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Research Papers: Heat and Mass Transfer

A Comprehensive Experimental Investigation of the Performance of Closed-Loop Pulsating Heat Pipes

[+] Author and Article Information
M. Halimi

Department of Mechanical Engineering,
Shahrood University of Technology,
University Boulevard,
P.O. Box 3619995161-316,
Shahrood, Iran
e-mail: mohammadhalimi1990@gmail.com

A. Abbas Nejad

Department of Mechanical Engineering,
Shahrood University of Technology,
University Boulevard,
P.O. Box 3619995161-316,
Shahrood, Iran
e-mail: abbasnejad@shahroodut.ac.ir

M. Norouzi

Department of Mechanical Engineering,
Shahrood University of Technology,
University Boulevard,
P.O. Box 3619995161-316,
Shahrood, Iran
e-mail: mnorouzi@shahroodut.ac.ir

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received November 11, 2016; final manuscript received March 14, 2017; published online May 2, 2017. Assoc. Editor: Zhixiong Guo.

J. Heat Transfer 139(9), 092003 (May 02, 2017) (11 pages) Paper No: HT-16-1734; doi: 10.1115/1.4036460 History: Received November 11, 2016; Revised March 14, 2017

Closed-loop pulsating heat pipes (CLPHPs) are a new type of two-phase heat transfer devices that can transfer considerable heat in a small space via two-phase vapor and liquid pulsating flow and work with various types of two-phase instabilities so the operating mechanism of CLPHP is not well understood. In this work, two CLPHPs, made of Pyrex, were manufactured to observe and investigate the flow regime that occurs during the operation of CLPHP and thermal performance of the device under different laboratory conditions. In general, various working fluids were used in filling ratios of 40%, 50%, and 60% in horizontal and vertical modes to investigate the effect of thermo-physical parameters, filling ratio, nanoparticles, gravity, CLPHP structure, and input heat flux on the thermal performance of CLPHP. The results indicate that three types of flow regime may be observed given laboratory conditions. Each flow regime exerts a different effect on the thermal performance of the device. There is an optimal filling ratio for each working fluid. The increased number of turns in CLPHP generally improves the thermal performance of the system reducing the effect of the type of the working fluid on the aforementioned performance. The adoption of copper nanoparticles, which positively affect fluid motion, decreases the thermal resistance of the system as much as 6.06–42.76% depending on laboratory conditions. Moreover, gravity brings about positive changes in the flow regime decreasing thermal resistance as much as 32.13–52.58%.

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References

Figures

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Fig. 1

Schematic arrangement of the heater plate and CLPHP's evaporator

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Fig. 2

Schematic diagram of the experimental setup: condensation section (1), evaporation section (2), entry and exit valve of working fluid (3), vacuum valve (4), and thermal plate (5)

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Fig. 6

Picture of bubbles in the combination of three types of regimes

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Fig. 7

Overall thermal resistance diagrams in terms of time for different working fluids (vertical mode): (a) water, CLPHP1; (b) water, CLPHP2; (c) ethanol, CLPHP1; (d) Ethanol, CLPHP2; (e) acetone, CLPHP1; and (f) acetone, CLPHP2

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Fig. 8

Average values of overall thermal resistance of water and copper nanofluid at different filling ratios (vertical mode): (a) CLPHP1 and (b) CLPHP2

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Fig. 9

Overall thermal resistance diagrams in terms of time for copper nanofluid (vertical mode): (a) CLPHP1 and (b) CLPHP2

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Fig. 10

Average values of overall thermal resistance of ethanol and water at different filling ratios (comparison of vertical and horizontal mode) (a) ethanol, CLPHP1; (b) ethanol, CLPHP2; (c) water, CLPHP1; and (d) water, CLPHP2

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Fig. 11

Evaporator and condenser temperature diagrams in terms of time for ethanol as the working fluid (CLPHP2, vertical mode)

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Fig. 12

Overall thermal resistance diagram in terms of time for ethanol as the working fluid (CLPHP2, vertical mode)

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