Thermo-hydraulic analysis of MPCM/green graphene based nanofluids in a minichannel heat sink with comma-shaped pin fins

Abstract

In the present work, the efficacy of placing comma-shaped pin fins in a minichannel heat sink is studied. The effect of different geometrical factors as well as fluid additives are evaluated. Pin fins’ distance and aspect ratio at five levels were introduced as a geometrical parameter. Moreover, three fluid additives including nanofluid based water, Micro-encapsulated PCM (MPCM) Slurry and MPCM Slurry with nanofluid at different concentrations were added to the base fluid. Water as a base fluid at 300 K and at five different Reynolds number enters the channel. Eight sets of comma-shaped pin fins are attached to the constant heat flux (100 kW/m²) surface of heat sink to enhance the heat transfer. In the numerical analysis, average temperature, Nusselt number, friction factor, and pressure drop are considered as output elements. The models presented in the current study is simulated using ANSYS Fluent software, which employs finite volume method. Results revealed that, as the pin fin distance increases, the average temperature decreases, and both the Nusselt number and the pressure drop rise. This is due to the specific shape of comma pin fins that intensifies the vortex formation along the channel as the fin distance increases. Furthermore, $\alpha$=0.8 is an optimum aspect ratio in which the Nusselt number is at the highest value that is about 7% higher than the other cases. It is also concluded that altering the fluid additive augments the heat trasnfer in fluid domain. Among different fluid structures, MPCM slurry has the highest Nusselt number at all Reynolds number while the pressure drop is high as well. Blending MPCM slurry with 15% concentration and nanofluid with 0.1% concentration offers lower average temperature up to 311 K compared to 335 K for pure water.

Keywords:

• Aspect ratio
• comma-shaped
• heat sink
• MPCM slurry
• nanofluids
• pin fin