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Yulong Ding - One of the best experts on this subject based on the ideXlab platform.
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Inhibiting hot corrosion of molten Li2CO3-Na2CO3-K2CO3 Salt through graphitization of construction materials for concentrated solar power
Solar Energy Materials and Solar Cells, 2020Co-Authors: Yaroslav Grosu, Yulong Ding, Argyrios Anagnostopoulos, María Elena Navarro, Abdessamad FaikAbstract:Abstract Next-generation concentrated solar power (CSP) plants are expected to work above the current temperature limit of 565 °C for the benefit of enhanced efficiency. This poses significant challenges in the construction materials, among others, in terms of corrosion. In this work, we investigate the spray-graphitization method to improve the compatibility of SS310 and SS347 with molten Li2CO3-Na2CO3-K2CO3 Carbonate Salt. Improved compatibility was observed due to the formation of protective Carbonate or carbide layers on SS347 and SS310 surfaces, respectively. Detailed characterization of the corrosion products, including chemical reactions and wettability allowed the mechanism of anticorrosion protection to be proposed, which could be used for other construction materials in direct contact with high-temperature molten Salts for next-generation CSP plants and beyond.
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Carbonate Salt based composite phase change materials for medium and high temperature thermal energy storage: a microstructural study
Solar Energy Materials and Solar Cells, 2019Co-Authors: Lin Cong, Xianglei Liu, Yimin Xuan, Yulong DingAbstract:Abstract We investigated the microstructures and their formation mechanisms of Carbonate Salt based composite phase change materials (CPCMs). Such materials typically consist of a Carbonate Salt as the phase change material (PCM), a thermal conductivity enhancement material (TCEM) and a ceramic skeleton material (CSM) for structure stabilisation, and are mainly for medium and high temperature thermal energy storage applications. Two Carbonate Salt based composites were studied with one being eutectic NaLiCO3 and the other Na2CO3. MgO and graphite flakes were used respectively as the CSM and TCEM for fabricating the composite modules. A scanning electron microscope with energy dispersive spectrometer (SEM-EDS) was used to observe the microstructures and the Salt distribution and redistribution within the composite structures during repeated melting-solidification cycles. The results showed Salt migration within the composite structure during the thermal cycling. Such a microscopic motion led to a more homogenous distribution of not only the Salt but also the CSM and TCEM. At a low graphite flake loading, breakage of the graphite flake was observed, suggesting stress generation during thermal cycling. The extent of the breakage reduced with increasing graphite flake loading, suggesting the stress generation be related to microscopic motion. The MgO based CSM particles were likely to be sintered, forming a porous structure. Such a structure reduced the swelling effect partially due to the use of graphite on which the Salts had a poor wettability.
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Investigation on the effective thermal conductivity of Carbonate Salt based composite phase change materials for medium and high temperature thermal energy storage
Energy, 2019Co-Authors: Yulong DingAbstract:Abstract This paper concerns the effective thermal conductivity of Carbonate Salt based composite phase change materials (CPCMs). Such materials typically consist of a Carbonate Salt as the phase change material (PCM), an MgO as the ceramic skeleton material (CSM) and a graphite flake as the thermal conductivity enhancement material (TCEM), and are mainly used for medium and high temperature thermal energy storage applications. Two Carbonate Salt based CPCMs are prepared and studied with one being NaLiCO3 and the other Na2CO3. A theoretical model based on the microstructure characteristics is proposed to predict the effective thermal conductivity of the composites. The model uses a unit cell modelled as two MgO spheres in contact with the PCM and TCEM mixture filled in the interparticle void of them. Two models reported in the literature are employed to determine the thermal resistance between the particles and to estimate the sintered neck parameters. A parallel-plate based experimental set up is constructed to measure the effective thermal conductivity of the composites. The modelling results are compared with experimental data and reasonably agreements are obtained. Various literature models for the effective thermal conductivity predication are also compared with each other and experimental data.
