Nanoencapsulated Phase Change Materials Research Articles

Double-diffusive natural convection with Soret/Dufour effects and energy optimization of Nano-Encapsulated Phase Change Material in a novel form of a wavy-walled I-shaped domain

BackgroundAs building segment grows in parallel with amplifying population, the necessity for consumption of energy needed to passive and active heating or cooling buildings for thermal comfort increases. Schemes such as developing green buildings for sustainable architecture were utilized to address this issue. The utilization of Phase Change Materials (PCMs) with the aim of active and passive cooling or heating of buildings illustrates a promising and modern technique. MethodsThis study's objective is to perform a numerical analysis using the finite element method, FEM for modeling free convection produced by double-diffusion (DDNC) with Soret/Dufour effects of Nano-Encapsulated PCMs within an I-shaped enclosure equipped with a novel type of corrugated vertical walls subjected to Neumann thermal and solutal conditions. FindingsResults are interpreted and assessed in relation to the governing factors, such as buoyancy ratio (N), Rayleigh and Lewis numbers (Ra, Le), the height of corrugated walls (a), Stefan number (Ste), non-dimensional fusion temperature (θf), Dufour (Df), and Soret (Sr) parameters. High values of N and Ra, and low values of Le and a, caused in the highest rate of heat and mass exchange. The irreversibilities due to the heat and mass transfer effects increase as the flow intensity within the system decrease. Decreasing the latent heat of the NEPCM cores and increasing their fusion temperature lowering the heat transfer rates, while improving mass transfer rates. This configuration can help in the design of the storage tank in hydronic apparatus for cooling, heating, and domestic hot water in buildings.

Enhancement of conjugate heat transfer in an enclosure by utilizing water and nano encapsulated phase change materials with active cylinder

Conjugate heat transfer in a differentially heated enclosure having an active cylinder placed at the center-line is studied numerically. The free space between the cylinder and the walls of the enclosure is filled with water (H2O) and nano-encapsulated phase change materials (NEPCMs). The governing equations take the form of a primitive formulation and are numerically solved using the finite element method. The controlling factors under consideration are the cylinder’s location, −0.2≤δ≤+0.2, the cylinder radius, 0≤R≤0.3, the rotation speed, −150≤Ω≤150, the thermal conductivity ratio, 0.5≤Kr≤10, the Rayleigh number, 104≤Ra≤106, and the NEPCMs concentration, 0≤ϕ≤0.05. The number, size, and shape of the cells change depending on where the inner cylinder is, how fast it is spinning, and how much NEPCMs are in the suspension. The placement of the peak Nusselt number values is heavily influenced by the rotational direction.

Dual convection of NEPCM inside an annulus between two circular cylinders mounted on rectangles

This paper adopts the incompressible smoothed particle hydrodynamics (ISPH) method for simulating the dual diffusion of nano-encapsulated phase change material (NEPCM) in an annulus. Here, the novelty is appearing in simulating the double diffusion of NEPCM within a novel complex shape composed from the paradigm of an annulus between two circular cylinders mounted on rectangles. The ISPH method solved the regulating equations of a physical problem. The scales of parameters are a fusion temperature θf(0.05≤θf≤0.95), buoyancy ratio 0≤N≤10, nanoparticle parameter 0.01≤φ≤0.05, a radius of a circular cylinder 0.1≤rc≤0.4, Darcy parameter 10-2≤Da≤10-5, and Rayleigh's number 103≤Ra≤106. The performed simulations showed that the different boundary conditions amongst an inner blockage and outer cavity walls are affecting the strength of concentration and temperature. The location of a phase change zone is varied according to the variations of variable boundary conditions and fusion temperature. The mean Nusselt and Sherwood numbers are improving under an enlargement in a radius of an internal circular cylinder, and Rayleigh numbers.

