Phase Change Material Capsules Research Articles

Investigation on the heat transfer and charge/discharge performance of phase change material capsule emulsion based on nanoparticles enhanced thermal conductivity

Both internal encapsulation and external added nanoparticles have been employed in this study to enhance thermal conductivity and explore the corresponding heat transfer characteristics. Specifically, the correlation between thermal conductivity and capsule, nanoparticle content, as well as the enhanced heat transfer/thermal energy storage performance facilitated by internal encapsulation are demonstrated through numerical and experimental study. Furthermore, it compares key parameters like heat transfer and pressure drop, providing quantifiable evidence that the addition of nanoparticles, whether internally or externally, leads to an increase of thermal conductivity by 6.63 %/2.75 % (5 wt%) and 5.92 %/4.26 % (10 wt%), respectively. Internal encapsulation was observed to yield a more substantial enhancement in heat transfer. Moreover, higher capsule concentrations tend to induce an inverted concentration profile near the heat exchange wall, particularly at higher flow rates. Furthermore, encapsulating nanoparticles within these capsules enhances heat transfer performance, with the level of enhancement scaling with the nanoparticle quantity. Increasing the flow rate of emulsion from 0.4 m·s−1 to 0.6 m·s−1 in a horizontal tube resulted in a 26.67 % increase in heat transfer and a 41.55 % increase in pressure drop. As a result of the disturbed heating, thermal fluctuations of external addition showed more pronounced thermal fluctuations due to disrupted heating, while a internal encapsulation exhibited a more stable temperature distribution and superior heat storage performance.

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.

An experimental study of melting behavior of the phase change material in cylindrical capsules for thermal energy storage

Intermittent solar energy needs energy storage to store during its peak availability. Phase change materials (PCM) store heat energy under a near isothermal condition. The PCM has a high energy storage density but its low thermal conductivity reduces its melting. The present study uses three heat transfer fluid (HTF) flow configurations, outer, inner, and combined flow (inner and outer), with gradually decreasing PCM capsule sizes, to expedite melting in a horizontal cylindrical thermal energy storage container. Three copper PCM capsules are attached to the inner heat transfer tube. The HTF at 65, 70, and 75 °C are used to analyze the PCM melting. The HTF at 75 °C expedites PCM melting due to more temperature gradients. The energy efficiency during PCM melting is about 17 % for the outer, 15 % for the inner, and 24 % for combined flow. The PCM melts at 16, 20, and 10 min for outer, inner, and combined flow. The solidification characteristics were studied by passing HTF at 30 °C after melting. The PCM solidifies at 46, 62, and 24 min for outer, inner, and combined flow. The combined flow is suitable for the expedited PCM fusion due to enhanced heat transfer and hence suggested for flat plate solar collectors and heat recovery systems.

Effect of orientation and nanoparticle addition of a encapsulated phase change material on heat transfer in a packed bed thermal energy storage system – A numerical analysis

Thermal energy storage technology research is growing globally due to the increased awareness of the clean energy demand and limitations of fossil fuel commodities. The packed bed latent heat thermal energy storage (PBLHTES) system is one among it promising a greater number of applications like solar water heating, industrial waste heat recovery process, thermal power generations, thermal comfort of buildings etc., Due to the high latent heat capacities, available in wide temperature ranges and minimal volume change, solid-to-liquid phase change materials (PCMs) are more attractive than any other latent heat materials to use in the PBLHTES system. Although, the low conductivity of PCM restricts the heat transfer while the charging and discharging periods. Therefore, it is necessary to incorporate thermal enhancement techniques in a PBLHTES system to improve the melting rate of the PCM. In this work, it is attempted to carry the 2-D numerical analysis of PBLHTES system provided with encapsulated PCM staggered in the flow direction of heat transfer fluid. The numerical results are validated with the experimental work. The effect of the inclination of PCM capsules with the flow direction (0°, 2.5°, 5°, 7.5°, and 10°), the addition of Multi-walled carbon nanotubes (MWCNT) nanoparticles (0 %, 1 %, 2 %, 3 %, 4 %, and 5 %) on energy absorbed by the PCM are studied. Also, the contours of temperature distribution and liquid fraction of the PCM with time are presented. The results revealed that the temperature distribution of HTF rises when PCM spheres orientated to the HTF shifted from 0 to 2.5° later it reduces. Though HTF temperature rises, the PCM temperature, liquid Fraction and energy absorbed decline when the capsules inclined to the flow direction. This is mainly due to the reason that the HTF moves outwards from the flow direction and towards the edges of the container, which makes the HTF carry a more amount of heat without sharing with the PCM capsules. Therefore, these arrangements will be helpful to switch over the ideal high-temperature HTF at the outlet without charging the TES system and vice versa. An improvement of 13.16 % melting rate is observed from 0 to 3 % of a nanoparticle addition and only 4 % enhancement is noted from 3 to 5 % MWCNT deposition. The effect of nanoparticles on energy absorbed by the PCM is nearly constant after 3 % of Multi-walled carbon nanotubes (MWCNT) addition. Therefore, this is the optimum MWCNT volume concentration to be added. The maximum energy absorbed with 3 % MWCNT for 60 min of time is 98.7 kJ and 97 kJ which are 3.5 % and 3.65 % more than the pure PCM for the standard case (0°) and 2.5° angle of attack of EPCMs with the flow direction.