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Investigation on the thermal performance of a high temperature packed bed thermal energy storage system containing Carbonate Salt based composite phase change materials
Applied Energy, 2019Co-Authors: Yulong DingAbstract:Abstract This paper concerns the thermal performance of a high temperature packed bed thermal energy storage (TES) system containing Carbonate Salt based composite phase change materials (CPCMs) that made of a eutectic Carbonate Salt of NaLiCO3 (phase change material, PCM), MgO (ceramic skeleton material, CSM) and graphite flakes (thermal conductivity enhancement material, TCEM). A rectangular packed bed configuration containing CPCMs bricks is built and a three-dimensional computational model is established to study the thermal performance of the system. The enthalpy-porosity approach and surface-to-surface (S2S) radiation model are respectively adopted to model the phase change process and the radiation heat transfer inside the system. A ferric oxide is also used as the sensible heat storage material to compare with the CPCMs based system. The numerical model is first compared with the published experimental data and reasonably good agreements are obtained, indicating the confidence of the model. Extensive modelling is then performed under different conditions to investigate the effects of various parameters including the radiation heat transfer, TCEM mass loading and heat transfer fluid (HTF) operation conditions on the system performance. The results indicate that the system containing CPCMs shows better charging and discharging performance in comparison with the system containing ferric oxide due to the large energy storage density and high thermal conductivity. The thermal radiation has an important influence on the system performance. The system heat transfer efficiency is apparently enhanced when the radiation heat transfer influence is taken into consideration. When the emissivity is at δ = 1, the total charging period of the system is respectively shortened by 10.6% and 25.7% than that of the emissivities at δ = 0.5 and δ = 0. The use of TCEM in the CPCMs significantly enhances the heat transfer performance of the system. An increase in the TCEM loading from 0% to 30% respectively leads to the reduction in charging and discharging processes by almost 30.3% and 29.2%. The results also indicate that, for a fixed charging/discharging power, both the overall charging and discharging periods of the system decrease with the increase of Re number or decrease of Ste number since an increase in the Re number (decrease in the Ste number) leads to an overall enhancement of the heat transfer between the HTF and the CPCMs bricks and hence an overall improvement in the charging and discharging rates.
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Heat transfer of composite phase change material modules containing a eutectic Carbonate Salt for medium and high temperature thermal energy storage applications
Applied Energy, 2019Co-Authors: Xiaohui She, Hui Cao, Peikun Zhang, Li Wang, Yulong DingAbstract:Abstract This paper concerns the heat transfer behaviour of Composite Phase Change Material (CPCM) modules made of a eutectic Carbonate Salt of NaLiCO3 (phase change material, PCM), MgO (ceramic skeleton material, CSM) and graphite flakes (thermal conductivity enhancement material, TCEM). The CPCM has a melting point around 500 °C and is suitable for medium and high temperature thermal energy storage applications including peak shaving of power grids, effective use of curtailed wind energy, and concentrated solar power generation. Disk-like CPCM modules were fabricated for the work. The effects of TCEM loading and surface cooling conditions on the heat transfer were experimentally investigated and analysed. The results showed that the use of TCEM not only significantly enhanced heat transfer of the CPCM modules, but also reduced the temperature difference and hence the thermal resistance between heater surface and CPCM module surface, leading to a significant extent of enhancement of overall heat transfer. Temperature measurements of a flat surface of the CPCM modules as well as that within the modules showed a non-uniform temperature distribution perpendicular to heat transfer direction, suggesting the effect of CPCM microstructure on heat transfer. This microstructural effect was further investigated using a scanning electron microscope with energy dispersive spectrometry. The results indicated Salt migration, particle breakage and particle redistribution in the interior of the CPCM modules during thermal cycling, leading to a more homogenous distribution of ingredients and more uniform heat transfer within CPCM modules.
Chen Lin - One of the best experts on this subject based on the ideXlab platform.