Laminar forced convection in a tube with a nano-encapsulated phase change materials: Minimizing exergy losses and maximizing the heat transfer rate

The present work investigates the potential of NEPCM mixtures via analyses of convective heat transfer and exergy losses, and trade-offs between them inside a tube with a constant wall temperature. Experimental data for viscosity and thermal conductivity of the mixture was used within numerical simulations over a broad range of dimensionless parameters, including Reynolds number, mass fraction, melting strength, phase change zone thickness, and location of phase change zone. The effect of these parameters on the melting process, convective heat transfer and exergy loss is evaluated. The findings indicate that, although employing a NEPCM can boost the Nusselt number and heat transfer rate by 9.3 % and 16.1 %, as compared to the water, the exergy losses were enhanced up to 17 %. Additionally, in some circumstances, the Nusselt number and heat transfer rate both increased by 5.9 % and 2.5 %, respectively, whereas the exergy losses were zero. An optimal value of ω=0.02 was found to provide reasonable improvement in heat transfer rate increase with no exergy losses. Importantly, the present study shows that although higher NEPCM mass fractions can continue to increase the heat transfer performance, their benefit is rapidly offset above ω=0.02 due to heat transfer related exergy losses. Additionally, it was concluded that, in comparison to other parameters, the location of the phase change and the mass concentration of NEPCMS substantially affected the percentage of molten NEPCM and the latent heat efficacy.

PMMA nano-encapsulated phase change material colloids for heat management applications

Phase Change Materials (PCM) emulsions or micro-nano-encapsulated into organic and inorganic shells have attracted scientific interest for their potential to enhance the thermal capacity and the efficiency of heat transfer liquids. In this work, RT21HC, a commercial PCM with transition temperature at 21 °C, has been successfully nano-encapsulated into Poly(methyl-methacrylate) (PMMA) shells by an emulsion polymerization process after the selection of proper surfactant and synthesis parameters, in order to obtain complete encapsulation and stable colloidal dispersions. Water-based colloidal dispersions containing 10 wt% PCM were obtained and characterized from point of view of microstructure, colloidal stability, rheological properties, apparent heat capacity and thermal diffusivity, in order to show the potential of these colloidal dispersions as advanced heat management fluids. With the aim to mitigate the phenomenon of PCM crystallization supercooling that is caused by nano-confinement and is cause of apparent thermal capacity loss, the effect of incorporation into the nano-capsules of two fatty esters, two fatty alcohols and a fatty acid as nucleating agents, has also been studied.

A novel photovoltaic/thermal (PV/T) solar collector based on a multi-functional nano-encapsulated phase-change material (nano-ePCM) dispersion

Overheating is a major problem encountered by photovoltaic (PV) cells that significantly deteriorates their performance and shortens their lifetime. For the first time, this study numerically investigated employing a nano-encapsulated phase-change material (nano-ePCM) dispersion in a double-pass photovoltaic/thermal (PV/T) solar collector, where the multi-functional nano-ePCM dispersion simultaneously operates as an optical filter, heat carrier, and storage medium. The water-dispersed nano-ePCM particles were made of silica shells and paraffin-based cores. The proposed system was optically, thermally, and electrically modeled and evaluated after rigorous validation against published results. The performance of the PV/T system was analyzed upon varying the PCM core material, flowrate, solar intensity, particle size and loading, and channel depth and length. In addition, the proposed system (SYS-1) was compared to two alternative configurations, where one was based on a cooling channel below the PV cells without an optical filtration channel (SYS-2), and the other was based on an optical filtration channel above the PV cells without a cooling channel (SYS-3). To investigate the optical filtration capabilities of the nano-ePCM dispersion, a performance metric known as the ‘spectral match’ (SM) was proposed. Results showed that all ePCM dispersions exhibited a SM > 70 % when the PCM cores were in their liquid phase and a SM > 30 % while in solid phase. As compared to SYS-2 and SYS-3, at the lowest investigated flowrate (0.0026 kg s−1), the proposed PV/T system exhibited mean cell temperatures lower by 5 and 10°while offering relative thermal exergy enhancements of 66 and 208 %, respectively. This was attributed to allowing the PV cells to operate at temperatures substantially lower than the dispersion outlet temperature to achieve both high-grade thermal outputs and enhanced PV efficiencies. This study paves the way for novel PV/T collectors that employ smart, multi-functional fluids offering superior electrical and thermal performance.

