Single Phase Microchannel Heat Sink Research Articles

Extremely high heat flux dissipation and hotspots removal with nature-inspired single-phase microchannel heat sink designs

A novel pyramid thermal dissipation unity with conduction–convection coupling thermal dissipation and nature-inspired hotspot removal channel heat sinks is proposed to degrade and dissipate ultra-high heat flux with the order of 103 W cm−2 by using single-phase coolant. A 3D conjugate thermal and flow numerical model is used to validate the feasibility of the proposed ultra-high heat flux dissipation method. The pyramid thermal dissipation unit consists of a spiral tube embedded with etched lotus leaf vein or snowflake-shaped channels. This configuration enables the dissipation of heat fluxes ranging from 1000 to 1500 W cm−2 while maintaining safe operating temperatures for the chip using a single-phase coolant. By utilizing high thermal conductivity materials, the proposed dissipation unit achieves chip working temperatures of 89.89 °C for 1500 W cm−2 and 66.58 °C for 1000 W cm−2. Furthermore, the new design allows for a reduction in the minimum required thermal conductivity for materials to 700 W m−1 K−1 at a pump power of 7.05 W, while still operating within the chip's safe temperature limit of ≤ 120 °C. This expanded range of thermal conductivity values provides more options for selecting suitable materials to fabricate the dissipation unit.

Investigation of the Temperature Fluctuation of Single-Phase Fluid Based Microchannel Heat Sink.

The temperature fluctuation in a single-phase microchannel heat sink (MCHS) is investigated using the integrated temperature sensors with deionized water as the coolant. Results show that the temperature fluctuation in single phase is not negligible. The causes of the temperature fluctuation are revealed based on both simulation and experiment. It is found that the inlet temperature fluctuation and the gas bubbles separated out from coolant are the main causes. The effect of the inlet temperature fluctuation is global, where the temperatures at different locations change simultaneously. Meanwhile, the gas bubble effect is localized where the temperature changes at different locations are not synchronized. In addition, the relation between temperature fluctuation and temperature gradient is established. The temperature fluctuation increases with the temperature gradient accordingly.

A 3D numerical study of heat transfer in a single-phase micro-channel heat sink using graphene, aluminum and silicon as substrates

The study describes numerical simulations conducted on micro-channel heat sinks. Three different shapes related to the micro-channel depth and width is chosen for examination. Silicon, aluminum, and graphene are used as substrate materials for this study. The overall heat sink consisted of an array of rectangular micro-channels. Three different surface heat fluxes and three different volumetric flow rates are used for three cases. Water with non-temperature-dependent thermal properties is used as a coolant for steady-state, fully developed laminar flow in the micro-channels. From a heat transfer (thermal performance) perspective, it is found that graphene most effectively reduce the thermal resistance. Based on these results, graphene was further studied as a substrate material for a micro-channel heat sink.

Hotspot Mitigating With Obliquely Finned Microchannel Heat Sink—An Experimental Study

Sectional oblique fins are employed, in contrast to continuous fins, in order to modulate the flow in a microchannel heat sink. The breakage of continuous fin into oblique sections leads to reinitialization of boundary layers and generation of secondary flows that significantly enhance the cooling performance of the heat sink. In addition, an oblique finned microchannel heat sink has the flexibility to tailor local heat transfer performance by varying its oblique fin pitch. Clusters of oblique fins at higher density can be created in order to promote a greater degree of boundary layer redevelopment and secondary flow generation to provide more effective cooling at the high heat-flux region. Thus, the variation of oblique fin pitch can be exploited for hotspot mitigation. Experimental studies of a silicon chip with two hotspot scenarios show that the temperature hike and the temperature difference for the enhanced microchannel heat sink with variable pitch are reduced by as much as 17.1 °C and 15.4 °C, respectively. As a result, temperature distribution across the silicon chip is more uniform. In addition, the associated pressure drop penalty is much smaller than the achieved heat transfer enhancement, rendering it as an effective hotspot mitigating strategy for the single-phase microchannel heat sink.

Numerical Study of Fluid Flow and Heat Transfer in the Enhanced Microchannel With Oblique Fins

Sectional oblique fins are employed in contrast to continuous fins in order to modulate flow in microchannel heat sink. The breakage of continuous fin into oblique sections leads to the reinitialization of both hydrodynamic and thermal boundary layers at the leading edge of each oblique fin, effectively reducing the thickness of boundary layer. This regeneration of entrance effect causes the flow to be always in a developing state thus resulting in better heat transfer. In addition, the presence of smaller oblique channels diverts a small fraction of flow into the adjacent main channels. The secondary flows thus created improve fluid mixing which serves to further enhance the heat transfer. Detailed numerical study on the fluid flow and heat transfer of this passive heat transfer enhancement technique provides insight to the local hydrodynamics and thermal development along the oblique fin. The uniquely skewed hydrodynamic and thermal profiles are identified as the key to the highly augmented and uniform heat transfer performance across the heat sink. The associated pressure drop penalty is much smaller than the achieved heat transfer enhancement, rendering it as an effective heat transfer enhancement scheme for single phase microchannel heat sink.