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effect of surface active agent on thermal properties of Carbonate Salt carbon nanomaterial composite phase change material
Applied Energy, 2015Co-Authors: Y B Tao, Chen LinAbstract:Surface active agent (SAA) was used to improve nanomaterial dispersion during preparation process of Carbonate Salt/nanomaterial composite phase change material (CPCM) by solution evaporation method. In order to investigate the effects of SAA on CPCM thermal performance, three kinds of PCM samples were prepared and their thermal performances were characterized. The results show that nanomaterial dispersion greatly affects CPCM thermal performance. For CPCM without SAA, its thermal performance is weakened instead of enhanced due to nanomaterial aggregation and the weakening phenomenon is more obvious when nanomaterial has larger specific surface area. SAA decomposes during high temperature CPCM working process. And the effect of SAA on CPCM thermal performance has duality: on the positive side, SAA can improve nanomaterial dispersion and enhance CPCM thermal performance; on the negative side, SAA decomposition products may weaken CPCM thermal performance. So, SAA and its mass fraction should be carefully selected. Sodium dodecyl sulfate (SDS) is a better SAA for high temperature nano-CPCM and a high mass ratio of SDS to nanomaterial is recommended. With mass ratio of SAA to nanomaterial 10:1, PCM thermal conductivity can be enhanced up to 58.75% by adding 1wt.% multi-walled carbon nanotubes.
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preparation and thermal properties characterization of Carbonate Salt carbon nanomaterial composite phase change material
Energy Conversion and Management, 2015Co-Authors: Y B Tao, Chen LinAbstract:To enhance the performance of high temperature Salt phase change material, four kinds of carbon nanomaterials with different microstructures were mixed into binary Carbonate eutectic Salts to prepare Carbonate Salt/nanomaterial composite phase change material. The microstructures of the nanomaterial and composite phase change material were characterized by scanning electron microscope. The thermal properties such as melting point, melting enthalpy, specific heat, thermal conductivity and total thermal energy storage capacity were characterized. The results show that the nanomaterial microstructure has great effects on composite phase change material thermal properties. The sheet structure Graphene is the best additive to enhance specific heat, which could be enhanced up to 18.57%. The single walled carbon nanotube with columnar structure is the best additive to enhance thermal conductivity, which could be enhanced up to 56.98%. Melting point increases but melting enthalpy decreases with nanomaterial specific surface area increase. Although the additives decrease the melting enthalpy of composite phase change material, they also enhance the specific heat. As a combined result, the additives have little effects on thermal energy storage capacity. So, for phase change material performance enhancement, more emphasis should be placed on thermal conductivity enhancement and single walled carbon nanotube is the optimal nanomaterial additive.
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Effect of surface active agent on thermal properties of Carbonate Salt/carbon nanomaterial composite phase change material
Applied Energy, 2015Co-Authors: Y B Tao, Chen LinAbstract:Surface active agent (SAA) was used to improve nanomaterial dispersion during preparation process of Carbonate Salt/nanomaterial composite phase change material (CPCM) by solution evaporation method. In order to investigate the effects of SAA on CPCM thermal performance, three kinds of PCM samples were prepared and their thermal performances were characterized. The results show that nanomaterial dispersion greatly affects CPCM thermal performance. For CPCM without SAA, its thermal performance is weakened instead of enhanced due to nanomaterial aggregation and the weakening phenomenon is more obvious when nanomaterial has larger specific surface area. SAA decomposes during high temperature CPCM working process. And the effect of SAA on CPCM thermal performance has duality: on the positive side, SAA can improve nanomaterial dispersion and enhance CPCM thermal performance; on the negative side, SAA decomposition products may weaken CPCM thermal performance. So, SAA and its mass fraction should be carefully selected. Sodium dodecyl sulfate (SDS) is a better SAA for high temperature nano-CPCM and a high mass ratio of SDS to nanomaterial is recommended. With mass ratio of SAA to nanomaterial 10:1, PCM thermal conductivity can be enhanced up to 58.75% by adding 1wt.% multi-walled carbon nanotubes.
