Newspaper article The Christian Science Monitor

Science Reveals How to Build the Perfect Fire

Newspaper article The Christian Science Monitor

Science Reveals How to Build the Perfect Fire

Article excerpt

From campfires made by our human ancestors to bonfires on the beach today, humans have tended to build fires relatively the same way for thousands, if not millions, of years.

"The question of when they controlled the fire ... is a very open question," says Richard Wrangham, a professor of Biological Anthropology at Harvard University and author of "Catching Fire: How Cooking Made Us Human." "I have argued that it emerged almost 2 million years ago," he says.

But have you ever thought about why we all build fires similarly? Adrian Bejan, a professor of Mechanical Engineering at Duke University, has a theory which is presented in the most recent edition of Nature Scientific Reports.

Bajan began by, "asking the question that hasn't been asked: why do we make the fire always this way?" Personal experiences growing up in Romania as well as teaching students from around the world inspired his interest.

"I spent many days and nights fishing on the banks of the Danube [River] where fire is essential," says Bejan. "It is amazing that what is in me is in everyone else."

Provided that there is an ideal height as indicated by the "tall limit" (in which the fuel viscosity is oriented vertically), and an ideal width as indicated by the "shallow limit" (where the fuel viscosity is oriented horizontally), the intersection between the two computed asymptotes eliminates the extreme regions which create inefficient fires.

The body temperature of the burning structure decreases both when the structure gets taller, and when it becomes shallower, allowing the optimal use of fuel to occur when the height is comparable to the base.

Conclusion: the "ideal" fire is roughly the shape of an equilateral triangle.

This finding falls in the field between evolutionary biology and thermodynamics and is consistent with the principles established by Bejan's earlier work in Constructal Law. …

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