Numerical study of heat-sink shape effect on heat transfer in the system containing paraffin


Аuthors

Bondareva N. S.*, Sheremet M. A.*

Tomsk State University, 36 Lenin Ave., Tomsk, Tomsk region, 634050, Russia

*e-mail: bondarevans@mail.tsu.ru

Abstract

To date, the relevance of heat and mass transfer problems in materials with phase transitions is closely connected with such materials application in temperature control and energy storage systems. High performance electronic devices requires developing cooling systems with high heat dissipation capacity. Heat sinks submerged partially or fully in paraffin are employed in modern electronic equipment to sustain operating temperatures. Paraffin possesses high latent melting energy and phase transition temperatures close to microprocessors operating temperature. Heat transfer process while melting is accompanied by natural convection flows in liquid melt and aggravated by interaction of circulatory flows with moving boundary and complex shape of a ribbed profile. It is rather difficult to experimentally evaluate the buoyant force contribution and monitor movement of the interphase boundary, while numerical modeling allows obtain more detailed pattern of thermal processes occurring in the system. The article presents the results of 2D numerical study of a heat removal system based on the energy of phase transformations, reinforced by a copper heat sink with rectangular ribbed profile. Mathematical model of the non-stationary heat and mass transfer process was formulated in the transformed variables “stream function – vorticity – temperature”. The latent heat is accounted for in the energy equation by introducing a smoothing function φ. This approach allowed solves one energy equation in the entire area without highlighting the interphase boundary. The obtained differential equations were solved by the finite difference method. The computation results allowed obtain and analyze thermo-hydrodynamic characteristics of the studied process at various melting phases depending on ribs location periodicity. Thermal patterns at various time instants, reflecting the movement of the phase boundary, formation and growth of ascending and descending heat fluxes, were obtained. The average Nusselt number variation on the profile surface depending on the ribs number, as well as the effect of the main factors, such as the flow intensity and melting rate, on heat-transfer coefficient were analyzed. Evaluation of ribs location effect on the temperature plumes forming was performed. It was demonstrated that natural convection and its interaction with the heat sink plays significant role in the melting process and effects significantly the heat removal intensity.

Keywords:

melting, natural convection, heat sink, paraffin

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