Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: P3.81 - Preparation and Heat Transfer Behavior of Paraffin based Composites Containing Nano-copper Particles
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 Material Information
Title: P3.81 - Preparation and Heat Transfer Behavior of Paraffin based Composites Containing Nano-copper Particles Micro and Nano-Scale Multiphase Flows
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Wang, N.
Yang, S.
Zhu, D.
Ju, X.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: phase change material
nano-copper particles
thermal properties
heat transfer rate
 Notes
Abstract: In this study, composite phase change materials (PCMs) consisting paraffin and nano-copper particles were prepared and their thermal properties and heat charging and discharging characteristics were investigated experimentally. Since the nanoparticles in liquid paraffin exists settlement appearance, surfactants were used to improve the stability of suspension. The tested mass fraction in the composites were 0.1%, 0.5%, 1% and 2% of nano-copper particles, respectively. Differential scanning calorimetric (DSC) results showed that dispersion of nano-copper particles in paraffin did not exert noticeable effect on the phase change temperatures and the latent heat reduced with the addition of nano-copper particles compared to the pure paraffin. The heat charging and discharging rate of the composites were obviously increased due to the composite had a high conductivity.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
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Volume ID: VID00550
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: P381-Wang-ICMF2010.pdf

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7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

Preparation and Heat Transfer Behavior of Paraffin based Composites Containing
Nano-copper Particles


Nan WANG1 Shuo YANG1 Dongsheng ZHU1 Xiaoping JU2

1 Key Lab of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, School of Chemistry and Chemical
Engineering, South China University of Technology, Guangzhou, Guangdong 510640, PR China
2 Technology Center, Guangzhou Wanbao Group Co., Ltd., Guangzhou 510470 PR China

E-mail:cedshzhu@tscut.edu.cn

Keywords: phase change material, nano-copper particles, thermal properties, heat transfer rate

Abstract

In this study, composite phase change materials (PCMs) consisting paraffin and nano-copper particles were prepared and
their thermal properties and heat charging and discharging characteristics were investigated experimentally. Since the
nanoparticles in liquid paraffin exists settlement appearance, surfactants were used to improve the stability of suspension. The
tested mass fraction in the composites were 0.1%, 0.5%, 1% and 2% of nano-copper particles, respectively. Differential
scanning calorimetric (DSC) results showed that dispersion of nano-copper particles in paraffin did not exert noticeable effect
on the phase change temperatures and the latent heat reduced with the addition of nano-copper particles compared to the pure
paraffin. The heat charging and discharging rate of the composites were obviously increased due to the composite had a high
conductivity.


Introduction

Phase change materials (PCMs) have received a great
interest in many applications .Such as: energy storage [1-2],
thermal protection [3-4], optimal utilization of energy, as
well as active/passive cooling of electronic devices [5]. It
provides much higher storage density, with a smaller
temperature difference between storing and releasing heat.
Among the investigated PCMs, paraffin has been
considered most promising due to its large latent heat, no
supercooling, varied phase change temperature, low vapor
pressure in the melt, good thermal and chemical stability,
and self-nucleating behavior, no phase segregation and
commercially available at low cost.
In spite of these desirable properties of paraffin, the
low thermal conductivity is its major drawback, which
reduces the energy charge and discharge rate during
melting and crystallization process. Different approaches
have been used to enhance the thermal conductivity of
paraffin, including encasing the PCM within finned tubes
[6-7], embedding high conductivity material matrix
structure [8-9], dispersing high conductivity such as:
carbon fibers, carbon nanotubes [10-11]. However, the
addition of particles causes a marginal reduction in the
volume of the PCM and also in the energy storage
capacity.
Due to the small size and particular thermal properties,
nanoparticles with high thermal conductivity have shown
tremendous potential for heat transfer application. Recently,
much studies were carried out to disperse nanopaticles into
the base fluids to enhance thermal performance. Choi was
the first to coin the term "nanofluids" for this new class of
fluids with excellent heat transfer performance [12].
Recently, some research have been reported to exploited
by dispersing nanoparticles in the phase change material
for enhancement in the thermal conductivity and hence
improvements in the heat transfer efficiency during


