Phase Change Material Emulsions Research Articles

Energy storage density enhancement in paraffin phase change material emulsions: A comparative study with two different base fluids

This investigation examined the thermophysical properties of emulsions comprising paraffin 56/58 phase change material (PCM) dispersed in water and ethylene glycol (60 wt%) aqueous solution to optimize energy storage density for low-temperature thermal applications. Dynamic Light Scattering analysis revealed a uniform dispersion of paraffin 56/58 PCM droplets in the basefluids, with an average diameter of approximately 150 nm achieved by incorporating sodium dodecyl sulfate surfactant. The latent heat of fusion for emulsions containing paraffin 56/58 PCM in ethylene glycol (60 wt%) exhibited values of 37.5/41.7, 58.5/63.9, 73.8/75.43, and 93/90.25 J/g for concentrations of 20, 30, 40, and 50 wt%, respectively, during melting/solidification phases. Furthermore, the highest energy storage densities of 306.95 and 361.3 kJ/kg were attained at a PCM concentration of 50 wt% in ethylene glycol (60 wt%) and water-based emulsions, respectively, surpassing those of similar working fluids. It is also indicated that water-based paraffin 56/58 PCMs offer superior energy storage density. However, under severe operating conditions such as extreme temperatures, ethylene glycol (60 wt%) based paraffin 56/58 emulsions demonstrate greater suitability, as the evaporation and freezing points of the basefluid can be adjusted by modulating the ethylene glycol concentration ratio.

Preparation and characterization of phase change material emulsions and their applications in liquid cooling systems for wind turbines

In order to improve the effect of liquid cooling system for wind turbine, this study used ultrasonic preparation method, stearic acid as phase change material, sorbitan trioleate and sodium lauryl sulfate as compound surfactants successfully prepared stearic acid phase change material emulsion as a cooling medium for investigation. The characterization, thermophysical properties, and fluidity of stearic acid phase change material emulsions at varying concentrations were examined through differential scanning calorimetry, thermal constant analysis, and viscometry. To investigate the cooling effects, a stator axial liquid cooling model was developed for both water and a 14 % stearic acid phase change material emulsion. Findings revealed that the 14 % stearic acid phase change material emulsion exhibited a latent heat of phase change of 22.5 J/g, reaching a peak melting temperature of 68.7 °C. Additionally, the latent heat of solidification was measured at 21.08 J/g, accompanied by a peak solidification temperature of 60.3 °C. The maximum thermal conductivity reached 0.5801 W/(m·K), and the specific heat capacity peaked at 5219.8 J/(K·mol), marking a notable improvement of 1.26 times. Under an inlet temperature of 30 °C and a flow rate of 1 L/min, stearic acid phase change material emulsion effectively lowered the temperatures of the windings, stator, rotor, and casing by 19.2 °C, 23.6 °C, 19.2 °C, and 9.6 °C, respectively. stearic acid phase change material emulsion demonstrates excellent temperature control effectiveness at 3600 r/min and a low flow rate of 1 L/min, showcasing efficient energy utilization efficiency.

Stability of n‐hexadecane phase change material emulsions using sugar‐based surfactants and the HLD platform

AbstractStoring thermal energy and using renewable energy are some of the most important challenges humanity faces today. Using phase change materials (PCM) is a suitable solution to prevent heat loss. PCM emulsions (PCMEs) have several advantages and are specifically applied in heat exchangers. Here, the formulation of these emulsions, the type of surfactants, and their composition based on freeze–thaw cycle stability are investigated. The Hydrophilic–Lipophilic‐Deviation (HLD) platform is used for this purpose. Considering the importance of stability during temperature changes in PCMEs, three types of surfactants that have different behaviors with respect to temperature are used: ethoxylates, ionics, and sugar‐based surfactants. By performing freeze–thaw cycles on emulsions made by individual surfactants, after 10 freeze–thaw cycles it was observed that the oil separation in each of the samples containing polysorbate80, AOT, lauryl‐myristyl‐alcohol‐polyethylene‐glycol‐ether, SDS, sorbitan‐monooleate, and decylglucoside occurred at the 2nd, 4th, 6th, 7th, 8th, and 10th‐cycle, respectively. Therefore, the sorbitan‐monooleate and decylglucoside had better freeze–thaw cycle stability compared to the others because of their non‐sensitivity to temperature. We also applied the emulsion cycle stability with two combinations of surfactants: (1) polysorbate80 and sorbitan‐monooleate, (2) decylglucoside and sorbitan‐monooleate. The former, despite the effect of temperature, showed no oil phase separation in the nine freeze–thaw cycles, but in the latter, the oil phase separation occurred in the 5th‐cycle. This study shows that synergism of surfactants is the most important factor in the stability of emulsions. To better explore these emulsion systems, the storage stability, freeze–thaw stability, droplet morphology, and viscosity tests were performed on different samples at various HLD values.

