (MEPCM) into a 3D printable geopolymer paste (GPP) derived from fly ashes. The research followed a systematic methodology, encompassing the assessment of fresh and hardened properties of geopolymer pastes with varying amounts of MEPCM, analyzing their thermal properties, and investigating the thermal performance by printing miniature houses without and with 20 vol% MEPCM. Notably, MEPCM demonstrated its dual functionality as a thermal energy management component and a viscosity modifier for 3D printable geopolymer paste. Overall, this study paves an innovative path toward sustainable construction, highlighting the significance of energy efficiency and waste reduction.

Macro encapsulated Cu-based phase change material for high temperature heat storage with characteristic of self-sealing and high durability

The objective of this research is to develop encapsulated phase change materials with applications exceeding 1000 °C that can be applied to concentrated solar power systems and industrial waste heat recovery. In this study, a macro-encapsulation phase change storage material with a copper-based core and an alumina-based shell was developed by slip-casting method and filling mixture of copper beads and Cu-40 %Al powder. The capsule was able to achieve self-sealing by local oxidation reaction at the entrance without leakage. After aging tests at 1100 °C for up to 1000 h, no leakage or damage was found and mass increase of the encapsulate phase change material was only 4.5 %, confirming the superior durability and oxidation resistance of the encapsulated phase change material. The heat storage density of the copper-based phase change material was evaluated as high as 147 J/g. The heat storage capacity did not decrease after 1000 h and ten cycles of aging. The mechanism of its high durability was explored by morphological observations and Raman spectroscopy. In the original material, a small amount of aluminum was oxidized with priority to alumina which significantly enhanced the durability of the capsules. This macro-encapsulated phase change material exhibits excellent thermal storage performance, as well as self-sealing and durability properties, which are of great significance for improving the efficiency of thermal energy recovery above 1000 °C.

A 3D pore-scale model for macro-encapsulated phase change material-metal foam hybrid energy storage system

A 3D pore-scale model is presented to predict the energy storage characteristics of a macro-encapsulated phase change material (PCM)-metal foam hybrid energy storage system. A single capsule with metallic shell filled with PCM-metal foam composite is considered. The energy transfer from a heat transfer fluid (HTF) flowing over the capsule, the evolution of temperature, and the melting of PCM in the metal foam pores within the capsule are simulated using the model. The model resolves the geometry of the individual pores in the metal foam and thus captures the local heat transfer between the metal foam and PCM, and the movement of PCM solid-liquid interface during melting inside each pore. Heat transfer from the HTF to the metal shell, metal foam, and PCM, and the resulting melting and energy storage characteristics are predicted by using the model. The effects of important geometrical parameters such as capsule size, capsule shell thickness, pore size distribution and porosity of the foam are studied. As a significant fraction of energy storage is in the form of sensible energy, the total energy storage with the variation of these parameters are quantitatively compared. For the range of parameters considered in the study, it is found that the increase in foam porosity from 50 % to 70 % increases the total energy storage by 5.41 % while increasing the average pore radius from 0.5 mm to 0.9 mm keeping the porosity 60 %, increases the total energy storage by only 1.54 %. Change in capsule inner diameter from 7 to 11 mm increases the total energy storage by 211.99 % although the energy stored per unit volume is reduced by 7.55 %. Similar effect is also observed for increase in shell thickness from 0.5 to 1.5 mm.

Macro-encapsulation of metal balls prepared by waste aluminum cans in ceramic capsules with reserved space

Phase change materials (PCMs) form the core of thermal energy storage (TES) for enhancing solar and industrial waste heat recovery. Metals have attracted growing attention due to their unique advantages, including high latent heat storage and high thermal conductivity. The application of metallic PCMs in TES is limited by the absence of appropriate packaging technology. Volume expansion during the solid-liquid phase can cause breakage of the protective coatings. This study proposes a “double-layer coating, recycling inner layer” method for the encapsulation of metallic PCMs. Waste aluminum cans (WACs) were selected as the PCM for cost reasons. The alloy balls prepared using the WACs were sequentially coated with an alkane mixture and ceramic slurry. The alkane mixture melts and discharges during the baking process, leaving a void for the phase-change volume expansion. The shell was gradually densified, and the metallic PCM was completely encapsulated after the heat treatment. The prepared MAEPCMs heat-treated at 1200 °C showed excellent mechanical properties, high heat storage capacity, and thermal cycle stability. The force required for compressive failure was approximately 2623 N. In addition, the total heat storage capacity reached approximately 198.6 kJ/kg at the temperature range of 600–700 °C, of which the latent heat accounted for more than 98.5%. There was no erosion between the alloy and the shell material, and the cumulative mass change was less than 8 wt. % after 600 thermal cycles. This study provides a structurally stable and low-cost technique for the preparation of durable macro-encapsulated PCMs with a high heat storage capacity and high thermal conductivity.

