Phase Transition Process Research Articles

Sub-ambient water wettability of hydrophilic and hydrophobic SiO2 surfaces.

The wettability of SiO2 surfaces, crucial for understanding the phase transition processes of water, remains a topic of significant controversy in the literature due to uncertainties in experiments. Molecular dynamics (MD) simulations offer a promising avenue for elucidating these complexities, yet studies specifically addressing water contact angles on hydrophilic and hydrophobic SiO2 surfaces at sub-ambient temperatures are notably absent. In this study, we experimentally measured water contact angles of hydrophilic and hydrophobic SiO2 surfaces at ambient temperature and employed MD to investigate water contact angles on Q3, Q3/Q4, and Q4 SiO2 surfaces across temperatures ranging from 220 to 300K. We investigated the effects of the distribution of hydroxyl groups, droplet size, and hydroxyl density and found that the hydroxyl density had the largest impact on contact angle. Moreover, hydrogen bond analysis uncovered enhanced water affinities of Q3 and Q3/Q4 SiO2 surfaces at lower temperatures, and the spreading rate of precursor films reduced with decreasing temperature. This comprehensive study sheds light on the intricate interaction between surface properties and water behavior, promoting our understanding of the wettability of SiO2 surfaces.

Effects of phase transition on the structure and microwave dielectric properties of (1-x)CeO2-0.5xSm2O3 (x=0-0.9) ceramics

(1-x)CeO2-0.5xSm2O3 (x=0-0.9) microwave dielectric ceramics are synthesized by the conventional solid-phase reaction method, with the effects of phase transition on structure and microwave dielectric properties being investigated in detail. The phase transition process is analyzed using the ionicity and lattice energy of (1-x)CeO2-0.5xSm2O3 ceramics, which is related to the coordination number and effective valence electron charge. With the increase of Sm3+ content, there are three phase regions: the cubic fluorite phase (0 ≤ x ≤ 0.4), the rare-earth C-type phase (0.4 <x ≤ 0.8) and the mixed phase (0.8 <x < 1.0). With the phase transition, the microstructures of (1-x)CeO2-0.5xSm2O3 (x=0-0.9) ceramics show a quasi-periodic change, where x=0.4 and x=0.8 are the critical points with similar grain size and distribution. When the phase transition occurs, the polarization, Q׃ values and the resonant frequency temperature coefficients (τƒ) of (1-x)CeO2-0.5xSm2O3 (x=0-0.8) ceramics are all mutated, which is due to the change of bond ionicity and effective valence electron charge caused by the phase transition. The microwave dielectric properties in each pure phase region vary regularly with bond ionicity and valence. Compared with the cubic fluorite phase (0 ≤ x ≤ 0.4), (1-x)CeO2-0.5xSm2O3 ceramics with rare-earth C-type phase (0.4 <x ≤ 0.8) have lower dielectric constant, with better Q׃ values and τƒ values.

Correlating the microstructure of titanium hydride with its hydrogenation conditions via thermodynamics and kinetics

Titanium hydride is widely considered as an important hydrogen storage material due to its high capacity, stability and low cost. The microstructure of titanium hydride, which is usually induced by the hydrogenation of titanium, strongly influences its storage performance. However, the relationship between the hydrogenation conditions and the derived microstructure of titanium hydride is still unclear, limiting the development of its structure design strategy. In this work, the microstructure of titanium hydride is correlated with its hydrogenation conditions through the thermodynamics and kinetics. By evaluating the effect of the hydrogenation temperature, pressure and cooling rate, three classes of the hydrogenation processes were clarified as kinetic-limited, continuous and stepwise. Besides, according to the SEM and FIB-STEM results, these different processes are confirmed to greatly vary the bulk microstructure. It is concluded that a fast and continuous transition induces a broken bulk morphology, while a stepwise process leads to a larger bulk grain size. In summary, this study presents a framework for designing titanium hydride structures by modifying phase transition processes through careful adjustment of hydrogenation parameters, namely, a condition-process-structure relationship. This relationship offers crucial guidance in managing the grain refinement or coarsening of hydrides within hydrogen storage components and metallurgical applications.