Natural convection of NEPCM in a partial porous H-shaped cavity: ISPH simulation

PurposeThis paper aims to investigate the conformable fractal approaches of unsteady natural convection in a partial layer porous H-shaped cavity suspended by nano-encapsulated phase change material (NEPCM) by the incompressible smoothed particle hydrodynamics method.Design/methodology/approachThe partial hot sources with variable height L_Hot are in the H-cavity’s sides and center. The performed numerical simulations are obtained at the variations of the following parameters: source of hot length L_Hot = (0.4–1.6), conformable fractal parameterα(0.97–1), fusion temperatureθf(0.05–0.9), thermal radiation parameterRd(0–7), Rayleigh numberRa(103–106), Darcy parameterDa(10−2to 10−5) and Hartmann numberHa(0–80).FindingsThe main outcomes showed the implication of hot source length L_Hot, Rayleigh number and fusion temperature in controlling the contours of a heat capacity within H-shaped cavity. The presence of a porous layer in the right zone of H-shaped cavity prevents the nanofluid flow within this area at lower Darcy parameter. An increment in the thermal radiation parameter declines the heat transfer and changes the heat capacity contours within H-shaped cavity. The velocity field is strongly enhanced by an augmentation on Rayleigh number. Increasing the Hartmann number shrinks the velocity field within H-shaped cavity.Originality/valueThe novelty of this work is solving the conformable fractal approaches of unsteady natural convection in a partial layer porous H-shaped cavity suspended by NEPCM.

Preparation and Characterization of n-Octadecane@SiO2/GO and n-Octadecane@SiO2/Ag Nanoencapsulated Phase Change Material for Immersion Cooling of Li-Ion Battery

Nanoencapsulated phase change materials (NePCMs) are promising thermal energy storage (TES) and heat transfer materials that show great potential in battery thermal management systems (BTMSs). In this work, nanocapsules with a paraffin core and silica shell were prepared using an optimized sol-gel method. The samples were characterized by different methods regarding chemical composition, thermal properties, etc. Then, the nanocapsules were used as the coolant by mixing with insulation oil in the immersion cooling of a simulative battery. The sample doped with Ag on the shell with a core-to-shell ratio of 1:1 showed the best performance. Compared to the sample without doping material, the thermal conductivity increased by 49%, while the supercooling degree was reduced by 35.6%. The average temperature of the simulative battery cooled by nanocapsule slurries decreased by up to 3.95 °C compared to the test performed with pure insulation oil as the coolant. These novel nanocapsules show great potential in the immersion cooling of a battery.

Analysis of nano-encapsulated phase change material confined in a double lid-driven hexagonal porous chamber with an obstacle under magnetic field

The magnetohydrodynamics (MHD) mixed convection of nano-encapsulated phase change material (NEPCM) contained within a double lid-driven hexagonal porous chamber contacting a square-shaped obstacle is numerically examined in this study. The enclosure's upper and lower walls are moving at the same speed; while the square-shaped obstacle is hot, the side walls are stationary and cold. The Galerkin Finite Elements method (GFEM) was applied to deal with the governing equations and their boundary conditions. The flow and thermal fields are presented and discussed in relation to the effects of the moving wall direction, moving wall velocity, magnetic field strength, and chamber permeability. These studied factors are examined in these ranges: Ha = 0 to 100, Da = 10–5 to 10–2, ø = 0 % to 5 % and Re = 1 to 500. The results showed that the heated body is surrounded by a circular flow when the two walls move in opposite directions. However, thermal activity is enhanced and strengthened when the upper and lower walls move in the same direction. According to the findings, the concentration of NEPCM particles has little effect on the quality of the thermal transfer and decreasing the space's permeability makes it more difficult for the suspension to move and reduces the amount of thermal energy transferred between the cold and hot surfaces. Additionally, a decrease in thermal transfer occurs when the intensity of the magnetic field is increased, which has a negative impact on the suspension's movement.