PCM-based ceiling panels for passive cooling in buildings: A CFD modelling

To relieve the upsurge of the energy demand associated to building indoor cooling, passive cooling employing phase change materials (PCMs) has been proposed as a promising technique to stabilise indoor air temperature fluctuation and reduce building energy demand. PCMs can exchange a large amount of latent heat during the melting and solidification processes, which can be utilised in line with the discharging and charging processes of a cooling system. The use of encapsulated PCM ceiling panels in buildings has immense application potential for passive cooling, which has attracted investigations in recent years. The geometry selection of the PCM ceiling panel is vital as it determines the exposed surface area to the surrounding air and the natural convection, and therefore the heat transfer rate to/from the PCM, which generally suffers from low thermal conductivity. This paper builds on the geometric optimisation of enclosed PCM capsules driven by natural convection, aiming to investigate the phase change behaviour and thermal performance of encapsulated PCM ceiling panels of different geometries. Here, the presented study focuses on the conjugate heat transfer phenomena through the surrounding air, panel shell, and PCM. A mixture of lauric, capric, and oleic acids was selected as PCM encapsulated in a thin-shell enclosure made of acrylonitrile butadiene styrene plastic, which forms the aesthetic panels attached to the ceiling. A computational fluid dynamics model was validated using full-scale experimental data and further employed to analyse the discharging process and design considerations of the PCM ceiling panels. The effects of various influencing factors were explored, such as panel volume, the initial temperature difference between PCMs and surrounding air, shell thickness, and geometrical features. The results indicate that the panel comprised of a pyramid array is more advantageous than the tetrahedral-based panel in terms of thermal performance, where the average melting rate is 20.8 % higher when the panel volume is 250 mL. In addition, tweaking the geometric features of the panel will largely impact its thermal performance as the effective heat transfer area and natural convection conditions are varied. Finally, it was found that hanging the panel to the ceiling will effectively enhance the heat transfer compared to directly attaching it to the ceiling. The results complement the knowledge body of macro-encapsulated PCM ceiling panels in terms of thermal performance and geometric optimisation. The effects of geometric features on the thermal performance of the PCM ceiling panels are studied in a more holistic manner.

Comparison of thermal conductivity of foamed geopolymers containing phase change materials

The aim of this work was to investigate the effect of Phase Change Materials on the insulation properties - thermal conductivity coefficient [λ], of fabricated foamed geopolymer panels. Phase Change Materials have been widely reported in the public literature, making them increasingly popular in recent times. PCMs have the ability to accumulate heat, which they can absorb or release due to thermal transformation, which contributes to energy efficiency. This paper presents the results of research on geopolymers based on fly ash with the addition of microencapsulated and macroencapsulated phase change materials (PCMs). Geopolymer composites were prepared by adding 0%, 5%, 10% and 15% PCM and the curing process was carried out at 60°C. Three different phase change materials with melting points of 28°C (MicroCapsPCM28 (Slovenia)) and 25°C and 42°C (PX25 and GR42 (Germany), respectively) were used. All the phase change materials used belong to the paraffin group. The obtained composite sheets were subjected to thermal conductivity tests in 3 temperature ranges (0-20°C; 20-40°C; 30-50°C). The paper also presents the density results of the foamed composites investigated, as well as the visual evaluation and the morphology of the porous structure using scanning electron microscopy. As a result of the study, it was found that foamed geopolymer composites without PCM addition have lambda coefficient values of 0.06 - 0.07 [W/m*K], while with the addition of phase change materials 0.07 - 0.085 [W/m*K]. The obtained test results give the potential to use these materials in construction as insulating materials. The use of these substances in building partitions results in the decrease of daily temperature amplitudes inside the building, as well as in the phase shift of the time of release of stored heat.

Experimental and numerical evaluation of phase-change material performance in a vertical cylindrical capsule for thermal energy storage

• Laboratory study of melting in a vertical cylinder heated from the bottom/side. • Directly visualized experimental results of convective and close-contact melting. • Original in-house numerical model encompassing all basic physical phenomena. • Melting patterns in a vertical cylindrical enclosure under realistic conditions. • Conclusions relevant for latent heat thermal energy storage units design. Thermal energy storage (TES) is considered vital for the advancement of renewable energy solutions. Latent heat thermal energy storage (LHTES) captures the thermal energy via a solid-liquid phase transition that occurs in phase-change materials (PCM). The PCM is usually encapsulated in some way. In this study, we consider PCM melting in a vertical cylindrical enclosure, that is a prototype of a capsule used in a future storage system. Moreover, we achieve the highly desirable close-contact melting (CCM), which speeds up the charging process significantly. First, different types of experiments are conducted to elucidate the melting behavior in an original experimental device that allows different types of melting in such configuration, demonstrating the prominent role of close-contact melting. The device main features are transparency of the melting chamber, separate heating methods for the periphery and the bottom of the chamber, and axisymmetric melting. To further investigate the heat transfer modes in the system, an in-house numerical model for combined convective and close-contact melting in an axisymmetric cylindrical geometry is validated with the experimental results. Then, this original model is used to simulate a vertical cylindrical shell in a practical configuration, namely, when an enclosure is exposed to fluid flow normal to its bottom. The results clearly illustrate the importance of close-contact melting for the overall melting process under practical conditions. The conclusions from this work would aid the design of LHTES installations which involve macro-encapsulated PCM.