Translational and rotational drives of micro-droplets of nematic liquid crystal with chiral dopant

The translational and rotational control of liquid crystal micro-droplets by electric fields has been explored for the future use in MEMS and lab-on-a-chip devices. The liquid crystal droplets are generated by the phase transition process of a liquid crystalline material, 4-n-4’-pentylcyanobiphenyl (5CB), from the isotropic to the nematic phase, and are thus suspended in the isotropic phase of 5CB. The addition of a chiral dopant to 5CB induces the symmetry breaking of the molecular orientation configuration within the droplet, leading to the formation of helical molecular orientation configurations. The helical configuration of the molecular orientation field is the key to enabling the translational and rotational drives of the droplet. Under electric fields, the translational drive of the droplets occurs in a direction perpendicular to both the electric field and the helical axis, and the rotational drive of the droplets occurs to align the helical axis perpendicular to the electric field. Finally, we propose the method for 2D and 3D manipulation of the droplets by combining the translational and rotational drives.

Dynamic phase transition region in electrically injected PT-symmetric lasers

Research on parity-time (PT) symmetry and exceptional points in non-Hermitian laser systems has been extensively conducted. However, in practical electrically injected PT-symmetric lasers, the frequency detuning and linewidth enhancement factor of the laser can influence the symmetry breaking of the system in another dimension. We find that the previous exceptional point now transforms into a dynamic phase transition region, where the states are temporally unstable, indicating the occurrence of multimode oscillation. The relative phase and field amplitude ratio in this region also exhibit many novel phenomena indicating its instability. This region can be manipulated by adjusting the coupling strength between adjacent waveguides and the pumping intensity in the loss waveguide. Experimentally, we characterize the near-field, far-field, and spectrum of several structures, and the results validate our theoretical model. This work elucidates the dynamic process and phase transition process of electrically injected PT-symmetric lasers, providing support for the practical application of PT-symmetric lasers.

Phase change material performance in chamfered dual enclosures: Exploring the roles of geometry, inclination angles and heat flux

This study presents a comprehensive thermal performance analysis of phase change materials (PCMs) within a chamfered dual enclosures subjected to constant heat flux. Utilizing numerical simulations, we investigate the impact of various PCM types, inclination angles (α = 0°, 15°, 30°, 45°, 60°, 75°, 90°), and heat flux levels (Q = 500, 1000, 1500, 2000 W/m²) on melting rates, temperature distribution, and energy storage efficiency. The study examines commercially available PCMs, including RT-25, RT-27, RT-31, RT-35, RT-38, RT-42, RT-47, and RT-50. Our findings reveal that the inclination angle significantly influences thermal performance, with optimal performance observed at angles between 45° and 90° The PCM at 45° exhibited the fastest melting rate and demonstrating the highest energy storage efficiency. Among the PCMs, RT-27 showed the slowest temperature increase, while RT-50 exhibited the highest heat absorption efficiency and rapid temperature rise, making it suitable for applications requiring quick thermal management. Additionally, higher heat flux levels accelerated the phase transition process, with melting rates increases higher at 2000 W/m² compared to 500 W/m². The energy storage capacity varied, with RT-47 and RT-50 demonstrating the highest storage rates, while RT-27 was effective for sustained thermal energy release despite its slower phase change rate. This research bridges gaps in the existing literature by integrating various parameters and providing a holistic understanding of PCM behaviour in thermal energy storage systems. The insights gained from this study can inform the design and optimization of PCM-based thermal management solutions across various applications, including solar heating systems, electronic device cooling, and industrial waste heat recovery.

Liquid Metal-Based Elastomer Composite with Selective Switchable Adhesion to Solids.

Selective switchable adhesion has recently attracted much attention due to its wide applications in transfer printing, information transfer, and flexible electronics. However, selective adhesive materials often have a complex adhesion or preparation process, which limits their use. To overcome this problem, this study prepares a composite of liquid metal foam and polydimethylsiloxane (PDMS) with selective photocontrolled adhesion, which can directly adhere to solids at room temperature. Utilizing the photoinduced phase transition of liquid metals, solid adhesion can be regulated by changing the backing layer modulus of the adhesive layer. Since the phase transition process is gradually completed by heat transfer from the illuminated side to the backlight side that adheres to the solid, the melting area on the backlight side can be regulated by controlling the light time, which determines the adhesion regulation area. Therefore, the accuracy of the adhesion regulation can reach less than 0.9 mm without relying on the accuracy of the infrared light. Moreover, based on the selective switchable adhesion, the selective transfer of solids with different scales can be achieved at room temperature. The findings of this study may provide strategies for the simple preparation of selective adhesive materials and the improvement of control accuracy.

