Heat exchangers are thermal management tools that are widely used across a variety of industries. Their basic function is to remove heat from designated locations by transferring it into a fluid. Inside the heat exchanger, the heat from this fluid passes to a second fluid without the fluids mixing or coming into direct contact. The original fluid, now cooled, returns to the assigned area to begin the heat transfer process again.
Additive manufacturing technologies have expanded in many directions in recent years with applications ranging across numerous industries and applications, including into the thermal management of electronics. As metal 3-D printing techniques have improved and become commercially viable, engineers are using it to create innovative cooling solutions, particularly heat exchangers.
Figure 1. 3-D developed heat exchangers can feature shapes not obtainable using traditional forming methods. [2]
Why are engineer turning to additive manufacturing?
One reason is that additive manufacturing allows for
generous cost savings. Companies can reduce 15-20 existing part numbers and
print them as a single component. A single part eliminates inventory, additional
inspections, and assemblies that would have been necessary when components were
produced individually.
As AdditiveManufacturing.com notes, “Some envision AM
(additive manufacturing) as a complement to foundational subtractive
manufacturing (removing material like drilling out material) and to a lesser
degree forming (like forging). Regardless, AM may offer consumers and
professionals alike, the accessibility to create, customize and/or repair
product, and in the process, redefine current production technology.” [1]
Developed at the Massachusetts Institute of Technology (MIT),
3-D printing is the most common and well-known form of additive manufacturing.
Three-dimensional objects are made by building up multiple layers of material. Thanks
to the continued (and rapid) development of the technology and advanced research
in materials science, the layers can be composed of metal, plastic, concrete,
living tissue or other materials.
In industrial applications, 3-D printing has encouraged
creativity. With additive manufacturing, designers can create complex geometric
shapes that would not be possible with standard manufacturing processes. For
example, shapes with a scooped out or hollow center can be produced as a single
piece, without the need to weld or attach individual components together.
One-piece shapes can provide extra strength, with few or no weak spots that can
be compromised or stressed. [4]
Making 3-D Printed Heat Exchangers
Heat exchangers are integral to thermal management. Any time
heat, cool air, or refrigeration are required, a heat exchanger has to be involved
to dissipate the heat to the ambient. This can be as simple as a standard heat
sink or a complex metal structure used in liquid cooling. It can be as small as
a few millimeters or as large as a building. Heat exchange is a
multi-billion-dollar industry touching everything from consumer goods to
automotive and aerospace engineering.
Compact heat exchangers are typically composed of thin sheets of material that are welded together. The complexity of the designs, particularly the density of the fin field, makes production both challenging and time-consuming, while the material used for the welding process adds to the overall weight of the part. Heat exchangers produced through 3-D printing techniques (such as those pictured below) can be made quicker, lighter, and more efficiently.
Figure 2. 3-D developed heat exchanger had a 20% increase in efficiency. [2]
In 2016, a Department of Energy-funded consortium of researchers developed a miniaturized air-to-refrigerant heat exchanger that was more compact and energy-efficient than current market designs. CEEE and 3-D Systems teamed to increase the efficiency of a 1 kW heat exchanger by 20 percent while reducing weight and size. The manufacturing cycle for the heat exchanger was reduced from months to weeks. [4]
Figure 3. A 3-D printed milli-structured heat exchanger made from stainless steel with a gyroid design. [5]
Using direct metal printing (DMP), manufacturers delivered a 20-percent more efficient heat exchanger and an innovative design. It was produced in weeks not months and with significantly lower weight. The one-part, 3-D-printed heat exchanger required minimal secondary finishing operations.
Ohio-based Fabrisonic uses a hybrid metal 3-D printing
process, called Ultrasonic Additive Manufacturing (UAM), to merge layers of metal
foil together in a solid-state thanks to high frequency ultrasonic vibrations.
[5]
Figure 4. Aluminum and copper heat exchanger printed using ultrasonic additive manufacturing. (Photo via Fabrisonic) [6]
Fabrisonic mounts its hybrid 3-D printing process on
traditional CNC equipment – first, an object is built up with 3-D printing, and
then smoothed down with CNC machining by milling to the required size and
surface. No melting is required, as Fabrisonic’s 6 ft. x 6 ft. x 3 ft. UAM 3-D
printer can scrub metal foil and build it up into the final net shape, and then
machines down whatever else is needed at the end of the process.
