Nanoencapsulated Phase Change Materials Research Articles

Hydrothermal and entropy generation analyses of natural convection of nano-encapsulated phase change materials suspension in a cavity subjected to the localized heating

Being heated electronic components significantly reduces their efficiency, and thus requiring high-efficient cooling strategies to keep such devices operating at an optimal temperature level. The present study is devoted to investigating the cooling performance of water-based nano-encapsulated phase change materials (NePCMs) suspension in the presence of a heat source with uniform temperature. The nano-sized PCM capsules are constructed by n-nonadecane as the core and polyurethane for the protective shell. The n-nonadecane is capable of absorbing/releasing a significant quantity of latent heat in the process of its phase transition, which is actually beneficial for improving the heat transfer performance. The home developed FORTRAN program based on the finite volume method (FVM) combined with the artificial compressibility algorithm is employed to solve the nonlinear coupled equations for fluid flow and heat transfer. The influences of the Rayleigh number (103≤Ra≤105), the Stefan number (0.1≤Ste≤0.9), the volume fraction of the nano-capsules (0≤ϕ≤0.04), and the heating position (0.25≤a≤0.75) on the hydrothermal behavior and entropy generation are explored. The findings reveal that there exists a capsule loading interval wherein the heat transfer enhancement can be achieved, but beyond that range, the deterioration of cooling performance may occur. Moreover, the contribution of suspending NePCMs to the heat transfer improvement is greatly more noticeable at low Rayleigh number, and particularly for the arrangement of upper heating. The average Nusselt number decreases with the increment of the Stefan number, and the variation approximately follows an exponential change for all considered Rayleigh numbers and heating positions. Concerning the entropy generation, it is essentially contributed by the heat transfer irreversibility, and the region with high irreversibility is always located around the intersection of the heated surface and the insulated vertical wall. This research can provide theoretical guidance for cooling the electronic components by utilizing the NePCMs suspension.

Recent Advances in Nanoencapsulated and Nano-Enhanced Phase-Change Materials for Thermal Energy Storage: A Review

Phase-change materials (PCMs) are becoming more widely acknowledged as essential elements in thermal energy storage, greatly aiding the pursuit of lower building energy consumption and the achievement of net-zero energy goals. PCMs are frequently constrained by their subpar heat conductivity, despite their expanding importance. This in-depth research includes a thorough categorization and close examination of PCM features. The most current developments in nanoencapsulated PCM (NEPCMs) techniques are also highlighted, along with recent developments in thermal energy storage technology. The assessment also emphasizes how diligently researchers have worked to advance the subject of PCMs, including the creation of devices with improved thermal performance using nano-enhanced PCMs (NEnPCMs). This review intends to highlight the progress made in improving the efficiency and efficacy of PCMs by providing a critical overview of these improvements. The paper concludes by discussing current challenges and proposing future directions for the continued advancement of PCMs and their diverse applications.

Experimental study on spray heat transfer enhancement by micro-structured surface with nanoencapsulated phase change material slurry (NPCMS)

Spray cooling is receiving increased attention due to the highly efficient and uniform heat transfer. However, previous investigations seldomly focused on its enhancement with the combination of phase change materials (PCMs) and micro-finned surface. Herein, in this article, we enhance the spray cooling with NPCMS and micro fins to improve the heat capacity of coolant, heat transfer area and nucleate sites of contact boiling. Results show that two peaks of heat transfer coefficient are observed in sequence as heatflux increases, separately derived from latent heat absorption of melting of core PCM and nucleate boiling of carrying fluid. Compared to the smooth surface, the convective heat transfer coefficients under three cubic fin heights (0.2 mm, 0.3 mm and 0.4 mm) are improved maximally by 22.3 %, 17.6 % and 11.8 % in phase change of NPCMS, while the maximum improvements of 45.8 %, 39.8 % and 39.8 % are obtained in the nucleate boiling. The staggered arrangement of cylinder fins can induce stronger capillary force, which is responsible for the best enhancement of nucleate boiling. Also, the shortest survival time of droplet on the staggered cylinder fins are observed, confirming that capillary force is the reason of increasing heatflux and lifting Leidenfrost point of boiling.

