Phase Change Material Slurry Research Articles

Experimental study on natural convection heat transfer performance of microencapsulated phase change material slurry in a square cavity

Microencapsulated phase change slurry (MicroEPCMS), consisting of microencapsulated phase change material (MicroEPCM) and base liquid, represents a novel latent heat functional fluid that can absorb a large amount of heat within its phase change temperature range. It has found widespread use as a functional liquid cooling medium for heat dissipation in batteries, electronic devices, and other devices. In this work, MicroEPCMS with different MicroEPCM concentration were prepared. The physical properties of MicroEPCMS including density, thermal conductivity, and dynamic viscosity were tested within different temperature ranges. The results showed that the MicroEPCMS exhibits a superior thermal energy storage capacity compared to water. In the phase change range of MicroEPCM, the MicroEPCMS has a higher thermal conductivity compared to water. In addition, the natural convection heat transfer characteristics of MicroEPCMS in a square cavity were investigated under varying heating power. The results indicated that MicroEPCMS can enhance natural convection heat transfer by absorbing heat with a minimal temperature rise during the phase change process compared to water. Moreover, higher heating power enables natural convection enhancement of MicroEPCMS in a square cavity. These results underscore the significant potential of MicroEPCMS as a functional liquid cooling medium for applications in thermal energy storage and thermal management.

Numerical study on the thermal performance of space radiator using microencapsulated phase change material slurry as working medium

Microencapsulated phase change material slurry (MPCMS) has good prospects in the field of heat transfer because of its high latent heat and stability. In this research, MPCMS is applied to a space radiator to increase its heat load and temperature stability. The thermal performance of the space radiator is numerically studied by using the two-phase Eulerian (TPE) model and a multi-scale coupling model. The effects of velocity, volume fraction, microcapsule size, and microcapsule size distribution on the thermal performance of the space radiator are studied. Results show that the temperature flat area in the tube increases with the increase in the volume fraction or flow rate of the particle phase in the MPCMS, which means the heat dissipation capacity of the space radiator is also enhanced, and the maximum increase is 14 %. Compared with the use of pure water, the temperature difference between the highest and the lowest temperature of the radiator surface can be reduced by 40 %, and the heat dissipation power can be increased by 5 %. In addition, the large size of microcapsules limits the heat transfer between the two phases, especially when the size is greater than 50 μm. Compared with uniform microcapsule size distribution, the effect of lognormal distribution of variance σ = 0.7 on heat transfer is less than 1 %.

Active and hybrid battery thermal management system using microchannels, and phase change materials for efficient energy storage

Efficient battery thermal management (BTM) is key to the safety and performance of Lithium-ion batteries. This study focuses on cooling a module of 15 prismatic Lithium-titanate cells at an 8C discharge rate using finite volume numerical modeling. Initially, the impact of Reynolds numbers and microchannel count on temperature is examined. Then, Phase change materials (PCM) are introduced to increase thermal management efficiency. Three cases for optimizing the hybrid-BTM system are compared: nanoparticles (1%–5% volume fraction), copper foam (93 % porosity), and micro-encapsulated PCM slurry (5%–15 % volume fraction). The results indicate that an increase in microchannels improves the performance evaluation criterion (PEC) by 93.1 %. Additionally, using copper foam increases the PEC by 18.43 %, 17.44 %, 16.53 %, and 16.31 % at Reynolds numbers 800, 1200, 1600, and 2000, respectively. Furthermore, the BTM system using 5 % nanoparticles demonstrates the best performance, reducing the module temperature by 2.41 % in the presence of copper foam and by 1.78 % in the pure state. Moreover, while the MPCM slurry effectively reduces the module temperature to a desirable level, the high pumping costs significantly decrease the PEC. Additionally, the total entropy of the BTM system follows frictional entropy, although thermal entropy effects dominate the PCM.

