The Drag Reduction Performances of Surfactant in Micro-channel

The Drag Reduction Performances of Surfactant in Micro-channel
SONG Fu-quan, ZUO Jia-chuan, WANG Jian-dong
College of Mathematics, Physics and Information Engineering, Zhejiang Normal University, Jinhua
Zhejiang, 321004, China
[email protected]
Abstract: The characteristics of drag reduction of surfactant for deionized water in micro-channels are
analyzed by experiments in which Cetyl Trimethyl Ammonium Bromide (CTAB) was used as the
adsorption in this paper. The experiments show that the flow rate of water in micro-channel without
CTAB agrees with the prediction of the conventional Hagen-Poisseuille equation. However, the flow
rate in micro-channel increases clearly after CTAB being adsorbed. This indicates that the friction of
water flow reduces 6.3% in micro-channel after CTAB being adsorbed in micro-channel with 50 micron
diameter. The reason is that the adsorption of CTAB changes the wettability of micro-channel from
hydrophilic to weak hydrophobic, and there is flow slippage at the interface between solid and liquid.
The relation between the efficiency of drag reduction and the time of adsorption is also studied, the
results suggest that: there are a maximum in the adsorption of CTAB, and there are two steps in the
course of adsorption: mono-layer adsorption and double-layers adsorption. The wettability of
micro-channel changes from hydrophilic to weak hydrophobic in the course of mono-layer adsorption,
and the efficiency of drag reduction will be the most value for saturated mono-layer adsorption.
Keywords: surfactant; drag reduction; hydrophilic; hydrophobic; micro-channel
0
Introductions
Recently, the machine size is becoming smaller and there are some problems about flowing and heat
dissipation, with the development of Micro-Electro-Mechanical System (MEMS). The specific surface
of liquid (unit volume of liquid occupied interfacial area) in micro meters is much larger than that in the
conventional scale, so the effect of resistance caused by interface becomes greater and it can not be
neglected. The drag reduction of flow in micro structures is very important, and it can become restrictive
factors in developing process for some equipments, for example, heat dissipation of computer chips.
It has not been very long to research the drag reduction in micro scale[1-3]. Nano-silica was injected
into oil formation to reduce the water injection pressure in oil recovery process [4-10]. The mechanism of
drag reduction is that nano-silica can be adsorbed on the pore surface, then changes the wettability of
pore from hydrophilicity to hydrophobicity, and decreases water injection pressure successfully.
Some researches show that there is flow slippage in the hydrophobic surface when liquid flow in
micro scale, but there is no unanimous opinion on the mechanism. Jia Ou and Blair Pero[11-12] found that
flow resistance reduced to 40% while liquid flow in hydrophobic micro-channel and the slippage length
more than 20um by experiments, the reason is that
solid-liquid interface is very little because of the
hydrophobic亲油基
group
existing of liquid-vapor interface. Tretheway and hydrophilic group
亲水基
Meinhart[13] measured the velocity in hydrophilicity
and hydrophobicity micro-channels by Micro-PIV,
experimental results show there was slippage length
about 0.92um, and the velocity becomes larger near the
wall surface in hydrophobic micro-channel and,
whereas the slippage is not exist in hydrophilic
micro-channel. Choi ect[14] measured the pressure
drop of liquid flow in hydrophilic and hydrophobic
Fig 1 the mechanism of wettability changed
micro-channels and calculated the slippage length, the
by surfactant
results show that the slippage length in hydrophobic
surface is far larger than the one in hydrophilic surface. Ling zhi-yong ect[15] changed the wettability of
459
micro pipes with diameter of 50µm by coating the wall of capillary with Octadecyltrichlorosilance(OTS),
results show that the flow resistance is greatly reduced and there is surface slippage.
Some surfactants with hydrophilic group and the hydrophobic group was injected into oil formation
during the oil developments, which can change the wettability of reservoir from hydrophilicity to
hydrophobicity, and the mechanism is that hydrophilic solid surface combined with hydrophilic group
and the lipophilic group is at the distal part of solid surface, to result the hydrophilic solid surface
becomes hydrophobic as shown in fig 1.
