Military Embedded Systems

New European program exhorts nano fluids to teach systems how to "be cool": Interview with David Mullen, NanoHex project director and mechanical engineer at Thermacore


July 14, 2010

No one's really 100 percent certain why the heat capacity of nano fluids is so much higher than other cooling fluids, but the fact is: They're really cool for hot electronics. They can offer up to a 350 percent cooling improvement over conventional coolants. But manufacturing nano coolants is slow, and the European Commission (EC) is looking for ways to ramp production and bring down the price. The avenue: the NanoHex nano cooling fluid project, headed by David Mullen of Thermacore, whom editor Chris Ciufo recently interviewed to get the whys and wherefores. Edited excerpts follow.

MIL EMBEDDED: Let’s start with a brief overview of what Thermacore is and what it provides.

MULLEN: Ok. Thermacore is a global company with corporate headquarters in Lancaster, Pennsylvania that specializes in advanced thermal solutions. However, I work for the Thermacore Europe subsidiary in the United Kingdom. Thermacore serves a variety of OEM applications across a diversified set of global markets that include military/aerospace, medical, computers, communication, energy conversion, power electronics, and government.

Essentially Thermacore’s core technology is based on heat pipes and heat pipe assemblies, but we also offer other thermal solutions such as liquid-cooling cold-plate components and systems, enclosure heat exchangers, and complex vacuum brazing heat exchangers. Thermacore has specialized in the development and application of heat pipe technology for more than 40 years, and our new NanoHex nano fluid coolant program [] is hopefully going to allow us to extend liquid-cooling technology as well.

MIL EMBEDDED: Can you explain briefly how a heat pipe works, and how or when you implement them?

MULLEN: Sure. Essentially a heat pipe is a heat superconductor. A heat pipe utilizes two-phase heat transfer to passively [no external energy] and efficiently move heat from a concentrated area and transfer it to a remote area where it can be removed to the external environment through natural convection, forced convection, or radiation. Thermacore’s engineering services include design using CFD [Computational Fluid Dynamics] analysis, Finite Element Analysis (FEA), as well as development and prototyping, and product qualification. Many of our customers come to Thermacore late in the design stage after they have discovered a thermal problem within their system. Obviously, the late-design stage challenge restricts us a little, though, and we prefer to be involved in the initial concept stages of the electronic or system design.

MIL EMBEDDED: OK so switching gears, let’s talk about your recent announcement of the NanoHex project. Set the stage for that, if you would, please.

MULLEN: Thermacore Europe has an ongoing program of recruiting PhD students, and then about 90 percent of those will be taken on as engineers by Thermacore after graduation. So we’re in quite a good position to take on forward-looking technologies. And liquid cold plates is one area that we want to try and improve the thermal technology.

Within Europe, there is a program called a framework program, funded by the European Commission [EC] to enhance the EU’s technical base by targeting technologies in European companies. The EC had identified 53 billion euros to invest in new technologies. So we learned that one EC “call” [meaning, a project bid request] was to upscale manufacturing on nano technology.

So we decided to, along with a few academic institutions with which we already had contacts, set up a project to target this particular call to develop nano fluid coolants.

MIL EMBEDDED: When was all this, and how much was the final price tag?

MULLEN: Let me put it this way: After three years, we won the NanoHex project from the European Commission. We believe if it’s not the biggest, it’s at least one of the biggest nano technology projects in the world. The EC funded it with 6.1 million euros, with additional contributions from our partners making it an 8.3 million euro project. The project actually started on September 1 of last year and will run for 3 to 3.5 years.

MIL EMBEDDED: Can you describe what the NanoHex project entails?

MULLEN: The original call was to upscale the production of nano technology, and in our case that’s nano fluid coolants. What the EC would like us to do is to take promising laboratory-based results, which can only produce perhaps a few kilograms of nano fluid coolant currently, and upscale that to create a pilot line to result in the eventual manufacture of a few tons of nano fluid coolants.

MIL EMBEDDED: So the challenge is manufacturing, which is a surprise to me. What are the additional end goals?

MULLEN: Beyond manufacturing a pilot line and producing a few tons of this material, per the EC’s directive, we also need to sell and commercialize the nano fluid coolants: The EC wants to see that we’re looking at even more opportunities in the industry that might be a fit for using the fluid. So, within the project we’ve identified two main areas: data center cooling and traction control IGBT cooling.