Improving the thermal performance of nano-encapsulated phase change material slurry by changing fins configurations in a rectangular cavity

The transition to renewable energy is heavily reliant on batteries and energy storage devices, making them a crucial technology of the modern era. The sensitivity of batteries to temperature has been a constant challenge in the development of this technology. Thermal management, creating uniform temperature and proper heat transfer by cooling is very critical in these systems. The popularity of nePCMs is increasing in energy storage and cooling systems due to their remarkable latent heat during phase change. This is because nano-encapsulated phase change materials are being widely used. They are considered to be one of the most promising particles in this application. This research is a case study free convection of nano-encapsulated Phase Change Materials (nePCM) slurry with a volume fraction of 5% and a polyurethane shell and n-nonadecane core in a rectangular chamber was homogeneously simulated and investigated. The temperature of the left wall remains consistent and there are three fins present to enhance the transfer of heat. The governing equations are transformed into dimensionless form and solved numerically using OpenFOAM software. Various parameters such as fin geometry, chamber angle, Rayleigh number, and melting point temperature are altered to assess their impact on velocity profile components, temperature distribution, Cr contours, Nusselt number, and fin efficiency. Based on the results, Y-shape and T-shape fin geometries can increase the efficiency of water-nePCM fluid by about 10% for Ra = 100 and about 26 % for Ra = 104 compared to I-shape fin. Also, increasing the Rayleigh number from Ra = 100 to Ra = 104 improves the average Nusselt number for water-nePCM nanofluids by about 100 % in each of the fin geometries.

Thermo‐hydraulic analysis of wavy microchannel heat sinks with porous fins based on field synergy principle

AbstractIn order to enlarge the area and intensity of convective heat transfer among the coolant and heated surface, the vertical fins of microchannel heat sinks (MCHSs) with microencapsulated phase change material slurry (MPCMS) as coolant are arranged into wavy porous channels to realize more heat being dissipated to the outside. The phase transition of microencapsulated particles in laminar flow state is described, and the Brinkman–Forchheimer–Darcy model based on volume average approach and the energy equation for local heat equilibrium are adopted to portray flow and heat transfer in porous medium. The impacts of geometrical parameters on flow and heat transfer behaviour of wavy porous MCHS are numerically analyzed, and performance evaluation factor (PEF) is defined to estimate the thermo‐hydraulic capability of heat exchanger. The numeric outcomes match well with the experiments. Results indicate that MPCMS has a significant heat transfer improvement in the newly designed channel configuration compared with the coolant fluid flowing in the straight microchannel. Based on field synergy principle, the comprehensive capability enhancement mechanism of MPCMS in new MCHS is explored, and its superior thermal performance can be attributed to the improvement of the synergistic degree among flow and temperature fields, and its reasonable structural design can effectively improve the heat rejection capacity in the limited space.

Experimental Investigation of the Viscosity and Density of Microencapsulated Phase Change Material Slurries for Enhanced Heat Capacity and Transfer

Working fluids that incorporate solid microencapsulated phase change materials (MPCMs) can benefit from properties such as density and viscosity, which are crucial for improving heat capacity and transfer. However, limited data are available on these parameters for specific slurry and mass ratios. In this study, we present a comparative analysis of the experimental results on the viscosity of three different MPCM aqueous dispersions, namely MPCM 31-S50, MPCM 25-S50, and Micronal 5428X. Varying MPCM mass ratios of distilled water were used to obtain different mass concentrations of the phase change material (PCM), and the resulting slurries were analysed at temperatures ranging from 15 to 40 °C. Our findings showed that all slurries exhibited non-Newtonian characteristics at low shear rates, with viscosity stabilising at higher shear rates, resulting in the characteristics of a Newtonian fluid. The viscosity results were highly dependent on the type of MPCM base dispersion, particularly at high mass ratios, with the slurries having viscosities higher than those of water. Furthermore, we conducted density experiments as a function of temperature, using a flow test setup and a Coriolis flowmeter (Endress+Hauser, Reinach, Switzerland) to determine the density of two MPCMs, namely MPCM 25-S50 and Micronal 5428X. The test samples were prepared at mass concentrations of 10%, 15%, and 20% of the phase change material. We found significant differences in density and viscosity for different MPCM slurries as a result of both the PCM concentration and the material studied. Our results also revealed an apparent PCM phase change process, in which the slurry density significantly decreased in the temperature range of the phase transition from solid to liquid.

