Design and Fabrication of Heat Exchangers Using Thermally Conductive Polymer Composite

At a Glance

Metadata	Details
Publication Date	2025-05-27
Journal	Applied Mechanics
Authors	Jian Liu, David Cheng, Pan Wang, Khin Oo, Ty-Liyiah McCrimmon
Institutions	PolarOnyx (United States)
Analysis	Full AI Review Included

Technical Analysis: Diamond-Enhanced Polymer Heat Exchangers

This documentation analyzes the research paper “Design and Fabrication of Heat Exchangers Using Thermally Conductive Polymer Composite,” focusing on the material science implications and leveraging 6CCVD’s expertise in MPCVD diamond fabrication to propose advanced solutions for thermal management applications.

Executive Summary

Application Focus: The research successfully demonstrated the 3D printing of a Triply Periodic Minimal Surface (TPMS) heat exchanger (HX) using a thermally conductive polymer composite (TCPC).
Material Composition: The TCPC utilized Acrylonitrile Butadiene Styrene (ABS) as the matrix (TC: 0.20 W/(mK)) and high-purity diamond powder (TC: 2000 W/(mK)) as the filler.
Key Thermal Finding: Microscale diamond particles (16.7 µm) provided significantly higher thermal conductivity (TC) enhancement than nanoscale particles (0.25 µm) at equivalent volume fractions, reaching a maximum composite TC of 0.55 W/(mK) at 70 wt% loading.
Performance Limitation: Despite the use of diamond, the resulting thermal conductivity of the composite material remains critically low, limiting the overall heat transfer coefficient ($U_c A_w$) of the HX to approximately 2.35 W/K.
Conclusion for Improvement: The polymer wall remains the primary source of thermal resistance. Future improvements require materials with higher intrinsic TC, larger filler aspect ratios, or the integration of solid, high-pconductivity diamond components.
Fabrication Success: A filament containing 50 wt% microdiamond was successfully extruded (twice) and used to 3D print a complete, leak-free HX structure, proving the technological feasibility of the manufacturing process.

Technical Specifications

The following data points were extracted from the investigation into the thermal and physical properties of the composite materials and the resulting heat exchanger performance.

Parameter	Value	Unit	Context
Intrinsic Diamond TC (Solid)	2000	W/(mK)	Filler material reference value
Intrinsic ABS TC (Solid)	0.20	W/(mK)	Polymer matrix reference value
Microdiamond Particle Size	16.7	µm	Filler size yielding higher TC
Nanodiamond Particle Size	0.25	µm	Filler size yielding lower TC
Maximum Measured Composite TC	0.55	W/(mK)	Achieved with 70 wt% (40 vol%) 16.7 µm diamond
ABS Density	1.02	g/cm³	Matrix material density
Diamond Density	3.5	g/cm³	Filler material density
HX Wall Thickness ($\delta_w$)	2	mm	Gyroid lattice design parameter
Overall Heat Transfer Coefficient ($U_c A_w$)	2.35	W/K	Calculated for HX using 0.20 W/(mK) material
Measured Heat Transfer Power ($q$)	94	W	Experimental result at 0.2 kg/s flow rate
FFF Print Temperature	260	°C	Extrusion temperature for 50 wt% composite
FFF Bed Temperature	80	°C	Printing parameter
Maximum Tensile Strength	59	MPa	Achieved when print direction aligns with force (Direction 3-45°)

Key Methodologies

The fabrication and testing of the thermally conductive polymer composite (TCPC) and the heat exchanger (HX) involved the following steps:

Material Preparation: ABS powder (150 mesh) and diamond powder (0.25 µm nano or 16.7 µm micro) were mixed using an electric food processor to ensure thorough blending.
Composite Sample Fabrication: Square samples (20 mm x 20 mm x 5 mm) were created by melting the mixed polymer composite in a molding box.
Void Reduction: Samples were heat-treated in a high-pressure cooker (120 °C, 200 kPa) for 30 minutes to remove internal air bubbles and voids.
Filament Extrusion: A mixed powder (50 wt% ABS, 50 wt% microdiamond) was extruded using an EX2 filament extruder. The filament was extruded twice to enhance quality and consistency.
Thermal Conductivity Measurement: The steady-state method was used, involving a steel cube, thermal paste, and a thermal camera to measure the temperature difference ($\Delta T$) across the sample relative to a base plate ($T_{plate} \approx 50$ °C).
HX Design: A polymer HX based on a Triply Periodic Minimal Surface (TPMS) gyroid lattice structure (12 mm x 12 mm x 12 mm unit cell, 2 mm wall thickness) was designed.
HX Fabrication: The entire HX structure was printed using the twice-extruded 50 wt% diamond composite filament via a commercial Sovol 04 3D printer (FFF/FDM).
Performance Validation: The printed HX was tested for leakage and its heat transfer capacity was evaluated experimentally and compared to ANSYS Fluent simulations.

