Proceedings of the Asian Conference on Thermal Sciences 2017, 1st ACTS
March 26-30, 2017, Jeju Island, Korea
ACTS-P00495
Experimental investigation on surface tension of water-based
graphene oxide nanofluids
Qinbo He1*, Geni Yan1, Yudong Liu2
1
Guangdong University Heat Pump Engineering Technology Development Center, Shunde Polytechnic,
Foshan Guangdong 528333, China
2
Key Laboratory of Low-grade Energy Utilization Technologies and Systems ,Ministry of Education,
Chongqing University, Chongqing 400044, China
*Presenting and Corresponding Author: [email protected]
ABSTRACT
The water-based graphene oxide nanofluids were prepared. The surface tension of nanofluids with
different mass fraction, temperature and different nanoparticle size was researched. The surface tension
value was measured through ringmethod. The experimental results show that the surface tension of
nanofluids is increased with increasing the mass faction of nanoparticles. But the surface tension of
nanofluids with maximum concentration (0.1wt%) is only increased up to 2.9% compared with deionized
water. The surface tension of nanofluids decreases with increasing temperature and decreasing nanoparticle
size. The results of this paper may provide reference for the research of absorption liquid for absorption
refrigeration cycle.
KEYWORDS: Surface tension, Nanofluids, Graphene oxide
1. INTRODUCTION
The surface tension of the gas-liquid interface is a very important physical parameters. In the
ammonia absorption refrigeration, surface tension is the same with solubility, thermal
conductivity and viscosity, which affect the capacity of water in the absorber's to absorb ammonia.
It plays a vital role for the overall performance of refrigeration units[1]. The major factors that
affecting surface tension include the material itself physical properties, pressure, temperature and
phase interface properties, etc. The research for nanoparticles affect the surface tension is less
compared with the above factors. Nanofluids, a relatively new class of fluids which consist of a
base fluid with nano-sized particles (1–100 nm) suspended within them. These particles are
generally metals or metal oxides. Nanoparticle volume fraction, types, size,dispersing agent and
additive amount can influence the surface tension of nanofluid. But there is no adequate, complete
experimental datas. Kumar[2] investigated the surface tension of CNT-H2O nanofluids, The
results show that the surface tension of nanofluids and water are very close when surfactant is
small relative to the nanoparticles content. When the amount of surfactant increases to a certain
proportion, the surface tension of the nanofluids reduces.
Murshed[3]performed the experiments of surface tension of TiO2-H2O nanofluids, the results
show that the surface tension of TiO2-H2O nanofluids is lower than that of water. With the
temperature rise, the surface tension of nanofluids reduces. Zhu[4] investigated the surface
tension of Al2O3-H2O nanofluids, the results show that the surface tension of nanofluids(1g/L) is
increased up to 5%. Chen’s [5] research has shown that adding Ag nanoparticles to deionized
water can significantly reduce the surface tension of the water. But to add 1% PVP into nanofluids,
1
nanoparticles effect on surface tension is gone. Tanvir [6] used boron, Al2O3 and carbon nanotubes
nanoparticles as the additive dispersed to kwai alkanes and ethanol. The surface tension of
nanofluids were measured, the results show that the size and concentration of the nanoparticles
and dispersant will influence the surface tension of nanofluids. Relative to the base fluid, carbon
nanotubes and dispersant reduced fluid surface tension. On the contrary, boron and Al2O3
nanoparticles increased the surface tension of the nanofluids. with the increase of particle size, the
surface tension (within the scope of the critical radius) significantly increased. Other relevant
literature [7] also studied the surface tension of the nanofluids.
In this study, water-based graphene oxide nanofluids had been prepared. The surface tension
of nanofluids under various particle sizes, mass fractions and temperature were investigated. The
main purpose of this study is expected to analyze the factors affected the surface tension of
nanofluids, and investigate the feasibility for nanofluids apply to absorption refrigeration systems.
