Preparation of paraffin and fatty acid phase changing nanoemulsions for heat transfer

Puupponen, Salla; Seppälä, Ari; Vartia, Olli; Saari, Kari; Ala-Nissilä, Tapio

doi:10.1016/j.tca.2014.12.020

Cited by 48 publications

(16 citation statements)

References 23 publications

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“…However, only minor deterioration of the latent heat (≤10%) was observed for these fluids, which is advantageous in terms of practical heat transfer applications. Similar behavior of the latent heat in smallscale systems has been reported in literature as well [15][16]. According to the DSC measurements, the melting of the particles in the fluids occurs at two almost separate periods: the first onset temperature is observed at ~30 °C, but the largest portion of the paraffin melts around ~53 °C (Fig.…”

Section: Latent Heat and Specific Heatsupporting

confidence: 85%

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: Latent Heat and Specific Heatsupporting

confidence: 85%

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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“…In addition, HIPE-ery melted at a wider temperature range than bulk erythritol indicating a broad void size distribution due to mechanical mixing in the emulsification. 30,31 Measurement If surface effects are ignored, the latent heat of polyol-polystyrene composite can be calculated from the mass fraction of the PCM in the product as:…”

Section: Thermal Properties Of Erythritol and Erythritol-polystyrene mentioning

confidence: 99%

Novel microstructured polyol–polystyrene composites for seasonal heat storage

et al. 2016

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We propose a robust route to prepare supercooling microstructured phase change materials (PCMs) suitable for long-term heat storage or thermal protection applications. The new preparation method is based on polymerization of high internal phase emulsion (HIPE). Two promising polyols, erythritol and xylitol, are successfully prepared as new type microencapsulated PCM-polystyrene composites with PCM mass fractions of 62w-% and 67 w-%, respectively, and average void diameter of ~50 µm. Thermal properties of polyol-polystyrene composites and bulk polyols are studied thoroughly with differential scanning calorimetry (DSC). Microscale engineering has a significant impact on the thermal properties of polyols. Crystallization of the microscale erythritol is accelerated as compared to the crystallization of bulk PCM due to high fraction of solid surfaces in the polymer-polyol composites. Furthermore, crystallization properties of the microstructured erythritol are preserved similar in the cycling experiments. Crystallization of the bulk erythritol is found to strongly depend on the cooling rate, thermal history of the sample and surface roughness of the crucible, whereas these factors have only little impact on the crystallization of microstructured erythritol. In addition, microstructured polyolpolystyrene composites show anomalous enhancement in the specific heat as compared to bulk polyols. This enhancement may be originated from the strong polyol-surfactant interactions occurring in the composites.

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“…Comparatively, PCM emulsions have several advantages such as simple process for emulsifying [18], negligible thermal resistance of the protective surfactant layer, and good operation stability [8]. Consequently, PCM emulsions have attracted an increasingly interest in recent years, which researches mainly focus on preparing stable PCM emulsions by selecting suitable emulsifiers [8,[19][20][21], reducing the supercooling of the PCM emulsions with low phase change temperatures by adding higher melting temperature PCM [22,23], suitable surfactants [24] as well as nanoparticles [25,26], together with investigations on the rheological properties of PCM emulsions [27,28]. It has been found that the viscosity of a PCM emulsion increases with the mass fraction of the PCM, and the PCM emulsions with a mass fraction of the PCM lower than 50 wt% is more suitable for practical application [27].…”

Section: Introductionmentioning

confidence: 99%

Graphite nanoparticles-dispersed paraffin/water emulsion with enhanced thermal-physical property and photo-thermal performance

Wang

Liu

Fang

et al. 2016

Solar Energy Materials and Solar Cells

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Preparation of paraffin and fatty acid phase changing nanoemulsions for heat transfer

Cited by 48 publications

References 23 publications

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Thermal properties and convective heat transfer of phase changing paraffin nanofluids

Novel microstructured polyol–polystyrene composites for seasonal heat storage

Graphite nanoparticles-dispersed paraffin/water emulsion with enhanced thermal-physical property and photo-thermal performance

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