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

Executive Summary

This research focuses on developing and fabricating lightweight, corrosion-resistant heat exchangers (HXs) using thermally conductive polymer composites (TCPCs) via 3D printing.

Material Enhancement: Acrylonitrile Butadiene Styrene (ABS) was reinforced with diamond powder fillers (0.25 µm nanoscale and 16.7 µm microscale) to create TCPCs, addressing the inherently low thermal conductivity (TC) of polymers.
Filler Performance: Microscale diamond fillers (16.7 µm) proved significantly more effective than nanoscale fillers (0.25 µm), achieving a maximum TC of 0.55 W/(mK) at 70 wt% loading. This suggests that larger particles reduce interfacial thermal resistance.
HX Design and Fabrication: A heat exchanger featuring a Triply Periodic Minimal Surface (TPMS) Gyroid lattice structure was successfully 3D printed using a high-loading composite filament (50 wt% microdiamond/ABS), demonstrating leak-free operation.
Thermal Bottleneck Identified: Simulation and testing confirmed that the polymer wall is the primary source of thermal resistance in the HX. Increasing the wall material TC beyond approximately 10 W/(mK) yields diminishing returns on the overall heat transfer coefficient (U_cA_w).
Mechanical Anisotropy: Mechanical testing revealed that the tensile strength of 3D-printed parts is highly dependent on the printing direction, achieving maximum strength (up to 58 MPa) when the force aligns with the print orientation.
Performance Comparison: The polymer HX exhibited lower friction factors (f) and Nusselt numbers (Nu) compared to a metal HX, attributed partly to the smoother internal surfaces of the polymer print versus the residual structures found on the metal lattice.

Technical Specifications

Parameter	Value	Unit	Context
Matrix Material	ABS	N/A	Polymer used for 3D printing
ABS Solid Thermal Conductivity (TC)	0.20	W/(mK)	Baseline TC of pure polymer
Diamond Filler Intrinsic TC	2000	W/(mK)	High thermal conductor
Microdiamond Particle Size	16.7	µm	Filler size yielding higher TC
Nanodiamond Particle Size	0.25	µm	Filler size yielding lower TC
Max TC Achieved (70 wt% Microdiamond)	0.55	W/(mK)	Experimental result for composite
HX Core Structure	Gyroid Lattice (TPMS)	N/A	Designed for high surface area
HX Wall Thickness (δ_w)	2	mm	Thickness of the 3D-printed lattice wall
Overall HX Dimensions	75 x 75 x 75	mm	Total size of the fabricated HX
Overall Heat Transfer Coefficient (U_cA_w)	2.35	W/K	Calculated for 0.20 W/mK wall TC
Measured Heat Transfer Power (q)	94	W	Tested at 0.2 kg/s flow rate
FFF Print Temperature	260	°C	Nozzle temperature for 50 wt% composite
FFF Bed Temperature	80	°C	Bed temperature for 50 wt% composite
Max Tensile Strength (Aligned Print)	58	MPa	Mechanical strength of 3D-printed ABS (Direction 2-0°)
Tensile Strength Reduction (45° Angle)	~40	%	Strength reduced to 60% of original value

Key Methodologies

The fabrication and testing process involved specialized steps to handle the high filler loading and ensure composite quality:

Composite Powder Mixing: ABS and diamond powders were thoroughly blended using an electric food processor to ensure homogeneous distribution of fillers.
Filament Extrusion: An EX2 filament extruder was used to create the composite filament (e.g., 50 wt% diamond/ABS). The filament was extruded twice (re-extruded) to improve quality and consistency for 3D printing.
Sample Molding and Curing: Small square samples were molded and then heat-treated in a high-pressure cooker (120 °C, 200 kPa) for 30 minutes to remove internal voids and air bubbles, enhancing density.
Thermal Conductivity Measurement: The steady-state method was employed. Samples were placed between a steel cube and a heated base plate (T_plate ~50 °C). Thermal paste was used at interfaces. Temperatures (T_s1, T_s2) were measured using a thermal camera after 30 minutes to ensure steady state.
HX Design: A Gyroid TPMS lattice structure was designed for the HX core, optimizing the surface area for heat transfer while maintaining structural integrity and flow characteristics.
HX Fabrication: The complete HX was printed using the extruded 50 wt% composite filament on a commercial Sovol 04 3D printer, successfully achieving a leak-free structure.
Mechanical Testing: Tensile test specimens were printed in three different orientations (Direction 1, 2, 3) and at 0° and 45° angles relative to the applied force, following the ASME E8 standard to quantify mechanical anisotropy.

Commercial Applications

This technology enables the production of customized, lightweight, and corrosion-resistant thermal management solutions for demanding environments.

Chemical Processing and Harsh Environments: Polymer HXs offer superior corrosion resistance compared to traditional metals, making them ideal for handling aggressive fluids (acids, bases, saltwater).
Aerospace and Defense: The lightweight nature of polymer composites is critical for reducing mass in aircraft, satellites, and portable military equipment requiring thermal regulation.
Automotive and Electric Vehicles (EVs): Used in battery thermal management systems where lightweight components and resistance to corrosive coolants are necessary.
Customized Electronics Cooling: Fabrication of complex, high-surface-area heat sinks (using TPMS structures) for specialized electronics where electrical insulation (provided by the polymer matrix) is required alongside thermal dissipation.
Additive Manufacturing Services: Offering rapid prototyping and low-volume production of highly customized heat exchangers with complex internal geometries (TPMS lattices) that are impossible to achieve with conventional manufacturing.

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]