Optimal preparation of PCM/diatomite composites for enhancing thermal properties

doi:10.1016/j.ijheatmasstransfer.2013.03.043

International Journal of Heat and Mass Transfer

Volume 62, July 2013, Pages 711-717

https://doi.org/10.1016/j.ijheatmasstransfer.2013.03.043 Get rights and content

Abstract

This paper deals with the thermal performances of PCM/diatomite composites for energy saving. The PCM/diatomite composites were prepared by incorporating PCMs in the pores of diatomite to increase the form stability of PCMs. In experiment, we used n-hexadecane, n-octadecane and paraffin wax as PCMs, which have latent heat capacities of 254.7 J/g, 247.6 J/g and 144.6 J/g, respectively; and melting points of 20.84 °C, 30.4 °C and 57.09 °C, respectively. The PCMs could be retained at 50 wt% in the pores of the diatomite without leakage. The thermal effect of vacuum impregnation was also analyzed through vacuum treatment during the preparation process of samples. An optimal preparing method for 50 wt% of PCM impregnation is proposed. Thermal properties of samples were determined using DSC and TGA. And SEM and FTIR analyses were carried out to analyze microstructure and chemical properties of samples. SEM results showed that the PCMs are well-infiltrated into the structure of diatomite. DSC analysis results showed that the latent heat capacities of PCM/diatomite composites were 50% the value of pure PCMs, and TGA analysis results showed that PCM/diatomite composites have greater thermal durability compared with pure PCM.

Introduction

Recently, the energy demand to provide a comfortable environment for humans in buildings has continuously increased worldwide. However, the energy used for heating, cooling and lighting increases the level of greenhouse gas emissions and decreases fossil fuel resources [1], [2]. Thermal energy storage systems are essential for reducing dependency on fossil fuels and contributing to a more efficient, environmentally friendly energy use. As the demand for thermal comfort in buildings rises, the energy consumption increases correspondingly [3]. Phase change materials (PCMs) have been widely used in many applications, such as passive cooling for electronic devices, protection systems in aircrafts, food processing, and energy conservation in buildings, because of their high latent heat, chemical stability, suitable phase-change temperature, and reasonable price. Experimental and analytical/numerical studies in published literature have focused on moving boundary problems [4], [5], [6], [7], [8], [9].

PCMs can be integrated with different buildings’ structures such as in gypsum board, plaster, concrete, clay minerals or other wall-covering materials. However, they also have some inherent limitations, such as low thermal conductivity, and the need for a container to prevent leaking and issues with flammability. To solve these problems, some investigators have studied the possibility of a container that can prevent the leaking of liquid PCMs by using Shape-Stabilized PCM (SSPCM) and Microencapsulated PCM techniques [10], [11], [12], [13], [14]. Shape-stabilized PCM and Microencapsulated PCM can maintain their shape even when the PCM changes from solid to liquid, by a physical combination with a polymer or mineral (HDPE, diatomite, etc.) [15], [16]. In recent years, shape-stabilized PCM (SSPCM) has attracted the interests of researchers. Liu et al. proposed a re-coating method using an inorganic polymer material for the SSPCM, and silica gel microcapsules containing SSPCM were prepared by in situ polymerization, in which the content of paraffin wax was up to 69.12 wt% and its enthalpy was 153.46 J/g [17]. Wang et al. prepared a kind of macro-capsule through in situ polymerization by using silica gel as the shell material and shape-stabilized phase change materials containing 50 wt% each of n-octadecane and of high density polyethylene as the core [18]. Karaman et al. determined thermal energy storage properties of polyethylene glycol/diatomite composite as a novel form-stable composite phase change material. The composite PCM was prepared by incorporating PEG in the pores of diatomite [17].

Diatomite is a sedimentary rock formed from the siliceous fossilized skeletons of diatoms (SiO₂ · nH₂O and crystallized silica). The material is a unicellular alga that existed during tertiary and quaternary periods. It is composed of rigid cell walls, called frustules. Depending on their species, frustule dimensions from less than 1 to more than 100 μm can be found with features like protuberances and pores close to 100 nm [19]. Diatomite has light weight, high porosity, high absorptivity, high purity, multi-shape, rigidity, and inertness. Both the chemical composition and the physical structure of diatomite make it suitable for many scientific and industrial purposes. Diatomite is used in many fields as a filtering agent; building material; heat, cold, and sound insulator; catalyst carrier; filler absorbent; abrasive; and ingredient in medicines [20]. Considering this, diatomite is a feasible candidate for an economical and light-weight building material for incorporating PCM for thermal energy storage in buildings.