Preparation and characterization of stable methyl myristate−in−water nanoemulsions as advanced working fluids for cooling systems

Phase change material emulsions (PCME) have gained increasing scientific interest due to their potential to enhance the storage capability of thermal facilities. Herein we present the design and characterization of oil−in−water (O/W) nanoemulsions by employing a dispersed phase mixture (2–12 wt%) enriched in methyl myristate as phase change material. The emulsifier and dispersed phase compositions were optimized based on dynamic light scattering and calorimetric analyses. A two−surfactant formulation composed of sodium dodecyl sulfate and BrijTM S2 (20:49 in weight) was selected to produce stable colloidal dispersions of a methyl stearate:n–hexadecane:methyl myristate mixture (at a mass proportion of 1:3:36) in water. No phase separation or significant growth in emulsified droplet size was detected under storage conditions or when the slurries were subjected to different heating−cooling cycles. The melting/crystallization transitions, rheological behavior, thermal conductivity and density of optimized nanoemulsions were experimentally investigated in order to further understand how the concentration and physical state of suspended droplets may influence those thermal and physical properties. According to differential scanning calorimetry studies, slurries showed moderate subcooling degrees (∼3 °C), even though their solid−liquid transitions extended over a slightly wider range of temperatures than the same mixture used as the dispersed phase but in bulk−form. The shear−thinning character observed for developed nanoemulsions at low temperatures disappeared with the melting of suspended droplets. Considering an operating temperature interval of 15 °C around melting−crystallization phase changes, the 12 wt% optimized suspension presented a storage capacity 18 % higher than that of water under the same conditions. Furthermore, thermal reliability tests verified that phase change characteristics did not significantly changed after 8 months of storage and throughout 500 thermal cycles.

Experimental study on the performance enhancement of PV/T by adding graphene oxide in paraffin phase change material emulsions

Traditional water-based PV/T systems have low heat storage density, high PV backsheet temperatures, and low energy utilization in practical applications. In this work, nanoparticles were applied to improve thermal conductivity and simultaneously emulsions were added to enhance energy storage density of the conventional heat transfer media. Furthermore, the synergistic effect of nanocomposite Phase Change Material Emulsions (PCME) as the heat transfer medium on the thermoelectric efficiency of PV/T was studied in a real system. Specifically, the water-based 30 % paraffin emulsions with graphene oxide (GO) concentration of 0.01, 0.02 and 0.03 wt% were prepared by ultrasonic stirring and their thermophysical properties were characterized. The results show that the 30 wt% paraffin emulsion with addition of 0.02 wt% GO has the phase change temperature of 35 °C, latent heat of 42.93 J/g, thermal conductivity of 0.505 W/(m·K) and viscosity coefficient of 0.91. It shows the thermal efficiency of the paraffin/GO emulsion increased by 92.28 %, the electrical efficiency increased by 8.87 %, the comprehensive efficiency increased by 45.75 %, and 15.8 % increase in heat collection for the heat exchange tank in comparison with the water. It is concluded application of PCME would improves the thermoelectric performance of the system than traditional water-based PV/T systems.

Development of highly stable n-Heptadecane/water-based phase change emulsion with mixed surfactant for thermal management applications

Phase change material (PCM) emulsions have grown in popularity due to their versatility and various thermal management applications. Therefore, new PCM materials and emulsion compositions have been investigated to enhance their functionality and widen their range of applications. In the present work, PCM emulsion was formulated using n-heptadecane as a dispersed phase, DI-water as base fluid, and sodium dodecyl sulfate and Brij30 as surfactant. The effect of mixed surfactants on the stability and other thermophysical properties of the PCM emulsions were investigated. The emulsions with mixed surfactants show excellent stability when compared to single surfactants. The average droplet size of the PCM emulsion was 102.8 nm with a phase change temperature and latent heat of fusion of 18.9 °C and 14.17 Jg−1, respectively, for 10 wt% PCM concentration. The thermal conductivity was decreased by about 16.4 %, and the viscosity increased by nearly 128 % when compared with DI-water for the 10 wt% dispersed phase emulsion with mixed surfactants. The gravimetric and structural studies confirm the stability of dispersed phase and base fluid in the presence of surfactant. Overall, it can be concluded that the PCM emulsion with mixed surfactant can be a potential heat transfer medium with improved heat storage and transportation capacity.