Thermal analysis of phase change materials storage in solar concenter

Thermal analysis of high-temperature phase change materials (PCM) is conducted with the consideration of a 20% void and buoyancy-driven convection in a stainless-steel capsule. The effects of the thermal expansion and the volume expansion due to phase change on the energy storage and retrieval process are explored. The used water to fill the void between two different wax paraffin and stearic acid spheres is considered as a potential PCM for concentrated solar power. The charging/discharging process into and from the capsule wall is simulated under different boundary conditions for laminar and turbulent flows. Computational models are conducted by applying an enthalpy-porosity method and volume of fluid method to calculate the transport phenomena within the PCM capsule, including an internal air void. A simplified two-dimensional model of the PCM contained within the spheres is constructed and thermal analyses are performed for the transition from solid to liquid states. Simulated charging process modes are compared with the theory. According to experiments, the temperature distributions from 40-60 mm without and with 60 mm with copper fin have different behavior. The paraffin takes less time than stearic acid for total transformation at a rate of 0.5. The size of the sphere increases over the amount of time and the phase of the sphere to complete changes as stearic acid expands more than paraffin during the transition. Inserting a rectangular fin, that is made from copper into the ball reduces the cycle time and increases output.

Assessment of the thermal resistance of novel roof structures incorporating nano-Phase Change Materials capsules under the influence of an external magnetic field

Controlling energy waste from different building bodies plays a key role in energy consumption management. Heat losses in buildings mostly occur through their envelopes and, more particularly, their roofs. Improving the thermal response of roofs is therefore an essential objective. In recent years, the incorporation of Phase Change Materials (PCM) into roof structures has proved to be an effective method in this regard, but still requires further optimization. Here, six different structures of a roof structure, in which PCM capsules have been placed in different positions and orientations, are considered to examine their role as a passive factor in controlling heat loss and increasing thermal resistance. Also, the effect of an external inclined magnetic field on the thermal behavior and energy loss is investigated. The thermal conditions in roofs are reproduced. Governing equations inside the solid parts and the PCM capsules are presented and solved numerically via the finite element method. Streamlines and isotherms, as well as plots of melted volume fraction and thermal resistance are presented. The main outcomes show that the magnetic field has a limited effect on thermal behavior due to the small size of the capsules. Orienting the capsules in the horizontal direction delays heat transmission, slows down the melting, and increases the thermal resistance of the roof structure. PCM melting can be further slowed down by moving the horizontal capsules down, close to the heated boundary. These results can be very useful for future roof designs in which capsules of PCM might be added.

Numerical investigation of the melting characteristics of spherical-encapsulated phase change materials with composite metal fins

A spherical phase change material (PCM) capsule with embedded composite fins for latent thermal energy storage is proposed and studied in this paper. A three-dimensional numerical model is established and validated by comparing with experimental data in the literature. The influences of the embedded fins with different structures, capsule size, and heating temperature on the melting performance are analyzed. Results show that the insertion of composite metal fins promotes the melting process owing to the extension of thermal surface. The fin with perforations exhibits higher energy storage performance as compared to the non-perforated one, which can be attributed to the reduction of the blockage effect as well as the increment in the filling volume of PCM. The punched fin with three perforations in each sheet is preferable to adopting in spherical PCM capsule in view of the less time required for completely melting and the higher energy storage capacity. However, as the size of capsule increases, the heat transfer enhancement contributed by the inclusion of the embedded fins reduces. In addition, the melting process can be accelerated significantly by raising the temperature of external shell surface from 340 to 360 K, while such improvement tends to be less pronounced for the further increase in heating temperature. This study can provide useful guidance for the optimal design of thermal energy storage system with spherical PCM capsules.