A few researchers studied the characteristics of the wettability reversion with surfactants in
reservoirs. Bi zhi-chu and Shi yan ect[16] researched the relation between wettability and the adsorption
of Cetyl Trimethyl Ammonium Bromide(CTAB) on silica wafer, they found that hydrophilicity of silica
wafer becomes weak and the contact angle can increases to 840 after mono-layer adsorption. Nian
jie-hua and Wang fu-hua[17] measured the adsorption of CTAB on surface of sandstone whose wettability
changed from hydrophilicity to hydrophobicity using Amott. Li ji-san and Yao tong-yu[18]researched the
interaction of CTAB and sandstone from other factors, such as adsorption law, surface wettability,
surface electrical behavior, experimental results show that CTAB can changes the wettability of
sandstone and the wettability changes from hydrophilicity to neutrality while the solution concentration
of CTAB reached the Critical Micelle Moncentration(CMC).
In the theoretical research, the flow rate of water in micro-channel is proportional to pressure
difference, and the flow rate agrees with the prediction of the conventional Hagen-Poisseuille equation.
The flow rate equation is
π d 4 ∆p
QHP =
128µ L
(1)
where, QHP is the theoretical flow rate, p is the pressure, µ is the liquid viscosity, d is the diameter of
tube, L is the length of micro-channel.
1
Experiment
Pressure Sensor
In this paper, The CTAB was used as
the adsorption surfactant in micro-channel
with 50 micron diameter, the flow rate of
deionized water without and with
adsorption of CTAB were measured to
analysis the reason of flow slippage. CTAB
is a very important kind of cationic
surfactant whose molecular formula is
C16H33-(CH3)3N-Br, where –Br is
hydrophilic group and -C16H33 is
hydrophobic group.
Amplifier
Liquid Container
Capillary Tube
tube
Filter
N2 tank
Microtube
The Measure System
Fig 2 Schematic diagram of the micro-flow experimental setup
1.1 Experimental Device
Fig 2 shows the experimental setup. The
high-pressure nitrogen was used as the pressure source, which is adjusted to the needed value of
experiments. By the pressure regulator, the precise value can be measured by the temperature-pressure
measurement system, and at the same time the experimental temperature can be measured. Various parts
of the instrument can be connected by plastic hose which can bear high pressure, and the connect place
can be sealed by hard seal.
1.2 Experimental Procedure
Because the experimental precision is high, the entire experimental process should maintain a clean
experimental environment. The experiments are carried out in a biology frame (made by BIOAIR
Corporation, AURA VERTICAL S.D.4). The specific operation procedures are as follows.
460
(1) a piece of the micro-channel with the length of about 5-8cm was cut, whose diameter is 50
micron, and the micro-channel into the steel pipe was sticked with AB rubber, when the other end was
connected to the plastic hose, then wait for about half an hour until the AB rubber dries. Next, one end
of the experimental tube was connected to the three contacts, and the other end passed through the
time-displacement measurement system.
(2) The experimental pressure and temperature can be recorded directly by the
temperature-pressure measuring system. The pressure can be accurate up to 0.001MPa, and the
temperature can be accurate up to 0.1°C.
(3) According to the displacement of air bubble and the time measured, the flow rate in
displacement pipe can be calculated. The water displacement can be measured by the
electricity-displacement instrumentation. The precision of displacement is 0.01mm, and the precision of
time is 0.01s. The flow rate in the experiment is 0.0001-0.1ul/s.
(4) The experimental pressure is taken from high pressure to low pressure. Each pressure drop was
measured five times to derive the average value, and then the relations of the pressure and the flow rate
were derived.
The experimental flow rate can be obtain from the equations
D2
v
4
Qexp = v ⋅ A = π
(2)
where, Qexp is the actual flow rate, A is the cross-sectional area of capillary, D is the inner diameter of
capillary, v is the velocity of water in capillary.
The solution of CTAB whose Concentration 1‰ was injected into the micro-channels after flow
test of deionized water. Then kept for 4 hours before the experiments, and the experimental procedures
are same with before. Finally we compared the experimental flow rate with traditional theoretical value.
