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Application Spotlight: 3D Printing for Heat Exchangers

[Image credit: Conflux Technology]
 
The range of industrial applications for 3D printing is growing by leaps and bounds. 
 
However, despite this growth, there remain a lot of gaps in understanding of the true capabilities of 3D printing. Supporting this fact is AMFG’s latest State of the 3D Printing Industry Survey 2019 report, which found that the lack of knowledge around 3D printing remains one of the biggest challenges for 3D printing service providers today. 
 
To shed light on how 3D printing is being used in industrial applications today, we’re launching a weekly Application Spotlight series. In the series, we’ll be looking at the use of 3D printing for a particular application, and diving into the key benefits and examples.  
 
Opening our series this week is 3D printing for heat exchangers. The technology offers a number of benefits for manufacturers looking to optimise the designs of heat exchangers. Among them are lighter weight, smaller size and superior performance.  
 
But before exploring the benefits in more detail, let’s first look at what a heat exchanger is, and why this application is a great fit for 3D printing.
 

What is a heat exchanger? 

<em> An example of a heat exchanger is car radiator</em>
An example of a heat exchanger is a car radiator

 
A heat exchanger is used for temperature regulation and is one of the most crucial pieces of industrial equipment. Heat exchangers allow heat from one fluid to pass to another fluid with the primary purpose of heating up elements or cooling them down.
 
Within the industrial sector, the cooling function is used more frequently to prevent equipment from overheating.
 
Heat exchangers have a very broad range of applications. Engines in cars, ships and planes all use heat exchangers to work more efficiently. Components within air conditioning and cooling systems like refrigerators require heat exchangers as well. 
 
Due to the sheer versatility of applications, designs of heat exchangers can vary greatly. The majority of conventionally-made heat exchangers feature either a coil or plate design. 
 
In their simplest form, coil heat exchangers use one or more coiled tubes, separating two fluids: one which flows inside the tube and another which flows on the outside. 
 
Plate heat exchangers use thin plates of metal to separate the two fluids. The fluids generally flow in opposite directions to improve the heat transfer.
 

Why is 3D printing suitable for heat exchangers? 

stratasys heat exchanger
A heat exchanger 3D printed in metal [Image credit: Stratasys]

 
Producing heat exchangers using conventional techniques is often a complex and time-consuming task, requiring multiple steps like forming and welding. 
 
Furthermore, there is an increasing demand to make heat exchangers more compact and efficient to improve ever-growing performance requirements. And yet the capabilities of current manufacturing techniques often prove inefficient to meet this demand. As a result, manufacturers often have to compromise between the design complexity, cost and lead time.
 
To overcome these limitations and enable new heat exchanger designs, companies are beginning to investigate the capabilities of 3D printing.  
 

How can heat exchangers benefit from 3D printing? 

 

Increased performance through more complex geometries

3D printing is known for its ability to bring complex shapes to life. When designing heat exchangers, this benefit can be used to create walls as thin as 200 microns and small, intricate flow channels inside the component. 
 
This means that engineers can design a heat exchanger with greater heat transfer surface inside. The larger the surface area, the more heat that can be removed, which increases the performance of a heat exchanger.
 

Reduced weight and size 

The majority of today’s heat exchangers have either rectilinear, rectangular or tube shell designs. Due to their unique shape, fitting these heat exchangers into a device can be challenging. 3D printing, on the other hand, allows engineers to make the device lighter and smaller, but with the same or even better performance 
 
New shapes and internal features made possible with 3D printing facilitate the miniaturisation of heat exchangers. As a result, 3D-printed heat exchangers have a much more compact shape that fits tight space requirements.
 

Simplified production  

Traditionally, the production of heat exchangers involves multiple steps, including forming, brazing and welding. However, these steps are expensive and time-consuming. 
 
When using 3D printing to produce a heat exchanger directly, all these operations can be eliminated, thus streamlining the production process. 
 

Better quality 

Furthermore, a 3D-printed heat exchanger is built in one operation so there are no seams or joints that could develop leaks. Due to a more straightforward production, process variability is lower and overall quality is expected to be much higher.
 

Examples of 3D-printed heat exchangers

The aerospace, motorsports and energy industries are currently leading the charge in developing 3D-printed heat exchangers. 
 

Conflux Core: a new benchmark for heat exchangers 

Heat exchanger, Conflux Technology
The Conflux Core heat exchanger features a complex internal shape which helps to enhance thermal performance [Image credit: Conflux Technology]

 
Conflux Technology is an Australian company which specialises in the metal 3D printing of thermal and fluid components. Such components are used in industries like automotive, motorsport and aerospace. 
 
By harnessing 3D printing, Conflux has developed and patented a unique heat exchanger design called the Conflux Core.  
 
The use of 3D printing enabled the creation of highly complex geometries inside the Conflux Core component, increasing its surface area. This allowed the thermal heat rejection to be tripled. The new design, when compared to a Formula 1 benchmark, was shown to be 22% lighter and 55 mm smaller in length. 
 
Additionally, 3D printing enabled an extremely fast development process, which took just six months.  
 
Finally, thanks to the design flexibility of 3D printing, the Conflux team was able to consolidate subcomponents into a single part. In addition to a simplified design, a consolidated part also requires less material for production, potentially reducing material expenses. For manufacturers using the Conflux Core, part consolidation could translate into a reduced assembly time and fewer failure points from joints and seams.
 

GE’s lung-inspired heat exchanger

GE's 3D-prited heat exchanger for power generation applications
A bio-inspired heat exchanger for power generation applications [Image credit: GE]

 
GE Research is developing a heat exchanger with increased operating temperature and thermal efficiency for power generation equipment. Surprisingly, to achieve this, the team came up with an innovative design inspired by human lungs. 
 
The GE heat exchanger features a trifurcating network of channels, which takes hot air coming out of a gas turbine. This network is intertwined with another network of channels filled with colder working fluid, running in the opposite direction. The hot air and cool fluid do not mix with each other, but their close proximity allows for efficient heat exchange.
 
This new kind of heat exchanger could help power plants handle temperatures of 1,650 degrees F (871°C). That’s more than 450 degrees F (232°C) higher than current heat exchangers. 
 
The team found that the only technology capable of producing such a design was 3D printing. 
 
The 3D-printed heat exchanger will be manufactured using a unique, high-temperature capable, crack-resistant nickel superalloy developed by GE Research specifically for this technology.
 
The combination of the design freedom offered by 3D printing and the strength of a superalloy is set to enable a step-change in heat exchanger performance. 
 

Using advanced technology to meet advanced requirements 

Heat exchangers are a great application for 3D printing. The technology provides significant design flexibility, enabling more compact shapes and higher performance.    
 
Thanks to its unique capabilities, 3D printing could become a key technology for manufacturing heat exchangers. With such a flexible technology onboard, heat exchanger manufacturers will be able to meet new size and performance requirements heads-on.
 
In our next article, we’ll be looking at 3D printing for bearings. Stay tuned!