The Conflux 3D Printed Water Charge Air Cooler
We set out to match or exceed an incumbent micro-tube heat exchanger for a transmission application at a significantly reduced price point. 3D Printing
Objective
Create an ultra-high performing additively manufactured water charge air cooler priced to compete
We saw the many advances in laser powder bed fusion (LPBF) – a type of metal 3D printing – as an opportunity to improve on the previous industry standard for air cooler heat exchangers like microtube heat exchangers.
Specifically, we wanted to achieve the maximum heat transfer performance alongside a host of other key performance-enhancing benefits:
- Reduced part size
- Reduced weight
- Reduced airside pressure drop
- Reduced coolant pressure drop
- Reduced cost
Design: Air Cooler Performance and an adjustable design
Challenge
The main challenge was making a design that works from a performance perspective; this meant hitting the weight and volume targets set for us. In other words, we needed to create a heat exchanger with very high compactness. Trying to insert the required surface area into a volume smaller than our competition, while besting pressure drop benchmark data took some creative thinking.
Another significant challenge with this WCAC was determining how to develop manifolds that could distribute fluids evenly from a single inlet connection to the many thin channels running throughout the core. Similarly, we needed to find an effective method for feeding high pressure air into the core while minimising airside pressure drop from the blockage of the core itself.
Lastly, we knew we needed to productionise the design effectively to add even further commercial value. Therefore the CAD model needed to be constructed in a way to allow rapid modification.
Solution
We invested time designing and simulating different core geometries at micro-fluidic scale. Rapid iterations of design and simulation allowed us to intensively develop a super-efficient core. We applied a similarly intensive development methodology to the manifolding to optimise the trade-off between the mass flow distribution and pressure drop on both sides of the core.
The design outcome was high heat transfer performance, low pressure drop and even mass flow distribution through the core. This is particularly impressive given its high level of compactness.
We utilised a parametric modelling approach to adjust the design easily. We can quickly adjust the core dimensions, the cross-sections, length of the part, inlet and outlet types and locations. This enables us to rapidly re-design to suit different applications; different boundary conditions and packaging requirements.
Simulation Phase: Heat transfer performance with minimal pressure drop
Challenge
Our primary concern at the simulation stage is meeting the customers performance targets. As mentioned above, the challenge with the Conflux WCAC was achieving the heat transfer performance for a very small pressure drop within the given volume.
With simulation, the finer the features, the larger the model, the larger the file size. As a consequence the simulations take a long time even on highly spec’d dedicated compute clusters.
Furthermore, the LPBF style of manufacturing results in a rough surface, as opposed to the smooth surfaces of a CAD model. This poses problems in accurately predicting the performance – particularly pressure drop within the heat exchanger.
Solution
Our solution was to develop a geometry that actually works. We did this by pragmatically simulating and developing in iterative design-simulate-design loops until we reach the desired performance.
This next step was to perform laboratory based calorimetric testing on the full-size AM WCAC. Part of our development process is comparing results of laboratory tests with the results from simulation. This allows us to correlate the simulation model, which in turn improves its predictive accuracy. When a customer comes to us with a different set of boundary conditions we have confidence based on the correlation work we have stored in our, ever-expanding, database.
Additive Manufacturing: Post processing and powder removal
Challenge
The Water Charge Air Cooler has over 60,000 ‘fins’ each with multiple connections, therefore potential for failure points is enormous. Managing the build process for the core geometry so that the part holds pressure was a considerable challenge.
Additionally, LPBF manufacturing results in un-melted powder remaining inside the core of the heat exchanger after build. The extremely small channels within the complex geometry of our core design meant that powder removal posed a significant problem. Small complex features with rough surfaces are very effective at retaining powder particles!
Solution
A developed, tested and optimised solution that is part specific is the only way to achieve successful builds, that hold pressure and are powder free. There are many factors that can affect the ability of thin-walled structures to be reliably and consistently built and they must all be considered and balanced.
Powder removal is an area that required a multi-faceted approach and can be very sensitive to different geometries. At Conflux, we employ several different and inventive techniques in harmony.
Results: High performance heat transfer
With the myriad thermal challenges met, Conflux has designed and produced a Water Charge Air Cooler heat exchanger that has exceeded the targets outlined at the beginning of the project.
With its adaptable design, embedded complexity, and high efficiency/low mass, Conflux’s water charge air cooler (WCAC) offers a gold standard for performance vehicles that can be easily modified to meet the needs of other applications.
For a deep dive into all the test results, contact our team for a technical presentation.