2.EXPERIMENTAL SETUP
The liquid surface tension measurement methods mainly include the capillary rise method, ring
method, the biggest bubble pressure method, drop-weight method[8]. In this paper, the ring
method was used to measure the surface tension of the nanofluids. Its principle is the round rings
made of platinum slowly rising in nanofluids, when the ring break away from nanofluids surface,
the maximum tension(F)is equal to the gravity(mg) and equal to the force that along the
circumferential surface tension against upward. Because liquid film has two sides(inside and
outside), so the circumference of annulus is 4R . According to the force balance:
F  mg  4 R
(1)
So the surface tension can be expressed as follows:
F

(2)
4 R
Where R is the average radius of platinum ring, as shown in Fig.1 After measured the
force(F), the surface tension can be obtained according to Equation(2). The liquid film is not a
standard cylinder when measured actually, So it need to be corrected. Equation(2) must multiply a
correction factor f.
F
f
(3)
4 R
R
R3
A large number of experiments show that the correction coefficient f is a function of
and
.
r
V
Where R and r are fixed values(as can be seen from Fig.1). V is the volume of liquid film.
Beacuse the force is the product of mass and gravitational acceleration(F=mg=Vρg),so the the
volume of liquid film can be expressed as follows:
V
F
g
(4)
Hence, the correction coefficient (f) is relate to fluid density(ρ). The density of nanofluids is
need to use in actual measuring. In this paper, nanofluids density was measured by a density
bottle method. The surface tension of nanofluids was measured by surface tension comprehensive
analyzer(France 3s). As shown in Fig.2, when test the surface tension of nanofluids, it need to be
adjusted the temperature by a thermostatic waterbath. First, the thermostatic waterbath should be
connected well with surface tension analyzer, then put the nanofluid samples into the sample
2
cup(it had best at a third level), at last, put the sample cup in the instrument slot. Adjusting the
constant temperature water bath to control the temperature of the sample cup sample.
Fig. 1 Mean radius R of platinum ring
Fig.2 Comprehensive analyzer of surface tension
The temperature of the sample was measured by thermocouple. When the temperature of
samples is reach to the required value, the data acquisition system begin to capture data. What
calls for special attention is that the platinum ring should be washed and burned onthe alcohol
lamp. It is In order to prevent the residue samples on the platinum ring affecting the measurement
accuracy.
3.RESULTS AND DISCUSSION
3.1EFFECT OF CONCENTRATION
Before the test, the instrument must be calibrated. The surface tension of deionized water was
measured at 20℃. The surface tension value is 73.90mN/m. Compared with literature[9], the
relative error is 1.58%. It indicated the accuracy of instrument meets the requirements.The surface
tension of graphene oxide nanofluids with different concentrations(20℃) is shown in Fig.3. 0wt%
is the deionized water. The surface tension specific datas of the nanofluids with various
concentration are shown in Table 1. As can be seen from Fig.3 and Table 1, the surface tension of
nanofluids increases with increasing the concentration. But the range of increasing is not large.
For example, the surface tension of nanofluids(0.1wt%) is increased up to 2.12%. Compared with
deionized water, the surface tension of nanofluids(0.1wt%) increased 2.20 mN/m, which
increased up to 2.98%. Therefore, after the graphene oxide nanoparticles adding to deionized
water, the change of surface tension is very small.
Table 1 Surface tension of graphene oxide nanofluids with different concentration under 20℃
W (%)
 (mN/m)
n  w
(%)
w
0
73.9
0.02
74.52
0.04
75.68
0.06
75.81
0.08
75.92
0.1
76.1
0
0.84
2.41
2.58
2.73
2.98
3.2EFFECT OF TEMPERATURE
Fig.4 shows the surface tension of graphene oxide nanofluids as a function of mass fraction at
3
different temperature. The measured values of deionized water’s surface tension are also shown in
Fig.4. Table 2 is the specific experimental datas. It can be seen from Fig.4 and Table 2, the surface
tensions of nanofluids and deionized water are reduced with temperature increasing. For example,
the surface tension of nanofluids(0.06wt%) is 75.81mN/m at 20℃ and 70.52mN/m at 60℃. The
surface tension was reduced by 6.97% after the temperature rise 40 ℃. When the temperature is
rised from 20 ℃ to 60 ℃, the surface tension of nanofluids with mass fraction 0.08wt% and
0.1wt% are reduced by 6.98%和 6.95%, respectively. While the surface tension of water is
73.90mN/m and 67.32mN/m at 20℃ and 60℃, respectively. The Surface tension is reduced by
9.0%. The range of surface tension decreases for nanofluids with increasing the temperature is
lower than that of deionized water.
