Evaluation of paraffin/water emulsion as a phase change slurry for cooling applications

Huang, Li; Petermann, Marcus; Doetsch, Christian

doi:10.1016/j.energy.2009.03.016

Cited by 147 publications

(64 citation statements)

References 14 publications

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“…[15][16][17][18][19] Additionally, solid to liquid phase change materials have been investigated, some employing a slurry of small particles of emulsified paraffin, and some employing carbon sheets impregnated with a phase change material. [20][21][22] Degradation of lithium-ion batteries is very complicated, with various interdependent mechanisms contributing to both capacity loss (capacity fade) and increased resistance (power fade). Degradation can occur during storage (calendar ageing) and during operation (cycle life), both of which have a strong dependence on temperature.…”

mentioning

confidence: 99%

Surface Cooling Causes Accelerated Degradation Compared to Tab Cooling for Lithium-Ion Pouch Cells

Hunt

Zhao

Patel

et al. 2016

J. Electrochem. Soc.

143

119

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One of the biggest causes of degradation in lithium-ion batteries is elevated temperature. In this study we explored the effects of cell surface cooling and cell tab cooling, reproducing two typical cooling systems that are used in real-world battery packs. For new cells using slow-rate standardized testing, very little difference in capacity was seen. However, at higher rates, discharging the cell in just 10 minutes, surface cooling led to a loss of useable capacity of 9.2% compared to 1.2% for cell tab cooling. After cycling the cells for 1,000 times, surface cooling resulted in a rate of loss of useable capacity under load three times higher than cell tab cooling. We show that this is due to thermal gradients being perpendicular to the layers for surface cooling leading to higher local currents and faster degradation, but in-plane with the layers for tab cooling leading to more homogenous behavior. Understanding how thermal management systems interact with the operation of batteries is therefore critical in extending their performance. For automotive applications where 80% capacity is considered end-of-life, using tab cooling rather than surface cooling would therefore be equivalent to extending the lifetime of a pack by 3 times, or reducing the lifetime cost by 66%. Due to their high energy and power densities, Lithium-ion batteries are a very important component of electric vehicles, and their use has increased dramatically in recent years as the uptake of hybrid and electric vehicles has increased.1-3 One of the major challenges of using lithium-ion batteries in hybrid and electric vehicles is thermal management, 4 which is important in order to manage degradation at an acceptable rate whilst maximizing the performance of the batteries and reducing the risk of thermal runaway. 5-7Many studies have shown that increased temperature leads to an increase in the rate of degradation, 4,[8][9][10][11] therefore the effectiveness of a thermal management system is vital in order to maximize the lifetime performance of the pack. The design of a good thermal management system for a battery pack should consider both the overall temperature of the pack and both intra-cell and internal thermal gradients. Poor design of thermal management systems could be a major contributing factor in increasing degradation rates to unacceptable levels. 12There are many different techniques that can be used to thermally manage batteries in hybrid and electric vehicles. It is possible to use either air or liquid as the cooling medium, and both of these can be used in either a direct (with cooling medium in contact with the cell) or indirect way. In addition to this, different areas of the cell can be cooled, namely the surfaces of the cell or the cell tabs. 13,14 In general, systems employing air as the cooling medium are considered to be simpler and cheaper to implement, although the performance is limited especially in applications where there is a high heat generation rate or if the batteries are being operated in a high ambient tempe...

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mentioning

confidence: 99%

Surface Cooling Causes Accelerated Degradation Compared to Tab Cooling for Lithium-Ion Pouch Cells

Hunt

Zhao

Patel

et al. 2016

J. Electrochem. Soc.

143

119

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“…As shown in Fig. 3 [24], they accumulate at the interface of oil and water, with the hydrophilic group pointing towards water and the hydrophobic group towards oil. The two main functions of surfactants during emulsification process are: a) To reduce interfacial tension between oil and water molecules.…”

Section: Surfactantsmentioning

confidence: 99%

“…For instance, as shown in Fig. 2, Huang [24] tested different percentages of RT10 emulsion (15, 30, 50 and 75 wt%) and found that their latent heat capacities increased proportionally. However all the samples covered a similar sizes range of 1-10 mm and had a mean diameter d 50 of 3-5 mm, which suggested that the paraffin fraction had no significant effect on the droplets size distribution.…”

Section: Paraffinmentioning

confidence: 99%

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Review of phase change emulsions (PCMEs) and their applications in HVAC systems

Shao

Darkwa

Kokogiannakis

2015

Energy and Buildings

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Phase change material emulsions (PCMEs) are multifunctional fluids consisting of phase change materials (PCMs) and carrier fluids. PCMEs could be potential candidates as heat transfer media in heating, ventilation and air conditioning (HVAC) systems. This is mainly because PCME could take advantage of its high heat capacity to reduce flow rate and thus saving pumping power whilst delivering the same amount of cooling effect. PCME can also simultaneously act as cold storage to shift peak-load to off-peak time and improve the COP of systems. However, the optimum design of integrated system requires a good understanding of flow behaviour and heat transfer characteristics of PCMEs. In this paper, comprehensive reviews of their thermophysical properties and potential applications as thermal energy storage and as alternative heat transfer fluids in air conditioning systems have been carried out to establish their limitations for future research. systems. This is mainly because PCME could take advantage of its high heat capacity to reduce flow rate and thus saving pumping power whilst delivering the same amount of cooling effect. PCME can also simultaneously act as cold storage to shift peak-load to off-peak time and improve the COP of systems. However, the optimum design of integrated system requires a good understanding of flow behaviour and heat transfer characteristics of PCMEs. In this paper, comprehensive reviews of their thermo-physical properties and potential applications as thermal energy storage and as alternative heat transfer fluids in air conditioning systems have been carried out to establish their limitations for future research.

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“…Such thermal resistance depends on the particles wettability characterized by contact angle between the particles and the carrier fluid. From the wettability point of view, particles' surface is often modified by adding surfactant to improve the physical/ mechanical stability 9,10 and reduce the flow resistance 11 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%

The role of contact angle in the thermal conductivity of microencapsulated phase change material suspensions

Qiu

Le²,

et al. 2017

Advances in Mechanical Engineering

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The purpose of this article is to investigate the effect of the wettability on the thermal conductivity of microencapsulated phase change material suspensions. The wettability of the capsules, characterized by contact angle between solid capsules and carrier fluid, was modified by mixing two selected surfactants into the suspensions, that is, cetyltrimethylammonium bromide and sodium dodecyl sulfate, and changing such surfactants' additive amount. Meanwhile, the static thermal conductivity of the microencapsulated phase change material suspensions was measured. The results indicated the effect of the cetyltrimethylammonium bromide is more significant than the sodium dodecyl sulfate when the mass fraction of surfactants falls into the range of 0-0.05 wt%. However, when the mass fraction of surfactants continues to increase from 0.05 wt%, the significance of the sodium dodecyl sulfate exceeded the cetyltrimethylammonium bromide. It was also found that the decrease in the contact angle led to the growth in thermal conductivity for Maxwell model and tested results. When the contact angle fell into the range of 45°-95°, the Maxwell model could predict the thermal conductivity 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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Evaluation of paraffin/water emulsion as a phase change slurry for cooling applications

Cited by 147 publications

References 14 publications

Surface Cooling Causes Accelerated Degradation Compared to Tab Cooling for Lithium-Ion Pouch Cells

Surface Cooling Causes Accelerated Degradation Compared to Tab Cooling for Lithium-Ion Pouch Cells

Review of phase change emulsions (PCMEs) and their applications in HVAC systems

The role of contact angle in the thermal conductivity of microencapsulated phase change material suspensions

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