The classical problem of inward solidification heat transfer inside a spherical capsule, with an application to thermal energy storage (TES), was revisited in the presence of nano-enhanced phase change materials (NePCM). The model NePCM samples were prepared by dispersing graphite nanoplatelets (GNPs) into 1-tetradecanol (C14H30O) at loadings up to 3.0 wt %. The transient phase change, energy retrieval, and heat transfer rates during solidification of the various NePCM samples were measured quantitatively using a volume-shrinkage-based indirect method. The data reduction and analysis were carried out under single-component, homogeneous assumption of the NePCM samples without considering the microscale transport phenomena of GNPs. It was shown that the total solidification time becomes monotonously shorter with increasing the loading of GNPs, in accordance with the increased effective thermal conductivity. The maximum relative acceleration of solidification was found to be more than 50% for the most concentrated sample, which seems to be appreciable for practical applications. In addition to enhanced heat conduction, the possible effects due to the elimination of supercooling and viscosity growth were elucidated. The heat retrieval rate was also shown to be increased monotonously with raising the loading of GNPs, although the heat storage capacity is sacrificed. Despite the remarkable acceleration of the solidification time, the use of a high loading (e.g., 3.0 wt %) was demonstrated to be possibly uneconomical because of the marginal gain in heat retrieval rate. Finally, correlations for the transient variations of the melt fraction and surface-averaged Nusselt number were proposed.

References

References
1.
Regin
,
A. F.
,
Solanki
,
S. C.
, and
Saini
,
J. S.
,
2008
, “
Heat Transfer Characteristics of Thermal Energy Storage System Using PCM Capsules: A Review
,”
Renewable Sustainable Energy Rev.
,
12
(
9
), pp.
2438
2458
.
2.
Cho
,
K.
, and
Choi
,
S. H.
,
2000
, “
Thermal Characteristics of Paraffin in a Spherical Capsule During Freezing and Melting Processes
,”
Int. J. Heat Mass Transfer
,
43
(
17
), pp.
3183
3196
.
3.
Xia
,
L.
,
Zhang
,
P.
, and
Wang
,
R. Z.
,
2010
, “
Numerical Heat Transfer Analysis of the Packed Bed Latent Heat Storage System Based on an Effective Packed Bed Model
,”
Energy
,
35
(
5
), pp.
2022
2032
.
4.
Pedroso
,
R. I.
, and
Domoto
,
G. A.
,
1973
, “
Perturbation Solutions for Spherical Solidification of Saturated Liquids
,”
ASME J. Heat Transfer
,
95
(
1
), pp.
42
46
.
5.
Chan
,
C. W.
, and
Tan
,
F. L.
,
2006
, “
Solidification Inside a Sphere—An Experimental Study
,”
Int. Commun. Heat Mass Transfer
,
33
(
3
), pp.
335
341
.
6.
Assis
,
E.
,
Ziskind
,
G.
, and
Letan
,
R.
,
2009
, “
Numerical and Experimental Study of Solidification in a Spherical Shell
,”
ASME J. Heat Transfer
,
131
(
2
), p.
024502
.
7.
Vadasz
,
J. J.
,
Meyer
,
J. P.
,
Govender
,
S.
, and
Ziskind
,
G.
,
2016
, “
Experimental Study of Vibration Effects on Heat Transfer During Solidification of Paraffin in a Spherical Shell
,”
Exp. Heat Transfer
,
29
(
3
), pp.
285
298
.
8.
Adref
,
K. T.
, and
Eames
,
I. W.
,
2002
, “
Experiments on Charging and Discharging of Spherical Thermal (Ice) Storage Elements
,”
Int. J. Energy Res.
,
26
(
11
), pp.
949
964
.
9.
Liu
,
M.-J.
,
Fan
,
L.-W.
,
Zhu
,
Z.-Q.
,
Feng
,
B.
,
Zhang
,
H.-C.
, and
Zeng
,
Y.
,
2016
, “
A Volume-Shrinkage-Based Method for Quantifying the Inward Solidification Heat Transfer of a Phase Change Material Filled in Spherical Capsules
,”
Appl. Therm. Eng.
,
108
, pp.
1200
1205
.
10.
Ogoh
,
W.
, and
Groulx
,
D.
,
2012
, “
Effects of the Number and Distribution of Fins on the Storage Characteristics of a Cylindrical Latent Heat Energy Storage System: A Numerical Study
,”
Heat Mass Transfer
,
48
(
10
), pp.
1825
1835
.
11.
Khodadadi
,
J. M.
,
Fan
,
L.
, and
Babaei
,
H.
,
2013
, “
Thermal Conductivity Enhancement of Nanostructure-Based Colloidal Suspensions Utilized as Phase Change Materials for Thermal Energy Storage: A Review
,”
Renewable Sustainable Energy Rev.