Hui Cao - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer of composite phase change material modules containing a eutectic Carbonate Salt for medium and high temperature thermal energy storage applications
Applied Energy, 2019Co-Authors: Xiaohui She, Hui Cao, Peikun Zhang, Li Wang, Yulong DingAbstract:Abstract This paper concerns the heat transfer behaviour of Composite Phase Change Material (CPCM) modules made of a eutectic Carbonate Salt of NaLiCO3 (phase change material, PCM), MgO (ceramic skeleton material, CSM) and graphite flakes (thermal conductivity enhancement material, TCEM). The CPCM has a melting point around 500 °C and is suitable for medium and high temperature thermal energy storage applications including peak shaving of power grids, effective use of curtailed wind energy, and concentrated solar power generation. Disk-like CPCM modules were fabricated for the work. The effects of TCEM loading and surface cooling conditions on the heat transfer were experimentally investigated and analysed. The results showed that the use of TCEM not only significantly enhanced heat transfer of the CPCM modules, but also reduced the temperature difference and hence the thermal resistance between heater surface and CPCM module surface, leading to a significant extent of enhancement of overall heat transfer. Temperature measurements of a flat surface of the CPCM modules as well as that within the modules showed a non-uniform temperature distribution perpendicular to heat transfer direction, suggesting the effect of CPCM microstructure on heat transfer. This microstructural effect was further investigated using a scanning electron microscope with energy dispersive spectrometry. The results indicated Salt migration, particle breakage and particle redistribution in the interior of the CPCM modules during thermal cycling, leading to a more homogenous distribution of ingredients and more uniform heat transfer within CPCM modules.
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wettability of eutectic nalico3 Salt on magnesium oxide substrates at 778 k
Applied Surface Science, 2018Co-Authors: Hui Cao, Yulong Ding, Li Wang, Guanghui Leng, Lifang ZhengAbstract:Abstract We investigated the wetting behavior of a eutectic Carbonate Salt of NaLiCO3 on MgO substrates at an elevated temperature of 778 K by measuring contact angle with a sessile drop method. Both sintered and non-sintered MgO were prepared and used as the substrates. The sintered substrates were obtained by sintering compacted MgO powders at 500–1300 °C. For comparison purposes, a single crystal MgO substrate was also used in the work. The different sintering temperatures provided MgO substrates with different structures, allowing their effects on Salt penetration and hence wettability and surface energy to be investigated. A scanning electron microscope equipped with energy dispersive spectrometry and an atomic force microscope were used to observe the morphology and structures of the MgO substrates as well as the Salt penetration. The results showed a good wettability of the Carbonate Salt on both the sintered and non-sintered MgO substrates and the wettability depended strongly on the structure of the substrates. The non-sintered MgO substrate has a loose surface particle packing with large pores and crevices, leading to significant Salt infiltration, and the corresponding contact angle was measured to be ∼25°. The contact angle of the Salt on the sintered MgO substrates increased with an increase in the sintering temperature of the MgO substrate, and the contact angle of the Salt on the single crystal substrate was the highest at ∼40°. The effect of the sintering temperature for making the MgO substrate could be linked to the surface energy, and the linkage is validated by the AFM measurements of the adhesion forces of the MgO substrates.
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Carbonate-Salt-based composite materials for medium- and high-temperature thermal energy storage
Particuology, 2014Co-Authors: Hui Cao, Guanghui Leng, Yue Qin, Yulong DingAbstract:This paper discusses composite materials based on inorganic Salts for medium- and high-temperature thermal energy storage application. The composites consist of a phase change material (PCM), a ceramic material, and a high thermal conductivity material. The ceramic material forms a microstructural skeleton for encapsulation of the PCM and structural stability of the composites; the high thermal conductivity material enhances the overall thermal conductivity of the composites. Using a eutectic Salt of lithium and sodium Carbonates as the PCM, magnesium oxide as the ceramic skeleton, and either graphite flakes or carbon nanotubes as the thermal conductivity enhancer, we produced composites with good physical and chemical stability and high thermal conductivity. We found that the wettability of the molten Salt on the ceramic and carbon materials significantly affects the microstructure of the composites. (C) 2013 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.
Jing Ding - One of the best experts on this subject based on the ideXlab platform.