6CCVD Solutions & Capabilities

The research confirms that while diamond powder significantly improves polymer thermal conductivity, the resulting composite TC (0.55 W/(mK)) is still the limiting factor for high-performance heat exchange. To achieve the high thermal efficiency required for practical applications, engineers must move beyond composite fillers and integrate solid, high-purity diamond components.

6CCVD specializes in MPCVD diamond materials that offer intrinsic thermal conductivity far superior to any composite, enabling the next generation of hybrid thermal management systems.

Requirement/Challenge from Paper	6CCVD Solution & Capability	Technical Advantage
Challenge: Low Composite TC (Max 0.55 W/(mK)).	Optical Grade Single Crystal Diamond (SCD) or High-Purity Polycrystalline Diamond (PCD) Substrates.	SCD offers TC > 2000 W/(mK). Integrating solid diamond plates as heat spreaders or flow channel walls bypasses the polymer’s thermal bottleneck entirely.
Requirement: Larger Filler Size and High Aspect Ratio.	Custom Large-Area PCD Plates (up to 125mm diameter).	Provides a continuous, high-aspect-ratio thermal pathway, eliminating the high interfacial thermal resistance (TBR) issues inherent in powder-matrix composites.
Requirement: Smoother Internal Flow Channels (Polymer HX advantage).	Precision Polishing Services (Ra < 1nm for SCD; Ra < 5nm for inch-size PCD).	Ultra-smooth diamond surfaces minimize fluid friction and pressure drop, enhancing the hydraulic performance of hybrid HXs compared to rough 3D-printed metal lattices.
Need for Hybrid Integration/Bonding.	In-house Custom Metalization (Au, Pt, Pd, Ti, W, Cu).	Enables robust, low-thermal-resistance bonding of solid diamond plates to metal fluid manifolds or structural elements within a 3D-printed polymer HX design.
Need for Custom Dimensions.	Custom Thicknesses and Dimensions (SCD: 0.1µm - 500µm; PCD: 0.1µm - 500µm; Substrates up to 10mm).	Allows engineers to specify exact diamond component geometry for integration into complex TPMS or gyroid lattice structures, optimizing heat transfer area ($A_w$) and wall thickness ($\delta_w$).

Applicable Materials for Replication and Extension

To replicate or significantly extend this research into high-performance hybrid heat exchangers, 6CCVD recommends the following materials:

Optical Grade SCD: For applications demanding the absolute highest thermal conductivity and purity, ideal for small, high-flux hot spots integrated into the polymer HX.
High-Purity PCD: Offers excellent thermal conductivity at larger dimensions (up to 125mm), providing a cost-effective solution for large-area heat spreading within the polymer structure.
Custom Metalized Diamond: Diamond plates metalized with Ti/Pt/Au for direct soldering or bonding into the fluid path, ensuring mechanical stability and minimal thermal contact resistance.

6CCVD’s in-house PhD engineering team specializes in material selection and thermal modeling for advanced thermal management projects, including hybrid heat exchangers and high-power electronics cooling.

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

View Original Abstract

Polymer heat exchangers (HXs) are lightweight and cost-effective due to the affordability of raw polymer materials. However, the inherently low thermal conductivity (TC) of polymers limits their application in HXs. To enhance thermal conductivity polymer composites, two types of diamond powders, with particle sizes of 0.25 µm and 16.7 µm, were used as fillers, while Acrylonitrile Butadiene Styrene (ABS) served as the matrix. Composite polymer samples were fabricated, and their density and thermal conductivity were tested and compared. The results indicate that fillers with larger particle sizes tend to exhibit higher thermal conductivity. A polymer HX based on a Triply Periodic Minimal Surface (TPMS) structure was designed. The factors influencing the efficiency of polymer HXs were analyzed and compared with those of metal HXs. In polymer HXs, the polymer wall is the primary source of heat resistance. Additionally, the mechanical strength of 3D-printed polymer parts was evaluated. Finally, an HX was successfully fabricated using a polymer composite containing 50 wt% diamond powder via 3D printing.

Tech Support

Original Source

DOI: https://doi.org/10.3390/applmech6020038

References

2018 - Thermal conductivity of polymers and polymer nanocomposites [Crossref]
2025 - Recent advances in polymer-based composites for thermal management and electromagnetic wave absorption [Crossref]
2015 - Evaluation of electric, morphological and thermal properties of thermally conductive polymer composites [Crossref]
2017 - Review of polymers for heat exchanger applications: Factors concerning thermal conductivity [Crossref]
2013 - Percolation transition in thermal conductivity of β-Si3N4 filled epoxy [Crossref]
2009 - Thermal conductivity of polymer composites with close-packed structure of nano and micro fillers [Crossref]
2013 - Effect of BN filler on thermal properties of HDPE matrix composites [Crossref]