Shear-Responsive Sol-Gel Transition of Phase Change Material Emulsions for an Injectable Thermal Insulation Platform.

Phase change materials (PCMs) have attracted significant attention as promising insulating materials. However, they often suffer from the simple yet critical problem of leakage in practical applications. Therefore, in this study, an injectable PCM emulsion insulation platform is developed. For this, n-hexadecane, as a PCM, emulsion droplets are armored with a metal-organic membrane (MOM) through the coordination of zinc ions and phytic acid. The MOM layer not only provides a rigid interfacial modulus but also allows the emulsion to exhibit viscoelastic behavior by shear stress-induced interdrop association. This MOM-enveloped PCM emulsion (PCMEMOM ) exhibited typical sol-gel transition behavior in response to applied shear stress, indicating the injectable characteristic of the PCMEMOM . After observing the rheological hysteresis and thermal stability of the PCMEMOM under repetitive heating and cooling cycles, the thermal insulation performance of PCMEMOM is quantitatively and visually demonstrated. These findings suggest an efficient method to exploit high-performance insulation systems.

Self-assembly of MXene-decorated stearic acid/ionic liquid phase change material emulsion for effective photo-thermal conversion and storage

As a typical latent functionally thermal fluid with large energy storage capacity and good liquidity, phase change material emulsion (PCME) plays a broad and important role in solar energy utilization. However, the high-temperature instability and supercooling problems of PCME limit its practical application. The ionic liquid (IL)-based PCME allows for the possibility of being used as a heat transfer fluid (HTF) under more extreme temperature conditions. In this work, stearic acid (SA)/IL PCME, prepared by one-step self-assembly of MXene nanosheets at the SA/IL interface, can effectively absorb and convert solar energy into thermal energy. Furthermore, MXene-decorated SA/IL PCMEs have good high-temperature stability, little supercooling degree (0.9–3.1 °C), and large energy storage capacity. The maximum apparent specific heat capacity and average absorbance of the MXene-decorated SA/IL PCME are 4.5 and 303.1 times higher than those of IL, respectively. Under 2 sun irradiation, the 0.05–20 wt% MXene-decorated SA/IL PCME achieves high photo-thermal conversion efficiencies (91.3% at 68.9 °C, 39.4% at 115.1 °C) due to its large energy storage capacity and excellent optical absorption property. The simple interfacial self-assembly provides a promising strategy to prepare high-performance SA/IL PCME used as a novel HTF for medium-temperature solar energy utilization systems.

Influence of the Physical State of Microencapsulated PCM on the Pressure Drop of Slurry in a Circular Channel.

Phase Change Material (PCM) is mainly used in thermal energy storage. The addition of small PCM particles to the working fluid circulating in the heat exchange systems allowed to increase the amount of transported energy thanks to the use of latent heat—the heat of phase change. Encapsulating PCM in microcapsules avoids the disadvantages of PCM emulsions and makes the resulting slurry an attractive heat energy carrier. The paper presents the effect of the aggregate state of PCM enclosed in microcapsules on the flow resistance of the slurry through a rectilinear tubular channel. The tests were carried out with the use of a tube with an internal diameter of 4 mm and a measuring section length of 400 mm. A slurry of 21.5 wt.% PCM microcapsules (MPCM) was used as the working fluid in distilled water. A slurry with temperatures of 18.4 °C (PCM encapsulated in a solid state), 26.1 °C (PCM is in a phase change), and 30.5 °C (PCM in a liquid state) flowed through the measuring section. The mass flow rate of the MPCM slurry reached 70 kg/h (Remax = 2150). It was shown that the higher the Re number, the higher the value of the flow resistance, and the more clearly this value depended on the temperature of the slurry. Detailed analyses indicate that the observed changes were not the result of a change in the viscosity of the slurry, but its density depending on the state of the PCM. Significant changes in the density of the slurry in the range of the phase transition temperature are the result of significant changes in the volume of the microcapsule containing the phase change material in different aggregate states.