Photovoltaic/thermal (PV/T) solar collectors employing phase-change nano-capsules as spectral filters: Coupled, decoupled, and partially-coupled configurations

The ineffective utilization of solar radiation poses negative impacts on the performance of photovoltaic (PV) cells in terms of their efficiency and durability. For the first time, this study numerically introduces a comparative performance analysis between multiple PV/T configurations (thermally decoupled, coupled, and partially coupled) that employ nano-encapsulated phase-change material (nano-ePCM) dispersions. The dispersions act as multi-functional fluids that can optically filter incident radiation to fit the spectral response of Si PV cells, and serve as both heat carriers and storage media to effectively cool PV cells. The water-dispersed ePCM particles are made of silica shells and paraffin cores. The numerical model developed for the proposed configurations mainly comprises of three mathematical models (thermal, optical, and electrical) that are coupled together to simulate the performance of the novel systems. To ensure that the presented results are of high accuracy and credibility, the optical, electrical, and thermal models were rigorously validated against published data. Performance of the three PV/T configurations was comparatively analyzed upon varying the PCM core material, mass flowrate, channel depth, inlet and ambient temperatures, and wind speed. The utilized dispersion exhibited a 73.8% spectral match with Si PV cells, thus hinting at the effective spectral filtration capabilities of the designed fluid. When compared to similar PV/T configurations from different literatures, total exergy efficiency enhancements of 43.2%, 76.8%, and 2.6% were evident for the coupled, decoupled, and partially coupled systems, respectively. In addition, results have shown that the thermally decoupled system outperforms the coupled and partially coupled systems in terms of thermal performance but exhibits the poorest performance when superior electrical performance is desired.

Nanoencapsulated phase change material in a trapezoidal prism wall under the magnetic field effect for energy storage purposes

Recently, Nano-encapsulated phase change materials (NEPCM) have attracted the attention of researchers due to their promising application in thermal management. This research investigates magnetohydrodynamic mixed convection of NEPCM contained within a lid-driven trapezoidal prism enclosure containing a hot-centered elliptical obstacle. The upper cavity wall is moving at a constant velocity; both inclined walls are cold, while the rest of the walls are insulated. The Galerkin Finite Element Method was used to solve the system's governing equations. The influence of Reynolds number (Re 1–500), Hartmann number (Ha = 0–100), NEPCM volumetric fraction φ (0–8%), and elliptical obstacle orientation α (0–3π/4) on thermal fields and flow patterns are introduced and analyzed. The results indicated that the maximum heat transfer rate is observed when the hot elliptic obstacle is oriented at 90°; an increment of 6% in the Nu number is obtained in this orientation compared to other orientations. Reducing Ha from 100 to 0 increased Nu by 14%. The Maximum value of the Bejan number was observed for the case of Ha = 0, α = 90° and φ = 0.08.

Conjugate entropy generation and heat transfer of a dilute suspension of nano-encapsulated phase change material in a partially heated wall cavity

https://www.rme-journal.org/index.php/asd/article/view/182

Natural convection heat transfer analysis of a nano-encapsulated phase change material (NEPCM) confined in a porous square chamber with two heat sources

This study focuses on the thermal behavior and performance of an insulated porous cavity containing square tubes, one as the hot block and the other as the cold block. The cavity is filled with a Nano-Encapsulated Phase Change Material (NEPCM) that combines the advantages of phase change materials (PCM) and nanofluid. The main purpose of this research is to examine the heat transfer mechanisms, phase change process, and overall thermal performance of the system. The governing equations of the NEPCM suspension are transformed into a dimensionless form and solved using the finite element approach. Various parameters, including nanoparticles concentration, fusion temperature, Darcy number, Rayleigh number, and Stefan number, are investigated to assess their impact on the system's thermal and dynamic performance. The results reveal that the optimal heat transfer performance is achieved when the NEPCM fusion temperature is set to 0.5. Moreover, a smaller Stefan number significantly improves the system's performance. Additionally, including NEPCM particles generally improves heat transfer, with a 33% increase in mean heat transfer observed when the volume fraction was raised from 0% to 2%.