Sustainability and operational performance assessment of supermarket air-conditioning architectures using secondary fluids and slurries

Secondary loop architectures and phase change material (PCM) slurries could reduce the environmental impact of refrigeration and air-conditioning systems by lowering significantly the amount of primary refrigerants. However, there is a barrier to their industrial development due to the lack of studies on their behaviour in operational scenarios. The present work analyses the behaviour of different secondary loop systems in an industrial context, here the air conditioning of a supermarket in France. For this purpose, a generic approach, developed in previous work, is proposed to assess their potential of adoption. This modelling approach is able to describe the sustainability and operational performance (energy, environmental, economic, social) of refrigeration systems. After validation of the model on real architecture and components, five standard or new architectures were tested: centralized direct expansion system; secondary loop system with ethylene glycol water; secondary loop system with ice slurries, TBPB hydrate slurries or CO2 hydrate slurries. The main results of this study show that new secondary systems using hydrate slurries have better cooling energy performance than direct expansion or classical brine / ice slurry secondary systems. Moreover, even including pumping power, the life cycle climate performance of secondary loop systems is much better than that of direct expansion systems. However, the total cost of ownership of direct expansion systems is lower than that of secondary systems, but with little differences for smaller pipes. Finally, trade-offs between several performances can be proposed. For example, some architectures with suitable pipe diameters could meet TCO/LCCP-based and CAPEX/pumping-based trade-offs.

Field synergy analysis on thermal-hydraulic behavior of phase change slurry in porous microchannel heat sink with graded porosity configuration

In this study, a novel design of porous microchannel heat sink (MCHS) with graded porosity configuration is proposed in the hope of attaining lower flow and thermal resistances than constant porosity (CP) configuration. The efficacy of new scheme is validated by utilizing a three-dimensional solid-fluid conjugate model based on the finite volume method, which considers the flow and heat transfer of microencapsulated phase change material slurry (MPCMS) inside the porous fins. It is reported that the thermal performance of porous MCHS with constant and graded porosity configurations is significantly better than that of non-porous MCHS. The feasibility of new design is verified by comparing the hydrothermal behavior of multiple graded porosity MCHSs and CP configuration for different fin designs (involving the number of graded equidistant fins N, graded length ratio R, and fin-to-pitch width ratio β) and operating conditions (including Reynolds number Re, mass fraction cm, and inlet velocity uin). The comprehensive performance improvement mechanism of MPCMS in graded porosity microchannels is discussed through the analysis of flow and thermal details, field synergy angle (θ) and field synergy number (Fc), and the overall performance of new design is evaluated by performance evaluation factor (PEF). Results indicate that the six types of porous MCHS with stepwise varying porosity exhibit lower thermal resistance than CP mode, and better thermal behavior and larger PEF can be obtained at N = 2 and β = 0.7. Smaller and larger R should be chosen for stepwise increasing porosity (SIP) and stepwise decreasing porosity (SDP) modes, respectively, to achieve higher heat transfer enhancement while avoiding greater friction losses. The Fc value of porous MCHS with various porosity configurations is about two orders of magnitude less than 1 and shows a monotonically reducing trend with Re, and the synergistic effect deteriorates at high Re. Compared to the CP mode, a low-θ “drift” toward the low porosity region of porous fin occurs within the graded porosity MCHS, which decreases and increases in the downstream and upstream directions of the “drift”, respectively. Among the novel MCHS designs, the z-directional SIP mode acquires the best overall performance due to the excellent synergy between the velocity and temperature fields, and its PEF consistently exceeds 1.13 and reaches up to 1.33. Generally speaking, the fin porosity of graded porosity MCHS near the channel cavity, channel top, and channel inlet should be greater for superior comprehensive performance.

Preparation, characterisation and property modification of a calcium chloride hexahydrate phase change material slurry with additives for thermal energy transportation

Efficient thermal energy distribution and rational energy management are effective solutions to address the significant and fast-ascending energy consumption in building heating, ventilation, and air conditioning (HVAC). Phase change material (PCM) slurries with excellent thermal energy transportation and storage characteristics have been recognised as promising secondary refrigerants to simultaneously facilitate efficient heat/cold transport and effective thermal energy storage in air conditioning systems. Among various PCM slurries, salt hydrate PCM slurries have attracted increasing attention in recent years due to their many inherent advantages. This paper presented the preparation, characterisation, and property modification of a CaCl2·6H2O slurry based on a methodology proposed for optimal salt hydrate PCM slurry development. Theoretical modelling was first carried out to assess the availability of salt hydrate PCM slurries based on the phase diagram and solid fraction, followed by a series of property measurements to reveal the mechanisms and address the problems behind the phase transition, crystal particle morphology, stability and rheologic characteristics, using nucleating agents, surfactants and stabilisers. It was found that the salt hydrate PCM slurry developed provides a unit volume enthalpy twice that of water over the phase change temperature range of 5°C, together with acceptable fluidity. The results also showed that the PCM particle size can be well controlled, and the slurry can be stabilised, with the assistance of surfactants and stabilisers. Compared to other types of PCM slurries, the proposed salt hydrate PCM slurry has the advantages of being cost-effectiveness, easy preparation, adjustable phase change temperature, etc., which is promising to facilitate energy saving and rationalisation in building HVAC.