Comparative Study on the Effect of External Magnetic Field on Aluminum Alloy 6061 and 7075 Resistance Spot-Welding Joints

This study investigates the effects of the external magnetic field on the microstructure and mechanical property aluminum alloy 6061-T6 and 7075-T651 resistance spot welding joints. The melting behavior of 6061 and 7075 was analyzed via the calculation of the phase diagram (CALPHAD) technique. The CALPHAD results indicate that, for the 6061 aluminum alloy, the liquid fraction shows a minimal increase at the beginning stage during the solid–liquid phase transition process but with a sharp rise at the ending stage (near the liquidus). In contrast, for the 7075 aluminum alloy, the liquid fraction gradually increases throughout the entire solid–liquid phase transition process. The differences in melting behavior between the 6061 and 7075 alloys lead to different liquation crack morphologies in their spot-welded joints. In the 6061 alloy, the cracks tend to be “eyebrow-shaped”, allowing the liquid metal in the nugget to feed the gaps, and this does not significantly compromise the mechanical properties of the joint. In contrast, the 7075 alloy develops slender cracks that extend through the partially melted zone (PMZ), making it difficult for the liquid metal to feed these gaps, thereby significantly deteriorating the joint’s mechanical strength. Compared to conventional resistance spot-welding joints, the heat exchange between the nugget and the workpiece is enhanced under the external magnetic field, leading to a wider PMZ. This exacerbates the detrimental effects of liquation cracks on the mechanical properties of the 7075 joints. Lap-shear tests indicate that the mechanical properties of the 6061 aluminum alloy joints are improved under electromagnetic stirring. For 7075 aluminum alloy joints, the mechanical properties improve when the welding current is below 34 kA. However, when the welding current exceeds 34 kA, because the widening of the PMZ increases the tendency for liquation cracks, the joint’s mechanical property is deteriorated.

Ultra-High Adsorption Capacity of Calcium-Iron Layered Double Hydroxides for HEDP Removal through Phase Transition Processes.

Antiscalant disposal in reverse osmosis concentrate (ROC) treatment is a significant obstacle in desalination. This study investigated the adsorption performance of LDHs for removing 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP). CaFe-LDH presented a specific adsorption behavior and ultrahigh adsorption capacity for HEDP, with a maximum adsorption capacity of 335.7 mg P/g (1116.5 mg HEDP/g) at pH 7.0. X-ray diffraction (XRD) demonstrated that HEDP adsorption induced a structural transformation of CaFe-LDH from a layered configuration to a highly ordered structure, leading to a noticeable phase transition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and Raman spectroscopy further confirmed that two distinct binding modes of HEDP, relating to chelation with Ca2+ and adsorption on Fe3+ simultaneously, are connected by phosphonic acid groups (-C-PO(OH)2), forming the CaFe-HEDP complex. X-ray fluorescence (XRF) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the CaFe-HEDP ternary complex exhibits a highly ordered arrangement in an oxygen-bridged framework. The construction of an oxygen-coordinated framework contributes to the incorporation of more HEDP into CaFe-LDH, leading to a well-aligned lattice in the new phase. These findings provide valuable insights into developing novel LDH-based adsorbents for removing phosphorus-containing antiscalants, establishing a sustainable approach to ROC management, and potential environmental risk reduction.

Macroscopic perspective on phase transition behavior of natural single-crystal graphite under different pressure environments

Comprehensive understanding of the direct transformation pathway from graphite to diamond under high temperature and high pressure has long been one of the fundamental goals in materials science. Despite considerable experimental and theoretical progress, current experimental studies have mainly focused on the local microstructural characterizations of recovered samples, which has certain limitations for high-temperature and high-pressure products, which often exhibit diversity. Here, we report on the pressure-induced phase transition behavior of natural single-crystal graphite under three distinct pressure-transmitting media from a macroscopic perspective using in situ two-dimensional Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. The surface evolution process of graphite before and after the phase transition is captured, revealing that pressure-induced surface textures can impede the continuity of the phase transition process across the entire single crystal. Our results provide a fresh perspective for studying the phase transition behavior of graphite and greatly deepen our understanding of this behavior, which will be helpful in guiding further high-temperature and high-pressure syntheses of carbon allotropes.

