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Research Papers: Two-Phase Flow and Heat Transfer

Effect of the Heat Pipe Adiabatic Region

[+] Author and Article Information
Taoufik Brahim

Laboratoire d'Etudes des Systèmes
Thermique et Energétique LESTE,
Université de Monastir,
Ecole Nationale d'Ingénieurs de Monastir,
Avenue Ibn Jazzar
Monastir 5019, Tunisia
e-mail: taoufik.brahim@yahoo.fr

Abdelmajid Jemni

Laboratoire d'Etudes des Systèmes
Thermique et Energétique LESTE,
Université de Monastir,
Ecole Nationale d'Ingénieurs de Monastir,
Avenue Ibn Jazzar
Monastir 5019, Tunisia
e-mail: abdelmajid.jemni@enim.rnu.tn

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received July 24, 2012; final manuscript received July 16, 2013; published online January 2, 2014. Assoc. Editor: Patrick E. Phelan.

J. Heat Transfer 136(4), 042901 (Jan 02, 2014) (10 pages) Paper No: HT-12-1404; doi: 10.1115/1.4025132 History: Received July 24, 2012; Revised July 16, 2013

The main motivation of conducting this work is to present a rigorous analysis and investigation of the potential effect of the heat pipe adiabatic region on the flow and heat transfer performance of a heat pipe under varying evaporator and condenser conditions. A two-dimensional steady-state model for a cylindrical heat pipe coupling, for both regions, is presented, where the flow of the fluid in the porous structure is described by Darcy–Brinkman–Forchheimer model which accounts for the boundary and inertial effects. The model is solved numerically by using the finite volumes method, and a fortran code was developed to solve the system of equations obtained. The results show that a phase change can occur in the adiabatic region due to temperature gradient created in the porous structure as the heat input increases and the heat pipe boundary conditions change. A recirculation zone may be created at the condenser end section. The effect of the heat transfer rate on the vapor radial velocities and the performance of the heat pipe are discussed.

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References

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Figures

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Fig. 1

Schematic of conventional cylindrical heat pipe and simulation cases investigated

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Fig. 2

Validation code with comparison at Q = 12,639 W/m2: (a) outer surface wall temperature distribution, (b) liquid and vapor pressure distribution, (c) maximal liquid velocity, and (d) mean vapor velocity

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Fig. 3

Axial and radial vapor velocities profiles at 0.5 with Q = 5000 W/m2 (left) and Q = 50,000 W/m2 (right) with and without adiabatic section

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Fig. 4

Axial vapor velocity streamlines for different fluxes and boundary conditions

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Fig. 5

Radial vapor velocity streamlines for different fluxes and boundary conditions

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Fig. 6

Liquid isotherms with and without adiabatic section and for the two kind boundary conditions (Q =50,000 W/m2)

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Fig. 7

Axial vapor velocity streamlines at condenser corner end at 50,000 W/m2 with and without adiabatic section for the two simulation case

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Fig. 8

Velocity profiles in porous media with and without adiabatic region (Q = 50,000 W/m2, first kind b.c)

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Fig. 9

Pressure and temperature profiles in porous media with and without adiabatic region (Q = 50,000 W/m2, first kind b.c)

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