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.

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%.

Chloroplast-granum inspired phase change capsules accelerate energy storage of packed-bed thermal energy storage system

Packed-bed thermal energy storage (PBTES) systems utilizing phase change capsules have found extensive applications in thermal energy harvesting and management to alleviate energy supply-demand imbalances. Nevertheless, the sluggish thermal charging rate of phase change materials (PCMs) capsules remains a significant impediment to the rapid advancement of PBTES. Here, bionic PCMs capsules are proposed by mimicking the internal and external structure of chloroplast-granum. The heat transfer and flow characteristics of the bionic PCMs capsules in the packed-bed are analyzed by experiments and numerical simulations. The results illustrate that the chloroplast-fin type PCMs capsule exhibits significantly faster heat storage compared to the sphere type PCMs capsule. This improvement is attributed to the bionic folded shape and inner membrane structure, which generate multiple local vortices to enhance heat convection, and shorten the heat transfer distance between the capsule wall and center PCMs to facilitate heat conduction. The PCMs capsules are further filled into the packed-bed in a staggered arrangement, resulting in increased heat transfer area and enhanced disturbance flow as compared to an aligned arrangement. Consequently, the melting time of the packed-bed filled with chloroplast-fin type capsules is reduced by 33.2%, meanwhile the average exergy storage rate and exergy efficiency are enhanced by 48.4% and 8.3%, respectively, compared to the packed-bed filled with sphere type capsules. This research offers a novel approach for designing high-performance PBTES system utilizing bionic capsules.

Charging performance of structured packed-bed latent thermal energy storage unit with phase change material capsules

A mathematical model of the charging process for a structured packed-bed latent thermal energy storage unit with phase change material capsules is established. The thermal-hydrodynamic characteristics of the unit are investigated. The impacts of the heat transfer fluid inlet velocity, heat transfer fluid inlet temperature, initial temperature of the latent thermal energy storage unit, and diameters of the phase change material capsules are analyzed. The charging performance of a scaled-up latent thermal energy storage unit is studied. The numerical results indicate that the structured packing configuration of the structured packed-bed latent thermal energy storage unit influences the periodic flow characteristics of the latent thermal energy storage unit. The melting behaviors in each phase change material capsule are synchronous due to the excellent heat transfer capacity of the latent thermal energy storage unit. With the increasing initial temperature of the latent thermal energy storage unit, the duration of the charging process varies little, but the total heat storage capacity of the unit decreases. The decreasing diameter of the phase change material capsule significantly shortens the charging process of the latent thermal energy storage unit. The total heat storage capacities of the latent thermal energy storage unit with different phase change material capsule diameters are nearly the same. The heat storage capacity of the phase change material unit can be easily scaled up by adding more phase change material capsules and extending the phase change material capsule zone. The scale-up of the structured packed-bed latent thermal energy storage unit does not affect the charging time of the latent thermal energy storage unit.

Thermal performance analysis of latent heat thermal energy storage with cascaded phase change materials capsules under varying inlet temperature

Thermal performance analysis of latent heat thermal energy storage with cascaded phase change materials capsules under varying inlet temperature

Albizzia pollen-inspired phase change capsules accelerate energy storage of packed-bed thermal energy storage system

Packed-bed thermal energy storage (PBTES) system using phase change capsules has been widely applied for thermal energy harvesting and management to alleviate unbalanced energy supply and demand problems. However, the slow thermal energy charging is always a daunting challenge limiting its fast development. Here, a bionic phase change materials (PCMs) capsule by mimicking the natural structure of albizzia pollen is proposed. The heat storage performance and economy of capsules with different internal fin structures are investigated numerically and experimentally. The thermal charging of pollen-type PCMs capsules is the fastest, whose melting time prominently reduces by 19 %, 24 %, 41 % and 61 % compared to the plate-type, ring-type, column-type, and pure PCMs capsules, respectively. That is because the contact area between the skeleton and the capsule wall is increased and the average distance between PCMs and the heat transfer surface is shortened. The pollen-type capsules exhibit the best economy with the exergy efficiency is improved by 15 % compared to pure PCMs capsule. By optimizing the ratio of fin length to radius (L/R) to 5/6, the melting time can be further reduced by 62 % and the exergy efficiency can be improved by 16 % owing to the enhanced heat transfer rate in the center of the pollen-type capsules. A PBTES system is further built based on optimized pollen-based capsules, and faster heat storage rate is successfully demonstrated in experiments. These results provide alternative solutions for optimizing PBTES systems and improving their thermal energy storage performances.

