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	Xiamen University of Technology, Shanghai University
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Rib Channel Heat Sinks

This document analyzes the research on channel heat sinks with diamond ribs, focusing on the thermal and hydraulic performance required for high-flux applications like Polymerase Chain Reaction (PCR) thermal management. It connects the paper’s findings to the superior material capabilities offered by 6CCVD’s MPCVD diamond products.

Executive Summary

Application Focus: The research successfully validates a novel microchannel heat sink (MCHS) design featuring rhombic (diamond) ribs for high-flux thermal management, specifically applied to cooling a Thermoelectric Cooler (TEC) in a PCR device.
Performance Enhancement: The introduction of diamond ribs significantly enhances heat transfer capability compared to smooth, straight channels, effectively reducing thermal resistance ($R_t$).
Optimal Geometry: 3D numerical simulation identified optimal geometric parameters for maximizing the heat-transfer enhancement factor ($\eta_f$) while minimizing pressure drop penalty.
Key Optimal Parameters (Re > 507.5): Rib angle ($\alpha$) of $135^{\circ}$ (or $150^{\circ}$), rib height ratio ($\beta$) of $25%$, and rib spacing ($s$) of $2.5 \text{ mm}$.
Thermal Cycling Achievement: The optimized heat sink design met the stringent thermal cycling requirements for PCR, achieving rapid heating and cooling rates (up to $7.9 \text{ K/s}$) necessary for efficient DNA amplification.
Material Upgrade Opportunity: While the study used copper, the high thermal flux density and rapid cycling requirements are ideally suited for an upgrade to 6CCVD’s Single Crystal Diamond (SCD) or Polycrystalline Diamond (PCD) substrates, offering thermal conductivity up to $5 \times$ that of copper.

Technical Specifications

The following hard data points were extracted from the numerical simulation and experimental validation of the channel heat sink performance:

Parameter	Value	Unit	Context
Simulated Heat Load ($Q$)	120	W	Applied to the heat sink base
Maximum Simulation Error	< 5	%	Accuracy relative to experimental $\Delta P$ and $T_w$
Channel Height ($H$)	3	mm	Total height of the flow channel
Channel Width ($W$)	2	mm	Width of a single flow channel
Optimal Rib Angle ($\alpha$)	135 (or 150)	°	Preferred for Re > 507.5
Optimal Height Ratio ($\beta$)	25	%	Preferred for Re > 507.5 ($\beta = h/H$)
Optimal Rib Spacing ($s$)	2.5	mm	Priority spacing for highest $\eta_f$
Critical Reynolds Number (Re)	507.5	-	Threshold for optimal $\beta$ selection
PCR Target Temperature Range	328.15 to 368.15	K	Cyclical temperature requirement ($\pm 3 \text{ K}$)
Maximum Heating Rate	7.9	K/s	Achieved during practical PCR thermal cycling
Base Material (Used in Paper)	Copper (Cu)	-	Thermal Conductivity: $401 \text{ W} \cdot \text{m}^{-1} \cdot \text{K}^{-1}$
Machined Surface Roughness ($R_a$)	$\pm 2$	µm	Uncertainty of copper heat sink/cover plate

Key Methodologies

The study utilized a combination of computational fluid dynamics (CFD) and experimental validation to optimize the heat sink design.

Model Design: A 3D model of a flow-channel heat sink was constructed, featuring 10 parallel channels, each containing uniformly arranged diamond-shaped (rhombic) fins.
Material Basis: The heat sink and cover plate were modeled using highly conductive copper (Cu). The coolant was liquid water.
Numerical Simulation: The Finite Volume Method (FVM) was used to solve the governing equations (Continuity, Momentum, Energy) under steady-state, incompressible, and single-phase flow assumptions.
Solving Algorithm: The pressure-based SIMPLE algorithm was employed, using a second-order upwind scheme for pressure, momentum, and energy.
Parameter Sweep: Performance metrics ($R_t$, $Nu$, $f$, $\eta_f$) were systematically evaluated across 15 different combinations of fin angle ($\alpha$), rib spacing ($s$), and height ratio ($\beta$).
Performance Metric: The heat-transfer enhancement factor ($\eta_f$) was used as the primary indicator to evaluate overall performance, balancing heat dissipation against fluid flow capacity (pressure drop penalty).
Experimental Validation: A physical prototype was tested using a TEC and ceramic heating plate to confirm the simulation accuracy, demonstrating that the design could achieve the required cyclical temperature control for PCR.