Heat transfer enhancement of electrospray cooling with microencapsulated phase change material slurry (MPCMS): A comprehensive numerical model and experimental study

Electrospray cooling (ESC) technology is increasingly emphasized due to its efficient heat removal capacity, minor coolant consumption and accurate thermal control. Previous articles had focused on either experimental exploration on ESC performance or numerical methods on solitary electrospray such as Volume of Fluid [1], Boundary Element Method [2] and Lagrangian model [3]. However, there is no comprehensive model characterizing the whole ESC process. Moreover, there was barely investigation on ESC enhancement using phase change materials (PCM). Herein, this study has bridged this gap by developing a new comprehensive model to explore the ESC enhancement with microencapsulated phase change material slurry (MPCMS), and conducted experiment to verify it. The influences of applied voltage, mass concentration and inlet temperature of MPCMS on the ESC were discussed. Results revealed that MPCMS offered superior cooling performance during melting process due to latent heat absorption compared to deionized water. Nevertheless, as wall temperatures increased, the deposition, higher viscosity and lower thermal conductivity of MPCMS would compromise cooling efficiency. Moreover, higher applied voltage enhanced cooling performance by increasing droplet velocity, and reducing the possibility of droplet rebound. When the inlet temperature approached the peak melting temperature, the convective heat transfer coefficient reached its maximum.

Numerical Investigation on Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry in a Rectangular Minichannel

Numerical Investigation on Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry in a Rectangular Minichannel

Thermally enhanced nanocomposite phase change material slurry for solar-thermal energy storage

This paper investigates the photothermal conversion performance of an innovative heat transfer fluid containing nano-encapsulated phase change material (PCM) with metallic shell materials in a solar thermal energy storage system. The influences of shell thickness, core size, shell material type, PCM mass and shell volume concentrations on the thermal performance of the heat storage medium are investigated and compared. The results show that the heat transfer rates of water-based Ag, Au, Cu and Al nanofluids are 6.89, 5.86, 7.05 and 6.99 W, respectively, while slurries formed by adding paraffin@Ag, Au, Cu and Al nano capsules to pure water enhance heat transfer by 6.18, 13.38, 10.8 and 11.33 %, respectively. The metallic nanoparticle-based shell materials further augment the temperature and energy storage gains by enhancing the solar radiation capture capability of the heat storage medium. Specifically, depending on the mass concentration of PCM, the storage capacity of paraffin@Cu slurry is augmented by up to 290 %. As the shell thickness of the Ag particles also decreases from 8 to 2 nm, it augments the slurry's storage ability for thermal energy by 7 %. The enhancement in the dimensions of the nano capsules, however, causes the surface area-to-volume ratio (SA:V) to reduce the photothermal conversion of the slurry by clustering. Therefore, the thermal energy storage behaviour of the Paraffin@Cu slurry is diminished by 5 % as the core size enhances from 10 to 40 nm. Further, the augmentation in the volume concentration of Al particles in the shell surprisingly reduces the thermal energy storage by 5 %. Finally, paraffin-based solid PCM is also experimentally tested for validation of the specific heat capacity model at various wind speeds and solar radiation.