All experiments are carried out at 20°C( µ =1× 10
2
-3
Pa ⋅ s ).
Experiment Results and Analysis
2
1.6
吸附前
without CTAB
吸附后
with CTAB
Flow rate(nL/s)
Fig 3 shows the characteristics of flow rate
)s/
-pressure gradient of deionized water flow in
Ln 1.2
microtubule with 50µm diameter. It shows that
（ 0.8
量流
the flow rate of water in micro-channel without
CTAB agrees with the prediction of the
0.4
conventional
Hagen-Poisseuille
equation.
However, the flow rate in micro-channel
0
increases clearly after CTAB being adsorbed.
0
2
4
6
8
10
12
14
压力梯度(MPa/m)
This indicates that the friction of water flow
pressure gradient(MPa/m)
reduces about 6.3% in micro-channel after CTAB
adsorbed, and there is a flow slippage at the
Fig 3 Relation between flow rate and pressure
gradient
interface between solid and liquid.
The wettability changing with CTAB
adsorption can also be proved by other methods, for example, one of two cleaned and drying glass slides
was immerged into CTAB solution with 1‰ concentration for 4 hours, then two glass slides were set at
a same inclined angle, it was found that water drop spreads rapidly and flows down slowly on the
surface of glass slide without CTAB absorption, but rolls quickly on the surface of another glass slide
with absorption.
461
Fig 4 shows the relation of drag reduction effect and the adsorption time, it is obvious that the drag
reduction effect changes with the adsorption time. There is a maximum efficiency 6.3% in the
adsorption course, when the time is 4 hours. This is expected because CTAB adsorption is mono-layer
adsorption and it is arranged the inner wall of micro-channel (see Fig.1). Because that the inner wall of
micro-channel is hydrophilic, the hydrophilic group of CTAB adsorbs the inner wall of micro-channel
while the orientation of hydrophobic group extends to outside, which leads weakened hydrophilic. So
flow resistance of deionized water
7
decreases and flow rate of deionized water
6
increases. The mono-layer adsorption of
5
CTAB become more and more compacter,
4
the hydrophilic of the inner wall of
micro-channel is more weaker with the
3
time increasing, and the flow resistance
2
becomes lower, the drag reduction
1
efficiency
becomes
stronger.
The
0
mono-layer adsorption is saturated and
0
2
4
6
8
10 12 14 16 18
drag
reduction
efficiency
reaches
吸附时间(h)
adsorption
time (t/h)
maximum when the time is 4 hours. After
Fig 4 Relation between drag reduction efficiency and
4hours, the CTAB adsorption changes from
adsorption
mono-layer to double-layer as show Fig.5.
The second layer hydrophilic group and the
first layer hydrophobic group of
hydrophobic
adsorption CTAB is opposite The direction
亲油基
hydrophilic
group
of hydrophilic adsorption group of second
亲水基
group
layer CTAB is external, hydrophilic of the
inner wall of micro-channel become
stronger and the flow resistance of
ultrapure water become bigger.
drag reduction effec
/%
）
η（
3
Conclusions
)%(
率
效
阻
减
Fig 5 Schematic diagram of double-layer adsorption
The characteristics of drag reduction of surfactant for deionized water in micro-channels with 50um
diameter are analyzed by experiments in which CTAB was used as the adsorption in this paper.
The experimental results show that:
(1) CTAB can changes the wettability of micro-channel from hydrophilicity to weak hydrophobicity,
the flow rate becomes bigger in the micro-channel with CTAB than ones without CTAB at the same
pressure gradient;
(2) There are two steps in the course of adsorption: mono-layer adsorption and double-layers
adsorption. The wettability of micro-channel changes from hydrophilic to weak hydrophobic in the
course of mono-layer adsorption, and it is opposite in the course of double-layers adsorption.
