Thermophysical properties and thermal characteristics of phase change emulsion for thermal energy storage media (original) (raw)
Related papers
Energy Reports, 2021
In the present study, nanoparticles of MgO, TiO 2 , and Graphite with mass ratios of 3, 5, 7, and 10% were added to the structure of the synthesized Lauric acid (LA) microcapsules, and the effect of nanoparticles on the thermal properties of microencapsulated Lauric acid as non-toxic phase change material for energy storage applications was investigated. The microcapsules containing nanoparticles were prepared by emulsion polymerization of Styrene as the shell. The microencapsulation ratio (E.R) of LA increases with the amount of MgO and TiO 2. However, the microencapsulation ratio was reduced by increasing the mass ratio of nano graphite. The highest microencapsulation ratio (69.90%) belonged to the microcapsules containing 10% of titanium oxide nanoparticles. Scanning electron microscopy (SEM) images showed that microcapsules obtained containing TiO 2 were spherical with a smooth surface and narrow particle size distribution. The thermal stability and thermal conductivity coefficient for the pure LA, microencapsulated LA with/without nanoparticles were examined. The thermal stability improved with the increasing mass ratio of the nanoparticles, no considerably. The microcapsules with 10% of TiO 2 nanoparticles had higher thermal stability. The weight loss temperatures in the first and second steps are 287 • C and 435 • C, respectively. The thermal conductivity of the lauric acid was increased by microencapsulation from 0.146 W/m.K to 0.149 W/m.K. The thermal conductivity coefficient of microcapsules increased by adding nanoparticles. Finally, the thermal energy storage performance of the obtained samples was evaluated in a designed experimental setup. The decrement percentage of the onset of the melting process time for lauric acid microcapsules and the microcapsules containing graphite nanoparticles, titanium oxide, and magnesium oxide were 1.2, 4.7, 8.5, and 16.7%, respectively.
Chemical Engineering & Technology, 2010
Performances of microcapsule phase change material (MPCM) for thermal energy storage are investigated. The MPCM for thermal energy storage is prepared by a complex coacervation method with gelatin and acacia as wall materials and paraffin as core material in an emulsion system. A scanning electron microscope (SEM) was used to study the microstructure of the MPCM. In thermal analysis, a differential scanning calorimeter (DSC) was employed to determine the melting temperature, melting latent heat, solidification temperature, and solidification latent heat of the MPCM for thermal energy storage. The SEM micrograph indicates that the MPCM has been successfully synthesized and that the particle size of the MPCM is about 81 lm. The DSC output results show that the melting temperature of the MPCM is 52.05°C, the melting latent heat is 141.03 kJ/kg, the solidification temperature is 59.68°C, and the solidification latent heat is 121.59 kJ/kg. The results prove that the MPCM for thermal energy storage has a larger phase change latent heat and suitable phase change temperature, so it can be considered as an efficient thermal energy storage material for heat utilizing systems.
Journal of Thermal Analysis and Calorimetry, 2020
In modern heat transfer systems, thermal storage not only causes the balance between demand and supply, but also improves the heat transfer efficiency in these systems. In the present study, a comprehensive review of the applications of micro-or nano-encapsulated phase change slurries (MPCMs/NPCMs), as well as their effects on thermal storage and heat transfer enhancement, has been conducted. MPCMs/NPCMs have a myriad of applications and various usages such as pipe and channel flows, photovoltaic/thermal, solar heaters, air conditioning systems, storage tanks and heat pipes that have been categorized and studied. It was found that there are many advantageous adding MPCM/NPCM to the base fluid. The most important effect is that the addition of PCMs to the base fluid can intensify the capacity of energy absorption in the base fluid. These materials can absorb a high proportion of received energy by changing their phase and prevent temperature increment of the base fluid. Thereupon, the specific heat of the fluid in the presence of the micro-/nano-capsules increases. Moreover, in most studies reviewed, heat transfer coefficient and Nusselt number increase by the addition of micro-/nano-capsules to the base fluid. Also, the addition of MPCM/NPCM to the base fluid could make this material pumpable, although increment in the concentration of micro-/nano-capsules raises the viscosity of the working fluid and thereupon the pumping power. On the other hand, for a same heat load, the pumping power decreases due to the lower required flow rate in comparison with pure working fluid. The most important factor that must be considered in the application of MPCMs/NPCMs is the complete phase change of the material. Given the favorable thermal and fluid characteristics of MPCMs/NPCMs, the utilization of these materials could be a promising method to transfer heat and store it with high efficiency and low pumping power.
Microencapsulation of phase change materials (PCMs) is an effective way of enhancing their thermal conductivity and preventing possible interaction with the surrounding and leakage during the melting process, where there is no complete overview of the several methods and techniques for microencapsulation of different kinds of PCMs that leads to microcapsules with different morphology, structure, and thermal properties. In this paper, microencapsulation methods are perused and classified into three categories, i.e. physical, physic-chemical, and chemical methods. It summarizes the techniques used for microencapsulation of PCMs and hence provides a useful tool for the researchers working in this area. Among all the microencapsulation methods, the most common methods described in the literature for the production of microencapsulated phase change materials (MEPCMs) are interfacial polymerization, suspension polymerization, coacervation, emulsion polymerization, and spray drying.
