Category Archives: Heat Exchangers

3-D-printed Heat Exchangers provide flexibility in thermal management

By Norman Quesnel
Senior Member of Marketing Staff
Advanced Thermal Solutions, Inc. (ATS)

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.

3-D Printed 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]

3-D Printed Heat Exchangers
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.

References

  1. http://additivemanufacturing.com/basics/
  2. https://www.3-Dsystems.com/learning-center/case-studies/direct-metal-printing-dmp-enables-ceee-manufacture-lean-and-green-heat
  3. https://www.spilasers.com/application-additive-manufacturing/additive-manufacturing-a-definition/
  4. https://www.3-Dsystems.com/learning-center/case-studies/direct-metal-printing-dmp-enables-ceee-manufacture-lean-and-green-heat
  5. http://fabrisonic.com/ultrasonic-additive-manufacturing-overview/
  6. https://aquicore.com/blog/3-D-printing-heat-exchangers/
  7. https://cdn2.hubspot.net/hubfs/3985996/Articles%20-%20published/NASA%20HX%20White%20Paper%20EWI.pdf
  8. https://www.confluxtechnology.com
  9. https://www.engr.wisc.edu/researchers-bring-3d-printing-cool-industry/
  10. https://3dprint.com/198933/hieta-renishaw-heat-exchangers/
  11. https://www.youtube.com/watch?v=r42Dc_PKBEc
  12. https://www.ge.com/research/newsroom/ge-researchers-utilize-3d-printing-design-ultra-performing-heat-exchanger-more-efficient
  13. https://www.ilt.fraunhofer.de/en/press/press-releases/press-release-2017/press-release-2017-08-30.html
  14. https://www.qmul.ac.uk/media/news/2018/se/scientists-design-material-that-can-store-energy-like-an-eagles-grip.html
  15. https://news.psu.edu/story/574464/2019/05/15/academics/heat-transfer-additive-manufacturing-powers-nsf-graduate-research
  16. https://vtnews.vt.edu/articles/2019/01/3d_printing_discovery.html

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. To register for Qpedia and to get access to its archives, visit 
https://www.qats.com/Qpedia-Thermal-eMagazine.

Recent Research Into Next-Generation Heat Exchangers for Electronics Thermal Management

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
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:

Since heat exchangers remain a popular topic for engineers, we will continue to add new pieces about the technology in the coming months.

Novel Power Electronics Three-Dimensional Heat Exchanger

Read the full paper at https://www.nrel.gov/docs/fy14osti/61041.pdf.

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

Read the full paper at http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1636343.

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 Unveils Heat Exchanger Selection Tool

In 2017, Advanced Thermal Solutions, Inc. (ATS) added to its liquid cooling products with a new line of tube-to-fin, liquid-to-air heat exchangers with the industry’s highest density fins, which maximize heat transfer and provide greater cooling than other heat exchangers on the market.

Heat Exchanger Selection Tool

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.

Heat Exchanger Selection Tool

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.

In addition to heat exchangers, ATS has an array of liquid cooling products, including cold plates that provide 30 percent better thermal performance than comparable products on the market.

To learn more about the full line of liquid cooling options from ATS, visit https://www.qats.com/Products/Liquid-Cooling.

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 Releases New Line of Tube-to-Fin, Liquid-to-Air Heat Exchangers

Advanced Thermal Solutions, Inc. (ATS) has introduced a new line of tube-to-fin, liquid-to-air heat exchangers that “push the boundaries of the technology with the industry’s highest density fins.” These new heat exchangers, available with or without fans, come in seven different sizes and 49 different options and are part of the array of liquid cooling products that ATS offers.

Heat Exchangers

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.

Read the full product release announcement at https://www.qats.com/News-Room/Press-Releases-Content/1183.aspx.

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:

Heat Exchangers

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.

Case Study: Designing Air-to-Air Heat Exchanger With Heat Pipes

Advanced Thermal Solutions, Inc. (ATS) engineers were tasked by a client to design an air-to-air, aluminum heat exchanger with multiple copper heat pipes that could meet high power demands (more than 400W) with a thermal resistance requirement of 0.046°C/W and could withstand a wide range of ambient temperatures from -40°C to 60°C. Also, the separation between the heat pipe’s evaporator and condenser sections needed to be air tight.

Heat Exchanger

ATS engineers were tasked with designing an air-to-air heat exchanger with heat pipes that would fit inside an enclosure. (Advanced Thermal Solutions, Inc.)

Using analytical modeling, ATS engineers calculated the system pressure drop from the heat pipe to the fin block to the flow turn and also the thermal performance of the fins in ducted flow to determine the proper amount of fins to avoid over pressurizing the fans, while at the same time meeting the thermal resistance demands of the system. It was calculated that a maximum of 14 fins per inch could be used, while the overall size was well within the client’s requirements.

Challenge: To design an air-to-air heat exchanger that could handle high power demands of more than 400W and specific requirements on thermal resistance (0.046°C/W).

Chips/Components: Electronics junction box that requires internal air cooling.

Analysis: ATS engineers conducted analysis of the pressure drop across the system from the heat pipe to the fin block to the flow turn section, as well as analyzing the thermal performance of the entire heat exchanger. This analysis included calculating the ducted flow, heat transfer coefficient, and the fin and heat pipe resistance of the exchanger. The analysis also explored the difference between designs with copper and with aluminum fins.

Design Data: The data showed that thermal resistance and pressure drop of the CFD model were within 16% of the analytical model. The thermal performance of the heat exchanger with heat pipes was 0.044°C/W, meeting the client’s requirements.

Solution: The ATS design was optimized for four heat pipes and a suggestion was made to enhance the heat exchanger by using copper fins, rather than aluminum, because of a higher fin efficiency and lower thermal resistance.

Net Result: The customer was supplied with a production design of a heat exchanger block with heat pipes that could fit into the enclosure and provide the necessary forced convection cooling to maintain the proper temperature for the system. ATS also supplied the heat exchangers from the prototype stage to production.

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.