Oxygen vacancy order–disorder transition process during topotactic filament formation in a perovskite oxide tracked by Raman microscopy and transmission electron microscopy

Vacancy-ordered perovskite oxides are attracting attention due to their diverse functions such as resistive switching, electrocatalytic activity, oxygen diffusivity, and ferroelectricity. It is important to clarify the chemical lattice strains arising from compositional changes and the associated vacancy order–disorder phase transitions at the atomic scale. Here, we elucidate the intermediate process of a topotactic phase transition in Ca-doped bismuth ferrite films consisting of alternating stacks of oxygen perovskite layers and a brownmillerite-type oxygen vacancy layer. We use Raman spectroscopy and transmission electron microscopy to closely examine the evolution of local strains exerted on the constituent sub-layers by electrochemical oxidation. A negative Raman chemical shift is observed during oxidation, which is linearly correlated with the local negative chemical expansivity of the oxygen layer. It seemingly contradicts with the general trend that oxides undergo lattice contraction upon oxidation. Oxygen vacancies initially confined in the vacancy layers can be understood to diffuse into the oxygen layers during melting of the ordered structure. The finding deepens our understanding of the electro-chemo-mechanical coupling of vacancy-ordered oxides.

Impact of Q-balls formed by first-order phase transition on sterile neutrino dark matter

We explore the mechanism that can explain the production of lepton asymmetry and two types of sterile neutrino dark matter. The first type involves heavy sterile dark matter produced directly by the decay of Q-balls which are formed by first-order phase transition in the early universe; the second consists of keV sterile neutrino dark matter, produced resonantly with the aid of lepton asymmetry from Q-ball decay. Besides, gravitational waves from cosmic strings generated during the phase transition process could be detected at future interferometers.

Comprehensive analysis of polyethylene glycol – lauric acid as a promising phase change material: Spectroscopic, thermal, and quantum insights

The increasing need for effective and environmentally sustainable energy storage technologies has delineated phase change materials (PCMs) as prospective candidates for thermal energy storage applications. In this study, we thoroughly analyzed polyethylene glycol (PEG 400) and lauric acid (LA) as promising PCMs by applying spectroscopic study, thermal, and quantum approaches. The thermal stability and chemical compatibility of PEG – LA were investigated using FTIR and Raman spectroscopy, revealing that optimal molecular interactions and structural changes occur at temperatures ranging from −10 °C to 30 °C, especially at higher LA volume fraction (VLA ≥ 60 %), as evidenced by marked blue shifts in the Raman spectra. TGA demonstrated the 2-step degradation of the PEG – LA (6:4), representing good material stability and high thermal conductivity enhancement of 32.24 % due to synergistic interactions among PEG and LA. DSC analysis established a high capacitive energy storage of 181.5 J/g and a phase transition of solid–liquid at room temperature (30–40 °C), which better crystallization properties based on higher LHR and supercooling degree compared with pristine LA. The thermal cycling reliability and FTIR spectra demonstrated the thermal and chemical stability of PEG – LA even after 1000 cycles. Quantum DFT analysis verified the experimental results, exhibiting robust hydrogen bonding interactions that contribute to the thermal stability, phase transition processes, higher energy storage capacity, and reactivity of PEG – LA. These results highlight PEG – LA as a promising and effective PCM for various thermal energy storage applications.

&lt;i&gt;In vitro&lt;/i&gt; synthesis and microscopic structural change of fetuin-A/calcium phosphate composite nanoparticles during phase transition process

&lt;i&gt;In vitro&lt;/i&gt; synthesis and microscopic structural change of fetuin-A/calcium phosphate composite nanoparticles during phase transition process

Experimental and numerical investigation of a double spiral tube heat exchanger in a novel composite phase change material

