Nano-encapsulated Phase Change Material Particles Research Articles

Thermal performance of forced convection of water- NEPCM nanofluid over a semi-cylinder heat source

1) BackgroundPhase change materials (PCMs) have been used statically, which has caused the use of these materials to face challenges. Encapsulating PCMs and combining them with the base fluid can significantly solve the problem of using PCMs in BTM systems. In the present study, based on computational fluid dynamics, forced convection heat transfer of nano-encapsulated phase change materials (NEPCM) in a BTM system are simulated. The main aim of the present research is to reduce the temperature at the surface of the hot cylinder. 2) MethodsIn this research, we simulated lithium battery thermal management systems in both steady and transient states. The effects of using NEPCM particles to water were investigated. Modeling is implemented using the finite volume method and the PIMPLE and SIMPLE algorithms in OpenFoam. Furthermore, the effects of battery heat flux, Reynolds number, and the presence of nanoparticles (NPs) were analyzed. We intend to evaluate the optimal state of the system by studying the mentioned parameters. 3) Significant FindingsOur study shows that adding 3.5% NEPCM to water can reduce the length of the vortex by 22% and in unsteady-state simulation, it is observed that the presence of NEPCM particles in water reduces battery temperature up to 0.66 K.

Turbulent Heat Transfer of Hybrid Nanofluid with Nano-Encapsulated Phase Change Material in a Square Channel

Investigation of turbulent mixed convection of different working fluids, namely, pure water, CuO/water nanofluid, n-octadecane/water nanofluid (or slurry), and a hybrid water-based suspension of CuO and n-octadecane nanoparticles in a uniformly heated vertical square channel is carried out. The shear stress transport/kappa-omega model is applied to simulate the turbulent flow. Eulerian–Lagrangian two phase model and homogeneous model are employed to simulate the nanofluid flow. It is shown that Eulerian–Lagrangian two-phase model predicts higher Nusselt number and friction factor than single-phase model and the results of two-phase model are closer to experimental data. It is found that a new hybrid nanofluid with dispersed nano-encapsulated phase change material particles provides better thermal and hydrodynamic performances compared to other nanofluids. Slurry containing 5% n-octadecane provides an improvement of nearly 37.2%, while hybrid nanofluid (1% CuO + 5% n-octadecane) offers added convective heat transfer enhancement of almost 60%. With increasing volume fraction, friction factor becomes slightly larger than that of pure water. For 5% n-octadecane/water and 1% CuO + 5% n-octadecane/water nanofluids, friction factor increases by 2.5% and 1.7%, respectively. Due to dominance of thermal entropy generation, total entropy generation reduces by increasing Reynolds number and volume fraction.

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%.

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.

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.

CONVECTIVE FLOW AND HEAT TRANSFER OF NANO-ENCAPSULATED PHASE CHANGE MATERIAL (NEPCM) DISPERSIONS ALONG A VERTICAL SURFACE

Nano-encapsulated phase change suspension is a novel type of functional fluid in which the nanoparticles undergo phase change that contribute to heat transfer. Thus, the working fluid carries heat not only by sensible heat but also in the form of latent heat stored in the particles. The natural convection and heat transfer of Nano-Encapsulated Phase Change Materials (NEPCMs) suspensions within a boundary layer along a heated flat surface are theoretically investigated in this work. The nanoparticles are core-shell structured with the core fabricated from PCMs covered by a solid shell. A similarity solution approach along with the finite element method is employed to address the phenomena. The outcomes indicate that a decisive factor in boosting the heat transfer is the temperature at which NEPCM particles undergo the phase transition. The heat transfer parameter can be enhanced by about 25% by just adding 5% of NEPCM particles, compared to the case with no NEPCM particles.

Hydrothermal behavior of micro-polar Nano-Encapsulated phase change materials (NEPCMs) in an inclined L-shaped cavity

This paper investigates natural convection and entropy generation of the Nano-Encapsulated phase change materials (NEPCMs) in an inclined L-shaped cavity. The NEPCMs are made up of core and shell in which the PCMs are the core section that are capsulated in Nano-shells. These NEPCM particles go through phase change from solid to the liquid while absorbing the heat and release it when their phase changes back to solid. The Navier-Stokes equations are solved by Finite Element Method (FEM) to simulate the behavior of NEPCMs under a set of defined boundary conditions. The effect of Rayleigh number (10 4 -10 6 ), micro-rotation parameter (0–2), Nano particle's concentration (0.01–0.05), Stefan number (0.1–0.5), and non-dimensional fusion temperature (0.1–0.3) on the Nusselt number and entropy generation of the fluid flow is also analyzed. The results reveal that the Stefan number, micro-rotation parameter, and non-dimensional fusion temperature have a negative impact on NC heat transfer of NEPCMs and reduce the Nu avg up to 25%, 42%, and 15% respectively. Conversely, the nanoparticle concentration enhances the Nu avg up to 36%.

