Optimizing Heat Transfer in Microchannel Heat Sinks: A Numerical Investigation with Nanofluids and Modified Geometries

The utilization of microchannel heat sinks stands as one of the most reliable solutions for dissipating heat generated in electronic chips. In this numerical study, a fractal microchannel heat sink employing three nanofluids Cu-water, Al2O3-water, and TiO2-water with variable volume fractions of 2 and 4 percent as the cooling fluid within the microchannels was investigated. The fluid flow inside the microchannels was analyzed from both hydrodynamic and thermal perspectives. The parameters such as pump power, Nusselt number, and performance evaluation criterion (PEC) were studied. Results demonstrate that heat transfer increases with an increase in the flow rate and volume fraction of nanoparticles. The maximum temperature reduction for the Cu-water nanofluid at an inlet flow rate of 200 ml/min and a volume fraction of 4% is 2.41%, the highest among the investigated nanofluids. However, this nanofluid also exhibits the highest pressure drop, reaching 25% at a 4% volume fraction. The PEC number analysis reveals an overall performance increase for all three microchannels. The Cu-water nanofluid exhibits the best comprehensive performance, providing an 8% overall enhancement, followed by Al2O3-water and TiO2-water nanofluids, which increase the system performance by 5% and 4%, respectively. Furthermore, the study introduced fins and cavities to the microchannel branches to enhance heat transfer and overall performance. Results indicate an increase in heat transfer for both modified geometries. The microchannel with fins exhibits a 3.5% lower maximum temperature compared to the original geometry at an inlet flow rate of 200 ml/min, while the microchannel with cavities showed a 1% reduction. However, the microchannel with fins experiences a 400% higher pressure drop than the initial geometry, while the microchannel with cavities has a 4% increase. PEC number analysis demonstrated that the microchannel with cavities improves system performance by 8%, whereas the microchannel with fins reduced system performance by 4%.