Facile self-assembly approach to construct a novel MXene-decorated nano-sized phase change material emulsion for thermal energy storage

In recent years, phase change material emulsions (PCMEs) with enhanced energy storage capacities and good flow characteristics have drawn significant attention. However, due to the thermodynamically unstable nature and tiny particle confinement, the nanomaterial modification strategies at PCM/water interface to improve stabilities and reduce supercooling of nano-sized PCMEs (NPCMEs) are very limited and challenging. Herein, we report a facile strategy for constructing MXene-decorated NPCME with good stability, little supercooling, and high thermal conductivity by self-assembly of MXene nanosheets at PCM/water interface. The concentrations of MXene have great influences on the average droplet diameters, stabilities, and thermophysical properties of the NPCMEs. The results show that the PCMs have been well dispersed into the water in the form of quasi-spherical droplets, with average droplet diameters of 242–805 nm. The thermal conductivity of 10 wt% n-tetradecane/water NPCME containing 9 mg ml-1 MXene is 0.693 W m-1·K-1, achieving an enhancement by 15.5%, as compared to that of water. Besides, the MXene-decorated paraffin/water NPCMEs exhibit little supercooling and enhanced heat storage capacities. More importantly, this facile self-assembly strategy opens a new platform for preparing high-performance NPCMEs, which can be used as novel heat transfer fluids for thermal energy storage systems.

Cooling storage performance of a novel phase change material nano-emulsion for room air-conditioning in a self-designed pilot thermal storage unit

The dynamic stability of phase change material (PCM) emulsions is a crucial factor for their practical applications. So far most previous studies on PCM emulsions have been focused on the static stability in the laboratory and cooling performance in small scale systems, but few or none on the dynamic stability and cooling performance in pilot- or larger-scale systems. This study was to evaluate the dynamic stability or service life and cooling storage performance of a novel PCM nano-emulsion for room air-conditioning application in a self-designed, pilot-scale latent heat thermal energy storage unit. The pilot unit was constructed with a chiller, a storage tank, three sets of ceiling panels, circulation pumps and flow control valves in a pipeline. The PCM nano-emulsion remained stable through 45 repeated charging and discharging cycles over a period of 70 days in the pilot unit and could be well regenerated for even longer period of operation. The PCM nano-emulsion retained a stable cooling capacity, e.g. with a discharging rate of 199.6 W in the 1st-5th cycles and 196.9 W in the 35th-40th cycles at a given flow rate. The droplet size increased to a maximum of ∼180 nm but was still small compared with many of the previously published ranges. Therefore, it is expected that the novel PCM nano-emulsion can have a long service life. Moreover, its volumetric thermal storage capacity was about 1.45 times higher than water in the range of 5.5–20 °C, with the highest average charging rate of about 1.4 kW during the phase transition process, and a high efficiency of ∼85% in the cooling energy release with no limitation by fast discharging flow rate, which make it favourable for practical situations.

Development and Thermophysical Profile of Cetyl Alcohol-in-Water Nanoemulsions for Thermal Management

This study focuses on the preparation, thermophysical and rheological characterization of phase change material nanoemulsions as latent functionally thermal fluids. Aqueous dispersions with fine droplets of cetyl alcohol (with a melting temperature at ~321 K) were prepared by means of a solvent-assisted method, combining ultrasonication with non-ionic and anionic emulsifiers. Eicosyl alcohol (melting at ~337 K) and hydrophobic silica nanoparticles were tested as nucleating agents. Droplet size studies through time and after freeze–thaw cycles confirmed the good stability of formulated nanoemulsions. Phase change analyses proved the effectiveness of eicosyl alcohol to reduce subcooling to a few Kelvin. Although phase change material emulsions exhibited thermal conductivities much larger than bulk cetyl alcohol (at least 60% higher when droplets are solid), reductions in this property reached 15% when compared to water. Samples mainly showed desirable Newtonian behavior (or slight shear thinning viscosities) and modifications in density around melting transition were lower than 1.2%. In the case of phase change material nanoemulsions with 8 wt.% content of dispersed phase, enhancements in the energy storage capacity overcome 20% (considering an operational temperature interval of 10 K around solid–liquid phase change). Formulated dispersions also showed good thermal reliability throughout 200 solidification–melting cycles.

Preparation of Stable Phase Change Material Emulsions for Thermal Energy Storage and Thermal Management Applications: A Review.