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Enhanced thermal conductivity of ternary Carbonate Salt phase change material with Mg particles for solar thermal energy storage
Applied Energy, 2017Co-Authors: Heqing Tian, Xiaolan Wei, Suyan Deng, Weilong Wang, Jing DingAbstract:Molten Salts with high thermal conductivity play a key role to achieve a high thermal energy transfer efficiency during heat charging and discharging processes in a high-temperature concentrating solar energy system. In this work, a novel highly thermal conductive composite phase change material (CPCM) was designed by blending magnesium (Mg) particles with eutectic ternary Carbonate Salt (Li2CO3-Na2CO3-K2CO3) and used as heat transfer fluid (HTF) and/or thermal energy storage medium in advanced high-temperature concentrating solar power (CSP) plants. The thermo-physical properties of the composite systems were measured. Experimental results indicated that Mg particles dispersed in the molten Salts with dendritic structure. The melting temperature of the CPCM had negligible change compared to pure Carbonate Salt, and the phase change enthalpy reached up to 160J/g. The effective thermal conductivity was 1.93W/(mK) for 2wt% of Mg, which was enhanced by 45.11% compared to pure ternary Carbonate Salts. The upper limit working temperature of the CPCM was measured to be 725°C in argon atmosphere. The wide working temperature range (ΔT=325°C) indicated its great thermal stability and high capacity of energy storage.
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Molecular dynamics simulations on the binary eutectic system Na2CO3-K2CO3
Energy Procedia, 2017Co-Authors: Jing Ding, Weilong Wang, Gechuanqi Pan, Xiaolan WeiAbstract:Abstract Molten Carbonate Salts as phase change materials have received particular attention for high-temperature thermal energy storage and heat transfer applications due to desirable thermal characteristics such as wide operating temperature range, low causticity and excellent thermal stability. In this study, molecular dynamics (MD) simulations were performed on the binary Carbonate Salt Na2CO3-K2CO3 (58-42 mol%) based on an effective pair potential model, a Born-Mayer type combined with a Coulomb term. The temperature dependences of thermodynamic properties including the density, sheer viscosity and thermal conductivity were simulated in detail from 1000 to 1400 K, which were all difficult to achieve from experiments on account of high-temperature extreme conditions. Moreover, the radial distribution functions (RDF) and coordination number curves of the binary Carbonate Salt were characterized to explore the mechanisms of their temperature dependences from microscopic view. The simulation results suggested that the changes of thermodynamic properties with temperature were induced by the distance changes between ions. Besides, it can be concluded that the high bond energy in the strong covalent bond C-O of molten Carbonate Salts must contribute to the large specific heat capacity in comparison with that of molten un-oxyacid Salts.
Y B Tao - One of the best experts on this subject based on the ideXlab platform.
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effect of surface active agent on thermal properties of Carbonate Salt carbon nanomaterial composite phase change material
Applied Energy, 2015Co-Authors: Y B Tao, Chen LinAbstract:Surface active agent (SAA) was used to improve nanomaterial dispersion during preparation process of Carbonate Salt/nanomaterial composite phase change material (CPCM) by solution evaporation method. In order to investigate the effects of SAA on CPCM thermal performance, three kinds of PCM samples were prepared and their thermal performances were characterized. The results show that nanomaterial dispersion greatly affects CPCM thermal performance. For CPCM without SAA, its thermal performance is weakened instead of enhanced due to nanomaterial aggregation and the weakening phenomenon is more obvious when nanomaterial has larger specific surface area. SAA decomposes during high temperature CPCM working process. And the effect of SAA on CPCM thermal performance has duality: on the positive side, SAA can improve nanomaterial dispersion and enhance CPCM thermal performance; on the negative side, SAA decomposition products may weaken CPCM thermal performance. So, SAA and its mass fraction should be carefully selected. Sodium dodecyl sulfate (SDS) is a better SAA for high temperature nano-CPCM and a high mass ratio of SDS to nanomaterial is recommended. With mass ratio of SAA to nanomaterial 10:1, PCM thermal conductivity can be enhanced up to 58.75% by adding 1wt.% multi-walled carbon nanotubes.