This 3-D printing process was recently given a stamp of
approval by NASA after testing at the Jet Propulsion Laboratory (JPL). A report
from NASA and Fabrisonic said, “UAM heat exchanger technology developed under
NASA JPL funding has been quickly extended to numerous commercial production
applications. Channel widths range from 0.020 inch to greater than one inch
with parts sized up to four feet in length.” [6]
There are challenges involved, to be sure. In an article
from Alex Richardson of Aquicore highlighting research done at the University
of Maryland, researchers discuss the problems that 3-D printing still has
competing on price against traditional manufacturing techniques and the
difficulties involved with physically scaling a technology up.
In the article, Vikrant Aute of the University of Maryland
Center for Environmental Energy Engineering noted that his research team was
“considering modularization to overcome the latter issue: Instead of making the
exchangers bigger, it might be possible to arrange lots of them together to
accomplish the same task.” [7]
Research Continues to Improve 3-D Printing Process
While there have been numerous advancements in the technology
of metal 3-D printing, research is continuing on campuses and in companies
around the world to try and improve the process and make it easier to create
increasingly complex heat exchangers.
For example, Australia-based additive manufacturing startup
Conflux Technology received significant funding to develop its technology specifically
for heat exchange and fluid flow applications. [8] Another example was the
University of Wisconsin-Madison, which received a grant from the U.S.
Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E) to
build heat exchangers with “internal projections to increase turbulence and
facilitate heat transfer. Such intricate shapes are impossible with traditional
manufacturing.” [9]
In 2018, U.K.-based Hieta Technologies partnered with British metrology company Renishaw to commercialize its 3-D-printed heat exchangers. Renishaw used its AM250 system to 3-D print walls of the heat exchanger as thin as 150 microns. The samples were heat treated and characterized to confirm that the laser powder bed fusion process was effective. The process took only 80 hours, was 30 percent lighter, and had 30 percent less volume, while still meeting the heat transfer and pressure drop requirements. [10, 11]
Last month, GE Research announced that it was leading a multi-million-dollar program with Oak Ridge National Laboratory (ORNL) and the University of Maryland to develop compact heat exchangers that can withstand temperatures as high as 900°C and pressures as high as 250 bar. This was also based on funding from ARPA-E, as part of its HITEMMP (High-Intensity Thermal Exchanger through Materials and Manufacturing Processes) program. [12]
Fig. 5. GE Research is leading a project to design a new, high-temperature heat exchanger with 3-D printing. [12]
To build the new heat exchanger, GE engineers are using a novel nickel superalloy that is designed for high temperatures and is crack-resistant. University of Maryland researchers are working with GE to create biological shapes that will make the heat exchanger more efficient and ORNL researchers are providing corrosion resistance expertise to develop the materials for long-term use.
These are just some examples of the many ways that 3-D printing has impacted electronics cooling. Researchers at the Fraunhofer Institute for Laser Technology ILT in Germany have demonstrated the feasibility of 3-D printing copper [13], U.K. researchers 3-D printed “smart materials” for energy storage [14], a researcher at Penn State (soon to be at MIT) is developing methods for creating rough surfaces through additive manufacturing to enhance boiling heat transfer [15], and at Virginia Tech researchers developed a new process for 3-D printing piezoelectric materials [16].
The technology is growing by leaps and bounds each year and
is enhancing the options for engineers in the thermal management industry.
Since it was published around one year ago, the “What is a Heat Exchanger” video (watch it below) has been one of the most watched on the ATS YouTube page. With the obvious interest in heat exchangers in particular (and liquid cooling in general), we are curating recent research into the technology and its applications in the thermal management of electronics.
Heat Exchangers are a common component in liquid cooling solutions for electronics. Below is recent research into this growing technology. (Advanced Thermal Solutions, Inc.)
The following are three examples of papers written about heat exchangers including applications in the automotive space to developing microchannels to enhance thermal performance to optimizing heat exchangers for use with high-powered electronics.
We have posted several pieces of content on this blog about
heat exchangers in the past. Examples include:
Abstract: Electric-drive systems, which include electric
machines and power electronics, are a key enabling technology to meet increasing
automotive fuel economy standards, improve energy security, address
environmental concerns, and support economic development. Enabling
cost-effective electric-drive systems requires reductions in inverter power
semiconductor area, which increases challenges associated with heat removal. In
this paper, we demonstrate an integrated approach to the design of thermal
management systems for power semiconductors that matches the passive thermal
resistance of the packaging with the active convective cooling performance of
the heat exchanger. The heat exchanger concept builds on existing semiconductor
thermal management improvements described in literature and patents, which
include improved bonded interface materials, direct cooling of the semiconductor
packages, and double-sided cooling. The key difference in the described concept
is the achievement of high heat transfer performance with less aggressive
cooling techniques by optimizing the passive and active heat transfer paths. An
extruded aluminum design was selected because of its lower tooling cost, higher
performance, and scalability in comparison to cast aluminum. Results
demonstrated a 102% heat flux improvement and a package heat density improvement
over 30%, which achieved the thermal performance targets.
