An evaluation of microencapsulated PCM for use in cold energy transportation medium

Yamagishi, Yasushi; Sugeno, Tomohisa; Ishige, Takashi; Takeuchi, Hiromi; Pyatenko, Alexander

doi:10.1109/iecec.1996.553442

Cited by 81 publications

(83 citation statements)

References 7 publications

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“…The fluids studied herein require rather a large temperature change (~30 °C) for complete melting of the particles. In addition, the fractions of PCM (≤10.0 w-%) are rather small when compared to those of some micro-scale phase change slurries measured in earlier studies (up to ~30%) [2,5,28]. Therefore, most of the energy is still carried as sensible heat, and the latent heat has a relatively small contribution (≤ 12.3%) to the total energy density.…”

Section: Figmentioning

confidence: 70%

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Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Mikkola

Puupponen

Saari

et al. 2017

International Journal of Thermal Sciences

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THERMAL PROPERTIES AND CONVECTIVE HEAT TRANSFER PERFORMANCE OF SOLID-LIQUID PHASE CHANGING PARAFFIN NANOFLUIDSWe aim to combine these two concepts for the first time by studying fluids containing nano-sized phase changing particles. In this study, the convective heat transfer performance and the thermal properties of solidliquid phase changing paraffin nanofluids are experimentally examined. Three water-based paraffin nanofluids with particle mass fractions of 5-10% are prepared and measured with an annular tube heat exchanger. The heat transfer measurements cover both laminar and turbulent regimes with Reynolds numbers varying in the range of 700-11000. The measurements also include pressure losses in order to study the suitability of the fluids for practical forced convection applications. In addition, the fluids are characterized: latent heats, specific heats, viscosities, thermal conductivities, densities and particle size distributions are all determined experimentally. In agreement with previous studies, the nanofluids are found to exhibit Nusselt numbers clearly higher than water when compared on the basis of equal Reynolds numbers. However, the differences in Prandtl numbers are shown to explain these deviations in Nusselt numbers. Indeed, the well-known Gnielinski correlation is able to explain the results quite adequately and thus, significant anomalies in the convection heat transfer caused by neither the melting of the phase change material nor the presence of the nanoparticles are observed. However, the nanofluids have systematically slightly higher Nusselt numbers than the correlation would predict, but the deviations are within the accuracy of the correlation (10%). When compared by using equal pumping powers, the nanofluids exhibit heat transfer performance poorer than that of water. The positive impact of the latent heat is outweighed by the negative effects of the increased viscosity and decreased specific heat.

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Section: Figmentioning

confidence: 70%

“…Naturally, more unexpected results might be obtained with yet higher concentrations. The particle fractions studied herein (5-10 w-%) are rather high for nanofluids, but even higher concentrations are often studied in the class of micro PCM fluids (~30%) [2,5,28]. …”

Section: Convective Heat Transfermentioning

confidence: 99%

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Mikkola

Puupponen

Saari

et al. 2017

International Journal of Thermal Sciences

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“…Research has shown that the effect of supercooling can be reduced by adding a nucleating agent [44]. Fan et al [45] has found that supercooling can be prevented by adding around 9 wt % of 1-octadecanol directly in the PCM, or 6 wt % of sodium chloride to the emulsion.…”

Section: Super Cooling Effectsmentioning

confidence: 99%

PCMs for Residential Building Applications: A Short Review Focused on Disadvantages and Proposals for Future Development

et al. 2017

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Phase change materials (PCMs) offer great potential as a latent heat energy storage technique to provide energy efficient systems in new and existing residential buildings. Due to their unique characteristic of high storage densities and latent heat properties, PCMs provide opportunities for greater energy storage in many applications for residential buildings. These applications include, but are not limited to, solar water heating, space heating/cooling, and waste heat recovery. This study reviews PCM systems in residential building applications, with a focus on their major disadvantages and concludes with proposals for future development. Several disadvantages of PCM use in the given application have been identified and include; super cooling, low thermal conductivity, phase segregation, fire safety, and cost. The issues caused by super cooling and phase segregation lead to thermal cycling degradation, limiting the useful lifecycle of the material. These issues could limit their potential in building applications, which require systems of a long lifespan. Low thermal conductivities can slow down the rate at which heat is distributed or absorbed from the building, which affect the occupants comfort and as well as the efficiency of the system. Ideas based on the current research on ways to limit these disadvantages are included in the study. This study also identifies that further research is required on novel maintenance ways for the PCM systems after they have been installed.

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“…Such thermal resistance depends on the particles wettability characterized by contact angle between the particles and the carrying fluid. From the wettability point of view, particles surface is often modified by adding surfactant to improve the physical/mechanical stability (Huang L, et al,2009, Shannaq R A andFarid M, 2015) and reduce the fluid resistance (Yamagishi Y, et al, 1996) in the application of MPCM suspension. There could be a little residue air or even a minor air gap between the surface of a hydrophobic particle and its surroundings, leading to a "thermal hydrophobic resistance".…”

Section: Introductionmentioning

confidence: 99%

Impact of microcapsules wettability on thermal conductivity of microencapsulated phase change material(MPCM) suspensions

Qiu

Qin

Zheng

et al. 2018

JTST

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The purpose of this paper is to investigate the effect of the wettability on MPCM suspensions thermal conductivity. The wettability of the capsules, characterized by contact angle between solid capsules and carrying fluid, was modified by mixing two selected surfactants into the suspensions, i.e.,cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate(SDS) and changing such surfactants' additive amount. Meanwhile, the Hot Disk 2500s thermal analyzer was applied to test the static thermal conductivity of the MPCM suspensions in which the mass fraction of capsules is 10wt.% and obtained the relation between the thermal conductivity and the contact angle. The results indicated, when the mass fraction of surfactants falls into the range of 0 -0.05wt.%, the effect of the CTAB is more significant than the SDS. However, when the mass fraction of surfactants continue to increase from 0.05wt.%, the significance of the SDS exceeded the CTAB. It was also found that the decrease in the contact angle led to the growth in thermal conductivity for both Maxwell model's theoretical value and experimental results. When the contact angle fell into the range of 45°-95°, the Maxwell model's theoretical results of the thermal conductivity could predict the thermal conductivity of MPCM suspensions with a good accuracy, but inversely when the contact angles were smaller than 45°, a significant gap was found between the two results.To remove such gap a correction factor "A" which is associated with contact angles was proposed.

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An evaluation of microencapsulated PCM for use in cold energy transportation medium

Cited by 81 publications

References 7 publications

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

PCMs for Residential Building Applications: A Short Review Focused on Disadvantages and Proposals for Future Development

Impact of microcapsules wettability on thermal conductivity of microencapsulated phase change material(MPCM) suspensions

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