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• Thermal behavior of rectangular fins located within a square cavity were analyzed. • Inverse CFD method and experimental data were adopted for heat transfer prediction. • Suitable turbulence model based on the RMSE of the flow model were selected. • Effect of fin geometry on the flow and heat transfer within a cavity was evaluated. • Effect of PCM heat sink on the flow and heat transfer within a cavity was studied. This study examines the fluid flow and heat transfer characteristics of rectangular fins positioned within a square cavity through the use of the inverse three-dimensional computational fluid dynamics (CFD) method, experimental analysis, and the constant heat transfer rate assumption. This paper proposes a heat sink that uses a phase change material (PCM) made of paraffin within a small cavity. The inverse CFD method, combined with the least squares method, root mean square error, and excessive experimental data, is adopted to predict the unknown heat transfer rate Q and absorption heat Q ab. One of the objectives of this study is to investigate the effect of the PCM heat sink on fluid flow and heat transfer characteristics within a cavity. A sequence of tests on various flow models indicates that employing the RNG k-ε turbulence model with the standard wall function is the most suitable choice for all scenarios in the three-fin model. Conversely, the zero-equation model proved to be a more adequate fit for the PCM heat sink. Another objective of this study is to study the effect of the height of the PCM heat sink on Q and Q ab. The incorporation of a PCM heat sink results in a further improvement in the efficiency of heat dissipation. Part of the heat created is absorbed by the PCM heat sink, which absorbs 22.5 % of the thermal energy. Under the same volume, the PCM heat sink with a lower height (H p = 0.012 m) absorbs 14 % more heat compared to H p = 0.02 m. Thus, a lower-height PCM heat sink has a better heat dissipation effect. [ABSTRACT FROM AUTHOR]

Highlights • Transient characteristics of nanofluid in a minichannel heat sink with MEPCM layer in its ceiling are studied. • The wall temperature rises sharply after sudden heat-pulse and then tend to rise slowly. • The dispersion of nanoparticles inside water leads to the clear decrement of wall and temperature. Abstract In this work, transient thermal characteristics of pure water or Al 2 O 3 /water nanofluid with 2–8 wt% concentrations as coolant flowing through a minichannel heat sink with MEPCM layer in its ceiling are experimentally investigated. The heat sink consists of eight minichannels with length, height, and width of 50 mm, 3 mm, and 1 mm for each minichannel, respectively. A uniform heat flux in the range of 1.2–6.8 W/cm2 is imposed to heat the heat sink and a heat pulse amplitude of 8 W/cm2 is suddenly applied for 10 min after steady-state heating condition and then the heating power is cut off immediately. The dimensionless wall temperature distribution, temperature of MEPCM layer, maximum wall temperature suppression, and heat transfer effectiveness of the system are assessed under sudden heat-pulse conditions. The measured results reveal that the wall temperature and MEPCM layer temperature rise sharply after sudden heat-pulse and then tend to rise slowly. Moreover, it is observed that the latent heat absorbed by the MEPCM layer during melting process can reduce the severe temperature variation caused by sudden heat-pulse. Furthermore, it is concluded that the dispersion of alumina nanoparticles inside pure water and the increase of its concentration lead to the significant decrement of wall temperature and MEPCM layer temperature and increment of the maximum wall temperature suppression. Finally, the comparison of the results obtained from the employment of nanofluid and pure water in the heat sink shows that the nanofluid-cooled heat sink with MEPCM layer in its ceiling outperforms the water-cooled one with/without MEPCM layer. [ABSTRACT FROM AUTHOR]