Abstract
This paper deals with the numerical simulation of heat transfer and entropy generation in a 2D square enclosure for convective melting. A thermal lattice Boltzmann method (TLBM) is used to handle the study, which has been conducted for Prandtl numbers from 0.02 to 70 at Rayleigh numbers of 104 and 105. The results are presented in terms of the total entropy generation, average Bejan number and average Nusselt number. Within the range considered for the key parameters, the entropy generation is found to be controlled by the heat transfer loss for low Prandtl numbers. However, for the large Prandtl numbers, its variation is dominated by shearing losses. Moreover, the presence of the latent heat state decreases the overall thermodynamic losses while increasing the quantity of heat transferred.
Highlights
Convective flows have been widely investigated for various applications in engineering, such as heat exchangers, drying processes, solar collectors, nanofluids, etc
It is useful to recall that the numerical prediction of heat transfer and entropy generation in a 2D
For small Pr ( < 1 ), the thermal boundary layer becomes very thin, indicating that the heat transfer irreversibility ( Sl,h ) is dominative in the vicinity of boundaries, the inner part of the simulation domain is dominated by the fluid friction irreversibility
Summary
Convective flows have been widely investigated for various applications in engineering, such as heat exchangers, drying processes, solar collectors, nanofluids, etc. Thermal gradients, shearing, phase changes, chemical reactions, etc., are irreversible processes that are frequently encountered in thermodynamic systems. They are generally provoked by losses emanating from two main causes: the transmission of heat through a limited temperature difference and the pressure drop caused by friction [5]. Design criteria and optimum efficiency for thermodynamic systems can be obtained by analyzing the entropy production. Up to date, studies involving entropy generation during phase changes remain sparse. All of this motivates this paper to perform the current research. Concerning entropy generation in natural convection, one can quote the works of Magherbi et al [7], Abu-Hijleh et al [8], Mahmud and Island [9] and Ellahi et al [10], among others
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