Thermal energy storage (TES) is an important means for the conservation and efficient utilization of excessive and renewable energy. With a much higher thermal storage capacity, latent heat storage (LHS) may be more efficient than sensible heat storage. Phase change materials (PCMs) are the essential storage media for LHS. PCM emulsions have been developed for LHS in flow systems, which act as both heat transfer and thermal storage media with enhanced heat transfer, low pumping power, and high thermal storage capacity. However, two major barriers to the application of PCM emulsions are their instability and high degree of supercooling. To overcome these, various strategies have been attempted, such as the reduction of emulsion droplet size, addition of nucleating agents, and optimization of the formulation. To the best of our knowledge, however, there is still a lack of review articles on fabrication methods for PCM emulsions or their latest applications. This review was to provide an up-to-date and comprehensive summary on the effective strategies and the underlying mechanisms for the preparation of stable PCM emulsions and reduction of supercooling, especially with the organic PCMs of paraffin. It was also to share our insightful perspectives on further development and potential applications of PCM emulsions for efficient energy storage.

A comparative assessment of the battery liquid‐cooling system employing two coolants: Phase change material emulsion and water

This work proposes a novel liquid-cooling system that employs the phase change material (PCM) emulsion as the coolant for the battery pack. To compare the proposed scheme with the traditional water cooling system, a thermal model is developed for the battery pack with cooling systems, where the system start-stop control and time hysteresis phenomenon are considered in simulations. The results show that either increasing the inlet velocity or temperature improves the battery temperature uniformity for the two schemes, but it enlarges the pumping energy consumption during the whole discharging process. Compared with the water cooling system, the proposed PCM emulsion cooling scheme can not only significantly decrease the battery temperature difference but also effectively shorten the system operating time. According to the calculation, the pumping energy consumption with using the PCM emulsions as the coolant decreases 18.9% in minimum and 66.6% in maximum than that with using the water as the coolant. Consequently, the proposed PCM emulsion cooling system is superior to the water cooling system in terms of the heat dissipation capacity, the temperature uniformity, the pump power requirement, and the pumping energy consumption, which is well-suited for the cooling system of the battery pack in electric vehicles. In addition, the proposed thermal model can be used well to simulate the thermal characteristics of the vehicle-mounted battery liquid-cooling system under actual operating conditions.

Natural convection characteristics of phase-change material emulsions in a rectangular vessel with vertical heating/cooling walls

Emulsions in which phase-change-material (PCM) particles are dispersed are termed PCM emulsions (PCMEs). PCMEs have a high fluidity and a high thermal energy storage density because of the latent heat of the PCM particles, and thus they have attracted attention for potential use as an efficient thermal energy storage and transport media. In thermal energy storage inside a heat storage tank, the heat is stored in PCMEs by natural convection heat transfer. Therefore, it is important in the practical use of PCMEs to understand the natural convection characteristics of PCMEs. In this study, the natural convection characteristics of PCMEs inside a rectangular vessel were investigated experimentally. The state of convection formed in PCMEs by natural convection and the heat-transfer characteristics were investigated. The aspect ratio of the rectangular vessel was changed to 2, 3 and 4, and the effect of the aspect ratio on the state of convection and the heat-transfer characteristics was investigated. The state of convection that formed inside PCME without a phase change of PCM particles was the same as that of a single-phase fluid, such as water. The formation of multiple convection layers was confirmed in PCME because of the phase change of PCM particles. The experimental results showed that the formation of the multiple convection layers was attributed to the density distribution of the PCMEs, which depends on the PCME temperature and the PCM particle state. The aspect ratio of the rectangular vessel did not affect the formation of multiple convection layers, and formation was confirmed in all 2, 3 and 4 aspect ratios. An examination of the heat-transfer characteristics of the PCME showed that the heat transfer was promoted when accompanied by a PCM particle phase change. The amount of PCM particles that melted and solidified in the rectangular vessel affected the heat-transfer promoting effect. This tendency was the same for all aspect ratio, but the heat-transfer promoting effect was most remarkable when the aspect ratio was 3.

Experimental investigation of nano/microencapsulated phase change material emulsion based building wall paint for solar thermal energy storage

Experimental investigation of nano/microencapsulated phase change material emulsion based building wall paint for solar thermal energy storage

Storage Capacity in Dependency of Supercooling and Cycle Stability of Different PCM Emulsions

