ABSTRACT
The work presented in this dissertation is devoted to the
numerical study of the heat transfer during melting of a phase change material
(PCM) within a rectangular enclosure heated by protruding heat sources. This
enclosure plays the role of the heat sink for the cooling management of
electronic components simulated by protruding substrate-mounted heat sources.
The advantage of this cooling strategy is that PCMs, which characterized by
high energy storage density and small transition temperature interval, are able
to store a high amount of generated heat; which provides a passive cooling of
electronic components. The proposed strategy is suitable and efficient for
situations where the cooling by air convection is not possible (thermal control
of electronic devices for spatial and metallurgy applications, for example). In
order to numerically study the thermal and flow fields and explore the thermal
behaviour and the cooling efficiency of the proposed PCM based heat sink during
the melting process, a 2D mathematical model based on the mass, momentum and
energy conservation equations was developed. The control parameters are next
identified, and the equations are discretized using the volume control
approach. The energy equation for the PCM is solved using the enthalpy method.
The model has been checked and then validated comparing the numerical results
with available experimental results. Numerical investigations have been
conducted in order to examine the impact of various control parameters on the
thermal behaviour and efficiency of the proposed PCM-based heat sink.
Correlations encompassing a wide range of parameters were developed for the
non-dimensional secured operating time (non-dimensional time required by the
heat sink before reaching the critical temperature, Tcr) and the
corresponding liquid fraction using the asymptotic computational fluid dynamics
(ACFD) technique. Abacuses were also provided for practical use.
Keywords: Phase change material; melting;
solidification; enthalpy method; latent heat storage latent; cooling of
electronic components.
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