Thermal pattern of nano-encapsulated PCM in a lid-driven cavity with presence of a heated body, magnetic field and limited permeability

This study attempts to improve the thermal characteristics of nano-encapsulated phase change materials (NEPCMs) for heating and cooling applications. The PCM particles are added to water to improve the thermal performance by the latent heat of phase change. NEPCM is confined in a porous prism lid-driven cavity with a lower zigzag wall. The cavity contains an elliptic heated cylinder and is subjected to magnetic field. The study is modeled using the Galerkin finite element method to solve the governing equations. The influential parameters are highlighted, including the impacts of medium permeability (Darcy number (Da) = 10−2 – 10−5), the strength of the magnetic field (Hartmann number (Ha) = 0–100), the orientation of an elliptic heated body (θ = 0° – 135°), and the speed of the lid (Reynolds number (Re) = 1–500). For all studied cases, it was observed that the thermal performance is improved by increasing the Re and Da and decreasing Ha. Increasing Re from 0 to 500 and Da from 10−5 to 10−2 enhances Nu by 335% and 94.7%, respectively. While raising Ha from 0 to 100 and the inclination angle to 90° decreases Nu by 5.3% and 6.7%, respectively.

Entropy generation and heat transfer performance analysis of a non-Newtonian NEPCM in an inclined chamber with complicated heater inside

The present research deals with thermic energy storage structures based on nano-encapsulated phase change material with a complicated charger inside the storage system. Flow structures, heat transfer, and entropy generation performance are studied using the partial differential governing equations based on non-Newtonian nature of the working medium. Analysis has been performed numerically using the finite element method. Effects of the cavity inclination angle, inner charger structure, power-law index for non-Newtonian nature of the working liquid, Rayleigh number, and nanoparticles volume fraction on flow structures, entropy generation fields and temperature fields have been studied. It has been found that the considered dilatant working fluid is not effective for the heat transfer applications, because Nusselt number decreases with a growth of the power-law index. At the same time, the cavity inclination angle and inner heater structure can be effective parameters to manage the heat transfer and entropy generation.

Cooling a cavity equipped with a hot electrical element using nano-encapsulated phase change material /water: Study of mixed convection and natural convection

According to phase change materials (PCMs) operate at their phase change temperature, they can store a lot of latent heat energy without changing the temperature, so these materials are widely used in thermal storage tanks. The direct use of PCMs is not possible in all systems, therefore encapsulation of PCMs has been suggested by researchers. In the present work, the thermal performance of the natural and mixed convection flow inside a nested cylinder with a hot electrical element is investigated. Nano-encapsulated phase change material (PCMs) are mixed with the water-based fluid. Also, the effects of forced convection due to inner cylinder rotation along with natural convection are studied. Fluid flow, temperature distribution, melting zone of PCM nanocapsules, Nusselt numbers, and thermal performance are simulated using computational fluid dynamics by developing OpenFOAM solvers using C++ code. The governing PDE equations are solved in the FVM method and solved using the SIMPLE algorithm. The simulations are modeled for different Ra numbers (102−104), Reynolds numbers (0–20), and θf values. θf values correspond to the dimensionless melting temperature of the core of nanocapsules. This number depends on the temperature of the cold and hot sources and the phase change temperature of the core of NEPCMs. Based on the results, it is showed that there is an optimal number for θf, which is in the range of 0.3–0.5 in the lower Ra numbers (102), and θf=0.5 at upper Ra numbers (104). In the case of dominant conduction heat transfer mechanism, the presence of nanocapsules did not affect heat transfer. However, at a high Ra number, it was able to enhance Nusselt number by up to 13%. Also, at high Ra numbers (104), the rotation of the inner cylinder does not help to improve heat transfer.