Mixed convection within trapezoidal-wavy enclosure filled with nano-encapsulated phase change material: Effect of magnetohydrodynamics and wall waviness

The present work investigates the mixed convection of nano-encapsulated phase change material (NEPCM) inside a trapezoidal-wavy cavity subjected to a magnetic field. The mixed convection results from the movement of the upper lid of the cavity and the temperature difference between the inclined cold side walls and the hot bottom wavy wall. The main goal of this study is to address the impact of wall waviness and the magnetic field on mixed convection on a disclosure filled with NEPCM. The governing equations representing the investigated case were solved by Galerkin finite element method (GFEM). The influences of lid velocity (Re = 1–1000), bottom wall undulation number (N = 1–4), and magnetic field strength (Hartmann number (Ha) = 0–100) on the thermal behavior and the flow patterns were examined and reported. The results revealed that the mean Nusselt number is directly proportional to the lid velocity (Re), whereas it is reverse proportional to the bottom wavy undulation number (N) and the magnetic field strength (Ha). The higher values of Re (e.g., Re = 1000) could lead to a 300% enhancement in local Nu values compared to those of lower Re values (e.g., Re = 1). At Re = 1000, increasing Ha from 0 to 100 and N from 1 to 4 reduced the mean Nusselt number by 53% and 30%, respectively. According to the findings of the present study, it is recommended that heat transfer augmentation should eliminate both the waviness of the bottom wall and the magnetic field since they hinder the free and mixed convection flow.

Thermo-regulated thermoplastic sugarcane bagasse-based biocomposite via solvent-free extrusion for energy-saving smart home

Phase change materials (PCMs) have been widely used in the sectors of solar energy conversion, thermal regulation, waste heat recovery, etc. However, it is still a huge challenge to utilize biodegradable room-temperature PCMs in thermo-regulated smart homes due to their poor shape stability and processability at high temperature. Herein, we report solvent-free reactive extrusion processes to prepare a thermoplastic sugarcane bagasse-based biocomposite (named TBP-50) containing 50 wt% dodecanol-based nanoencapsulated PCM (NPCM). The developed TBP-50 with the phase change point near room temperature and the enthalpy of about 52 J g−1 is thermo-processable and thermally stable below 180 °C. The high mass ratio of supramolecular lock-shell NPCM (50 wt%) endows TBP-50 with excellent heating/cooling cycling reliability and thermal regulation ability that have been verified by a series of simulated calculations about an incubator (30 L) and a bedroom (4.5 m × 3.5 m × 3 m) decorated with dimensionally stable TBP-50 sheets. Moreover, TBP-50 shows acceptable mechanical properties: the tensile strength of 9.6 MPa, the tensile modulus of 6.73 GPa, the impact strength of 3.18 kJ m−2, and the Shore surface hardness of 68 D. Obvious biodegradation in the local soil environment is detected for TBP-50 and the six probable degradation steps are proposed in this work. Considering the next generation of energy-saving and environmental-friendly home-decorating materials, the herein prepared TBP-50 biocomposite via typical extrusion molding is an ideal choice as ceiling, clapboard, floorboard, wardrobe, desk, and so on.

Entropy and hydrothermal analyses of nano-encapsulated phase change materials within a U-shaped enclosure: Impact of diverse structures of baffles and corrugated wall

The entropy and hydrothermal inspections of natural convection (NC) flow and heat transfer (HT) within cavities may absorb a raft of researchers' attention owing to their significant industrial applications in the electronic devices' cooling, solar collectors, heat exchangers, micro-electro-mechanical systems, etc. Based on this requirement of efficient and long-time cooling, internal baffles, encapsulation of phase change material (PCM) by nanoparticle (NEPCM), internal corrugated hot triangular wavy wall are considered in this examination to ameliorate HT into PCM, thereby HT increment speeds up the rate of PCM melting and reduces the operating period for PCM-based thermic management. The present study investigates the NC of magnetic NEPCMs within a U-shaped enclosure with the bottom as a triangular wavy corrugated wall (subject to stable heat flux due to sunlight transmitted from a PTSC's reflector) and comprised of two cold baffles of variable length. The FEM is the numerical approach to achieving the desired solution. The results are that growth of Hartmann number results in the reduction of streamlines, isotherms, and horizontal and vertical velocities. Ascent of baffle length (l) yields amelioration of the local HT rate while the height of corrugated wall exhibits a reverse effect with/without magnetic field impact.