Phase change energy storage technology effectively harnesses energy, and phase change materials have been garnered significant attention due to their high latent heat capacity. The heat transfer capacity and phase transition of HCNT − CH3COONa·3H2O/Na2HPO4·12H2O composites in a double spiral tube heat storage unit were investigated. The effects of different flow rates and temperatures on the heat transfer characteristics of phase change materials were studied, and the thermal performance of the storage units was evaluated by calculating the power, energy and energy efficiency ratios. The phase change process of the composite during heat transfer was further revealed via simulation, and the heat storage and heat release of the composite were compared with those of other phase change materials. The results show that the effects of the flow velocity on the transformation time and power of the phase change material are negligible. However, an increase in flow rate can significantly increase the heat storage and heat release of the phase change unit. In particular, when the flow rate is 4 LPM, the energy efficiency ratio can reach 76.6 %. When the temperature increases from 80 °C to 90 °C, the melting time decreases by 30.23 %, indicating that increasing the temperature has a significant effect on the phase transition process. Through simulation calculations, the composite phase change material shows significant performance advantages under the same working conditions; its heat storage capacity is 108 % greater than that of the other materials, and the heat release capacity is 206 % greater, which indicates that it has greater energy storage and release efficiency and a better thermal energy conversion capacity. In addition, the experimental and simulation results also reveal the existence of a diagonal region of slow phase transition in the heat storage unit. In summary, this paper analyses the heat transfer performance of a double spiral tube heat storage device, provides a theoretical basis for practical application, and provides an important reference for improving the performance of a phase–change energy storage system.

Experimental and first-principles novel insights of atomic collapsed structure and composition-driven ω-precipitates

A complex ω phase transition is often observed in titanium alloys; nevertheless, the underlying knowledge of ω-embrittlement are not yet fully understood and require deeper insight. In this study, the ωT and ωH phases, as well as their interfacial structures, have been systematically investigated to examine compositional partitioning and to estimate Z values. A combination of aberration-corrected HAADF-S/TEM advanced characterization techniques, together with first-principles density functional theory calculations were performed under various heat treatment conditions. The results revealed that the low-temperature ageing process suppresses ω-assisted secondary α precipitations at ωT/β interfaces, whereas high-temperature ageing process promotes ω-assisted secondary α precipitations at ωH/β interface, due to relatively higher concentrations of Mo and Al contents. The interfacial energies (γ{ωβ}) between β and ω phases increase with decreasing local compositions of Mo and Al, suggesting increased stability of the ω phase and decreased stability of the β phase. Furthermore, the formation energies of β and ω phases were computed with Mo content at different Al composition, results indicate that the ω phase transition process is affected by the reduced Al content. The observations of this work provide deeper understanding of the ω phase transition mechanism in titanium alloys.

Heat transfer analysis and melting behavior of nano composite phase change materials (NCPCMs) in a reverse flow solar air heater

This paper presents a CFD investigation on heat transfer analysis and melting behavior of Nanocomposite Phase Change Materials (NCPCMs) in a Reverse Flow Solar Air Heater (RFSAH). Semicircular tubes filled with PCM are embedded on the top surface of the absorber plate. The study was conducted with three different nanoparticles (CuO, Al2O3, Fe3O4) based NCPCMs at three concentrations of 0.1, 0.2, and 0.3 % by weight. The constant geometrical parameters such as pitch ratio (P/e = 6), height ratio (e/Dh=0.1571), and Reynolds number (Re = 5000) is considered for this study. A 2-D transient numerical analysis using the RNG k-ε turbulence model is performed for the melting behavior of NCPCMs inside the semicylindrical tubes. The incorporation of nanoparticles into the base PCM enhances thermal conductivity but reduces the latent heat of NCPCMs. Thus, it is observed that NCPCMs have a faster melting rate. The CuO based NCPCM shows a more quick and uniform phase transition compared to the Fe3O4, and Al2O3 based NCPCMs and reached their peak value at a higher mass fraction of 0.3. Furthermore, the heat transfer and melting fraction improves with increasing in mass fraction of nanoparticles. The phase transition process of CuO based NCPCM is approximately 1.9 times, and 1.01 times, 1.03 times faster as compared to the base PCM, and Fe3O4, Al2O3 based NCPCMs respectively.

