Nature and Engineering cut heating bills

11 June 2015
Posted by Ziyad Yehia.

Your heating bills could be in for a reduction thanks to engineering insights gleaned from nature.

Design in Nature

Natural systems, such as trees, animals, rivers and lightning strikes can be regarded as "flow systems": "currents" flow into them in the form of nutrients, air, water, or electricity, and other things, flow out.

The constructal law, a phenomenon published in 1996 by Duke University scientist Adrian Bejan, states that, in order for any finite-sized flow system to survive or exist, it must evolve over time to provide easier access to the currents flowing through it.

Bejan argues that evolution is not a purely biological phenomenon, but rather it has a natural place in the realm of physics as life and the world evolves to become more efficient at accessing its "flows".

The branching patterns seen in tree canopies, lightning strikes and our own circulatory systems are thought to have evolved in precisely this way to make the flow of their respective currents more efficient.

The same branching designs, Bejan suggests, could open up new avenues for engineering. 

Energy storage installations called "phase-change" systems work by storing and releasing energy in a material which melts or solidifies at certain temperatures.

The idea is that the energy can be stored at one time in the material and then kept for later when it will be more useful. For example, phase change energy storage systems can be used to soak up the day's heat and then gradually release it at night when it's colder, helping to save on heating.

Now, in a recent study, Bejan has applied this principle to man-made engineering designs and tested whether using these branched structures can improve the performance of phase-change energy storage systems.

In phase change designs, transferring heat rapidly and efficiently is crucial for optimal function. And as branching structures are very common in nature, Bejan wondered whether using branching structures to transfer heat in phase-change designs would result in more efficient heat transfer and better performance than conventional, man-made heating and cooling coils used currently.

Now, writing in the Journal of Applied Physics, Bejan has performed computational simulations and found that the branching structures performed better than coils, and found that factors such as the number of branches, number of levels of the branch and the size of the branch angle would all affect the efficiency of the heat transfer. 

Furthermore, by allowing the branch structure to grow and evolve freely over time, more and more efficient transfers are observed.

According to Bejan, "technology is destined to continue to improve, because we as humans want to continue to improve. We want to improve the access of our flows, to us."

So our homes could be evolving their way to better energy efficiency and a warmer winter, all thanks to the laws of nature...

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