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Vol. 18 (2013)，17〜22

Flow Characteristics in the Grooved Channel for Pulsatile Flow

Flow Characteristics in the Grooved Channel for Pulsatile Flow
Yongning BIAN*1, Hirofumi ARIMA*2, Congling LI*1 and Yasuyuki IKEGAMI*2*1

State Key Laboratory of Structural Analysis for Industrial Equipment
Dalian University of Technology, 116024, China*2
Institute of Ocean Energy, Saga University, 840-8502, Japan

Experimental system of two-dimensions grooved channel for pulsatile flow had been calibrated. On this basis, theavailable pulsatile operating range was decided. Furthermore, the overall pressure drop and the local pressure for thegrooved channel had been measured and their characteristics of pulsatile behaviors were described. It is showed that themaximum oscillatory fraction and the maximum oscillatory period are P=0.28 and T=2.4s, respectively. Moreover, it isfound that the overall pressure drop changes with the pulsatile flow rate in the same phase shift, while the local pressurechanges in an opposite trend with a little phase shift.
Key Words : Grooved channel, Pulsatile flow, Operating range, Oscillatory fraction, Oscillatory period

1. Introduction
It is well known that the plate type heat exchanger has been widely applied to the practical engineering since its
higher heat transfer efficiency, especially in the ocean thermal energy conversion system(OTEC). Even so, it still
could not meet the requirement for the much higher efficiency depending only on the complex channel shape.
The novel technique used to enhance the heat or mass transfer rate has attracted the attention of many researchers.
The earlier study was conducted by Bellhouse et al.[1], they pioneered the study of how large fluid oscillations
can improve fluid mixing and mass transfer in a 2-D furrowed channel and found that the combination of a large
laminar oscillation with a much smaller mean flow through a wavy-walled channel could achieve a higher masstransfer rates. Nishimura et al.[2] systematically studied the flow and mass transfer characteristics in wavy-walled
channels for pulsatile flow. They pointed out that the mass transfer enhancement depends on three parameters: net
flow Reynolds number, oscillatory fraction of the flow rate, and Strouhal number. The enhancement factor
increases with the increment of these three parameters in their experimental range. Ghaddar et al.[3] numericallyinvestigated the relationship between the flow instability and the heat transfer enhancement in grooved channels.
They indicated that the occurrence of T-S wave is a common feature for the 2-D channels, and they further
pointed out that the oscillatory flow imposed at the T-S frequency will lead to a resonant excitation and associatedtransport enhancement. Based on the above results, Sun et al.[4] completed the experimental study in the grooved
channels with different groove length for steady flow. They obtained the first and second frequency of the T-Swave. Moreover, they found that increasing pressure will result in a higher amplitude of the T-S wave, thisbehavior is significant for the efficient heat transfer in practical engineering. For the pulsatile flow, Arima et al.[5]numerically and experimentally examined the imposed oscillatory flow on the fluid flow at lower net Reynolds
number in a grooved channel, and described the effects of operating conditions on the vortex strength and the heattransfer Nusselt number. There also have many experimental and numerical studies on 3-D channels for thepulsatile flow[6~9], they mainly focused on the effects of the pulsatile operating conditions on the heat or masstransfer for laminar and turbulent pulsatile flow.
To lay a foundation for the in-depth study, in the present work, the pulsatile operating conditions for thegrooved channel experimental system will be calibrated, and then, the operating range of the pulsatile parameter*

Acceptance 2013.6.10
E-mail: ybian@dlut.edu.cn17

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Yongning BIAN, Hirofumi ARIMA, Congling Li, and Yasuyuki IKEGAMIwill be confirmed. Finally, some pulsatile flow behaviors will be described.

2. Experimental apparatus and parameters
The experimental system is shown in Fig. 1, which is almost the same as that used in reference [4], only adding
a solenoid valve and a time controller before the flow enters the grooved channel. The time controller is used tochange the time of the solenoid valve in On or Off so as to obtain the different pulsatile period. The definitions of
the oscillatory fraction P and the oscillatory period T used in this study are identical with the reference [5]. The
test section is shown in Fig. 2, and its dimension is L=20mm, W=200mm, h=2.5mm and l=12mm.

Fig. 1 Sketch of experimental system






L=20mm, W=200mm, h=2.5mm and l=12mm

Fig. 2 Dimension of grooved channel

3. Results and discussion
3.1 Representative form of pulsatile flow
The pulsatile flow generated by the self-circulating experimental system is shown in Fig. 3, which is obtainedat the net flow rate Q=200ml/s(±4ml/s) with On=Off=0.7s. To express the time-history of the pulsatile flow rate
clearly, all the experimental data have been treated with Matlab software. The straight line above is the fitting
steady flow (i.e. the net flow) and the smooth curve below is the fitting pulsatile flow. Obviously, the pulsatile
flow rate changes approximately in the form of sinusoidal wave. But because of the special setting location of thesolenoid valve, the flow rate of the pulsatile flow is much smaller than that of the steady flow. Therefore, theamplitude of pulsatile flow generated from this experimental system is very low. For this figure, the oscillatory

19

Flow Characteristics in the Grooved Channel for Pulsatile FlowFig. 3 Variation of pulsatile flow rate
fraction is P=0.121.