Enhanced Thermal Transport in Microchannel Using Oblique Fins

Sectional oblique fins are employed, in contrast to continuous fins in order to modulate the flow in microchannel heat sinks. The breakage of a continuous fin into oblique sections leads to the reinitialization of the thermal boundary layer at the leading edge of each oblique fin, effectively reducing the boundary layer thickness. This regeneration of entrance effects causes the flow to always be in a developing state, thus resulting in better heat transfer. In addition, the presence of smaller oblique channels diverts a small fraction of the flow into adjacent main channels. The secondary flows created improve fluid mixing, which serves to further enhance heat transfer. Both numerical simulations and experimental investigations of copper-based oblique finned microchannel heat sinks demonstrated that a highly augmented and uniform heat transfer performance, relative to the conventional microchannel, is achievable with such a passive technique. The average Nusselt number, Nuave, for the copper microchannel heat sink which uses water as the working fluid can increase as much as 103%, from 11.3 to 22.9. Besides, the augmented convective heat transfer leads to a reduction in maximum temperature rise by 12.6 °C. The associated pressure drop penalty is much smaller than the achieved heat transfer enhancement, rendering it as an effective heat transfer enhancement scheme for a single-phase microchannel heat sink.

Numerical Investigation of Heat Transfer Enhancement in a Microchannel With Grooved Surfaces

This paper presents a numerical investigation for two types of grooves (rectangular and arc shapes) fabricated in the microchannel surfaces, which leads to enhancement in single-phase cooling. The pressure drop and heat transfer characteristics of the single-phase microchannel heat sink were investigated numerically for laminar flow. For this purpose, the conjugate heat transfer problem involving simultaneous determination of temperature fields in both solid and liquid regions was solved numerically. The numerical model was validated with comparison to experimental data, in which good agreement was seen. A simple microchannel with available experimental data was selected, and it was shown that using grooved surfaces on this microchannel has a noticeable effect and heat removal rate can be increased using this technique. The results depict that the arc grooves have a higher heat removal flux compared with rectangular grooves but the latter have a higher coefficient of performance for the case in which grooves are made in the floor and both side walls. Also, it was shown that a grooved microchannel with higher wall thickness and lower mass flow rate of cooling water has a higher heat removal flux and coefficient of performance compared with a simple microchannel with minimum wall thickness. Effect of various sizes and distances of the floor grooves was determined, and the cases for maximum heat removal rate and coefficient of performance for both rectangular and arc grooves were obtained.

Evaluation of Heat Transfer Augmentation in a Nanofluid-Cooled Microchannel Heat Sink

Present investigation deals with appraising heat transfer enhancement of single phase microchannel heat sink (MCHS) by ultra fine Cu particle incorporation in base coolant fluid. The particle diameter is of nanometer size and base fluid in combination of nanoparticles is called nanofluid. Governing equations for fluid flow and heat transfer are based on well established “porous medium model” and accordingly, modified Darcy equation and two-equation model are employed. Appropriate equations for both fluid flow and heat transfer are derived and cast into dimensionless form. Velocity profile is obtained analytically and in order to solve conjugate heat transfer problem a combined analytical–numerical approach is employed. For heat transfer analysis, thermal dispersion model is adopted and latest proposed model for effective thermal conductivity – which considers the salient effect of interfacial shells between particles and base fluid – is integrated into model. The effects of dispersed particles concentration, thermal dispersion coefficient and Reynolds number are investigated on thermal fields and on thermal performance of MCHS. Additionally, the impact of turbulent heat transfer on heat transfer enhancement is considered.

Experimental and numerical study of pressure drop and heat transfer in a single-phase micro-channel heat sink

The pressure drop and heat transfer characteristics of a single-phase micro-channel heat sink were investigated both experimentally and numerically. The heat sink was fabricated from oxygen-free copper and fitted with a polycarbonate plastic cover plate. The heat sink consisted of an array of rectangular micro-channels 231 μm wide and 713 μm deep. Deionized water was employed as the cooling liquid and two heat flux levels, q″ eff =100 W/cm 2 and q″ eff =200 W/cm 2 , defined relative to the planform area of the heat sink, were tested. The Reynolds number ranged from 139 to 1672 for q″ eff =100 W /cm 2 , and 385 to 1289 for q″ eff =200 W /cm 2 . The three-dimensional heat transfer characteristics of the heat sink were analyzed numerically by solving the conjugate heat transfer problem involving simultaneous determination of the temperature field in both the solid and liquid regions. Also presented and discussed is a detailed description of the local and average heat transfer characteristics of the heat sink. The measured pressure drop and temperature distributions show good agreement with the corresponding numerical predictions. These findings demonstrate that the conventional Navier–Stokes and energy equations can adequately predict the fluid flow and heat transfer characteristics of micro-channel heat sinks.