melting/freezing process. Ho and Kao [13] studied the
thermophysical properties of nanoparticle-in-paraffin
emulsion prepared by emulsifying alumina (A1203)
particles in paraffin. The results show that the measured
thermal conductivity increase with the mass fraction of the
nanoparticles compared with that for the pure paraffin.
Zeng et al. [14], synthesized a organic phase change
material (1-tetradecanol)/Ag nanoparticles composite and
measured the effect of containing Ag nanoparticles on the
thermal conductivity of the composite PCM. The thermal
conductivity of the composites PCM was found to increase
with the loading of Ag nanparticles. Elgafy and Lafdi [10]
studies the thermal performance of nanocomposite carbon
nanofibers filled paraffin wax experimentally and
analytically. It was found that the nanocomposite thermal
conductivities were enhanced significantly causing the
cooling rate to increase. An analytical model was
introduced based on one-dimensional heat conduction
approach to predict the effective thermal conductivity for
the new nanocomposites and its founding showed good
agreement with the experimental data. Wang and Xie [11]
studied the thermal properties of composites containing
multi-walled carbon nanotubes.
In the present study, we prepared nanocomposites
consisting pure paraffin and nano-copper particles by
means of a surfactant and further investigated the
compatibility between them. Their effective
thermophysical properties including melting point, latent
heat, and heat transfer behavior were then investigated
experimentally.

2. Experiment

2.1 Preparation of the composite PCMs

Paraffin wax with melting temperature of 58-60C
was obtained from Shanghai Specimen and model Factory,









with a purity of 99.99%. Copper nanoparticles were
supplied by Shenzhen Junye Nano Material Co. Ltd.. The
average diameter, purity, and specific surface area of the
copper nanoparticle were 25nm, 99.9%, and 30-50 nm/g,
respectively. The transmission electron micrograph (TEM)
of copper nanoparticle is shown in Fig.1. The particles are
basically spherical or near spherical.


Fig.1 TEMmicrographof copper nanoparticles

50r


25 35 45 55
d/nm


Fig. 2 Mass fraction vs. particle size for nano-copper

An anionic surfactant, arabic gum in chemical grade,
from Shanghai Lingfeng Reagent Co.Ltd., was used. All
chemicals were used as received without any further
purification.
In this experiment, the nanoparticles were first coated
with the surfactant of 1/2 of its mass fraction. The treated
copper nanoparticles were dispersed into melting paraffin
in a mixing container. In order to prepare well dispersed
and homogeneous composite PCM, the mixer was stirred
thoroughly and ultrasonicated (KQ2200DE Ultrasonic
Cleanser, 100W, Kunshan of Jiangsu Equipment Company,
China) for at least Ih. During ultrasonic vibrating, the
samples were kept sufficiently above melting point of the
paraffin .Five samples were prepared and the mass fraction
were 0.1%, 1.5%, 1%, 2%,respectively.

2.2 Methods

The melting temperature (Tm) and latent heat (Hs) of
pure paraffin and five composite samples were analyzed by
differential scanning calorimetry(DSC) instrument
(NETZSCH Instruments Manufacturing Co., Ltd.
German ). DSC measurements were under taken with a
heating rate of 5 C/min and temperature range of 20-80 C.
Fifty grams of the pure paraffin and 50g of the
composite PCM ( with 0.1% mass fraction of copper


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

nanoparticle) were melt and then separately filled into two
glass test tubes with the same shell thickness and diameter.
In order to evaluated the thermal conductivity performance
of two samples, Two thermocouples (type T) were fixed in
the centers of the tubes. The thermocouples were
connected to a PC via a data acquisition apparatus (Agilent
34970A). The temperature of the center of he was recorded
sampling rate of once per 10 seconds. After the samples
were solidified, The test tubes were put into a water bath at
constant temperatures of 70 C for the melting process. The
temperature change of the samples were recorded until it
reached stable. After then, they were directly subjected to
solidification process in another water bath at constant
temperatures of 25 C until the temperature reached stable.

3 Result and Disscusion
3.1 Sedimentation stability of the composite
PCMs


(a)(b)(c)(d)(e)


Fig 3 Photographs of the samples with different
mass fraction of particles in liquid state

In order to investigate the sedimentation stability of
nano-copper particles/paraffin composite PCMs, the
composites were put into a constant temperature water bath
and kept 70 C for 24h. Then the samples were removed
from the water bath and taken photos to see if there was any
delamination. Four samples were prepared and the mass
fraction were 0.1 %, 0.5%, 1%, 2%, respectively. Fig.3
shows the photos of four samples. It is observed that the
nano-copper particles/paraffin composies are very
homogenous.

3.2 Melting temperature and latent heat

DSC analysis was conducted to investigate the
influence of nano-copper particles addition on the thermal
properties including temperatures and the latent heat
capacities. Fig.4 shows the DSC curves of the pure
paraffin and the composite materials containing
nano-copper particles. Similar shapes of all the DSC
curves were obtained at different scans, indicative of good
thermal stability of the composite materials. This is
because there is no chemical reaction between the paraffin
and nano-copper particles in the preparation of the
composite materials. The phase change temperatures and
the latent heat values obtained for the pure paraffin and
composites are shown in table 1. The addition of the
nano-copper particles with different percent loadings


5 Is









slightly change the melting temperature of paraffin in the
range of 0-1 C.Dispersion of nano-copper particles in
paraffin does not exert noticeable effect on the phase
change temperatures. It is observed that for all the
composite materials, with an increase in the percent
volume fraction, the latent heat become reduced compared
with that of the pure paraffin.


