Elsevier

Applied Energy

Volume 115, 15 February 2014, Pages 320-330
Applied Energy

Preparation, thermal and rheological properties of hybrid nanocomposite phase change material for thermal energy storage

https://doi.org/10.1016/j.apenergy.2013.11.029Get rights and content

Highlights

  • Hybrid nanocomposite PCM achieved improved thermal properties and heat storage.

  • Thermal conductivity of hybrid nanocomposite PCM was improved by 52%.

  • Hybrid nanocomposite PCM exhibited enhanced thermal stability than pure PCM.

  • Energy efficiency and savings was obtained with freezing rate reduction of 23.9%.

  • Increased mass loading of nanocomposite resulted in 4% increased viscosity of PCM.

Abstract

This paper presents the experimental investigation on the thermal properties and viscosity of the new organic ester phase change material embedded with the silver–titania hybrid nanocomposite (HyNPCM) with the mass proportions ranging from 0.1% to 1.5%. The HyNPCM embedded with the surface functionalized hybrid nanocomposite exhibited improved thermal conductivity from 0.286 W/m K to 0.538 W/m K, congruent phase change temperature (6.8 °C), high latent heat capacity (90.81 kJ/kg), substantial reduction in the supercooling degree (1.82 °C), thermal stability (191 °C) and chemical stability, while compared to the pure PCM. Experimental results reveal that, the freezing and the melting times of the HyNPCM were reduced by 23.9% and 8.5% respectively, when compared to the pure PCM. The increased mass proportion of HyNC resulted in the increased viscosity up to 3.89%, which suggests the existence of relative dependencies between the thermal properties and the viscosity of the HyNPCM. In total, the improved thermal properties and the heat storage potential of the HyNPCM has facilitated them to be considered as a viable candidate for the cool thermal energy storage applications in buildings without sacrificing energy efficiency.

Introduction

Incessant value-added engineering design and incorporation of the energy efficient thermal interface systems for cooling applications in buildings are greatly necessitated, in recent years. From this perspective, thermal energy storage (TES) systems are primarily intended for enhancing the performance of cooling systems in terms of storing and releasing heat energy on short-term or diurnal or seasonal basis depending on the thermal load requirements. Energy redistribution requirements can be effectively met by using TES systems integrated with the dedicated cooling systems in buildings. In this context, research interests towards developing thermal energy storage (TES) systems incorporating efficient phase change materials (PCM), which would offer energy redistribution requirements in buildings, are increasingly popular [1], [2], [3], [4], [5], [6].

Phase change materials are a class of heat storage materials, which would eventually store and release the thermal energy, by undergoing phase transition typically at isothermal conditions. In the category of heat storage materials, organic PCM are much preferred for their smaller temperature swings, good latent heat capacity, congruent phase transition characteristics, low supercooling, non-corrosiveness, and reliability on long term usage [7], [8], [9], [10], [11]. The thermophysical properties and the heat storage characteristics of organic PCM being improved by embedding thermally conductive materials into the PCM at its purest form have been reported in [12], [13], [14], [15], [16].

Interestingly, the organic PCM under the fatty acid ester classification have been considered as an effectual heat storage material for latent thermal energy storage (LTES) systems. The inherent ester bonding linkages and the carbon chains attributed for accomplishing good latent heat enthalpy, thermal storage and thermal reliability [17], [18]. On the other hand, the increasing carbon chains in such kind of ester PCM would increase the fusion temperature noticeably; thereby constricting their usage for cool thermal storage applications.

Many research studies performed on conceptualizing the process of incorporating heat enhancement materials produced at nanometer scale into the PCM are increasingly attractive, in recent years [19], [20], [21], [22], [23], [24], [25]. The nanomaterials prepared in the range of 1–100 nm, having high surface to volume ratio, are doped into the PCM in order to acquire fast nucleation as well as thermal conductivity enhancement, during the charging and discharging processes.

In addition, the infused nanoparticles would contribute in the formation of the stable nucleus (cluster of small nuclei) or ice-like crystals in the PCM during the freezing process; thereby enabling the nucleation to occur at a faster rate [32]. Furthermore, the effective thermal properties of the nanomaterials would facilitate the PCM to exhibit increased thermal conductivity, good latent heat potential, better heat storage and release characteristics and thermal reliability.

In the present work, a new organic ester phase change material embedded with the silver–titania (Ag–TiO2) hybrid nanocomposite (HyNPCM) was prepared and the thermal properties were investigated experimentally for the different mass proportions of the HyNC. The organic ester PCM tested in this study was ethyl cinnamate (EC), which has got a wide range of utilization ranging from the domestic cosmetics to non-cosmetic product applications [26]. Besides, the thermal properties and the heat storage potential of the EC PCM embedded with the HyNC were explored in this work, which stands distinct in its class of organic PCM with reference to the past literatures.