MIL EMBEDDED: Any other areas for possible usage, beyond those two?

MULLEN: One of the key technologies we’re targeting for the nano fluid coolant is housed within data centers, where there is an ever-pressing need to reduce energy costs. Predominantly, energy is used to cool the servers or cool the environment in which they work. What we hope to offer the data center is nano fluid coolants with up to a 350 percent improvement when compared to a traditional coolant. We hope to utilize it in the data centers’ hot spots within cabinets, and to provide some exceptional cooling that will ultimately lead to reduction in energy costs, perhaps even increasing the actual server’s density so that we can even look to reduce the overall size of the data centers. There are lots of possibilities.

MIL EMBEDDED: Can cooling racks of equipment reduce the energy consumed by the servers, or would it reduce the energy used in cooling the servers themselves?

MULLEN: Predominantly, it’s the energy used in cooling the servers.

MIL EMBEDDED: I see. So the servers are still going to consume what they consume but you could reduce the amount of cooling required because you’re putting it right where it needs to be.

MULLEN: Yes. And our technology goes even a step beyond that because we want to take the nano liquid coolant directly to the chip. So it’s taking the heat directly from the chip or any other component within the server blade, out – and then perhaps into a heat exchanger on the cabinet and then to a heat exchanger outside the building. It could even then be used, as some people have started to use the coolant, to heat their office space, for example.

MIL EMBEDDED: With a heat exchanger, you take the hot air out of the data center and then route it into the rest of the offices of the building?

MULLEN: Not the air. What we’re doing is taking a nano fluid coolant and circulating that around a data cabinet where the servers are, taking more heat out because of the extra performance we can get from nano fluids, into a heat exchanger on the back of the cabinet. And then more coolant, not air, would take that heat energy outside of the building via a heat exchanger.

MIL EMBEDDED: What’s the practical distance of that, within the building itself?

MULLEN: Data centers can vary in size from half a football pitch to even four football pitches or the size of a small office block. But a lot of data centers have been built with the infrastructure to support liquid cooling underneath the floors. Pipe works are generally already there. So we’ll be utilizing what’s already there to take the heat from the processor within the server cabinet to the heat exchanger or to that pipe or that infrastructure that already exists.

MIL EMBEDDED: Is the nano cooling fluid proprietary, patented, standard materials, or what?

MULLEN: It’s not proprietary. It’s patented by a couple of the partners within the project. There are 12 project partners in total, many academic and several industrial. We have two partners – a UK company called Dispersia and also ITN Nanovation in Germany – who already produce nano fluid coolants on only a laboratory scale. They employ two different techniques of producing nano fluid. So if we find one is too risky to upscale, we’ve always got an alternative. But at the moment, both technologies appear feasible in achieving the pilot lines.

MIL EMBEDDED: What are the technical challenges in producing the fluid itself?

MULLEN: One challenge is in the manufacturing, that is, the actual particle conditioning and also coating the particles’ surfaces to create a nano fluid coolant where the particles don’t agglomerate. That way, they remain very stable and very dispersed within the actual base carrier fluid. Another challenge is to upscale the fluid and be able to repeat what we see in the laboratory at an industrial level.

And the final challenge is to turn the nano fluid coolant into something that can be used, so we’re looking to develop very advanced cooling devices because the condition of the fluid as it flows through these heating devices is very, very critical to its performance.

Lots of people have done work on nano fluid, but nobody understands the fundamentals of how it transfers that heat, which is what has primarily hindered a lot of nano fluid development worldwide. We have a good knowledge, and a certain part of the project entails understanding that mechanism of heat transfer and developing very specific transfer devices or cold plates that can harness that.

David Mullen is a Senior Research and Development Engineer at Thermacore Europe Ltd. Since 1987, he has worked in a number of senior engineering capacities and is a chartered member of the Institution of Mechanical Engineers. Predominantly, he has specialized in engineering project management, including a number of multimillion-dollar projects. NanoHex, which David will be coordinating, represents a significant opportunity to develop an advanced thermal solution to reduce energy usage around the world. He can be contacted at [email protected].

Thermacore +44 (0) 1670 859518

For more information on the NanoHex project, go to


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