Water-based nano-PCM emulsion flow and heat transfer in divergent mini-channel heat sink—An experimental investigation. (February 2020) - Ho, C.J.
Highlights: Water-based nano-PCM emulsion flow and heat transfer in divergent mini-channel heat sink is investigated. The mean heat transfer effectiveness is higher than unity for smaller values of the Reynolds number. The FOM is decreased about 23.13% by increasing the concentrations of PCM nanoparticles from 2% to 10% at Re = 305 and q h ″ = 4.79 W / c m 2 . The friction factor increases about 21.36% by increasing the concentrations of PCM nanoparticles from 2% to 10% at Re = 1000. Abstract: In this work, an experimental investigation is performed to study the water-based nano-PCM emulsion flow and heat transfer in the divergent mini-channel heat sinks (MCHSs). The divergent rectangular MCHS is selected in this study as it provides a higher heat transfer along with smaller value of pressure drop as compared with the parallel one. The water-based microencapsulated n -eicosane PCM suspension is considered as the coolant. Indeed, the particles of microencapsulated n -eicosane PCM are suspended in the water. The diameter of these particles is 130 nm. The divergent angle of 2.06° is used for fabricating the divergent mini-channels. The influences of various parameters such as the Reynolds number, the heat flux, and the concentration of nano-PCM particles on the thermal resistances, the figure of merit (FOM), the friction factor, coefficient of performance (COP), and the heat transfer effectiveness are investigated. The findings of this study indicate that the mean and maximum thermal resistances decrease about 0.5% and 4.92%, respectively by increasing the input heat flux from 40.38 W to 60.08 W at Re = 100 for the case of base fluid. The maximum FOM value is equal to 1.02 that can be achieved at ωPCM = 2%, Re = 305, and q h ″ = 4.79 W / c m 2 . Using the nano-PCM emulsion with a large concentration increases considerably the pressure drop penalty and provides a poor FOM index. The mean heat transfer effectiveness is higher than unity for smaller values of the Reynolds number. However, the mean heat transfer effectiveness diminishes for larger values of the Reynolds number.