Heat transfer enhancement of paraffin wax using compressed expanded natural graphite for thermal energy storage

Zhong, Yajuan; Li, Sizhong; Wei, Xing; Liu, Zhanjun; Guo, Quangui; Shi, Jingli; Liü, Lang

doi:10.1016/j.carbon.2009.09.033

Cited by 157 publications

(54 citation statements)

References 18 publications

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“…However, the main drawback that hinders the further application of paraffin wax is its low thermal conductivity (0.21-0.24 W/mK). Some methods have been used to enhance heat transfer properties in the PCMs, including impregnations of porous material [7,8], dispersion of high thermal conductivity particles in the PCM [9][10][11], and placing metal structure in PCM [12]. Among these, adding high thermal conductivity material into paraffin wax is a widely used technique for enhancing the heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of enhanced heat transfer by addition of CuO nanoparticle

2011

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An energy storage system has been designed to study the thermal characteristics of paraffin wax with an embedded nano size copper oxide (CuO) particle. This paper presents studies conducted on phase transition times, heat fraction as well as heat transfer characteristics of paraffin wax as phase change material (PCM) embedded with CuO nanoparticles. 40 nm mean size CuO particles of 2, 5 and 10% by weight were dispersed in PCM for this study. Experiments were performed on a heat exchanger with 1.5-10 l/min of heat transfer fluid (HTF) flow. Time-based variations of the temperature distributions are revealed from the results of observations of melting and solidification curves. The results strongly suggested that the thermal conductivity enhances 6, 6.7 and 7.8% in liquid state and in dynamic viscosity it enhances by 5, 14 and 30% with increasing mass fraction of the CNEPs. The thermal conductivity ratio of the composites can be augmented by a factor up to 1.3. The heat transfer coefficient during solidification increased about 78% for the maximum flow rate. The analysis of experimental results reveals that the addition of copper oxide nanoparticles to the paraffin wax enhances both the conduction and natural convection very effectively in composites and in paraffin wax. The paraffin wax-based composites have great potential for energy storage applications like industrial waste heat recovery, solar thermal applications and solar based dynamic space power generation with optimal fraction of copper oxide nanoparticles.

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Section: Introductionmentioning

confidence: 99%

Experimental study of enhanced heat transfer by addition of CuO nanoparticle

2011

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“…Due to the porous structure and enhanced thermal conductivity of expanded graphite (EG), many researchers have employed two or more materials to prepare composite shape-stable phase change materials (e.g., PCMs, EG) (Zhao et al 2011;Zhong et al 2010;Sarı and Karaipekli 2007;Zhang et al 2012;Wang et al 2014), indicating that efficient enhanced thermal conductivity occurred in composite shape-stable phase change materials. Some reports have suggested that EG has great application potentials in the field of phase change materials (Huang et al 2014;Tian et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Enhanced thermal conductivity of waste sawdust-based composite phase change materials with expanded graphite for thermal energy storage

Yang

Wang

Liu³

et al. 2017

Bioresour. Bioprocess.

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Background: With the current rapid economic growth, demands for energy are progressively increasing. Energy shortages have attracted significant attention due to the shrinking availability of non-renewable resources. Therefore, thermal energy storage is one of the solutions that lead to saving of fossil fuels and make systems more cost-effective by the storage of wasted thermal energy. In particular, the application of phase change materials (PCMs) is considered as an effective and efficient approach to thermal energy storage because of the high latent heat storage capacity at small temperature intervals. Nevertheless, leakage problems and low thermal conductivity limit the practical applications of PCMs. Therefore, form-stable phase change materials with high thermal conductivity are urgently needed. Results:A novel form-stable composite phase change material was prepared by incorporating PEG into waste sawdust with 5% EG. In the composites, PEG served as a phase change material, while waste sawdust acted as a carrier matrix. EG was added to help increase the thermal conductivity of the composites. The melting temperature of CPCMs-4 with 5% EG was found to be 58.6 °C with a phase change enthalpy of 145.3 kJ/kg, while the solidifying temperature was 48.5 °C with a phase change enthalpy of 131.4 kJ/kg. The thermal conductivity of CPCMs-4 with 5% EG increased by 23.8% compared with that of CPCMs-4. Moreover, no obvious changes in melting, solidifying temperature, or latent heat after 200 heating-cooling cycles were detected. The supercooling extent of CPCMs-4 with 5% EG decreased by 19.2% compared with PEG. The volume change properties and wettability properties of CPCMs-4 with 5% EG are suitable for thermal energy in terms of practical application. Conclusions:The prepared composites have excellent thermal and form-stable properties and they can be recognized as potential candidates for thermal energy storage as form-stable composite phase change materials. Using simple impregnation techniques with waste sawdust as a supporting material, this study demonstrates an innovative technology for practically and markedly enhancing the adsorption capacity of phase change materials.

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“…Composite materials incorporating carbon have enhanced thermal conductivity and have been proposed for solar thermal applications (e.g. [Zhong et al, 2010 andHaillot et al, 2011]). However in some materials, increased thermal conductivity comes at the expense of energy density, which can be reduced by 35% or more due to the volume of the conductive material [Haillot et al, 2011].…”

Section: Overview Of Materialsmentioning

confidence: 99%