In attempts to improve thermal management in modern electronics and other heat-generating systems, the use of nanofluids in minichannel heat sinks has emerged as a potential option. These nanofluids outperform typical cooling fluids in terms of heat transmission due to the unique features of nanoparticles dispersed inside a fluid. Minichannel heat sinks expand this potential by providing improved heat dissipation capabilities in small geometries.

In this simulation, we investigate the complexities of modeling Two-phase Nanofluid in Minichannel Heat Sink by means of ANSYS Fluent with the objective of validating an experimental paper. This paper is entitled “An experimental investigation of heat transfer enhancement of a minichannel heat sink using Al2O3–H2O nanofluid [1]”.

• Reference [1]: Sohel, M. R., et al. “An experimental investigation of heat transfer enhancement of a minichannel heat sink using Al2O3–H2O nanofluid.” International Journal of Heat and Mass Transfer74 (2014): 164-172.

Figure 1: Thermal resistance data in Two-phase Nanofluid in Minichannel Heat Sink – validation study

Simulation Process

The minichannel benefits from a symmetrical design, allowing us to model a section of it while considering symmetric boundaries. Table 2 in the reference paper represents some of the geometrical specifications. After designing the model using Design Modeler, a structured grid is vital to divide computational zones into cells. Further, the al2o3 nanoparticles are dispersed in water, making a nanofluid. This is put into work by using Mixture multiphase model. More importantly, the thermophysical properties such as density and specific heat are not constant. Thus, a user-defined function (UDF) is written to consider governing relations.

Figure 2: Schematic of the mini channel heatsink [1]

Post-Processing

Our CFD simulation lines up nicely with the experimental data, especially at Reynolds number 700 where the validation accuracy peaks. The graph clearly shows how thermal resistance drops as Reynolds number increases – simply put, faster-flowing nanofluids cool things better. You can also see that adding more nanoparticles to the water consistently improves cooling performance. When we bumped up the volume concentration from 0.1% to 0.3%, thermal resistance dropped by around 15% across all flow rates. The close match between our simulation line and the experimental dots confirms our mixture multiphase model correctly captures the real-world physics.

Figure 3: Validation of thermal resistance in Two-phase Nanofluid Mini channel Heat Sink

The velocity rendering reveals how the Al2O3-H2O nanofluid moves through the mini channel. Peak velocity hits 1.309 m/s at the channel center, creating the classic parabolic profile you’d expect in laminar flow. Near the walls, velocity drops to almost zero due to the no-slip condition. This flow pattern explains why our model achieved that remarkably low thermal resistance of 0.011698232 K/W. The temperature barely rises (just 0.2K) between inlet and outlet despite significant heat absorption, proving the heat transfer enhancement capabilities of nanofluids in compact geometries. These validated results show why engineers are increasingly turning to nanofluids for cooling next-gen electronics.

Figure 4: Velocity rendering inside the fluid domain of nanofluid CFD simulation using Mixture multiphase model