The influence of the design features of the fuel injector atomizer on the process of diesel fuel injection

Abstract. Problem. Increasing the demands for the technical and economic characteristics and the resource of modern augmented diesel engines requires finding ways and approaches to improve their design and systems, in particular, their fuel supply system. Changing the design parameters of the fuel injector atomizer allows to influence the conditions of fuel injection, its atomization in the combustion chamber, and the efficiency of the engine. The number and mutual arrangement of the nozzle holes of the fuel injector atomizer and their diameter are chosen by manufacturers based on the design features of the engine, in particular, the configuration of the combustion chamber and the conditions for filling the cylinder with fresh air. Goal. The purpose of the work was to carry out comparative numerical modelling to assess the influence of the number and diameter of the nozzle holes of the fuel injector atomizer on the diesel fuel injection process. Methodology. The problem is considered in a three-dimensional non-stationary setting. For numerical modelling, the geometry of the flow part of the fuel injector atomizer was formed, taking into account its design features (standard and modernized versions). The standard version has 7 nozzle holes with a diameter of 0.25 mm (evenly arranged relative to the axis of the atomizer, and the modernized version has 4 holes with a diameter of 0.3 mm in the standard place, evenly arranged relative to the axis of the atomizer and, additionally, 4 holes with a diameter of 0.2 mm from above (in the area of the closing cone) evenly arranged relative to the axis of the atomizer, but with a rotation around the axis of the atomizer by 45 degrees relative to the lower holes. To describe the process of the diesel fuel flow in the flow part of the fuel injector atomizer, the k - ε turbulence model is used, and to describe the process of phase transition from a liquid state to a vapour state – a mixture model is used. Results. The obtained results showed that the use of two rows of nozzle holes of different diameters for the atomizer of the fuel injector of the transport diesel engine allows to effectively organize the fuel injection process. For the atomizer nozzle of the modernized design, the volumetric fuel consumption is 30% for the upper holes and 70% for the lower ones. Originality. The scientific novelty of the work lies in determining the influence of the number and diameter of the nozzle holes of the fuel injector nozzle on the conditions of diesel fuel injection, taking into account cavitation effects. Practical value. The total area of the nozzle holes in the modernized version was increased by 20%, which makes it possible to increase the cycle supply of diesel fuel. It is especially important when using new types of fuel with a lower paraffin content and, accordingly, lower caloric content

Giant electro-optic response in transparent rhombohedral ferroelectric Sm-PIN-PMN-PT crystal based on domain engineering

The relaxor ferroelectric crystal Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), located near the morphotropic phase boundary (MPB), exhibits exceptionally high piezoelectric and electro-optic (EO) responses. Nevertheless, lower optical transparency and phase transition temperature of PMN-PT limit its optical applications. The ternary system Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) holds promise in addressing these challenges with a higher Curie temperature. Additionally, specific ferroelectric domain polarization techniques can eliminate domain scattering, substantially enhancing the transparency of the crystal. In this study, we explore the optical properties of Sm-doped PIN-PMN-PT. We achieve a 2R domain-engineered state by polarizing along the (110) direction of the crystal. The high transparency allows us to extract an effective EO coefficient of up to 431.5 pm/V from the Sm-PIN-PMN-PT crystal at the telecommunications wavelength. Second-harmonic generation (SHG) probing verified the domain-engineered state in Sm-PIN-PMN-PT. The temperature-dependent SHG reveals the ferroelectric phase transition process, laying the groundwork for studying the stability of the EO response. The Sm-PIN-PMN-PT crystal exhibits an exceptionally high EO coefficient, which is crucial for the development of enhanced EO devices with high integration and low driving voltages.

Passive domestic air-conditioning using PCM modules

Passive cooling systems have garnered much attention in recent years as a sustainable and cost-effective method of regulating indoor temperatures. Phase change materials (PCM) are a promising technology for such systems, as they can store and release large amounts of thermal energy during the phase transition process while maintaining the temperature in a very specific range. In this study, we investigated the performance of a passive cooling system using PCM modules and evaluated the effect of different variables on its cooling efficiency. Several tests were conducted, varying the ambient temperature, number of plates, and PCM type to determine the optimal conditions for the system. A PCM with a melting temperature of around 22 °C was used and was compared to ice. While ice showed a larger cooling effect, the advantage of the PCM emerged with elevated ambient temperatures. Compared to ice, and due to the smaller the temperature difference ΔT between the PCM melting temperature and the ambient temperature, the cooling effect of the PCM, lasted for a significantly longer time. Moreover, increasing the number of plates proved to elongate the cooling effect, due to increasing the overall thermal storage capacity of the system. Overall, our findings suggest that a passive cooling system using PCM technology can be an effective solution for regulating indoor temperatures. However, careful consideration must be given to the choice of PCM type and melting temperature, as well as the number of plates in the system, to optimize its performance.