00-

-05-

-10-

-15-

20- -[::

-25- /o
-3-
20 30 40 50 60 70
T(CO


Fig.4. DSC results of pure paraffin and composite PCMs

Table 1. Melting temperature and latent capacity of paraffin
and composite PCMs

PCMs Tm(C) L,(kJ/kg)
paraffin 60.32 200.9
0.1% 60.23 214.3
0.5% 59.84 178.2
1.0% 60.19 175.0
2.0% 60.71 170.9

3.3Heat Charging and Discharging Characteristics
of Pure paraffin and Composite PCMs

The heat charging/discharging curves(the variation of
the temperature of the PCM VS time) of the pure paraffin
and the composite PCMs are shown in Figures 5-6. As
shown from the temperature curves, at the early stage of
the heat charging process, the temperatures of the pure
paraffin and the composite PCMs were rapidly increased.
As the test time increased further, the slope of temperature
curves decrease at 58-60 C, in which period the
solid-liquid phase change (heat storage process) occurred.
After the phase change completely ended, the temperature
increased again. Then entered the heat discharging
processes. At initial heat discharging period, the
temperature was quickly decreased until the pure paraffin
and the composite PCMs passed through liquid to solid
phase (heat release process). After this stage, the decrease
in temperature continued again.
The figure shows a comparison between the heat
transfer rate of pure paraffin and that of composite PCM.
When a material has a higher thermal conductivity, its
thermal response must be more sensitive than others in the
same condition .At heat storage process, the temperature
rising curve of composite is steeper than the curve of
pure paraffin and appeared at upper side. At heat release
process, the temperature change speed of composite PCM
is also higher than pure paraffin. It was concluded from
these results that the heat transfer rate in the composite


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

PCMs was obviously higher than that in the pure paraffin
due to the high thermal conductivity.
The improved thermal conductivities of pure paraffin
by adding nano-copper particles was also tested by
comparing melting and solidification times of composite
PCM with those of pure paraffin. From the figure 5 and
figure 6, we can see that the melting times of pure paraffin
and composite PCMs with nano-copper particles mass
fraction of 0.5% and 1% werel400s, 1080s and 930s
respectively. The solidification times of pure paraffin and
composite PCMs with nano-copper particles mass fraction
of 0.5% and 1% were also evaluated from the curves as
930s, 730s and 700s respectively. By comparing the
melting times of pure paraffin with composite PCMs it is
found that the melting times of composite PCMs with
nano-copper particles mass fraction of 0.5% and 1%
reduce 22.9% and 33.6% by pure paraffin and the
solidification times of composite PCMs with nano-copper
particles mass fraction of 0.5% and 1% reduce 21.5% and
24.8% by pure paraffin


0 300 600 900
Tim(s)


1200 1500


Fig.5 Heat charging temperature curves of pure paraffin and
composite PCMs

72
D --0%o
64 -----0.5 /o
C ----lVto
U 56 -

248-




32

0 4)0 800 1200 1600
Tinr(s)
Fig.6 Heat discharging temperature curves of pure paraffin
and composite PCMs.

4 Conclusion

Composite phase change materials (PCMs) consisting
paraffin and nano-copper particles were prepared. By
adding an anionic surfactant and ultrasonic dispersion, the
table and homogeneous composites were obtained and
their thermal properties and heat charging/discharging
characteristics were investigated experimentally. The DSC


12
D
64-

56 -

48

0 "to
40

32 ---- 0.5 "v%
A --l 1









measurement indicates that dispersing the nano-copper
particles in paraffin exerts litter effect on the melting
temperature and the latent heat reduce as the increasing
mass fraction of nano-copper particles. The heat charging
and discharging experiment showed that the prepared
composites have good thermal energy storage-release
characteristics. By comparing the melting times of pure
paraffin with composite PCMs it is found that the melting
times of composite PCMs with nano-copper particles mass
fraction of 0.5% and 1% reduce 22.9% and 33.6% by pure
paraffin and the solidification times of composite PCMs
with nano-copper particles mass fraction of 0.5% and 1%
reduce 21.5% and 24.8% by pure paraffin. The heat
transfer rate in the composite PCMs was obviously higher
than that in the pure paraffin owing to the composite PCMs
had a high thermal conductivity.

Acknowledgements

This study is supported by The National Natural
Science Foundation of China (Grant No. 20346001),
Program for New Century Excellent Talents in University
(Grant No. NCET-04-0826) and Science and Technology
Project of Guangzhou (2008Z1-1061).

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7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

materials. Carbon 43(2005) 3067-3074.
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