Structure-property correlation of thermally activated nano-size phase change material in the cementitious system

Recently, energy-efficient building design has emerged as a prominent research focus for maximizing energy savings. In light of this, various attempts are made to improve the thermal mass of buildings. Increasing the heat capacity of construction materials with the incorporation of phase change material (PCM) has been considered an easy and effective technique to increase the thermal mass of concrete structures. However, the incorporation of microencapsulated phase change material (MPCM) into cementitious system possesses drawbacks of weaker hydration activity and leakage problems. Therefore, this study has been aimed to explore the chemical and morphological evolution of thermally activated nanoencapsulated phase change material (NPCM) with principal hydrated phase of ordinary Portland cement (OPC) at 60 °C. With an average size of ∼450 nm, silica encapsulated paraffin-based NPCM is synthesized via facile in-situ polycondensation method. 1% NPCM has boosted the hydration reaction with the occurrence of a low quantity of C3S + C2S, whereas a denser cement matrix with minimum pore structures has been accomplished due to better pozzolanic activity and existence of CaCO3 on the surface of NPCM. The emergence of needle-shaped CaCO3 polymorph on the NPCM surface proves that NPCM acts as secondary nucleation sites for the formation of additional C–S–H, which has manifested pore-filling effects as well as further leakage protection. The activation of NPCM at high-temperature curing has ascertained excellent structural and durability performances over an extended period. Thus, this study may bring out better insight to the researchers toward the direction of energy storage materials applications in building structures.

EFFECTS OF MAGNETIC FIELD AND THERMAL RADIATION ON DOUBLE DIFFUSION OF A SOLID PHASE IN THE TWO CONNECTED CIRCULAR CYLINDERS SUSPENDED BY NEPCM AND POROUS MEDIA

The novelty of the present work is studying the influences of thermal radiation and magnetic field on the double diffusion of solid phase in the novel cavity of two linked cylinders suspended by nano-encapsulated phase change materials (NEPCMs) and porous media. The complex cavity contains two circular cylinders connected by an open gate occupied by solid particles. Two different boundary conditions including hot and cold for the solid phase are conducted in this work. The incompressible smoothed particle hydrodynamics (ISPH) method is improved to solve the time-fractional governing equations of the physical problem. The mesh-free nature of the ISPH method helps in treating the different materials of the solid and fluid phases efficiently. The physical parameters are dimensionless time parameter τ, Hartmann number Ha, thermal radiation parameter Rd, fractional time-derivative α, Darcy parameter Da, Rayleigh number Ra, and fusion temperature θ<sub>f</sub>. The main findings of the numerical simulations indicated that the fractional time-derivative parameter changes the transmission of heat-mass and nanofluid developments during the initial time steps. The Rayleigh number works well in improving the interactions between the solid and fluid phases due to the high buoyancy forces. Increasing the Rayleigh number improves the intensity of the temperature, concentration, and nanofluid speed in a cavity at Case 1 (C1) and Case 2 (C2). The phase change zone is changing according to the alterations of boundary conditions, Rayleigh number, and fusion temperature. Increasing thermal radiation parameter shrinks the nanofluid movements and mean Nusselt number Nu.

Modelling and optimisation of a battery thermal management system with nano encapsulated phase change material slurry for 18650 Li-ion batteries

Modelling and optimisation of a battery thermal management system with nano encapsulated phase change material slurry for 18650 Li-ion batteries

Ultrafast and continuous synthesis of phase change nanocapsules using salt-accelerated microwave-assisted polymerization

Using a microwave-assisted polymerization method for the continuous and ultrafast preparation of nanoencapsulated phase change materials (NanoPCMs) for energy storage.

Efficacy of exothermic reaction on the thermal-free convection in a nano-encapsulated phase change materials-loaded enclosure with circular cylinders inside

The current research may well be carried out to dissect the efficacy of exothermic reaction on the thermal behavior of suspension of Nano-Encapsulated Phase Change Materials (NEPCMs) particles in a complex adiabatic enclosure which entails two differently heated circular cylinders. These cylinders have the potential to move horizontally and to rotate clockwise. The equations governed for thermal-natural convective flow considering exothermic reaction may be solved utilizing FEM. Results described the impact of Stefan and Rayleigh numbers (Ste, Ra), aspect ratio (AR), and non-dimensional fusion temperature (θf) on the thermo-hydrodynamic features of the suspension. The overall heat transmission was found to be reinforced by escalating Ra up to 144.74 % and be lessened by growing AR up to 49 %. Also, there is an optimum value of the latent heat of the PCM cores for a maximum heat transfer rate at a specific value of fusion temperature. Further, results reveal that making the fusion temperature near to the cylinders' temperatures diminishes the heat transfer.