Phase-change materials (PCM) play off their advantages over conventional heat storage media when used within narrow temperature ranges. Many cooling and temperature buffering applications, such as cold storage and battery cooling, are operated within small temperature differences, and therefore, they are well-suited for the application of these promising materials. In this study, the storage capacities of different phase-change material emulsions are analysed under consideration of the phase transition behaviour and supercooling effect, which are caused by the submicron size scale of the PCM particles in the emulsion. For comparison reasons, the same formulation for the emulsions was used to emulsify 35 wt.% of different paraffins with different purities and melting temperatures between 16 and 40 °C. Enthalpy curves based on differential scanning calorimeter (DSC) measurements are used to calculate the storage capacities within the characteristic and defined temperatures. The enthalpy differences for the emulsions, including the first phase transition, are in a range between 69 and 96 kJ/kg within temperature differences between 6.5 and 10 K. This led to an increase of the storage capacity by a factor of 2–2.7 in comparison to water operated within the same temperature intervals. The study also shows that purer paraffins, which have a much higher enthalpy than blends, reveal, in some cases, a lower increase of the storage capacity in the comparison due to unfavourable crystallisation behaviour when emulsified. In a second analysis, the stability of emulsions was investigated by applying 100 thermal cycles with defined mechanical stress at the same time. An analysis of the viscosity, particle size and melting crystallisation behaviour was done by showing the changes in each property due to the cycling.

A delayed cooling system coupling composite phase change material and nano phase change material emulsion

To improve the working performance of lithium-ion batteries under long-term charge–discharge cycles, a delayed cooling system coupling composite phase change material (CPCM) and nano phase change material emulsion (NPCME) is proposed and numerically studied. In this study, optimisation of the dissipate structure was first conducted to obtain the optimal design. Subsequently, the cooling performance of a hybrid battery thermal management system (BTMS) coupling the CPCM and NPCME was comprehensively investigated. The effects of operating conditions such as inlet temperature, CPCM melting point, and NPCME melting point on the cooling performance were separately studied, and the optimal operating conditions were obtained. Finally, the thermal behaviour of the delayed cooling system was studied both in a single charge/discharge operation and continuous charge/discharge cycles. Simulation results indicated that the NPCME/CPCM system offers better cooling performance than the conventional Water/CPCM system, and the NPCME/CPCM cooling system can restrain the target ΔTmax at lower flow rates than Water/CPCM cooling. Compared with the existing hybrid cooling system, power consumption can be significantly reduced without sacrificing the cooling performance. The temperature and temperature difference of the battery pack were below 48 °C and 4 °C in three charge–discharge cycles, respectively, with a CPCM utilisation of 90 vol% and a working time of liquid cooling less than one-quarter of the cycle process.

Experimental study of heat transfer characteristics of phase change material emulsions in a horizontal circular tube

Phase change material emulsions have been attracting attention for their potential to be utilized as efficient thermal energy storage and transport media. To understand their heat transfer performance, the heat transfer experiments in a horizontal circular tube were performed. The horizontal circular tube possessed thermocouples embedded in a circumferential direction and a constant heat flux incident on the flowing phase change material emulsion. A significant temperature distribution was observed when phase change material emulsion flowed with phase change material particle melting. Moreover, it was found that the local Nusslet number at the upper position of the horizontal tube was significantly enhanced and the Nusselt number of phase change material emulsion was up to about 2.5 times higher than that of the single-phase fluid. On the other hand, no temperature distribution was observed when phase change material emulsion flowed upward, even with phase change material particle melting. These results imply the presence of a secondary convection induced by phase change material particle melting owing to the density difference between the solid and liquid phase change material particles. The present findings suggest that the flow direction should be considered when using phase change material emulsions as thermal energy storage and transport media.

Mini-channel cold plate with nano phase change material emulsion for Li-ion battery under high-rate discharge

This paper presents a 4 mm ultrathin mini-channel cooling system based on a nano phase change material emulsion (NPCME) for prismatic Li-ion batteries under high-rate discharge. The NPCME has a larger specific heat capacity than water and no subcooling. Experiments were conducted to compare the cooling performance of water versus NPCME. The results indicate that NPCME can obtain a better cooling effect than water if the inlet temperature is below and near the melting point. At the discharge of 9C, the temperature and temperature difference of the battery pack cooled by 10 wt% NPCME-OP44E were 46 °C and 3.5 °C, compared with 49.5 °C and 4.8 °C under water cooling. Beyond that, the NPCME was able to reach the same cooling performance as water using lower pumping power. The pumping power of the 10 wt% NPCME-OP44E cooling system was only 18.5% that of the water cooling system when the cooling target for the battery temperature difference was 3.5 °C. With regard to charge-discharge duties, the 10 wt% NPCME-OP44E cooling system could limit Tmax and ΔTmax to 45.5 °C and 4 °C throughout all four cycles.