The surface functionalized HyNC was analyzed in terms of their morphology, size distribution, surface structure and crystalline nature. The inherent thermal properties of the functional HyNPCM including phase transition temperature, latent heat potential, thermal conductivity, thermal reliability, thermal conductivity, thermal stability and the heat storage performance were investigated experimentally. The significance of the incorporation of the HyNC into the ester PCM was explained and the experimental results are presented. The interdependency between the heat storage performance and the rheological aspects (viscosity) of the HyNPCM due to the increased mass concentration of HyNC are discussed.

Section snippets

Materials

Ethyl trans-cinnamate (as PCM) was procured from Alfa Aesar, silver nitrate (as precursor) was obtained from Ranbaxy, titania (as precursor) was purchased from Qualigens Fine Chemicals-Fischer Scientific, ascorbic acid (as reducing agent) was purchased from SRL Chemicals, and ethanol was used as the dispersant. The chemicals used in the experiment were designated to be of analytical grade and they were used without further purification. The de-ionized double distilled water (DDW) obtained from

Results and discussion

Based on the experimental results, the vital aspects of embedding the HyNC into the PCM for improving their thermal properties and the thermal energy storage potential are discussed.

Conclusions

In the present work, the thermal properties and the heat storage characteristics of the new HyNPCM being experimentally investigated has helped in making the following conclusions:

  • The HyNPCM embedded with the surface functionalized HyNC exhibited improved thermal conductivity up to 52%, congruent phase change temperature (6.8 °C), high latent heat capacity (90.81 kJ/kg), substantial reduction in supercooling degree (1.82 °C), thermal stability (191 °C) and chemical stability, while compared to the

Acknowledgments

The authors gratefully acknowledge DST, New Delhi for providing financial support to carry out this research work under PURSE scheme and UGC Major Research Project (F. No. 42-894/2013 (SR)). One of the authors, Mr. R. Parameshwaran is thankful to DST, New Delhi for the award of DST-PURSE fellowship.

References (53)

  • W. Mhike et al.

    Thermally conductive phase-change materials for energy storage based on low-density polyethylene, soft Fischer–Tropsch wax and graphite

    Thermochim Acta

    (2012)
  • A. Sarı et al.

    Thermal energy storage properties and thermal reliability of some fatty acid esters/building material composites as novel form-stable PCMs

    Solar Energy Mater Solar C

    (2012)
  • A.A. Aydın

    Diesters of high-chain dicarboxylic acids with 1-tetradecanol as novel organic phase change materials for thermal energy storage

    Solar Energy Mater Solar C

    (2012)
  • L. Zhang et al.

    Thermal and electrical conductivity enhancement of graphite nanoplatelets on form-stable polyethylene glycol/polymethyl methacrylate composite phase change materials

    Energy

    (2012)
  • K. Pielichowska et al.

    Crystallization behaviour of PEO with carbon-based nanonucleants for thermal energy storage

    Thermochim Acta

    (2010)
  • J. Wang et al.

    Enhancing thermal conductivity of palmitic acid based phase change materials with carbon nanotubes as fillers

    Solar Energy

    (2010)
  • S. Kalaiselvam et al.

    Analytical and experimental investigations of nanoparticles embedded phase change materials for cooling application in modern buildings

    Renew Energy

    (2012)
  • J.M. Khodadadi et al.

    Thermal conductivity enhancement of nanostructure-based colloidal suspensions utilized as phase change materials for thermal energy storage: a review

    Renew Sustain Energy Rev

    (2013)
  • S.P. Bhatia et al.

    Fragrance material review on ethyl cinnamate

    Food Chem Toxicol

    (2007)
  • R. Parameshwaran et al.

    Study on thermal storage properties of hybrid nanocomposite-dibasic ester as phase change material

    Thermochim Acta

    (2013)
  • S. Angkaew et al.

    Preparation of silver–titania titanium dioxide core–shell (Ag@TiO2) nanoparticles: effect of Ti–Ag mole ratio

    Proc Eng

    (2012)
  • Z. Abbas et al.

    Synthesis, characterization and particle size distribution of TiO2 colloidal nanoparticles

    Colloids Surf A

    (2011)
  • B. Xu et al.

    Paraffin/diatomite composite phase change material incorporated cement-based composite for thermal energy storage

    Appl Energy

    (2013)
  • A.A. Aydın et al.

    High-chain fatty acid esters of myristyl alcohol with odd carbon number: novel organic phase change materials for thermal energy storage—2

    Solar Energy Mater Solar C

    (2011)
  • S. Zhang et al.

    Effective dispersion of multi-wall carbon nano-tubes in hexadecane through physiochemical modification and decrease of supercooling

    Solar Energy Mater Solar C

    (2012)
  • C. Jiao et al.

    Preparation and properties of lauric acid–stearic acid/expanded perlite composite as phase change materials for thermal energy storage

    Mater Lett

    (2012)
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