Three-dimensional simulation on heat transfer in the flat evaporator of miniature loop heat pipe

Zhang, Xianfeng; Li, Xuanyou; Wang, Shuangfeng

doi:10.1016/j.ijthermalsci.2011.12.002

Cited by 32 publications

(6 citation statements)

References 18 publications

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“…One can then again distinguish two types of works as regards the modelling of heat and mass transfers in the porous wick of evaporator: the works where the wick is assumed to be liquid saturated, e.g. [8][9][10][11][12], and the works where the wick can be partially invaded by the vapour. The latter is the situation of primary interest for the present study.…”

Section: Introductionmentioning

confidence: 99%

Three dimensional liquid and vapour distribution in the wick of capillary evaporators

Mottet

Coquard

Prat

2015

International Journal of Heat and Mass Transfer

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a b s t r a c tHeat and mass transfer with liquid-vapour phase change in a representative unit cell of a capillary evaporator is studied using a mixed pore network model. The model combines the computation of temperature and pressure fields in vapour and liquid pores according to mean field approaches with pore scale invasion rules depending on the capillary pressure thresholds associated with each local constriction between two pores. The metallic body through which heat is transferred to the porous wick is also taken into account in the simulations. After comparisons with a visualisation experiment, numerical simulations performed in three dimensional pore networks lead to the identification of three main regimes depending on the applied heat load. Compared with previous works using the so-called vapour pocket assumption, the 3D simulations reveal a regime where the phase distribution within the wick is fundamentally different. This regime is characterised by the coexistence of both the liquid and vapour phases underneath the casing within the wick. This regime is shown to correspond to the best evaporator performance.

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Section: Introductionmentioning

confidence: 99%

Three dimensional liquid and vapour distribution in the wick of capillary evaporators

Mottet

Coquard

Prat

2015

International Journal of Heat and Mass Transfer

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“…They are supposed to be equal to the compensation chamber pressure and temperature (Eqs. (10) and (11)). The groove temperature T g is taken at the saturation temperature corresponding to the groove pressure P g (Eq.…”

Section: Boundary Conditionmentioning

confidence: 94%

“…Heat and mass transfer in capillary evaporator have been studied when the vaporisation only occurs at the wick/groove interface (liquid saturated wick) ( [8][9][10]) or within the wick (using the so-called ''vapour pocket" assumption, e.g. [11][12][13]).…”

Section: Introductionmentioning

confidence: 99%

“…Several parameters and/or properties have been investigated numerically and/or experimentally in order to improve the evaporator performances. Amongst other the geometrical dimensions and the position of vapour grooves [10], the choice of the working fluid ( [18,19]) or the use of a bilayer wick ( [20][21][22]) were investigated. In this context, the use of a bimodal capillary wick has been considered in the literature and seems to be promising to improve LHP performance.…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulation of heat and mass transfer in bidispersed capillary structures: Application to the evaporator of a loop heat pipe

Mottet

Prat

2016

Applied Thermal Engineering

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a b s t r a c tHeat and mass transfer with phase change in an evaporator unit cell is analysed using a mixed pore network model. Two different kind of wick are investigated: a monoporous capillary structure characterised by a monomodal pore size distribution and a bidispersed capillary structure characterised by a bimodal pore size distribution. The evaporator thermal performance, i.e. the conductance, and the overheating of the casing are compared at different heat loads with experimental results and show a good agreement. For a large range of flux, the bidispersed wick has higher thermal performance than the monoporous wick. A bidispersed wick prevents the overheating of the casing which is the most encountered limit in LHP application. The liquid-vapour phase distribution, as well as the vapour saturation and the vapour mass flow rate are investigated to explain these behaviours.

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“…Li and Peterson (2011) developed three-dimensional models for a square flat wick, which has a liquid reservoir at the top and a heating substrate at the bottom. Chernysheva and Maydanik (2012) as well as Zhang et al (2012) presented 3D models for capillary porous wicks with longitudinal replenishment. In these studies, the liquid flow is assumed to be perpendicular to the heat flux at the wick wall, whereas in Li and Peterson (2011) the fluid and energy flows are counter current.…”

Section: Introductionmentioning

confidence: 99%

Pore Network Simulations of Heat and Mass Transfer inside an Unsaturated Capillary Porous Wick in the Dry-out Regime

Kharaghani

Kirsch

et al. 2016

Transp Porous Med

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In this work, a two-dimensional pore network model is developed to study the heat and mass transfer inside a capillary porous wick with opposite replenishment in the dry-out regime. The mass flow rate in each throat of the pore network is computed according to the Hagen-Poiseuille law, and the heat flux is calculated based on Fourier's law with an effective local thermal conductivity. By coupling the heat and the mass transfer, a numerical method is devised to determine the evolution of the liquid-vapor interface. The model is verified by comparing the effective heat transfer coefficient versus heat load with experimental observations. For increasing heat load, an inflation/deflation of the vapor pocket is observed. The influences of microstructural properties on the vapor pocket pattern and on the effective heat transfer coefficient are discussed: A porous wick with a non-uniform or bimodal pore size distribution results in a larger heat transfer coefficient compared to a porous wick with a uniform pore size distribution. The heat and mass transfer efficiency of a porous wick comprised of two connected regions of small and large pores is also examined. The simulation results indicate that the introduction of a coarse layer with a suitable thickness strongly enhances the heat transfer coefficient. Area fraction of the vapor region H evp Evaporation latent heat (J/kg) L Throat length (m) M Mass flow rate (kg/s) n Outward unit normal vector p Pressure (Pa) Q Heat rate (W) q Heat load (W/m 2 ) r Throat radius (m) r 0 Mean throat radius (m) T Temperature ( • C) v Superficial velocity (m/s) v 0 Interstitial velocity (m/s) W Network thickness (m) Greek symbols α Heat transfer coefficient (W/m 2 K) ε Porosity ξ Parameter used in the stopping criterion of the algorithm (Sect. 3.5) λ Thermal conductivity (W/m K) μ Dynamic viscosity (Pa s) σ Surface tension (N/m) σ 0 Throat radius standard deviation (m) υ Kinematic viscosity (m 2 /s) ρ Liquid mass density (kg/m 3 )

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Three-dimensional simulation on heat transfer in the flat evaporator of miniature loop heat pipe

Cited by 32 publications

References 18 publications

Three dimensional liquid and vapour distribution in the wick of capillary evaporators

Three dimensional liquid and vapour distribution in the wick of capillary evaporators

Numerical simulation of heat and mass transfer in bidispersed capillary structures: Application to the evaporator of a loop heat pipe

Pore Network Simulations of Heat and Mass Transfer inside an Unsaturated Capillary Porous Wick in the Dry-out Regime

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