Objective

2

With the rapid increase in the integration level of microsystems， electronic components are continuously developing toward miniaturization， integration and high power， which renders high heat flux density heat dissipation a critical bottleneck restricting the development of high-end electronic devices. Piezoelectric micropumps are regarded as an ideal candidate for lightweight and thin heat dissipation systems owing to their high integration， high power-to-weight ratio and excellent controllability. In this paper， a microchannel heat sink with fence pin-fin walls driven by a piezoelectric pump is proposed. To evaluate the fluid flow and heat dissipation within the heat sink， a three-dimensional numerical modeling was performed， followed by experimental validations. The heat transfer enhancement mechanism of fence pin-fin walls is revealed， and the effects of fin spacing， area fraction and layout region of fence pin-fin walls on the thermal performance of the heat sink are analyzed.

Methods

2

In this study， numerical simulations of the microchannel heat sink are performed using Fluent software， where a no-slip coupled boundary condition is applied to the fluid-solid interface， mixed boundary conditions are assigned to the top and bottom surfaces of the heat sink， and no-slip adiabatic boundary conditions are adopted for the remaining walls. Grid independence verification is conducted， and the total number of meshes is determined to be approximately 7.56 million. With the Reynolds number of the working fluid ranging from 35～40， the laminar model is adopted for numerical calculation， and the convergence residual criterion is set to 10⁻⁸. Furthermore， experimental tests are implemented to validate the accuracy and reliability of the established numerical model.

Results and Discussions

2

Numerical results reveal the heat transfer enhancement mechanism of the fence pin-fin walls structure， and clarify the effects of fence pin-fin walls spacing， area fraction and layout region on the thermal performance of microchannel heat sinks. Compared with conventional microchannels with smooth continuous wall， the fence pin-fin walls heat sink with a fin spacing of 0.2 mm reduces pressure drop by 18.87 Pa and increases flow rate by 1.03 mL/h. Such improvements decrease the thermal resistance

R

by 4.31% and raise the

TPF

（Thermal performance factor） by 6.45%， indicating that the proposed structure synergistically strengthens flow disturbance and enlarges the heat transfer area. When the fin spacing increases to 1.0 mm， the average Nusselt number

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3.72533321

2.79399991

and

TPF

increase by 13.66% and 13.95%， respectively， while

R

decreases by 1.01%， compared with the 0.2 mm spacing case. Although the convective heat transfer area declines by 3.03% due to the reduced fin number， the average heat transfer coefficient

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1.60866666

2.70933342

increases by 13.66%， effectively improving the overall thermal performance. The enhanced convective capacity fully compensates for the performance loss caused by the reduced heat transfer area. At a fixed fin spacing of 0.6 mm， increasing the fence pin-fin walls area fraction from 4.19% to 18.15% reduces thermal resistance stepwise and improves

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3.72533321

2.79399991

and

TPF

. Furthermore， the fence pin-fin walls arranged in the heat source coverage region （

e

1

～

e

3

） play a dominate role in heat transfer enhancement and thermal resistance reduction， whereas extending this structure to the non-heat source region （

e

4

～

e

6

） yields lower enhancement benefits.

Conclusions

2

Simulation results indicate that the microchannel heat sink with fence pin-fin walls achieves superior overall thermal performance compared with the smooth continuous wall microchannel heat sink. Appropriately enlarging pin-fin spacing strengthens the convective heat transfer inside channels， and such performance gain can offset the adverse effect arising from the reduction of heat transfer area. Within limited space， the fence pin-fin walls should be preferentially arranged in the core heat source region to fully utilize their advantages in reducing thermal resistance. According to the conclusions of this work， fence pin-fin walls with specific spacing are recommended to replace traditional smooth continuous walls in piezoelectric micropump-driven microchannels under low Reynolds number conditions. Deploying fence pin-fin walls structures preferentially in the heat source coverage region can yield better overall heat transfer performance.