6CCVD Solutions & Capabilities

The research demonstrates the critical need for materials with exceptional thermal performance and precise micro-structuring for high-flux thermal management systems, particularly those involving rapid thermal cycling (like PCR). While copper was used in the study, 6CCVD’s MPCVD diamond offers a transformative material upgrade.

Requirement from Paper	6CCVD Diamond Solution (The Ultimate Upgrade)	Technical Advantage
High Thermal Conductivity Substrate	Single Crystal Diamond (SCD) or High Thermal Grade Polycrystalline Diamond (PCD)	Copper ($401 \text{ W} \cdot \text{m}^{-1} \cdot \text{K}^{-1}$) limits performance. SCD offers thermal conductivity up to $2200 \text{ W} \cdot \text{m}^{-1} \cdot \text{K}^{-1}$. Utilizing diamond as the base material for the heat sink drastically reduces the overall thermal resistance ($R_t$), enabling superior heat spreading and lower base temperatures.
Microchannel & Rib Fabrication	Custom MPCVD Diamond Processing	We provide SCD and PCD plates up to 125mm. Our advanced laser cutting and etching capabilities allow for the precise fabrication of complex microchannel geometries, including the optimized rhombic (diamond) rib structures ($s=2.5 \text{ mm}, H=3 \text{ mm}$) directly into the diamond material.
Rapid Thermal Cycling (PCR)	Low Thermal Mass & High Diffusivity	Diamond’s exceptional thermal diffusivity enables significantly faster and more uniform temperature response than copper, directly improving the heating and cooling rates (7.9 K/s achieved) required for high-speed thermal cycling applications like PCR.
Interface Quality & Friction Reduction	Ultra-Low Roughness Polishing	The paper noted a machined roughness of $\pm 2$ µm for copper. 6CCVD guarantees superior surface quality: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD. This ultra-smooth finish minimizes fluid friction losses and maximizes thermal contact efficiency at the TEC interface.
Integration and Bonding	In-House Custom Metalization	For robust thermal and electrical contact with the TEC or other components, 6CCVD offers internal metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu stacks, tailored for specific bonding or soldering requirements.

Applicable Materials

To replicate or extend this high-performance thermal management research, 6CCVD recommends:

Optical Grade SCD: Ideal for applications requiring the absolute highest thermal conductivity ($> 2000 \text{ W} \cdot \text{m}^{-1} \cdot \text{K}^{-1}$) in smaller dimensions, ensuring minimal thermal resistance at the TEC interface.
High Thermal Grade PCD: Recommended for larger-scale heat sinks (up to 125mm diameter) where high thermal conductivity ($> 1000 \text{ W} \cdot \text{m}^{-1} \cdot \text{K}^{-1}$) and cost-effectiveness are required.

Customization Potential

6CCVD specializes in providing custom dimensions and complex structuring necessary for advanced microchannel designs:

Custom Dimensions: We can supply PCD wafers up to 125mm in diameter and SCD plates up to $10 \text{ mm} \times 10 \text{ mm}$ with thicknesses ranging from $0.1 \text{ µm}$ to $500 \text{ µm}$. Substrates up to $10 \text{ mm}$ thick are available for robust heat sink bases.
Precision Structuring: We offer laser cutting and etching services to precisely define the optimized rhombic rib geometry ($\alpha=135^{\circ}, \beta=25%, s=2.5 \text{ mm}$) directly into the diamond material.

Engineering Support

6CCVD’s in-house PhD engineering team is available to assist researchers and engineers in transitioning from copper-based prototypes to diamond-based solutions for high-flux thermal management projects, particularly those involving TEC cooling, high-speed PCR thermal cycling, and advanced microchannel heat sink optimization. We provide expert consultation on material selection, geometric design translation, and metalization strategies to maximize thermal performance.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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]