Microchannel Heat Exchanger for Electronics Cooling
Applications
Abstract: The power consumption of electronic devices, such
as semiconductor diode laser bars, has continually increased in recent years
while the heat transfer area for rejecting the associated thermal energy has
decreased. As a result, the generated heat fluxes have become more intense
making the thermal management of these systems more complicated. Air cooling
methods are not adequate for many applications, while liquid cooled heat
rejection methods can be sufficient. Significantly higher convection heat
transfer coefficients and heat capacities associated with liquids, compared to
gases, are largely accountable for higher heat rejection capabilities through the
micro-scale systems. Forced convection in micro-scale systems, where heat
transfer surface area to fluid volume ratio is much higher than similar
macro-scale systems, is also a major contributor to the enhanced cooling
capabilities of microchannels. There is a balance, however, in that more power
is required by microchannels due to the large amount of pressure drop that are
developed through such small channels. The objective of this study is to
improve and enhance heat transfer through a microchannel heat exchanger using
the computational fluid dynamics (CFD) method. A commercial software package
was used to simulate fluid flow and heat transfer through the existing
microchannels, as well as to improve its designs. Three alternate microchannel
designs were explored, all with hydraulic diameters on the order of 300
microns. The resulting temperature profiles were analyzed for the three
designs, and both the heat transfer and pressure drop performances were
compared. The optimal microchannel cooler was found to have a thermal
resistance of about 0.07 °C-cm2 /W and a pressure drop of less than half of a
bar.
Thermal Analysis of
the Heat Exchanger for Power Electronic Device with Higher Power Density
Read the full paper at http://pe.org.pl/articles/2012/12a/70.pdf. Abstract: Liquid cooling system has been used in high power electronic device systems to cool down the temperature of power electronic device. Heat exchanger is an important part of liquid cooling system to transfer the heat generated by power electronic device into air. In this paper, a Streamline-upwind/Petrov-Galerkin (SUPG) stabilized finite element analysis method was proposed to solve the water and air governing formulas including the mass conservation equation, the momentum conservation and the energy conservation equation. Furthermore, the thermal characteristic of a heat exchanger is simulated, and the result was compared with an experiment. The comparison shows that this method is effective.
For more information about Advanced Thermal Solutions, Inc. (ATS) thermal management consulting and design services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com.
ATS released a line of tube-to-fin, liquid-to-air heat exchangers with the industry’s highest density fins to optimize heat transfer. (Advanced Thermal Solutions, Inc.)
ATS heat exchangers are available in seven different sizes and can be ordered with or without fans depending on your specific design requirements. Altogether, ATS offers 49 different heat exchanger options (not including the customized options to meet customer needs).
To make the selection process easier for engineers, ATS has recently unveiled a new Heat Exchanger Selection Tool that will point engineers to the exact option that will meet the inputted criteria.
The tool asks five questions (measurement type in parentheses):
Air temperature from inlet to heat exchanger (Tai°C)
Heat need to be extracted by heat exchanger (QtotalW)
Water exit temperature from heat exchanger (Tfo°C)
Water flow rate (GPM)
Fan voltage (V)
Plug answers in to these questions and hit the “Optimum Heat Exchanger” button to see which of the ATS heat exchangers fits your specific liquid cooling system needs. Once you have the right part number, you can now purchase the right heat exchanger from Digi-Key Electronics.
For more information about Advanced Thermal Solutions, Inc. (ATS) thermal management consulting and design services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com.
ATS has released a new line of tube-to-fin, liquid-to-air heat exchangers that boast the industry’s highest density fins. (Advanced Thermal Solutions, Inc.)
ATS heat exchangers maximize heat transfer from fluid to air, which allows liquid to be cooled to lower temperatures than other heat exchangers on the market. The fins and tubes are made of copper and stainless steel and are suitable for a variety of different liquids, including water, dielectric fluids and custom designed heat transfer fluids.
ATS heat exchangers can be used in a variety of applications including laser cooling, cooling medical equipment and imaging devices, compressor cooling, semiconductor processing, HVAC, food and beverage processing, and other liquid cooling applications.
The following table shows the different heat transfer capacities and dimensions of the different heat exchangers that ATS has released:
The heat exchangers have silver-solder brazed joints and have been internally cleaned and externally coated for corrosion protection. They are available with or without fans.
Watch the short video below to learn more:
For more information about Advanced Thermal Solutions, Inc. thermal management consulting and design services, visit www.qats.com or contact ATS at 781.769.2800 or ats-hq@qats.com.