Design and Scalable Fabrication of Liquid Metal and Nano-Sheet Graphene Hybrid Phase Change Materials for Thermal Management.

Here, a paraffin/liquid metal (LM)/graphene hybrid thermal composite material with a high thermal-conductivity as well as high latent heat is developed. The paraffin is encapsulated in calcium alginate, which produces leakage-free phase change material (PCM) capsules. LM is filled amongthe gaps of PCM capsules to enhance overall heat conduction. Graphene nano-sheets coating attains efficient heat dissipation because of its high spectral emissivity (>91%) in the spectrum of the mid-infrared region. The developed material is verified to have strong compatibility and durable stability. The composite is utilized as a thermal buffer (TB) for central processing unit thermal management to demonstrate the synergy of these superior thermal properties. In certain cases, active cooling normally used could be replaced by the developed TB without any energy consumption for thermal management, demonstrating a completely passive cooling strategy. Compared to traditional heat sink active cooling, general energy savings of 10.4-26.3% could thus be achieved by the developed composite in wider operating conditions, proving itspotential for more efficient and sustainable data center cooling alongside thermal management of other ground-based electrical/electronic equipment.

Effects of mushy-zone parameter on simulating melting and solidification phenomena inside a spherical capsule

The research on latent heat storage technology is beneficial for the large-scale popularization and application of energy storage technology. In order to solve the difficulties in the latent thermal energy storage (LTES) technology, numerical studies of the solid–liquid phase-change process of LTES units using the enthalpy-porosity method have become research hotspots. Among them, the importance of studying the mushy-zone parameter has been neglected. In this paper, a two-dimensional numerical model is created based on the enthalpy-porosity method to investigate the effects of different mushy-zone parameters within a wide range [104–108 kg/(m3·s)] on the melting and solidification processes of the spherical phase change material capsule. A comprehensive examination of the fluid flow and heat transfer characteristics during two phase-change processes is conducted. Meanwhile, the morphology of the solid–liquid phase boundary and the evolution of the mushy zone under different mushy-zone parameters are discussed in detail. It is worth mentioning that a new analytical perspective is innovated by proposing the “eccentricity phenomenon,” and the eccentricity law is further explored. The results show that the influence mechanisms of the mushy-zone parameters on the melting and solidification processes differ greatly. This paper emphasizes the significance of exploring the mushy zone and provides adequate guidance for future simulation studies to determine the mushy-zone parameter.

Experimental results of embedded phase change material capsules for increasing the performance of a wrapped heat pump water heater

To enhance the capacity of heat pump water heaters (HPWHs), high energy density phase change material (PCM) was used in two experimentally tested HPWH prototypes. Preliminary findings showed that in the PCM, stored thermal potential energy could be effectively converted into sensible heat in the water over a slight temperature difference, with the goal of increasing the capacity of hot water above a desired cut-off temperature. This exchange of energy results in an increased amount of hot water necessary for mixing at the location utilized by the consumer. It was also found that for a wrapped HPWH, there was an average increase of 27.7% in the capacity when 7.6 L of novel PCM filled spherical capsules were added to a 22.7 L tank downstream of the HPWH. In the second design (Beta), PCM capsules were immersed into the tank with a cylindrical geometry, and the UEF was increased by 5.5% over the baseline HPWH test result. As for the Beta design, heat loss was reduced significantly compared to a typical HPWH and the Alpha design. Food-grade PCMs were selected as appropriate. The novel encapsulation design increased the effective conductivity inside the capsule by adding metal fins.