Investigating the thermal performance of nano-encapsulated phase change materials-water nanofluid in the presence of a heat source as applied in electronic devices

BackgroundGlobal warming and the human need for power resources in the last decades have highlighted the concerns related to energy saving for long-term applications. Thermal energy-saving systems are an important technique to overcome this issue. MethodsIn the present study, we aim to simulate the performance of a thermal energy-storing system with Nano-Encapsulated Phase Change Materials (NEPCMs) by Computational Fluid Dynamics (CFD). Free convection heat transfer through a square enclosure is numerically simulated, and a hot block is located at pisitions of the enclosure. The simulation is done with the FVM method and SIMPLE algorithm. The analyzed parameters are different Ra numbers (5 × 103 − 105), non-dimensional melting temperatures (0.1 ≤ θf ≤ 0.9), and NEPCM melting intensities (0.01 ≤ χ ≤ 0.03). Significant FindingsT The results revealed that the θf = 0.3 is corresponding to the optimum heat transfer rate, and it is independent of the Ra number. In the case with the highest heat transfer rate, adding NEPCMs to the based fluid caused the heat transfer to improve by 12.5%. Furthermore, in this θf number, uniform heat transfers through the cold walls of the enclosure. A low number of χ also revealed less Nusselt number. Increasing AR in high Ra number improves Nusselt number by 5%.

An intelligence parameter classification approach for energy storage and natural convection and heat transfer of nano-encapsulated phase change material: Deep neural networks

An intelligence parameter classification approach for energy storage and natural convection and heat transfer of nano-encapsulated phase change material: Deep neural networks

Magneto-bioconvection flow in an annulus between circular cylinders containing oxytactic microorganisms

The present work focuses on the numerical investigations of the existence of oxytactic microorganisms on the bioconvection flow of nano-encapsulated phase change material (NEPCM) inside an annulus. The novel geometry of an annulus contains an inner wavy cylinder and an outer circular cylinder considering a rotational circular velocity of an inner wavy cylinder. The incompressible smoothed particle hydrodynamics (ISPH) method solved the dimensionless form of controlling equations. The novel annulus between the embedded circular cylinder and the outer circular cylinder can be applied in the tube bundles in heat exchangers. Further, rotation of an inner wavy cylinder in a circular cavity can be used in thermal fin's vibration and cooling of the electric devices. The effects of pertinent parameters such as a rotational frequency number ω, bioconvection Rayleigh number Rab, thermal radiation Rd, Lewis number Le, and Hartmann number Ha on the contours of oxygen concentration ϕ, temperature θ, heat capacity ratio Cr, oxytactic microorganisms N, and velocity field V as well as the average Nusselt & Sherwood numbers Nu¯ and Sh¯ are conducted. Increasing ω enhances the maximum of V by 56.6% and lowers Nu¯. The variations of Rab are enhanced the contours of N and maximized the velocity field from 0.86 at Rab=1 to 8.22 at Rab=100 due to the power in bioconvection flow. Increasing Le diminishes the strength of oxygen concentration ϕ and microorganisms N. Increasing Ha from 0 to 50 slows down the velocity field's maximum by 47.2% and enhances the value of Nu¯.

Analysis of the improvement of a lithium-ion battery module cooling system employing nanofluid and nano encapsulated phase change materials by means of a lumped electro-thermal model