3.2 Available experimental range
To confirm the available experimental operating range, the experiments at different net flow rate with thevarious On and Off time combinations are carried out. When Q=100~900ml/s, On=0.2~1.2s and Off=0.1~1.2s,
the distribution of the available experimental operating range is shown in Fig. 4, the area surround by the dottedlines determined the minimum and the maximum T and P, respectively, that is T=0.5~2.4s, P=0.001~0.28.
Obviously, the maximum P is smaller, therefore, it is necessary to design a new oscillatory flow generating device
to gain the more effective pulsatile flow.

32.5

T [s]

21.5
Q=100ml/s, Off=0.3s,Tmin
Q=200ml/s, Off=1.2s, Pmax
Q=400ml/s, Off=0.5s, Pmin
Q=900ml/s, Off=1.2s, Tmax

10.5
00

0.05

0.1

0.15

0.2

0.25

0.3

P [-]
Fig. 4 Available experimental operating range
3.3 Effects of the oscillatory period and the net flow rate on the oscillatory fraction
According to the experimental data, the better pulsatile flow with a obvious amplitude is obtained when theOn and Off time is equivalent. Fig. 5 shows the relationship between the oscillatory fraction P and the oscillatory
period T. It is seen that the P increases with the T increasing, and except the net flow rate Q=100ml/s, the P

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Yongning BIAN, Hirofumi ARIMA, Congling Li, and Yasuyuki IKEGAMI

0.3
Q=100ml/s
Q=200ml/s
Q=300ml/s
Q=400ml/s
Q=500ml/s
Q=600ml/s
Q=700ml/sQ=800ml/s
Q=900ml/s

0.25

P [-]

0.20.15
0.1
0.05
000.5

11.5

22.53

T[s]
Fig. 5 Effect of the oscillatory period on the oscillatory fraction

0.3
T=0.6s
T=0.8s
T=1.0s
T=1.2s
T=1.4s
T=1.6s
T=1.8s
T=2.0s
T=2.2s
T=2.4s

0.25

P [-]

0.20.15
0.1
0.05
00200

4006008001000

Q[ml/s]Fig. 6 Effect of the net flow rate on the oscillatory fraction
decreased with the increment of Q from 200ml/s to 900ml/s. Fig. 6 could illustrates this phenomenon moreclearly. These two figures mean that the maximum P=0.28 could be obtained at Q=200ml/s, T=2.4s (i.e. On=Off=1.2s).
3.4 Characteristics of overall pressure drop and local pressure
After the available experimental range is decided, the characteristics of pulsatile flow about the overall pressure
drop dP and the local pressure P7 were explored. At On=Off=0.6s, Q=400ml/s, the time histories of the dP and
the P7 were recorded as shown in Fig. 7. For the convenient compare, the pulsatile flow rate was also displayed
here. For this case, the oscillatory fraction is very small, only is P=0.052. The results showed that when the flow
starts to oscillate, the dP will be triggered the same behavior with the zero phase shift. Meanwhile, the P7
displayed a different behavior, that is, P7 changes in an opposite trend with a little phase shift during the periodsof the pulsatile flow rate increasing and decreasing. Generally, the pulsatile flow will promote the motion of the21

Flow Characteristics in the Grooved Channel for Pulsatile Flow350

Q [ml/s]340
330
320310dP [kPa]3001.100 .5

11 .5

22 .5

3

00 .5

11 .5

22 .5

3

00.5

1

1.5

2

2.5

3

1.05
10.95
16

P7 [kPa]

1412
1086
4

Time [ s ]Fig. 7 Characteristics of overall pressure drop and local pressure
varies with time for pulsatile flow
flow vortex and thus enhance the heat and mass transfer in the flow channel. But it could not measure the above
performance with the present experimental apparatus. To have a good insight to the pulsatile flow, it should
consider to improve the flow channel and the measurement system.

4. Conclusions
The performance of the used grooved channel experimental system for pulsatile was calibrated, and then, thetime-histories of the overall pressure drop and the local pressure had been recorded. Based on the above
experiments, the conclusive remarks could be drawn as follows:(1) With the present experimental system, the pulsatile flow in the form of sinusoidal wave could be generated
by the solenoid valve. The available pulsatile operating range are decided, that is, the pulsatile period T=0.5~2.4s,
the oscillatory fraction P=0.001~0.28. The maximum P=0.28 could be obtained only at Q=200ml/s with
On=Off=1.2s, i.e. T=2.4s.
(2) For the pulsatile flow, the overall pressure drop dP will change with the pulsatile flow rate in the same
phase shift, but the local pressure P7 will change in an opposite trend with a little phase shift. These flow
behaviors will be relative to the enhancement of heat and mass transfer in the grooved channel. It is necessary to
carry out some studies to prove it.
Acknowledgments This study is sponsored by the Cooperative Research Program of IOES (No.12006A ) and theNatural Science Foundation of China (No. 11172059).

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Yongning BIAN, Hirofumi ARIMA, Congling Li, and Yasuyuki IKEGAMI

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