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preparation and thermal properties characterization of Carbonate Salt carbon nanomaterial composite phase change material
Energy Conversion and Management, 2015Co-Authors: Y B Tao, Chen LinAbstract:To enhance the performance of high temperature Salt phase change material, four kinds of carbon nanomaterials with different microstructures were mixed into binary Carbonate eutectic Salts to prepare Carbonate Salt/nanomaterial composite phase change material. The microstructures of the nanomaterial and composite phase change material were characterized by scanning electron microscope. The thermal properties such as melting point, melting enthalpy, specific heat, thermal conductivity and total thermal energy storage capacity were characterized. The results show that the nanomaterial microstructure has great effects on composite phase change material thermal properties. The sheet structure Graphene is the best additive to enhance specific heat, which could be enhanced up to 18.57%. The single walled carbon nanotube with columnar structure is the best additive to enhance thermal conductivity, which could be enhanced up to 56.98%. Melting point increases but melting enthalpy decreases with nanomaterial specific surface area increase. Although the additives decrease the melting enthalpy of composite phase change material, they also enhance the specific heat. As a combined result, the additives have little effects on thermal energy storage capacity. So, for phase change material performance enhancement, more emphasis should be placed on thermal conductivity enhancement and single walled carbon nanotube is the optimal nanomaterial additive.
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Preparation and thermal properties characterization of Carbonate Salt/carbon nanomaterial composite phase change material
Energy Conversion and Management, 2015Co-Authors: Y B Tao, Chih-hong Lin, Y L HeAbstract:Abstract To enhance the performance of high temperature Salt phase change material, four kinds of carbon nanomaterials with different microstructures were mixed into binary Carbonate eutectic Salts to prepare Carbonate Salt/nanomaterial composite phase change material. The microstructures of the nanomaterial and composite phase change material were characterized by scanning electron microscope. The thermal properties such as melting point, melting enthalpy, specific heat, thermal conductivity and total thermal energy storage capacity were characterized. The results show that the nanomaterial microstructure has great effects on composite phase change material thermal properties. The sheet structure Graphene is the best additive to enhance specific heat, which could be enhanced up to 18.57%. The single walled carbon nanotube with columnar structure is the best additive to enhance thermal conductivity, which could be enhanced up to 56.98%. Melting point increases but melting enthalpy decreases with nanomaterial specific surface area increase. Although the additives decrease the melting enthalpy of composite phase change material, they also enhance the specific heat. As a combined result, the additives have little effects on thermal energy storage capacity. So, for phase change material performance enhancement, more emphasis should be placed on thermal conductivity enhancement and single walled carbon nanotube is the optimal nanomaterial additive.
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Effect of surface active agent on thermal properties of Carbonate Salt/carbon nanomaterial composite phase change material
Applied Energy, 2015Co-Authors: Y B Tao, Chen LinAbstract:Surface active agent (SAA) was used to improve nanomaterial dispersion during preparation process of Carbonate Salt/nanomaterial composite phase change material (CPCM) by solution evaporation method. In order to investigate the effects of SAA on CPCM thermal performance, three kinds of PCM samples were prepared and their thermal performances were characterized. The results show that nanomaterial dispersion greatly affects CPCM thermal performance. For CPCM without SAA, its thermal performance is weakened instead of enhanced due to nanomaterial aggregation and the weakening phenomenon is more obvious when nanomaterial has larger specific surface area. SAA decomposes during high temperature CPCM working process. And the effect of SAA on CPCM thermal performance has duality: on the positive side, SAA can improve nanomaterial dispersion and enhance CPCM thermal performance; on the negative side, SAA decomposition products may weaken CPCM thermal performance. So, SAA and its mass fraction should be carefully selected. Sodium dodecyl sulfate (SDS) is a better SAA for high temperature nano-CPCM and a high mass ratio of SDS to nanomaterial is recommended. With mass ratio of SAA to nanomaterial 10:1, PCM thermal conductivity can be enhanced up to 58.75% by adding 1wt.% multi-walled carbon nanotubes.