Constructal Theory: The Applications


Nature builds from the bottom up. From simple molecules, life can form the giant sequoia tree. Likewise, constructal theory provides a way to make shapes, from the bottom up. So, what can we build with constructal theory? Applications of constructal theory are limitless, but one significant constructal approach is to design from a finite size (small) and build up to larger optimized structures. This is what IBM has discovered in their new chip cooling system. The 'greening' of the computer has begun. Companies are emerging that promise increased efficiencies, and IBM and Intel race to achieve amazing new chip designs. But how do you optimize performance with efficiency? Heat management with energy consumption? IBM's radical new cooling system is a good example of how we can begin to optimize structures for a sustainable future- and coincidentally, their cooling system looks like a tree.Computers have become an integral and necessary part of modern life- without which we could hardly function (isn't it a miracle we got this far without them?). But computers are also an expensive use of resources and energy. In biology, whenever something is necessary but expensive nature demands that the design be optimal and sustainable. This is achieved through biological evolution. The cactus doesn't know it is perfectly adapted to hold onto water in the desert- but we can look and see the genius of the cactus.

Similarly we can evolve design. IBM sought to increase the efficiency of their cooling system, and a scientist versed in biology, computers, and constructal theory took them down the path to a radical evolution in design that has demonstrated cooling power densities of up to 370 Watts per square centimeter with water as coolant (Six times beyond current limits of air-cooling technology- with less energy). Bruno Michel, manager of the Advanced Thermal Packaging research group at IBM's Zürich lab talked with me about how his team built the system from the bottom up. He confirmed that constructal theory, along with other optimization and creative techniques, played a role in the teams final design. You can see constructal organization throughout the design, from the vascular-like structure for the inlet and outlet tree to the hierarchical forest-like structure of channels that spread the coolant paste most efficiently.

From the article by Nicole Herfurth:

"The approach used by IBM addresses the connection point between the hot chip and the various cooling components used today to draw the heat away, including heat sinks. Special particle-filled viscous pastes are typically applied to this interface to guarantee that chips can expand and contract owing to the thermal cycling. This paste is kept as thin as possible in order to transport heat from chip to the cooling components efficiently. Yet, squeezing these pastes too thin between the cooling components and chip would damage or even crack the chip if the conventional technologies are used.

Using sophisticated micro-technology, the IBM researchers developed a chip cap with a network of tree-like branched channels on its surface. The pattern is designed such that when pressure is applied, the paste spreads much more evenly and the pressure remains uniform across the chip. This allows the right uniformity to be obtained with nearly two times less pressure, and a ten times better heat transport through the interface."

The bold above is my emphasis, as it demonstrates a principle of constructal theory- the optimal distribution of imperfection. The image below is from IBM's research- this is an example of how to 'optimally distribute' the paste with a hierarchical 'tree' - notice the different size and proportion of channels. This is one example of 'providing easier access to the currents that flow through' the system. Simply put, the channels become increasingly wider.

You can see below another hierarchical 'tree' structure from Adrian Bejan's earlier work on constructal trees as heat exchange- where a single contact draws heat from a rectangular area. Again notice the increasingly wider 'channels' through which something would flow- Much like a stream to a river.

Interesting IBM's tree channel structure for distribution of the paste leaves a familiar constructal design on the paste itself - This is an image of what the paste looks like after it is pressed onto the chip. Notice the organic looking pattern of channels- something you might see in a leaf-

And here is an optimized structure designed by Adrian Bejan and his group for a circular area heat exchanger-

Lastly IBM gives us a more visceral tree. This Inlet outlet system designed by IBM looks very much like a lung system, vascular exchange system, or simply a tree.

The application of a bottom up constructal approach led to these shapes- and to a cooling structure that is more efficient than anything out there today. Constructal theory provides the tools engineers need to create sustainable, and beautiful technology. This is not the only application of a constructal approach, far from it. The constructal website features scientific applications from social dynamics and the structure of coral colonies, to climate models and how dust aggregates form in the atmosphere. Constructal theory can help us understand nature, and teach us how to design like nature. So I ask again, what can we do if we build from the bottom up?

Constructal Theory: Introduction to the Inverse of Biomimicry

Constructal Theory: Sustainability
Constructal Theory: The Science
Constructal Theory: The Applications
::IBM Zurich
::Constructal Web Portal
::Shape and Structure, From Engineering to Nature
Images used with permission from author.

Tags: Biomimicry


treehugger slideshows