Unsteady natural convection of nano-encapsulated phase change materials (NEPCMs) inside a random porous medium considering local thermal non-equilibrium condition

A local thermal non-equilibrium analysis is undertaken to simulate unsteady free convective heat transfer inside a square enclosure filled with a random porous medium. There is a time-varying temperature profile at the hot wall. The fluid is a suspension comprising nano-encapsulated phase change materials (NEPCM) particles dispersed in water while aluminum foam, copper foam, or glass balls are considered for the solid matrix. It is found that when the hot wall temperature reaches its minimum value during one oscillation period, most of the cavity is occupied by the NEPCM particles in the solidious phase. For the metallic foams, the heat transfer of the medium is substantially higher than the NEPCM particles. Meanwhile, the Nusselt number of the glass balls is much lower than the suspension. A rise in the dimensionless frequency or amplitude of the temperature profile as well as approaching the dimensionless fusion temperature to 0.5 elevates Nusselt number of the suspension. However, no general conclusion can be drawn for their consequences on the heat transfer in the solid matrix. Among the current alterable parameters, only the contributions of the non-dimensional interface heat transfer coefficient and the non-dimensional amplitude of the temperature profile are found significant.

Jet Impingement Cooling Enhanced with Nano-Encapsulated PCM

In the present study, the laminar flow and heat transfer of water jet impingement enhanced with nano-encapsulated phase change material (NEPCM) slurry on a hot plate is analytically investigated for the first time. A similarity solution approach is applied to momentum and energy equations in order to determine the flow velocity and heat transfer fields. The effect of different physical parameters such as jet velocity, Reynolds number, jet inlet temperature, and the NEPCM concentration on the cooling performance of the impinging jet are investigated. The volume fraction of NEPCM particles plays an essential role in the flow and heat transfer fields. The results show that NEPCM slurry can significantly enhance the cooling performance of the system as it improves the latent heat storage capacity of the liquid jet. However, the maximum cooling performance of the system is achieved under an optimum NEPCM concentration (15%). A further increase in NEPCM volume fraction has an unfavorable effect due to increasing the viscosity and reducing the conductivity simultaneously. The effect of adding nano-metal particles on the heat transfer performance is also investigated and compared with NEPCM slurry. NEPCM slurry shows a better result in its maximum performance. Compared with the water jet, adding nano and NEPCM particles would overall enhance the system’s thermal performance by 16% and 7%, respectively.

Investigation of the effect of adding nano-encapsulated phase change material to water in natural convection inside a rectangular cavity

The present simulation aims to investigate adding NEPCM nanoparticles to water in the natural convection inside a cavity by using FVM method and SIMPLE algorithm. Nano-encapsulated phase change material (NEPCM) consists of a shell and core with phase change property. The NEPCM particles in base fluid have the ability to transfer heat by absorbing and dissipating heat in the liquid-solid phase change state. In this study, the energy wall phenomenon due to the phase change of NEPCM core has appeared that the whose energy transfer strength is proportional to the latent heat of NEPCM core and the thickness of the energy wall. Moreover, the relationship between the energy wall and the heat transfer rate is payed attention, and the effects of the energy wall parameters including strength, thickness, and event location of energy wall and volume fraction are studied on the energy wall and heat transfer rate. According to the obtained results, adding NEPCM to the water enhances its heat transfer up to 48% in order to increase heat capacity of water-NEPCM mixture. Also, best heat transfer rate happens when the energy wall is at the center of the cavity. Moreover, a relation is presented for the thermal expansion coefficient of NEPCM, which considers the effects of the thermal expansion coefficient of the core and shell material.

