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Research Papers: Heat and Mass Transfer

Effects of Superhydrophobic and Superhydrophilic Surfaces on Heat Transfer and Oscillating Motion of an Oscillating Heat Pipe

[+] Author and Article Information
Tingting Hao

Institute of Chemical Engineering,
Dalian University of Technology,
Dalian 116024,
Liaoning Province, China
e-mail: haotingting224@mail.dlut.edu.cn

Xuehu Ma

Mem. ASME
Institute of Chemical Engineering,
Dalian University of Technology,
Dalian 116024,
Liaoning Province, China
e-mail: xuehuma@dlut.edu.cn

Zhong Lan

Institute of Chemical Engineering,
Dalian University of Technology,
Dalian 116024,
Liaoning Province, China
e-mail: lanzhong_dut@sohu.com

Nan Li

Institute of Chemical Engineering,
Dalian University of Technology,
Dalian 116024,
Liaoning Province, China
e-mail: dagonglinan@mail.dlut.edu.cn

Yuzhe Zhao

Institute of Chemical Engineering,
Dalian University of Technology,
Dalian 116024,
Liaoning Province, China
e-mail: zyzallen@hotmail.com

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received December 25, 2013; final manuscript received April 2, 2014; published online May 2, 2014. Assoc. Editor: Bruce L. Drolen.

J. Heat Transfer 136(8), 082001 (May 02, 2014) (13 pages) Paper No: HT-13-1666; doi: 10.1115/1.4027390 History: Received December 25, 2013; Revised April 02, 2014

The effects of superhydrophobic surface and superhydrophobic and superhydrophilic hybrid surface on the fluid flow and heat transfer of oscillating heat pipes (OHPs) were investigated in the paper. The inner surfaces of the OHPs were hydrophilic surface (copper), hybrid surface (superhydrophilic evaporation and superhydrophobic condensation section), and uniform superhydrophobic surface, respectively. Deionized water was used as the working fluid. Experimental results showed that superhydrophobic surface influenced the slug motion and thermal performance of OHPs. Visualization results showed that the liquid-vapor interface was concave in the OHP with copper surface. A thin liquid film existed between the vapor plug and the wall of the OHP. On the contrary, the liquid-vapor interface took a convex profile in the OHP with superhydrophobic surface and the liquid-vapor interface contact line length in the hybrid surface OHP was longer than that in the uniform superhydrophobic surface OHP. The liquid slug movements became stronger in the hybrid surface OHPs as opposed to the copper OHP, while the global heat transfer performance of the hybrid surface OHPs increased by 5–20%. Comparing with the copper OHPs, the maximum amplitude and velocity of the liquid slug movements in the hybrid surface OHPs increased by 0–127% and 0–185%, respectively. However, the maximum amplitude and velocity of the liquid slug movements in the uniform superhydrophobic OHPs was reduced by 0–100% and 0–100%, respectively. The partial dryout phenomenon took place in OHPs with uniform superhydrophobic surface. The liquid slug movements became weaker and the thermal resistance was increased by 10–35% in the superhydrophobic surface OHPs.

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References

Figures

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Fig. 1

Schematic of the experimental setup

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Fig. 2

(a) Construction of the plate OHP and (b) photo of the charged OHP

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Fig. 3

ESEM images of (a) copper surface, (b) superhydrophobic surface, and (c) superhydrophilic surface. The top-right insets show the contact angles of the surfaces.

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Fig. 4

Flow patterns in the evaporation section with the copper surface at the heat input of (a) 50 W, (b) 70 W, and (c) 80 W (cooling water temperature: 25 °C)

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Fig. 5

Flow patterns in the evaporation section with the superhydrophilic surface at the heat input of (a) 50 W, (b) 70 W, and (c) 80 W (cooling water temperature: 25 °C)

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Fig. 6

Flow patterns in the evaporation section with the superhydrophobic surface at the heat input of (a) 50 W, (b) 70 W, and (c) 80 W (Cooling water temperature: 25 °C)

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Fig. 19

Superhydrophobic surface on the startup characteristic of the OHPs

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Fig. 18

Superhydrophobic surface on (a) heat transfer coefficient of evaporation section and (b) heat transfer coefficient of condensation section of the OHPs

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Fig. 17

Superhydrophobic surface on (a) thermal resistance and (b) average evaporation temperature of the OHP

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Fig. 12

Superhydrophobic surface on the (a) slug position and (b) velocity at the steady state (cooling water temperature: 25 °C)

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Fig. 11

Superhydrophobic surface on the (a) slug position and (b) velocity at the steady state (heat input: 70 W)

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Fig. 10

Liquid slug position and liquid-vapor interface contact length of (a) copper, (b) hybrid surface, and (c) uniform superhydrophobic OHPs (cooling water temperature: 5 °C, heat input: 70 W)

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Fig. 9

Liquid slug position and liquid-vapor interface contact length of (a) copper, (b) hybrid surface, and (c) uniform superhydrophobic OHPs (cooling water temperature: 15 °C, heat input: 70 W)

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Fig. 8

Liquid slug position and liquid-vapor interface contact length of (a) copper, (b) hybrid surface, and (c) uniform superhydrophobic OHPs (cooling water temperature: 25 °C, heat input: 70 W)

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Fig. 7

Liquid-vapor interface in the condensation section of (a) copper, (b) hybrid surface, and (c) uniform superhydrophobic OHPs (cooling water temperature: 25 °C, heat input: 70 W)

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Fig. 16

Superhydrophobic surface on the (a) average and (b) maximum liquid-vapor interface length at the end of the slug at the steady state

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Fig. 15

Superhydrophobic surface on the (a) average velocity and (b) maximum velocity of the slug at the steady state

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Fig. 14

Superhydrophobic surface on the (a) average amplitude and (b) maximum amplitude of the slug at the steady state

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Fig. 13

Superhydrophobic surface on the (a) slug position and (b) velocity at the steady state (heat input: 105 W)

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