Fig. 3 Surface tension of graphene oxide
nanofluids with different concentrations
Fig. 4 Surface tension of graphene oxide
nanofluids wtih different temperatures
3.3EFFECT OF PARTICAL SIZE
Fig.5 shows the surface tension of graphene oxide nanofluids with different nanoparticle
size(80nm,30nm,14nm). The temperature is 20℃, and mass fraction is 0.05wt%. It can be seen
from Fig.5, with the decrease of the particle size, the surface tension of nanofluids also decreases.
The surface tension of nanofluid(14nm) is decreased up to 3.29% compared with nanofluid
(80nm). The specific experimental datas are shown in Table 3.
Fig. 5 Surface tension of graphene oxide nanofluids wtih different nanoparticle size
4
Table 2 Surface tension of graphene oxide nanofluids with different temperature
T(℃)
σ(mN/m) 0wt%
σ(mN/m) 0.06wt%
σ(mN/m) 0.08wt%
σ(mN/m) 0.1wt%
20
73.90
75.81
75.92
76.10
30
72.65
74.48
74.75
75.16
40
70.71
72.94
73.12
73.51
50
68.72
72.05
72.13
72.48
60
67.32
70.52
70.62
70.81
Table 3 Surface tension of graphene oxide nanofluids with different size
D(nm)
σ(mN/m)
80
76.94
30
75.71
14
74.41
CONCLUSIONS
The surface tension of water-based graphene oxide nanofluids is increased with increasing the
mass faction of nanoparticles. But compared with deionized water, the increasing of surface
tension of nanofluids is not obvious. Hence, Adding graphene oxide nanoparticles in deionized
water has a little effect on its surface tension. The surface tension of nanofluids reduces with
increasing temperature and decreasing particle size of the nanoparticles.
ACKNOWLEDGMENTS
This work was supported by Natural Science Fundation of China (No. 51276204) and the
Program from Guangdong University Heat Pump Engineering Technology Development
Center(Grant No. KJZX-0058)
REFERENCES
[1] W.L. Chen, C.Liu, R. Zhao, et al., Experimental Study on Surface Tension of Ammonia - water Solution with Additives, Fluid
machinery. 33(2005)52-56. (In Chinese)
[2] Ranganathan Kumar, Denitsa Milanova, Effect of surface tension on nanotube nanofluids, Appl. Phys. Lett, 94(2009)073107.
[3] S. Murshed, N. T. Nguyen, Characterization of temperature dependence of interfacial tension and viscosity of nanofluid,
Proceedings of The Micro/Nanoscale Heat Transfer International Conference 2008, PTS A AND B, 2008: 545-548.
[4] D. S. Zhu, S. Y. Wu, N. Wang, Surface Tension and Viscosity of Aluminum Oxide Nanofluids, Melville:Amer Inst Physics.
1207(2010)460-464.
[5] R. H. Chen, T. X. Phuoc, D. Martello, Surface tension of evaporating nanofluid droplets, International Journal of Heat and Mass
Transfer. 54 (2011)2459-2466.
[6] S.Tanvir, L.Qiao, Surface tension of Nanofluid-type fuels containing suspended nanomaterials, Nanoscale research letters.
7(2012)226.
[7] B. A. Suleimanov, F. S. Ismailov, E. F. Veliyev, Nanofluid for enhanced oil recovery, Journal of Petroleum Science And
Engineering. 78 (2011)431-437.
[8] Z.Shen, Z. G. Zhao, G. T. Wang, Colloid and Surface Chemistry[M].Beijing: chemical industry press.(2004)198-200. (In
Chinese)
[9] Y. X. Hu, T.Q. Liu, X.Y. Li, S.F. Wang, Heat transfer enhancement of micro oscillating heat pipes with self-rewetting fluid,
International Journal of Heat and Mass Transfer. 70(2014)496–503.
5