Heat storage and increasing the rate of heat transfer in polymer electrolyte membrane fuel cell by adding nano-encapsulated phase change material to water in the cooling process

Polymer electrolyte membrane fuel cell (PEMFC) is a promising technology in the field of renewable energy production, especially in electric transportation systems. High heat produced and the temperature sensitivity of the expensive membrane have always reduced the lifespan and efficiency of PEMFCs and prevented their commercialization. Choosing an optimal cooling method is always one of the best solutions studied by researchers. Phase change cooling with nePCM particles is one of the newest microchannel cooling methods, which in addition to good heat transfer and uniform cooling, capability waste heat recovery (WHR) by heat storage. Nano-encapsulated of phase change material (nePCM) is a new type of PCMs that can absorb high heat without noticeable temperature change due to high latent heat during the phase change process while improving heat transfer. These particles consist of a phase change material in the core and a polymer shell, which, significantly improves its heat transfer properties when added to the base fluid. Based on computational fluid dynamics (CFD) simulation, the performance of water-nePCM suspension with an n-nonadecane core and polyurethane shell as a new cooling nanofluid in the microchannel of a PEMFC was evaluated for the first time. The governing equations are solved numerically using the finite volume method (FVM), PIMPLE algorithm, and C++ code development, by OpenFoam software. After examining the effect of different heat transfer parameters, the results show that using 4 % of nePCM particles increases the Nusselt number and heat storing (ηNEPCM %), by 20 % and 18 % respectively. Also, lower Reynolds numbers cause more heat storage in nePCM particles. As a result, this has led to more uniform cooling of the PEMFC plates and the thermal stability of the system.

Heat transfer intensification of NEPCM-water suspension filled heat sink cavity with notches cooling tubes by applying the electric field

The effects of an electric field on heat transfer, free convection, and entropy generation of nano-encapsulated phase change material (NEPCM) dissolved in water in a complex inclined chamber are studied. The enclosure consists of a rectangular cavity heated from below and the remaining walls are considered adiabatic. The fluid is cooled by eight cooling tubes, each with four notches. The effects of the electric field, inclination angle (ζ = 45° and ζ = 90°), and Rayleigh number (Ra = 103, 104, and 105) in equal concentration of NEPCM (ϕ = 2 %) are studied using ANSYS Fluent CFD code. The dimensionless form of fluid governing equations, electric potential equation, electric charge density equation, and entropy generation equation are used to set the primitive parameters. Grid verification and validation tests are performed to ensure the reliability of the solution. Calculations show that with increasing Ra, the average Nusselt number (Nuave) decreases from ζ = 45° to 90°, but when an electric field is applied, the results are reversed. As the Rayleigh number increases in conjunction with the electric field, the buoyancy effect becomes more pronounced. Furthermore, owing to its high heat transfer potential and lowest irreversibility, the straight cavity (ζ = 90°) is desirable at Ra = 105.

Effect of waviness on thermal-flow characteristics in an inclined trapezoidal cavity filled with nano-encapsulated phase change material and water

This study examines the free convection in an inclined trapezoidal enclosure generated by a temperature difference between a flat cold wall and a wavy hot wall. The trapezoidal enclosure is filled with hybrid nanofluids. This new type of fluid consists of nano-encapsulated phase-change material (NEPCM) suspended in the base fluid. The NEPCM utilizes polyurethane as the cover with n-nonadecane as the core. The mathematical model is expressed in terms of partial differential equations and numerically solved using the finite element method. Parametric studies are used to analyse the effects of the inclination angle, NEPCM volume fraction, sloping wall angle, number of corrugation and the Rayleigh number. It is found that the extracted energy from the charging process is optimal for moderate values of the fusion temperature and undulation number at a high value of the NEPCM volume fraction.