In this study an analysis of the employment of nanoparticles and nano encapsulated phase change materials for battery cooling is provided. By using a previously validated electro-thermal model of a lithium-ion battery module, the effect of 5 different nanoparticles and 6 different nano encapsulated phase change materials is estimated. The analysis is provided for a battery module charge process at 4C, with a coolant mass flow of 2 l/min and with ambient and fluid temperature equal to 20 °C. The concentration of the nanofluid is varied between 0.01 % and 5 %. By increasing the concentration, a beneficial effect is observed on the battery cooling, in terms of maximum temperature achieved during the charge process and heat dissipated into the coolant. Among the 30 different combinations of nanoparticles and nano encapsulated phase change materials analyzed in this work, it is concluded that the best results in terms of dissipated heat and maximum temperature are obtained for copper oxide (CuO) combined with octadecane. In this case, at 20 °C, a reduction of the maximum temperature of about 2 °C is obtained with a volume fraction equal to 5 %, with respect to the case in which there are no nanoparticles. Furthermore, the total heat dissipated in the coolant is increased by 28 %. Finally, the study proposes a design of experiment to evaluate the performance of a phase change material for battery cooling. For this analysis, 4 variables are considered (concentration, melting temperature, heat of fusion and characteristic temperature range) and the effect on the maximum temperature and on the temperature spatial difference is observed: it is found that the thermal evolution of the cells is mostly affected by melting temperature and concentration.

Heat transfer characteristics of fluids containing paraffin core-metallic shell nanoencapsulated phase change materials for advanced thermal energy conversion and storage applications

The influence of heat transfer characteristics of fluids filled with paraffin core-metallic shell nanoencapsulated phase change material (PCM) on photothermal conversion and storage in a volumetrically heated solar system is numerically analysed. The results show that nanoencapsulated paraffin/Al, paraffin/Au, paraffin/Ag, and paraffin/Cu filled heat transfer fluids enhance the energy storage by 68, 73, 92 and 86 %, respectively as compared with the water-based Al, Au, Ag and Cu nanofluids. It is found that the phase change slurry (PCS) improves the temperature and storage gain, as the utilization of nanoencapsulated PCM and the rise in PCM mass concentration enhance the solar energy absorption power of the slurry. The maximum enhancement in stored energy is also observed for paraffin/Cu PCM filled slurry for a particle diameter of 15 nm. The enhancement in mass concentration of paraffin from 5 to 20 %, improves the thermal performance from 312 to 554 % compared to pure water, respectively. Increasing the size of the core/shell architecture of the PCM, however, reduces the surface area-to-volume ratio of the capsule, causing aggregation of the particles and decreasing the heat transfer between the capsule and the host fluid. This in turn results in decrease in temperature gain. Furthermore, it is noticed that the merger of mono- and hybrid- nanoparticles augments the thermal performance of the PCS. The findings of the study indicate that the paraffin core-metallic shell nanoencapsulated PCMs would significantly enhance the performance of advanced photothermal energy conversion and storage devices.

Use of Nano-Encapsulated phase change material mixed with water for natural convection cooling in combination with nickel foam

This study investigated the potential benefits of using free convection mechanisms to cool parts, as opposed to forced convection mechanisms that require energy to transfer heat and mass. The research team cooled a hot plate, which had a uniform heat flux, by utilizing the free convection flow inside a square cavity. They also installed a partial nickel porous media with different porosities on the hot plate and injected nano-encapsulated phase change material (NEPCM) particles into water to form a cooling fluid mixture. For the NEPCM particles, the researchers selected n-docosane with a melting temperature of 317.65 K for the core and polyurethane for the shell. The researchers used computational fluid dynamics (CFD) to simulate the cooling process with varying parameters, including porosity, deflection angles, and NEPCM volume fraction. The results showed that the cooling performance of nickel foam was significantly better than that of NEPCM. For example, when the porosity of the nickel foam decreased from 0.98 to 0.93, the average Nusselt number increased by 142 %, indicating a considerable improvement in cooling efficiency. In comparison, increasing the NEPCM volume fraction from 0 to 6 % only resulted in a modest 5.6 % increase in the average Nusselt number.

Dual rotations of rods on thermosolutal convection in a porous cavity suspended by nanoencapsulated phase change materials

The fractional of a time derivative for the incompressible smoothed particle hydrodynamics (ISPH) method is adopted to handle thermal radiation on thermosolutal convection in a porous cavity barred by nanoencapsulated phase change materials (NEPCMs). A novel work on the rotational velocities of two rods during thermosolutal convection of NEPCMs within a novel cavity of two connected circular cylinders is introduced. The management of heat-mass transfer and velocity magnitude inside distinct designed materials below various boundary conditions carries improvements for energy efficiency. The physical factors are thermal radiation [Formula: see text], Fusion temperature [Formula: see text], Rayleigh number [Formula: see text], hot source length [Formula: see text], Darcy number [Formula: see text], and fractional order parameter [Formula: see text]. This study reported the role of thermal/solutal conditions in varying the dual convection flow and heat capacity contour. The lower Da provides an elevated porous resistance which decelerates the nanofluid velocity. The fusion temperature alters a heat capacity contour.

