News Brief: Common campfire style is still the best

A structure of roughly equal height and width produces hottest flames, new calculations show

Heaps of firewood or charcoal that are as tall as they are wide make the hottest fires. Fires built tall or squat burn cooler, new calculations show. 

ERIC DUFRESNE/WIKIMEDIA COMMONS (CC BY 2.0)

Ah, summer vacations. Thinking about them, you can almost smell the smoke from marshmallow-toasting campfires and backyard barbeques. What’s even better: Building those controlled blazes may require little thought, a new study shows.

Humans tend to build very efficient fires, perhaps unwittingly, says Adrian Bejan. He’s a physicist at Duke University. And he has crunched the numbers to back up his assertion.

Across cultures, countries and time, people have built fires in a similar way. They pile wood or other fuel into a pyramid or cone shape. Those piles tend to be about as tall as they are wide at the base, Bejan says. And there may be no need to learn this skill, he adds. People seem to do it instinctively. The question was why.

For a new study, Bejan made calculations of how air and heat flow through structures. Fires with proportions like those of common campfires produced the hottest flames for their volume of fuel, he finds. Fires lost more of their heat if they were relatively tall or short compared to their width, he now reports.

The calculations, appearing June 8 in Scientific Reports, suggest no scout handbooks are needed for those leisurely summer blazes.

Power Words

(for more about Power Words, click here)

fuel  Any material that will release energy during a controlled chemical or nuclear reaction. Fossil fuels (coal, natural gas and petroleum) are a common type that liberate their energy through chemical reactions that take place when heated (usually to the point of burning).

pyramid     A monumental structure with a square or triangular base and sloping sides that meet in a point at the top. The best known are those made from stone as royal tombs in ancient Egypt.

physicist  A scientist who studies the nature and properties of matter and energy.

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