scholarly journals Experimental Investigation of the Apparent Thermal Conductivity of Microencapsulated Phase-Change-Material Slurry at the Phase-Transition Temperature

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4124
Author(s):  
Krzysztof Dutkowski ◽  
Marcin Kruzel
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Phase Transformation ◽  
Liquid Form ◽  
Microencapsulated Phase Change Material ◽  
Apparent Thermal Conductivity ◽  
Mass Fractions ◽  
Change Material ◽  
Base Liquid

The article presents the results of detailed studies of the thermal conductivity of the water slurry of microencapsulated PCM (mPCM) and slurry based on water–propylene glycol solutions. The starting product, MICRONAL® 5428 X, which contains about 43% microencapsulated paraffin with a transformation temperature of 28 °C, was mixed with the base liquid to obtain slurries with mass fractions of mPCM of 4.3, 8.6, 12.9, 17.2, 21.5, 25.8, 30.1, 34.4, 38.7, and 43.0%. Detailed measurements were carried out in the temperature range of 10–40 °C. It was found that: (a) an increase in the temperature of the slurry caused an increase in its thermal conductivity, both when PCM was in the form of a solid and a liquid; (b) the thermal conductivity of the mPCM slurry when the PCM was in liquid form was greater than the thermal conductivity of the slurry when the PCM was liquid; (c) during the phase transformation, a significant increase in the thermal conductivity of the slurry was observed, and its peak occurred when the temperature of the slurry reached the temperature declared by the manufacturer at which the phase-transition peak occurs.

scholarly journals Hybrid Microencapsulated Phase-Change Material and Carbon Nanotube Suspensions toward Solar Energy Conversion and Storage

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4401
Author(s):  
Jun Li ◽  
Lisi Jia ◽  
Longjian Li ◽  
Zehang Huang ◽  
Ying Chen
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Solar Energy ◽  
Energy Conversion ◽  
Solar Energy Conversion ◽  
Microencapsulated Phase Change Material ◽  
Energy Conversion And Storage ◽  
New Type ◽  
And Storage ◽  
Change Material

In this study, a new type of functional hybrid suspension for solar energy conversion and thermal energy storage was prepared by adding carbon nanotube (CNT) and microencapsulated phase-change material (MEPCM) into deionized water. MEPCM with octadecane as the core material and titania (TiO2) as the shell material was synthesized by the sol–gel method. The MEPCMs were spherical particles with diameters of 2–4 μm, and the thickness of the shell was about 100 nm. The MEPCM achieved better thermal stability and thermal conductivity than the pure octadecane due to the TiO2 shell. The melting and solidification latent heats of the MEPCM were about 154.24 and 154.26 J/g, respectively. The encapsulation efficiency of octadecane was calculated to be 65.84%. Most of all, the novel hybrid CNT and MEPCM suspensions exhibited remarkable dispersion stability owing to the stable reticular structure composed of CNT in the suspension. Compared with pure water, the thermal conductivity, specific heat of the MEPCM/CNT suspension improved by 34.48 and 43.57%, respectively and the photo-thermal conversion efficiency reached a high value of 86.0%. This work provided a new type of hybrid functional suspension towards direct absorption solar collector for solar energy conversion and storage.

Characterization of Thermal Properties and Heat Transfer Behavior of Microencapsulated Phase Change Material Slurry and Multiwall Carbon Nanotubes in Aqueous Suspension

2007 ◽  
Author(s):  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Curt Thies ◽  
Guillermo Soriano ◽  
Paritosh Garg
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Microencapsulated Phase Change Material ◽  
Change Material

In the last decade, microencapsulated phase change material (MPCM) slurries have been proposed and studied as novel coolants for heat transfer applications. Such applications include electronics cooling, and secondary coolants in air conditioning systems among others. Experiments have shown that MPCM’s increase the overall thermal capacity of thermal systems by taking advantage of the phase change material’s latent heat of fusion. However, research has also shown that the overall heat transfer coefficient is diminished due to a reduction in the effective thermal conductivity and increased viscosity of the slurry. For this reason, there is an urgent need to modify the content of microcapsules containing phase change material to increase their effective thermal conductivity and the overall heat transport process. Our solution consists of increasing the thermal conductivity of MPCM by adding carbon nanotubes to the shell and core of the microcapsules. Carbon nanotubes have shown to increase the thermal conductivity of liquids by 40% or more in recent experiments. In this paper, MPCM slurry containing octadecane as phase change material and multi-wall carbon nanotubes (MWCNTs) embedded in the capsule material and core are compared with pure water as heat transfer fluid. Thermal and physical properties of MPCM slurry containing carbon nanotubes were determined using a differential scanning calorimeter and concentric viscometer, respectively. Experimental convective heat transfer coefficient data for MWCNT aqueous suspensions under laminar flow and constant heat flux were determined using a bench-top heat transfer loop. Experimental heat transfer results are presented.

Modeling and Simulations of Laminar Mixed Convection in a Vertical Pipe Conveying Slurries of a Microencapsulated Phase-Change Material in Distilled Water

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
David A. Scott ◽  
Alexandre Lamoureux ◽  
Bantwal R. Baliga
Keyword(s):  
Mathematical Model ◽  
Experimental Investigation ◽  
Mixed Convection ◽  
Phase Change ◽  
Specific Heat ◽  
Bulk Temperature ◽  
Distilled Water ◽  
Microencapsulated Phase Change Material ◽  
Laminar Mixed Convection ◽  
Change Material

Steady, laminar, mixed convection in a straight and vertically oriented pipe conveying slurries of a microencapsulated phase-change material (MCPCM) suspended in distilled water (flowing upwards), with essentially uniform heat flux imposed on its outside surface, are considered. A cost-effective homogenous mathematical model is proposed and shown to be applicable to the aforementioned mixed convection phenomena with slurries of a sample MCPCM. Correlations for the effective properties of the sample MCPCM slurries and procedures for their implementation are presented. The energy equation, in which the latent-heat effects are handled using an effective specific heat, is cast in a form akin to that of a general advection-diffusion transport equation. Difficulties with the standard definition of bulk temperature when the specific heat of the fluid changes significantly with temperature are elaborated, and a modified bulk temperature that overcomes these difficulties is proposed. A finite volume method (FVM) was used to solve the mathematical model. The proposed model and FVM were validated by using them to solve problems involving slurries of the sample MCPCM, and comparing the results to those of a complementary experimental investigation. The numerical results compare very well with those of the complementary experimental investigation. They also demonstrate the need for optimizing the various parameters involved, if full benefits of the MCPCM slurries are to be achieved for specific applications.

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