Mixed convection of EG/NEPCM inside a lid-driven cavity with a rotating cylinder

Using the potential of nature's phenomena such as free convection phenomenon could help to cooling a piece, such as a moving hot plate in lid-driven problems. Moreover, adding modern nanostructures named nano-encapsulated phase change material (NEPCM) with ability of phase transition could greatly improve the heat transfer processes. In this study, the mixed convection of ethylene glycol (EG) and NEPCM was simulated inside a lid-driven cavity with a rotating cylinder to evaluate the contribution of Grashof number, cylinder speed, and concentration of NEPCM on the heat transfer characteristics. Hence, the findings of current numerical study indicated that the NEPCM with 6% concentration increased the mean Nusselt number by 41.7%. Moreover, the cylinder speed enhanced the mean Nusselt number by 38.7%. Finally, there was an optimum value for concentration occurred in 4% brought for Grashof number of 104.

Convective flow analysis for moderate Rayleigh numbers of nano encapsulated phase change materials-water filled enclosure with various thermal conditions

The numerical study of free convection heat transfer inside a square enclosure having exponential and sinusoidal thermal profiles filled with hybrid nanofluid is reported. The hybrid nanofluid is nano-encapsulated phase change materials (NEPCMs) and water (H2O). The NEPCMs are constructed by a polyurethane as a shell and an n-nonadecane as a core. The n-nonadecane undergoes a phase transition and capable of storing or releasing a large quantity of latent heat. The study focuses on the effect of heating exponent and heating frequency to the convective flow and melting distribution. A Galerkin finite element method is applied to solve the governing equations. The result from the present model is compared with the previously published articles. The controlling parameters under consideration are the heating exponent, 0≤λ≤2, the heating frequency, 1≤N≤4, the Rayleigh number, 104≤Ra≤106. It is found that the lowest exponent and frequency of heating gives the best thermal performance.

Thermal and structural properties of cement mortar embedded with hybrid nanocomposite based phase change nanocapsules for building application

A novel Cu-TiO2 Hybrid Nanocomposites adsorbed Nanoencapsulated Phase Change Material (HNNP) was developed. The current research work aims to develop PCM-based cement mortar used as plastering material with increased Energy Utilization Efficiency. The work addresses the poor thermal conductivity of the polymer based shell material (melamine) by adsorbing Cu-TiO2 hybrid nanocomposites on the nanocapsule (HN). The HNNP capsules are capable of freezing and melting at a temperature of 24.02 °C and 25.76 °C, with latent heat of 146.71 J/g and 144.46 J/g respectively. The phase change temperatures of HNNP are in the human comfort temperature zone. The adsorption of HN over nanoencapsulated PCM (NP) has greatly enhanced the thermal conductivity by 137.19% over NP. The HNNP exhibited excellent thermal stability and thermal reliability. Furthermore, the behaviour of the cement mortar in terms of thermal conductivity and compressive strength was studied by dispersing NP and the HNNP capsules. The maximum inclusion of HNNP in the cement mortar greatly enhanced its thermal conductivity, whereas the behaviour of cement mortar with NP inclusion, was contrary, resulting in reduced thermal conductivity. The compressive strength was reduced with the increased percentage of both NP and HNNP capsules in the cement mortar. Albeit, the compressive strength was reduced due to the maximum inclusion of NP and HNNP in the cement mortar, the resulted compressive strength is acceptable for plastering material. From the above stated results, the HNNP is a viable candidate, having a great potential for cooling needs in buildings.