Impact of Surface Undulation on Flow and Heat Transfer Characteristics in an Enclosure Filled with Nanoencapsulated Phase Change Materials (NEPCMs)

The present study investigates the natural convection in a wavy enclosure caused by a thermal difference between a cold wall and a hot undulated wall. The enclosure is filled with hybrid nanofluids. The hybrid nanofluids are formed of a phase change material (PCM) suspended in the water. The PCM utilizes polyurethane as the shell and nonadecane as the core. The core absorbs or releases its energy in the shape of latent heat inside the water and contributes to thermal energy storage and heat transfer. The governing equations are expressed in PDEs and solved by the finite element method (FEM). Parametric studies were used to analyze the solid concentration, fusion temperature, amplitude of corrugation, number of corrugations, and Rayleigh number. It is found that the heat transfer rate enhances by the rise of the latent heat of the NEPCM cores. The global heat transfer can be improved by more than 12 % by adding 1 % of NEPCM particles volume fraction. However, the heat transfer tends to decrease by applying the wavy surface.

Convective heat transfer of nano-encapsulated phase change material suspension in a divergent minichannel heatsink

The convection heat transfer of nano-encapsulated phase change material (NEPCM)-water suspensions in a divergent minichannel heatsink was experimentally investigated. The mini heatsink was made of eight minichannels with a divergent angle of 1.38°. The minichannel was heated at the bottom, and the NEPCM-water was used as the cooling working fluid. The average Nusselt number, the index of performance, and the pressure drop of NEPCM-water compared to the pure water were examined. The experiments show that employing NEPCMs could be advantageous in low Reynolds number flows and low heating powers. The phase change heat transfer of NEPCM particles promoted the heat transfer by 82% compared to pure water. Moreover, using the NEPCM particles was not advantageous at large Reynolds numbers, where the sensible heat was the dominant mechanism of heat transfer.

Free convective melting-solidification heat transfer of nano-encapsulated phase change particles suspensions inside a coaxial pipe

The nano encapsulated phase change materials are of the great energy storage potential in various engineering applications. Since they are new nanomaterials, new models for understanding their thermal behavior and capability are essential. This work aims to investigate the unsteady thermal behavior of Nano-Encapsulated Phase Change Material (NEPCM) suspensions in a cylindrical cavity. The particles contain a Phase Change Material (PCM) core, which can absorb/release a substantial amount of thermal energy upon phase change. The phase change particles are well dispersed in a liquid fluid and freely move along with the fluid. The flow, heat transfer, and the particle phase change were modeled using partial differential equations. A non-dimensional approach was employed to generalize the study. The unsteady charging and discharging behavior of the NEPCM suspension are investigated for the volume fraction of the NEPCM particles, fusion temperature of nanoparticles, Stefan number, and the Rayleigh number. Numerical results show that an increment in the Stefan number, i.e., Ste, can significantly reduce the Nusselt number, i.e., Nua, at the charging mode of the system. However, the dependency of the Nua at the discharging mode on the Ste is negligible. Also, it was found that the effect of the fusion temperature of the particle’s core (θf) on heat transfer depends on the working mode of the system. In the charging mode, using a higher value of θf decreases the heat transfer rate. Reversibly, a higher value of θf inhibits the Nua during discharging state. Furthermore, the results show that for Ra = 106, Ste = 0.2, and θf = 0.1, a rise of ϕ from 0 to 0.05 leads in about 1.73 and 1.55 times of improvement in the value of Nua for the cases of the melting and solidification of the core of NEPCM particles.

Entropy generation and natural convection flow of a suspension containing nano-encapsulated phase change particles in a semi-annular cavity

Abstract The natural phase change convection of a new type of hybrid nanofluids, suspensions of Nano-Encapsulated Phase Change Materials (NEPCM), was addressed in a semi-annular inclined enclosure. The nanoparticles consist of a polymer shell and a nonadecane shell, in which the nonadecane core can change phase at its melting temperature and absorb/release a significant quantity of latent heat. The NEPCM-suspension circulates in the enclosure due to the natural convection, and the NEPCM particles contribute to heat transfer by phase change. The equations governing the movement and heat transfer of the suspension and nanoparticles were inserted in the form of partial differential equations. The finite element method was used to numerically solve the equations. Then, the entropy generation of NEPCM suspension in the attendance of the phase change was examined. The influence of the fusion temperature and volume fraction of nanoparticles, Stefan number, Rayleigh number, and inclination angle of enclosure on the thermal behavior and entropy generation of the suspension was explored. The results showed that the contribution of phase change core of nanoparticles was significant, and the heat transfer was enhanced by the presence of NEPCM particles. The fusion temperature of particles controls the Bejan number (entropy generation) behavior of the NEPCM suspension. There is an optimum phase change temperature for nanoparticles, which results in maximum heat transfer. For a horizontal enclosure, the optimum fusion temperature is the average temperature of the active walls. This optimum phase change temperature is a function of the tilting angle of the enclosure.