Thermal Performance of the Thermal Storage Energy with Phase Change Material
Acta Mechanica et Automatica
Values of energy supply and demand vary within the same timeframe and are not equal. Consequently, to minimise the amount of energy wasted, there is a need to use various types of energy storing systems. Recently, one can observe a trend in which phase change materials (PCM) have gained popularity as materials that can store an excess of heat energy. In this research, the authors analysed paraffin wax (cheese wax)’s capability as a PCM energy storing material for a low temperature energy-storage device. Due to the relatively low thermal conductivity of wax, the authors also analysed open-cell ceramic Al2O3/SiC composite foams’ (in which the PCM was dispersed) influence on heat exchange process. Thermal analysis on paraffin wax was performed, determining its specific heat in liquid and solid state, latent heat (LH) of melting, melting temperature and thermal conductivity. Thermal tests were also performed on thermal energy container (with built-in PCM and ceramic foams) for transient...
2017
Latent heat thermal energy storage (LHTES) system uses a phase change material (PCM) to store or release thermal energy, thus reducing the overall consumption of energy in a system. But, the problem with the PCM is their low thermal conductivity that increases the melting and solidification time, which is not suitable for specific application areas, such as, battery thermal management, electronic cooling etc. To increase the thermal conductivity of PCM, different studies examine different approaches including extension of the heat transfer area using fins and honeycombs, thin metal strips, porous metals, copper chips, metal foam matrices, metal screens and spheres, carbon fiber brushes and chips, graphite matrices, microencapsulated PCM, multiple PCMs, carbon-based nanostructures graphene flakes, carbon nano-tubes, metallic nanoparticles, silver nano-wires, and bio-based composite PCM. The current study incorporates nanoparticle in PCM (nano-PCM) to increase the thermal conductivity of the PCM. Experimental studies are performed using Copper Oxide (50nm) and Aluminum Oxide (50nm) nanoparticles supplied by Sigma Aldrich and Rubitherm (RT-18) as base PCM, supplied by Rubitherm GmbH. The vertical cylindrical LHTES is composed of two concentric pipes; with the inner one carrying a heat transfer fluid at a constant temperature and the annular space containing a nano-PCM. The initial temperature of the nano-PCM is 5 C while the temperature of the heat transfer fluid is 40 C. The experimental results show that using nano-PCM reduces the melting time when compared to base PCM, but enhanced melting is observed when Copper Oxide nanoparticle is used.
Physical Properties of Phase-Change Emulsions
Langmuir, 2006
Phase-change emulsions (PCE) are important in a variety of applications, from ultrasound imaging to the explosive material used in the mining industry, but until now there has been no adequate theory to describe their activation properties. The PCE consists of a low-boiling-point liquid, known as the volatile phase, dispersed in an aqueous phase. The volatile phase boils as a result of an increase in the temperature of the emulsion. The volume of the emulsion will increase during this phase transition, with the transition temperature and final volume of the emulsion highly dependent on the initial radius of the liquid droplets. Here a description of the change in boiling point and freezing point of the volatile phase, as well as the volume change of a droplet in the emulsion as a function of the initial droplet radius, is presented. The influence of volatile phase solubility, liquid-liquid interfacial tension, and final temperature are explored, accounting for the influence of confinement on the properties of the volatile phase. Beyond this, a means by which the diffusivity of the gas in the continuous liquid phase can be measured is derived.
Storage Capacity in Dependency of Supercooling and Cycle Stability of Different PCM Emulsions
2021
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 enthal...
Solar Energy Materials and Solar …, 2009
This study is focused on the preparation, characterization, and determination of thermal properties of microencapsulated docosane with polymethylmethacrylate (PMMA) as phase change material for thermal energy storage. Microencapsulation of docosane has been carried out by emulsion polymerization. The microencapsulated phase change material (MEPCM) was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of MEPCM were measured by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC analysis indicated that the docosane in the microcapsules melts at 41.0 1C and crystallizes at 40.6 1C. It has latent heats of 54.6 and À48.7 J/g for melting and crystallization, respectively. TGA showed that the MEPCM degraded in three distinguishable steps and had good chemical stability. Accelerated thermal cycling tests also indicated that the MEPCM had good thermal reliability. Based on all these results, it can be concluded that the microencapsulated docosane as MEPCMs have good potential for thermal energy storage purposes such as solar space heating applications.
IOP Conference Series: Materials Science and Engineering
The paper presents experimental investigations to evaluate thermal performance of heat pipe using Nano Enhanced Phase Change Material (NEPCM) as an energy storage material (ESM) for electronic cooling applications. Water, Tricosane and nano enhanced Tricosane are used as energy storage materials, operating at different heating powers (13W, 18W and 23W) and fan speeds (3.4V and 5V) in the PCM cooling module. Three different volume percentages (0.5%, 1% and 2%) of Nano particles (Al 2 O 3) are mixed with Tricosane which is the primary PCM. This experiment is conducted to study the temperature distributions of evaporator, condenser and PCM during the heating as well as cooling. The cooling module with heat pipe and nano enhanced Tricosane as energy storage material found to save higher fan power consumption compared to the cooling module that utilities only a heat pipe.