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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]

This research study investigated the cooling performance of a minichannel heat sink that employed suspensions of microencapsulated phase change material (MEPCM) particles as the working fluid. The heat sink made from copper consisted of 10 rectangular minichannels, with a length of 50 mm, depth of 1.5 mm and a width of 1 mm. A uniform heat flux was used for heating the mini channel heat sink and the Reynolds numbers were in the range of 133–1515. The concentration of the MEPCM particles scattered in the water varied from 0 to 10 wt%. The experimental data showed that the wall temperature highly relied upon the Reynolds number and the increment of Reynolds number lead to the reduction of wall temperature for the coolant with or without MEPCM suspension in the minichannel heat sink. Moreover, the wall temperature got reduced for a coolant with MEPCM, compared to that without MEPCM especially at lower Reynolds numbers. Interestingly, the measured results revealed that the coolant with MEPCM particles was effective in cost performance than the pure coolant. The best cooling performance compared to that of pure water was observed for 2% MEPCM concentration within the considered range of flow rates. [ABSTRACT FROM AUTHOR]