Free convection heat transfer analysis of a suspension of nano–encapsulated phase change materials (NEPCMs) in an inclined porous cavity

In the current study, free convection heat transfer of a suspension of Nano–Encapsulated Phase Change Materials (NEPCMs) is simulated and discussed in an inclined porous cavity. The phase change materials are capsulated in nano-shells layers, while the core stores/releases large amounts of energy during melting/solidification in the vicinity of the hot/cold walls. The governing equations are introduced and transformed into non–dimensional form before being solved by using the finite element method. Simulation results are validated thoroughly. Thereafter, the consequences of the fusion temperature and the Stefan number on the distributions of streamlines, isotherms, and the heat capacity ratio, as well as the heat transfer characteristics, are analyzed for different inclination angles of the cavity. Inspection of the results demonstrates that the best heat transfer performance occurs for the non–dimensional fusion temperature of 0.5 and the inclination angle of 42°. It is found that a decrease in the Stefan number improves heat transfer. The results also show that the presence of the NEPCM particles generally leads to heat transfer improvement.

Parametric evaluation of a hydrofoil-shaped sidewall rib-employed microchannel heat sink with and without nano-encapsulated phase change material slurry as coolant

The application of hydrofoil-shaped sidewall ribs (SWRs) in microchannel heat sinks (MCHSs) with nano-encapsulated phase change material (NEPCM) particle slurry as coolant has recently been proven as an improvised solution for enhancing heat transfer, with a reasonable penalty in pressure drop. However, the further mitigation of high-power densities of modern micro/nanoscale devices is limited owing to manufacturing complications and design constraints. By using the geometrical and thermophysical parameters of hydrofoil-shaped SWRs and NEPCM slurry, the present study numerically evaluates the thermal and hydrodynamic performance of an MCHS device. The preliminary results reveal the superior performance of NEPCM slurry with hydrofoil-shaped SWRs compared with that of water without ribs in an MCHS owing to the improved latent heat storage capability of the former fluid as well as the enhanced heat transfer area of the rib structure. Increase in the width and height of hydrofoil-shaped SWRs and particle diameter, latent heat of fusion and mass concentration of the NEPCM slurry at a constant Reynolds number (Re) and inlet temperature enhances heat transfer. However, increase in the pitch of the hydrofoil-shaped SWRs and melting temperature range of the NEPCM slurry degrades heat transfer. The inlet temperature of the NEPCM slurry, with a slightly lower value than the melting point of the NEPCM particles, yields superior performance. The maximum ratios of the Nusselt number, that is, Nuavg,SWR/Nuavg,ref and Nuavg,NEPCM/Nuavg,ref, are 1.88 and 2.68, respectively. A particle loading of more than 10% at a high Re of 1000 is not reasonable from the thermodynamic efficiency perspective. The findings are expected to serve as a benchmark for the selection of the geometric, thermophysical and operational parameters of future MCHS devices with hydrofoil-shaped SWRs and NEPCM slurry as coolant.

Forced convection heat transfer of Nano-Encapsulated Phase Change Material (NEPCM) suspension in a mini-channel heatsink

In the present experimental study, Nano-Encapsulated Phase Change Material (NEPCM) nanoparticles with particle sizes in the range of 250–350 nm are synthesized. The core of nanoparticles is made of eicosane and can undergo liquid-solid phase change by absorbing/releasing latent heat. The eicosane core of the NEPCM particles is enclosed in a formaldehyde shell, and the particles are suspended in the water as the base fluid. The synthesized NEPCM-water suspension is employed as the working-fluid for heat removal from a microchannel heatsink. The heatsink is made of red-copper, and it consists of eight rectangular microchannels with an aspect ratio of 1.5 and a hydraulic diameter of 1.2 mm. Under the heatsink, a heating plate is embedded, which produces a uniform heat flux. The working-fluid, NEPCM-water, enters the microchannel and absorbs the heat from the microchannel walls in the form of sensible and latent heat. The impact of the nanoparticle's concentration, the heating-power, and the flow rate is investigated on the channel wall temperature, Nusselt number, convection ratio, performance index, and coefficient of performance. The results show that the presence of NECPM-particles improves heat transfer and the index of performance up to 70% and 45%, respectively. The observed enhancement of heat transfer is particularly notable at low Reynolds numbers. However, at the high Reynolds numbers, the presence of NECPM particles may reduce the convection ratio and performance index, which is mainly due to the increase of the viscosity and reduction of the sensible heat of the working-fluid in the presence of NEPCM nanoparticles.