The most important characteristic to consider is the heat capacity and melting point of the PCM in its application to building materials. In this paper, we used three types of PCMs which have different melting points, for application to various building sections such as radiant floor heating systems, insulation and ceiling panels. Each building section needs a different temperature control. Therefore this study aims to prepare the PCM/diatomite composites to obtain high thermal performance. Also we suggest an optimal preparation of PCM/diatomite composites to get high latent heat capacity.

Section snippets

Materials

We used three types of liquid organic PCMs with different melting points. In this experiment, n-hexadecane, n-octadecane and paraffin wax were used as organic PCMs. The n-hexadecane, n-octadecane and paraffin wax have molecular formulae of C₁₆H₃₄, C₁₈H₃₈ and C₂₅H₅₂ as alkane series and they have latent heat capacities of 254.7 J/g, 247.6 J/g and 144.6 J/g and melting points of 20.84 °C, 30.4 °C and 57.09 °C, respectively. The PCMs were obtained from Celsius Korea, South Korea. Diatomite samples were

Morphology and microstructure of composite PCMs

Scanning electron microscopy observations were performed for the pure PCMs and the composite PCMs. The pure PCMs and composite PCMs were broken up in liquid nitrogen and the fractured surfaces were coated with gold before SEM investigations. Fig. 4 shows SEM micrographs of diatomite and after PCM impregnation. It can be seen that each PCM sample is incorporated into the pores of the diatomite. Comparison between the diatomite and the PCM/diatomite composite images is shown in Fig. 4. Porous

Conclusion

We prepared PCM/diatomite composites for the reduction of energy saving by improving thermal efficiency through latent heat storage. PCM/diatomite composites designed to produce high thermal performance were prepared through vacuum impregnation. We suggested an optimal preparation of PCM/diatomite composite to produce high latent heat capacity. Vacuum treatment was effective in conserving the thermal properties of pure PCM. SEM, FTIR, DSC and TGA analyses were performed to confirm the

Acknowledgments

This work was supported by a National Research Foundation of Korea (NRF) grant, funded by the Korea government (MEST) (No. 2012-0005188).

References (26)

A.M. Khudhair et al.
A review on energy conservation in building applications with thermal storage by latent heat using phase change materials
Energy Conv. Manage.
(2004)
I. Dincer
On thermal energy storage systems and applications in buildings
Energy Build.
(2002)
V.V. Tyagi et al.
Development of phase change materials based microencapsulated technology for buildings: a review
Renew. Sustainable Energy Rev.
(2011)
V.R. Voller et al.
A fixed grid numerical modelling methodology for convection-diffusion mushy region phase-change problems
Int. J. Heat Mass Transfer
(1987)
V.R. Voller et al.
An analytical solution for a Stefan problem with variable latent heat
Int. J. Heat Mass Transfer
(2004)
T.J. Scanlon et al.
A numerical analysis of buoyancy-driven melting and freezing
Int. J. Heat Mass Transfer
(2004)
P. Lamberg et al.
Numerical and experimental investigation of melting and freezing processes in phase change material storage
Int. J. Therm. Sci.
(2004)
L.F. Cabeza et al.
Heat transfer enhancement in water when used as PCM in thermal energy storage
Appl. Therm. Eng.
(2002)
S. Jeong et al.
Performance evaluation of the Microencapsulated PCM for wood-based flooring application
Energy Conv. Manage.
(2012)
X. Wang et al.
Raising evaporative cooling potentials using combined cooled ceiling and MPCM slurry storage
Energy Build.
(2008)

X. Xu et al.

Modeling and simulation on the thermal performance of shape-stabilized phase change material floor used in passive solar buildings

Energy Build.

(2005)

B.M. Diaconu

Transient thermal response of a PCS heat storage system

Energy Build.

(2009)

P. Zhang et al.

Effect of expanded graphite on properties of high-density polyethylene/paraffin composite with in tumescent flame retardant as a shape-stabilized phase change material

Sol. Energy Mater. Sol. Cells

(2010)

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Optimal preparation of PCM/diatomite composites for enhancing thermal properties

Abstract

Introduction

Section snippets

Materials

Morphology and microstructure of composite PCMs

Conclusion

Acknowledgments

Energy Conv. Manage.

Energy Build.

Renew. Sustainable Energy Rev.

Int. J. Heat Mass Transfer

Int. J. Heat Mass Transfer

Int. J. Heat Mass Transfer

Int. J. Therm. Sci.

Appl. Therm. Eng.

Energy Conv. Manage.

Energy Build.

Energy Build.

Energy Build.

Sol. Energy Mater. Sol. Cells