Numerical simulation of heat transfer and melting process in a NEPCM: Using new fin shape

Nowadays, phase change materials (PCMs) have gained further importance as they are the main substance in thermal energy storage systems. The observations indicated that the rate of thermal storage is related to the rate of melting and thermal distribution within these materials, where it has been concluded in almost works that convection is an effective contributor to boosting heat transfer, mainly in the upper layers of PCM capsules unlike in the lower layers. This article aims to accelerate heat distribution and fusion rates of NEPCM inside rectangular capsules by using novel fins in the shape of dendrites planted in the lower region of the capsule. Three different cases are considered and analyzed; in the first case without fins, in the second case fin branches length is decreasing downward (type 1), and in the third case, fin branches length is increasing downward (type 2). The porosity enthalpy method is used in modeling heat transfer during phase change. The impact of nanoparticles volume fraction is investigated by three different concentrations (ϕ = 0, 3%, and 6%). The findings indicated that enriching the weight of the nano-elements and using fins yield improving the thermal conductivity characteristic of the base PCM, besides, integrating the fin in the lower region of the PCM, i.e. under the heat source extends the heat transfer area, particularly where the dominated heat transfer in the low region is conduction, thereupon, as a result, both the thermal resistance and fusion time diminish. The maximum heat transfer rate and shorter fusion time were achieved by case 3 (fin type 2) with ϕ = 6%, where, fin-type 2 increased the melting rate by 33% compared to no fin case due to the largest branch of the fin is located in the bottom area, whereas the conduction is more dominated as approaching the lower wall. Finally, it is recommended to further investigate the dimension characteristic of this new kind of fins, for instance, the number of branches, spacing between the fin branches, and the branches' angle.

Wet spinning of strong cellulosic fibres with incorporation of phase change material capsules stabilized by cellulose nanocrystals

Incorporating a phase change material (PCM) into fibres allows the fabrication of smart textiles with thermo-regulating properties. Previously, such fibres have been made from thermoplastic polymers, usually petroleum-based and non-biodegradable, or from regenerated cellulose, such as viscose. Herein, strong fibres are developed from aqueous dispersions of nano-cellulose and dispersed microspheres with phase changing characteristics using a wet spinning technique employing a pH shift approach. Good distribution of the microspheres and proper compatibility with the cellulosic matrix was demonstrated by formulating the wax as a Pickering emulsion using cellulose nanocrystals (CNC) as stabilizing particles. The wax was subsequently incorporated into a dispersion of cellulose nanofibrils, the latter being responsible for the mechanical strength of the spun fibres. It was possible to produce fibres highly loaded with the microspheres (40 wt%) with a tenacity of 13 cN tex−1 (135 MPa). The fibres possessed good thermo-regulating features by absorbing and releasing heat without undergoing structural changes, while maintaining the PCM domain sizes intact. Finally, good washing fastness and PCM leak resistance were demonstrated, making the fibres suitable for thermo-regulative applications. Continuous fabrication of bio-based fibres with entrapped PCMs may find applications as reinforcements in composites or hybrid filaments.

Optimization design and performance investigation on the cascaded packed-bed thermal energy storage system with spherical capsules

Most of the previous researches on the cascaded packed-bed latent heat storage (CPTES) system are the thermal performance optimization based on numerical calculation. Experimental studies are few and mainly focus on single design parameter at low-temperature conditions. Lack of the detailed temperature - flow field experimental data and optimization scheme for the CPTES system. In this paper, an optimized two-layered filling structure of packed-bed heat storage system (OT-PTES) was proposed, which considers melting temperature of phase change material (PCM), capsule diameter, and filling volume ratio. The heat transfer process of PCM capsule and heat transfer fluid (HTF) during charging/discharging process were studied in detail by experiments. Under consistent working conditions, the average charging/discharging rate, total heat capacity, overall efficiency, and exergy efficiency was evaluated. And the influences of HTF inlet flow and the volume filling ratio of two-layered on thermal performance were analyzed. Finally, the concentric diffusion model was used to simulate the system to further optimize its hierarchical structure. The results are concluded as follows: (1) The temperature difference between PCM capsule and HTF at the interface changes continuously, and there is also an obvious temperature gradient in the radial direction of HTF, which improves the heat transfer efficiency. (2) Through experiments, the packed-bed with single large/small size PCM capsules are compared with the OT-PTES system. The overall efficiency of the latter is 74.2%, increased by 3.38% and 8.28%, and the exergy efficiency is 62.7%, increased by 7.5% and 52%. It is proved that the OT-PTES system has better charging/discharging performance. (3) When the volume filling rate = 1/2, the system has the best thermal performance (75.04%) and exergy efficiency (67.1%). (4) The numerical simulation results show that the overall performance of the packed-bed is optimal when the capsule size composition is 20–30 mm and the temperature difference of PCMs melting point is 60 ℃. In summary, OT-PTES is an optimized system with better heat storage performance. This study can provide experimental data support for the optimal design of the PLTES system and useful guidance for industrial applications.

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.