Natural convection of nanoencapsulated phase change suspensions inside a local thermal non-equilibrium porous annulus

In this study, the heat transfer, fluid flow and heat capacity ratio are analyzed in an annulus enclosure filled with porous and saturated by a suspension of nanoencapsulated phase change materials (NEPCMs). It consists of phase change material core and a polymer or non-polymer shell. The presence of nanoparticles in the base fluid and the phase change capability of the nanoparticle’s core improve the thermal properties of the base fluid and thermal control process. The inner cylinder wall is reserved at hot temperatures where the encapsulated particles absorb the heat, while the outer cylinder wall is reserved at cold temperatures where the encapsulated particles release the heat. A local thermal non-equilibrium model is adopted for the porous medium. The parameters studied are Rayleigh number (104 ≤ Ra ≤ 106), Stefan number (0.2 ≤ Ste ≤ ∞), melting point temperature of the core (0.05 ≤ θf ≤ 1), the concentration of the NEPCM particles (0% ≤ ϕ ≤ 5%), radius ratio (1.67 ≤ Rr ≤ 2.5), eccentricity (− 0.67 ≤ Ec ≤ 0.67), Darcy number (10−4 ≤ Da ≤ 10−1), porosity (0.3 ≤ e ≤ 0.9) and interface heat transfer coefficient (1 ≤ H ≤ 1000). The results show that the dimensionless temperature of fusion (θf) plays the main role in the improvement in NEPCM on the heat transfer process.

Local thermal nonequilibrium conjugate natural convection of nano‐encapsulated phase change particles in a partially porous enclosure

This paper analyzes the heat transfer process of nano‐encapsulated phase change material (NEPCM) particles suspended in a base fluid. NEPCMs are polyurethane‐nonadecane, and the base fluid is water. The formed suspension fills a system of two different layers: a porous layer and a clear layer. A thermally conductive solid wall transmits heat to the porous layer. These three partitions are confined in a square cavity. The cavity is heated from the left side of the solid wall and cooled from the right side of the clear layer. The solid matrix of the porous layer and the suspension are in local thermal nonequilibrium. A Galerkin‐weighted residual finite element method is adopted for numerical computations. The impacts of Stefan number, fusion temperature, and the nanoparticles volume fraction are inspected, graphically. Results show that the maximum heat transfer can be attained with lower Stefan number, higher nanoparticles volume fraction, and a fusion temperature range between 0.2 and 0.6. For a certain circumstance, it is found that enhancement of about 29% in heat transfer can be gained when the volume fraction of the NEPCM particles is raised from 0 to 0.05.

Natural convection flow of a suspension containing nano-encapsulated phase change particles in an eccentric annulus

The free convective flow of a Nano-Encapsulated Phase Change Material (NEPCM) suspension in an eccentric annulus is investigated numerically. The inner cylinder is heated and kept at a temperature higher than that of the outer cylinder. The core of the NEPCM particles is made of nonadecane while the shell is made of Polyurethane. The nanoparticles are dispersed in water as the base fluid. The equations governing the flow and heat transfer of the NEPCM suspension in the annulus are developed and written in the non-dimensional form. The numerical solutions of these equations are obtained using the finite element method. The validity of the numerical method is ensured by comparing its predictions to the results of previously published studies. The main outcomes point out to the impact of the volume fraction of the NEPCM particles and Stefan number on the thermal and hydrodynamic characteristics of the suspension. A 5% volume fraction represents the optimal value for heat transfer enhancement. Heat transfer is also enhanced when the fusion temperature of the NEPCM core is far from the temperatures of the hot and cold walls. Furthermore, increasing the annulus eccentricity and moving the inner cylinder towards the top tends to inhibit heat transfer in the annulus.