Heat transfer and thermal stress of a parabolic trough solar collector with secondary reflector using microencapsulated phase change material slurries

The traditional parabolic trough solar collectors (PTSC) often face the problems of high thermal stress and the deformation of the tubular receiver. In this paper, a secondary reflector (SR) is put into the traditional PTSC, and the microencapsulated phase change material (MEPCM) slurries with 7 vol%, 12 vol%, and 15 vol% are used as the operating fluids. By associating the Monte Carlo ray-tracing (MCRT), finite volume (FVM), and finite element (FEM) methods, the optical-thermal–mechanical coupling problem of the absorber tube is settled, the flow and heat transmission of MEPCM slurries in the collector tube are numerically investigated by applying the Eulerian-Eulerian multiphase flow model. The results show that the solar flux and wall temperature of the absorber tube with the SR are more uniform along the circumferential direction. The use of SR enhances the local heat transfer of the MEPCM slurries at the phase change section in the absorber tube, while when the phase changes finish, the local heat transfers of the slurries in the PTSC with SR have no difference with the traditional PTSC. Compared with the water, the MEPCM slurries obviously enhance the heat transfer of the absorber tube due to the phase change and the interactive motion of the microencapsulated particle, and the higher the slurry concentration, the larger the mean Nusselt number, the smaller the thermal stress. The addition of SR significantly decreases the thermal stress of the absorber tube, the maximal equivalent stress is reduced by 81.8%

Heat transfer characteristics of PCM slurry using ammonium alum and propylene glycol

For latent heat transportation at temperatures higher than room temperature, a phase change material slurry using ammonium alum, propylene glycol (PG), polyvinyl alcohol (PVA), cationic surfactant, and sodium salicylic acid was proposed. The slurry's phase change characteristics changed with the fraction of PG. In this study, we first confirmed whether PVA and surfactants affected the slurry's phase-change characteristics and viscosity. The results showed that the phase-change characteristics were unaffected, but the viscosity changed to that of a non-Newtonian fluid. Owing to these characteristics, the PVA/surfactant demonstrated a drag-reduction effect in the flow characteristic measurement in a circular pipe flow. However, the drag reduction effects decreased when the PG fraction was large. Using these slurries, heat transfer measurements were performed using a double-tube heat exchanger with an 8-mm inner tube diameter. The samples in the inner tubes were cooled with water. It was observed that the latent heat of ammonium alum enhanced heat transfer and a model of the heat transfer characteristics using the modified Prandtl number was proposed. Finally, the heat transportation efficiency was examined, and it was determined that efficient heat transportation using ammonium alum was feasible under certain PG fraction and flow velocity conditions.

Investigation on the flow characteristics of a phase change material slurry in horizontal and U-shaped tubes based on CFD-PBM

Ice slurry is broadly used as the medium for refrigerating medium, which can effectively reduce energy consumption. However, the change of ice particle size makes the flow properties of ice slurry more complicated, which limits its application in cooling system. A coupled model combining CFD and PBM techniques is developed in this article to effectively depict the variations in ice particle size and the flow of ice slurry. Based on this model, the flow properties of ice slurry isothermally in horizontally placed straight and U-shaped pipes are studied. It is found that velocity determines the degree of agglomeration and fragmentation of particles. The particle fragmentation effect is enhanced and the particle size is reduced as the flow velocity increases, which promotes the homogeneous particle distribution. With increasing the ice content, the size of particles and particle agglomeration increases. And the ice particle size presents a symmetrical distribution. The larger the initial average particle size, the weaker the agglomeration effect, and conversely the weaker the fragmentation effect. In the bending section of the U-shaped tube, the agglomeration effect between particles becomes stronger as the flow velocity decreases and the ice volume and curvature ratio increase.

Flow and heat transfer characteristics of microencapsulated phase change material slurry in bonded triangular tubes for thermal energy storage systems

Three nanoscale metal oxides composed of nano TiO2, nano Al2O3, and nano MgO were added to the phase change microcapsule slurry for optimising the heat transfer behaviour. The thermal and rheological properties of the resulting microencapsulated phase change materials (MPCMs) and microencapsulated phase change material slurries (MPCSs) were characterized to determine the effects of added metal oxides in optimising the performance of MPCSs. The impacts of factors like metal oxides, concentrations, and flow rates on the heat transfer behaviour of MPCSs were investigated by forced convective heat transfer experiment with various working conditions. Compared to 6 wt% MPCSs, the heat transfer coefficients (hx) of 6 wt% slurries containing 1 wt% TiO2, 1 wt% Al2O3, and 1 wt% MgO increased by 4.0 %, 2.5 %, and 7.13 %, respectively. Nano-MgO showed the most significant heat transfer enhancement effect on MPCSs. Moreover, the heat transfer performance gradually enhanced as a function of the concentration for nano MgO. Overall, the addition of metal oxides enhanced heat transfer by increasing the thermal conductivity of the slurry, as well as improved the micro-convection effect. The proposed MPCSs are promising for applications in solar photovoltaic/thermal (PV/T) systems, chip cooling, thermal management, buildings, and automotive cooling.

