Numerical Simulation and Application of a Channel Heat Sink with Diamond Ribs

At a Glance

Metadata	Details
Publication Date	2023-10-20
Journal	Water
Authors	Dongxu Zhang, Guoqiang Liu, Yongkang Lai, Xiaohui Lin, Weihuang Cai
Institutions	Shanghai University, Xiamen University of Technology
Citations	3
Analysis	Full AI Review Included

Executive Summary

This study presents the numerical simulation and experimental validation of a microchannel heat sink (MCHS) featuring diamond-shaped ribs, optimized for high heat flux applications, specifically in Polymerase Chain Reaction (PCR) devices.

Core Achievement: The diamond-ribbed MCHS significantly enhances heat transfer performance (Nu/Nu₀ up to 1.82) compared to smooth, straight channels, while maintaining an acceptable pressure drop penalty through geometric optimization.
Validation: A 3D numerical model using the Finite Volume Method was validated against experimental data, showing a maximum computational error of less than 5% for both pressure drop and base temperature.
Optimal Design (High Flow, Re > 507.5): Priority is given to a fin height ratio ($\beta$) of 25%, a rib angle ($\alpha$) of 135°, and a rib spacing (s) of 2.5 mm.
Flow Resistance Management: Extreme rib angles (e.g., $\alpha$ = 90°) must be avoided, as they increase flow resistance (f/f₀) by over 13 times, severely penalizing the overall heat-transfer enhancement factor ($\eta_f$).
PCR Application Success: The optimized heat sink successfully met the stringent thermal requirements for TEC cooling in PCR devices, achieving rapid cyclical temperature control (heating/cooling rates of ~7.9 K/s) necessary for DNA amplification.

Technical Specifications

Parameter	Value	Unit	Context
Heat Sink Material	Copper	N/A	Thermal conductivity: 401 W/mK
Coolant Fluid	Liquid Water	N/A	Inlet temperature: 299.15 K
Total Heat Load (Q)	120	W	Applied by ceramic heat source
Total Heat Sink Dimensions	54 x 54	mm	Length x Width
Channel Dimensions	42 x 2 x 3	mm	Length x Width (W) x Height (H)
Optimal Rib Angle ($\alpha$)	135 or 150	°	Recommended to keep friction factor ratio (f/f₀) < 3
Optimal Height Ratio ($\beta$)	25	%	Preferred for Re > 507.5
Optimal Rib Spacing (s)	2.5	mm	Yields lowest f/f₀ and highest $\eta_f$
Maximum Nu/Nu₀	1.82	N/A	Achieved at $\alpha$ = 90°, Re = 315.32
Maximum f/f₀ Penalty	13.25	N/A	Occurs at $\alpha$ = 90°, Re = 630.64
PCR Temperature Range	328.15 ± 3 to 368.15 ± 3	K	Required cyclical temperature
Experimental Flow Rate	100	mL·min^-1	Corresponds to Re = 525.53 in PCR test
Experimental Heating Rate	7.9	K/s	Achieved during PCR test
Experimental Cooling Rate	7.8	K/s	Achieved during PCR test

Key Methodologies

The study utilized a combination of 3D numerical simulation and experimental validation to characterize the thermal and hydraulic performance of the heat sink.