References
[1]
LIU Qi-ming, XIA Guo-dong, QI Jingzhi. Influence of Surfactant on Frictional Pressure Drop in
Manifold Microchannel[J]. Journal of Chemical Industry and Engineering, 2006 57(11):
2526-2530(in Chinese)
[2] KANG Chun-xia, HUANG Xin-bo. Analysis on the Fluid Resistance of the Micro-channel
Convection heat Transfer System. Micronanoelectronic Technology[J],2004,7:39-41(in Chinese)
[3] XIAO Ru-ting, LI Nai-xuan, WU Zhi-dong,et al. Influence of Adhesive Work Between Inwall and
Liquid Upon Flow Resistance in Smooth Straight Conduit[J]. Journal of Experimental
，
462

Mechanics,2000,3:258-262
LU Xian-liang, L
Guang-zhong, LUAN Zhi-an, et al. Application of Polesilicon in Low
Permeability Oil Field[J]. Petroleum Exploration and Development,2003,30(6):110-116(in
Chinese)
[5] Su Xian-tao, Yan Jun, Lu Guang-zhong, et al. Application of Nanometer Polysilicon in Oil Field
Development[J]. Oil Drilling & Production Technology,2002,24(3):48-51(in Chinese)
[6] DI Qin-feng, GU Chun-yuan, SHI Li-yi, et al. Pressure Drop Mechanism of Enhancing Water
Injection Technology With Hydrophobicity Nanometer SiO2[J]. Drilling & Production
Technology,207,30(4):91-94(in Chinese)
[7] Guo Dong-hong. Application of Nano-technology in Enhancing Oil Recovery[J]. Advances in Fine
Fetrochemicals,2004,5(7):1-5(in Chinese)
[8] Zhang Ji-chao, Cao Xu-long,Tang Zhan-hong, et al. Experiment of Polysilicic Material for
Improving Waterflooding Effect in Low Permeability Oil Reservoir[J]. Oil & Gas Recovery
Technology,2003,10(4):59-61(in Chinese)
[9] Hong Xiang-zhen. The Research and Application of Injection-increased Technology about Active
Nanometer Material[J]. Fault-block Oil & Gas Field,2004,11(3):49-51(in Chinese)
[10] L Guang-zhong, ZHANG Jiang-qiao. A Laboratory and Application of Nanometer Pole Silicon[J].
Journal of Functional Materials,2006,37(7):1110-1113(in Chinese)
[11] Jia Ou, Blair Perot, Jonathan P.Rothstein. Laminar Drag Reduction in Microchannels Using
Ultrahydrophobic Surfaces[J].Physics of Fluids, 2004,16 (12):4635-4643.
[12] Jia Ou, Jonathan P.Rothstein. Direct Velocity Measurements of the Flow Past Drag-reducing
Ultrahydrophobic Surfaces[J]. Physics of Fluids, 2005,17: 103606.
[13] Tretheway D C, Meinhart C D. Apparent Fluid slip at Hydrophobic Microchannel Walls[J]. Physics
of Fluids, 2002,14: L9-L12.
[14] Choi C, Westin J A, Breuer K S. Apparent Slip Flows in Hydrophilic and Hydrophobic
Microchannels. Physics of Fluids[J], 2003,15: 2897-2902.
[15] Ling Zhi-yong,Liu Yong,Zhuang Zhi-wen, et al. Experimental Study of the Characteristic of Fluid
Slip in Hydrophilic and Hydrophobic Microchannels[J]. Lubrication Engineering, 2006,12:104-106
(in Chinese)
[16] BI Zhi-chu, SHI Yan, YAN Wen-hua, et al. Adsorption of Cetyl Trimethylammonium Bromide on
Surface of Silicon Dioxide[J]. Chemical Reagents, 1997, 19(6): 331-333(in Chinese)
[17] YAN Jie-Nian, WANG Fu-Hua, Wettability Alteration of Silica Induced by Surfactant
Adsorption[J]. Oilfield Chemistry,1993,10(3):195-200(in Chinese)
[18] LI Jishan, YAO Tongyu. Study of Interaction between Cetyl Trimethylammonium Bromide and
Sandstone[J]. Journal of Jianghan Petroleum Institute , 2005, 27(3): 531-533(in Chinese)
[4]
463