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.

Experimental analysis on thermal energy storage performance of micro-encapsulated stearic acid and stearyl alcohol PCM slurries; A comparative study

This study examined the thermal performance of a slurry containing micro-encapsulated phase change materials (me-PCMs) for thermal energy storage (TES) applications such as solar thermal or PVT systems. Specifically, the study focused on stearic acid (SAC) and stearyl alcohol (SAL) as the phase change materials, dispersed within an ethylene glycol aqueous solution. The research revealed that increasing the concentration of PCM in the slurry led to improved latent heat energies for both micro-encapsulated stearic acid (me-SAC) and micro-encapsulated stearyl alcohol (me-SAL) slurries during melting and solidification processes. Moreover, me-SAL slurries exhibited higher latent heat energies compared to me-SAC slurries at the same concentrations. The addition of CTAB surfactant positively influenced the stability of the slurry dispersion, ensuring a more even distribution of me-PCMs within the base fluid. These findings highlight the potential of me-SAC and me-SAL slurries as effective materials for TES applications. Significantly, me-SAL slurries outperformed me-SAC slurries in TES performance due to their greater latent heat energies during melting and solidification.

Uniform cooling for concentrator photovoltaic cell by micro-encapsulated phase change material slurry in double-layered minichannels

The concentrator photovoltaic (CPV) systems often suffer high heat flux, leading to cell temperatures rising, which will affect its performance and reduce the service life. Double-layered minichannel heat sink (DL-MCHS) is an efficient cooling technology, which could effectively lower down the top temperature of CPV cell. Micro-encapsulated phase change material slurry (MPCS) is a novel type of latent heat functional fluid and has a good application prospect in the field of cooling. Therefore, MPCS flowing in the DL-MCHS, as the thermal management device was investigated for the cooling of CPV cell. Three configurations of minichannels, including staggered arrangement, parallel arrangement and dual unequal arrangement were compared and optimized. On the basis of optimization, the flow and heat transfer performance of MPCS with different concentrations in double-layered straight and wavy minichannels had been numerically studied. The results indicated that the lowest top temperature of dual unequal DL-MCHS obtained by counter arrangement could be reduced by 0.56 °C compared with the parallel arrangement at Re = 152. Both the ΔP and h were significantly influenced by concentrations. When Re reached 262, ΔP of 5 wt% MPCS in wave minichannel with 5 mm wavelength was 44 % larger than that of pure water in straight minichannel, which would consume more pumping power. However, the heat dissipation performance was improved significantly and Nusselt number in double-layered wavy minchannels also increased with the wavelength decreasing. Therefore, Performance Evaluation Criteria (PEC) was proposed to evaluate the overall performance, which was also greatly influenced by particle concentration and channel wavelength. After optimization, the highest PEC of MPCS in the wavy minichannel was achieved to 1.60. Because of the wavy minichannel with concave-convex structure, the obstacle of total thermal resistance became smaller for the wavelength decreasing. These findings of MPCS in minichannel can provide a good theoretical basis and engineering application in the cooling technology of CPV.

Flow pattern determination and rheological characteristics of high-density phase change material slurry in homogeneous flow

Erythritol slurry has shown great potential as a heat transport medium. We investigated the versatility of the flow pattern determination method and the effect of gravity on the rheological characteristics of erythritol slurry, with a focus on homogeneous flow. In vertical flow, the flow pattern was always homogeneous, whereas in horizontal flow, it depended on the flow velocity. Thus, the plots obtained from the horizontal flow were divided into two parts using linear regression analysis, and the discussion focused on the homogeneous part, which is the high-velocity region. Erythritol slurry behaved as a power law fluid in a homogeneous flow, regardless of the flow direction. However, the viscosity indices differed in the vertical and horizontal flows. The non-Newtonian behavior became more pronounced in the horizontal flow than in vertical flow. These findings may be valuable for the design and optimization of heat transport systems that use high-density PCM slurry.