Numerical Modeling (CFD):
- Method: Three-dimensional numerical simulation using the Finite Volume Method (FVM) was employed to solve steady-state continuity, momentum, and energy conservation equations.
- Solver: SIMPLE algorithm was used for pressure-velocity coupling, with second-order upwind schemes for momentum and energy.
- Meshing: Polyhedral mesh was generated using Fluent. Grid independence was verified by ensuring that deviations in average base temperature (T_w,ave) and pressure difference (AP) were less than 5% when the maximum element size was set to 0.002 m.
- Boundary Conditions: Mass flow inlet (constant temperature 299.15 K); Pressure outlet (atmospheric); Constant heat flux (120 W) applied to the bottom surface; Outer walls treated as adiabatic.
Experimental Setup and Validation:
- Apparatus: An experimental setup included a DC power source, a pump, a thermostatic water bath, a pressure transducer, and a data acquisition system connected to an integrated copper heat sink.
- Heat Source: A ceramic heating plate was used to simulate the 120 W heat load.
- Measurements: Inlet pressure (P1) and outlet pressure (P2) were measured to determine the overall pressure differential (AP). An embedded thermocouple measured the central base surface temperature (T_w).
- Validation: Simulation results for AP and T_w were compared against experimental data across a Reynolds number range corresponding to flow rates from 100 to 300 mL·min^-1. The maximum error was confirmed to be less than 5%.
Geometric Parameter Study:
- The validated model was used to systematically investigate the influence of three key geometric parameters on performance metrics (R_t, Nu/Nu₀, f/f₀, $\eta_f$):
  - Rib Angle ($\alpha$): Varied from 90° to 150°.
  - Height Ratio ($\beta = h/H$): Varied from 25% to 100%.
  - Rib Spacing (s): Varied from 1.0 mm to 2.5 mm.

Commercial Applications

The optimized channel heat sink design is highly relevant for applications requiring high heat flux removal and precise thermal control in compact systems.

Biomedical and Diagnostic Devices:
- PCR Thermal Cyclers: Direct application for cooling the Thermoelectric Cooler (TEC) working face, enabling the rapid, stable, cyclical temperature changes required for DNA amplification.
High-Performance Computing (HPC) and Electronics:
- VLSI and Integrated Circuits: Cooling high-density electronic components where thermal flux density is high, preventing hot spot formation and ensuring component reliability.
- Data Centers: Use in compact liquid cooling loops for servers and processors.
Power and Energy Systems:
- High-Power LEDs: Thermal management for high-power light-emitting diode (LED) modules, reducing substrate temperature and enhancing efficiency.
- Battery Thermal Management: Integration into cooling systems for large prismatic lithium-ion batteries to maintain temperature uniformity and prevent thermal runaway.
- Concentrated Photovoltaics (CPV): Cooling solar cells to maintain high electrical efficiency under concentrated sunlight.

View Original Abstract

This paper presents a channel radiator with ribbed ribs and primarily investigates the fluid flow and heat-transfer characteristics of the channel radiator. A three-dimensional numerical simulation of the radiator’s pressure-drop and heat-transfer process was conducted using the finite volume method. A comparison between the experimental data and the simulation results demonstrates that the simulation in this paper is accurate, with a maximum error not exceeding 5%. Furthermore, the radiator was further subjected to geometric parameter studies, principally including the height ratio between the fins and the channel, the fin angle, and the spacing between the fins. The thermal resistance, Nusselt number, friction factor, and heat-transfer enhancement factor were calculated. The results indicate that if the geometric parameters are selected appropriately, the heat sink will enhance heat-transfer performance within an acceptable pressure drop. When the Reynolds number is greater than 507.5, the height ratio of 25%, the rib angle of 135°, and the rib spacing of 2.5 mm can be given priority. This heat sink is used in PCR devices, and experimental results show that the novel channel heat sink can meet the heat dissipation requirements of the TEC during the PCR process.

Tech Support

Original Source

DOI: https://doi.org/10.3390/w15203677

References

2014 - Numerical study of thermal enhancement in micro channel heat sink with secondary flow [Crossref]
2018 - Optimization of thermal design of heat sinks: A review [Crossref]
2020 - Structural optimization and heat transfer performance analysis of a cone-column combined heat sink [Crossref]
2019 - A conjugate heat transfer analysis of performance for rectangular microchannel with trapezoidal cavities and ribs [Crossref]
2018 - A comprehensive study on heat transfer enhancement in microchannel heat sink with secondary channel [Crossref]
1981 - High-performance heat sinking for VLSI [Crossref]
2021 - Effect of liquid cooling on PCR performance with the parametric study of cross-section shapes of microchannels [Crossref]
2019 - The performance management of a Li-ion battery by using tree-like mini-channel heat sinks: Experimental and numerical optimization [Crossref]
2016 - Thermal management for high power lithium-ion battery by minichannel aluminum tubes [Crossref]
2016 - Performance enhancement of concentrated photovoltaic systems using a microchannel heat sink with nanofluids [Crossref]