,
24
(
10
), pp.
418
444
.
12.
Jesumathy
,
S.
,
Udayakumar
,
M.
, and
Suresh
,
S.
,
2012
, “
Experimental Study of Enhanced Heat Transfer by Addition of CuO Nanoparticle
,”
Heat Mass Transfer
,
48
(
6
), pp.
965
978
.
13.
Ho
,
C. J.
, and
Gao
,
J. Y.
,
2013
, “
An Experimental Study on Melting Heat Transfer of Paraffin Dispersed With Al2O3 Nanoparticles in a Vertical Enclosure
,”
Int. J. Heat Mass Transfer
,
62
(
1
), pp.
2
8
.
14.
Fan
,
L.-W.
,
Zhu
,
Z.-Q.
,
Zeng
,
Y.
,
Ding
,
Q.
, and
Liu
,
M.-J.
,
2016
, “
Unconstrained Melting Heat Transfer in A Spherical Container Revisited in the Presence of Nano-Enhanced Phase Change Materials (NePCM)
,”
Int. J. Heat Mass Transfer
,
95
, pp.
1057
1069
.
15.
Fan
,
L.-W.
,
Zhu
,
Z.-Q.
,
Liu
,
M.-J.
,
Xu
,
C.-L.
,
Zeng
,
Y.
,
Lu
,
H.
, and
Yu
,
Z.-T.
,
2016
, “
Heat Transfer During Constrained Melting of Nano-Enhanced Phase Change Materials in a Spherical Capsule: An Experimental Study
,”
ASME J. Heat Transfer
,
138
(
12
), p.
122402
.
16.
Rahman
,
M. M.
,
Hu
,
H.
,
Shabgard
,
H.
,
Boettcher
,
P.
,
Sun
,
Y.
, and
McCarthy
,
M.
,
2016
, “
Experimental Characterization of Inward Freezing and Melting of Additive-Enhanced PCM Within Millimeter-Scale Cylindrical Enclosures
,”
ASME J. Heat Transfer
,
138
(
7
), p.
072301
.
17.
Fan
,
L.
, and
Khodadadi
,
J. M.
,
2012
, “
A Theoretical and Experimental Investigation of Unidirectional Freezing of Nanoparticle-Enhanced Phase Change Materials
,”
ASME J. Heat Transfer
,
134
(
9
), p.
092301
.
18.
Fan
,
L.
, and
Khodadadi
,
J. M.
,
2012
, “
An Experimental Investigation of Enhanced Thermal Conductivity and Expedited Unidirectional Freezing of Cyclohexane-Based Nanoparticle Suspensions Utilized as Nano-Enhanced Phase Change Materials (NePCM)
,”
Int. J. Therm. Sci.
,
62
(
9
), pp.
120
126
.
19.
Chandrasekaran
,
P.
,
Cheralathan
,
M.
,
Kumaresan
,
V.
, and
Velraj
,
R.
,
2014
, “
Enhanced Heat Transfer Characteristics of Water Based Copper Oxide Nanofluid PCM (Phase Change Material) in a Spherical Capsule During Solidification for Energy Efficient Cool Thermal Storage System
,”
Energy
,
72
(
7
), pp.
636
642
.
20.
Sathishkumar
,
A.
,
Kumaresan
,
V.
, and
Velraj
,
R.
,
2016
, “
Solidification Characteristics of Water Based Graphene Nanofluid PCM in a Spherical Capsule for Cool Thermal Energy Storage Applications
,”
Int. J. Refrig.
,
66
, pp.
73
83
.
21.
Temirel
,
M.
,
Hu
,
H.
,
Shabgard
,
H.
,
Boettcher
,
P.
,
McCarthy
,
M.
, and
Sun
,
Y.
,
2017
, “
Solidification of Additive-Enhanced Phase Change Materials in Spherical Enclosures With Convective Cooling
,”
Appl. Therm. Eng.
,
111
, pp.
134
142
.
22.
Moallemi
,
M. K.
,
Webb
,
B. W.
, and
Viskanta
,
R.
,
1986
, “
An Experimental and Analytical Study of Close-Contact Melting
,”
ASME J. Heat Transfer
,
108
(
4
), pp.
894
899
.
23.
Groulx
,
D.
, and
Lacroix
,
M.
,
2006
, “
Study of Close Contact Melting of Ice From a Sliding Heated Flat Plate
,”
Int. J. Heat Mass Transfer
,
49
(23–24), pp.
4407
4416
.
24.
Groulx
,
D.
,
2015
, “
Numerical Study of Nano-Enhanced PCMs: Are They Worth It?
,”
First Thermal and Fluid Engineering Summer Conference (TFESC)
, New York, Aug. 9–12, Paper No.
TFESC-129
.
You do not currently have access to this content.