Can this temperature separation be explained?

The vortex tube effect was discovered in 1933 by French metallurgist Georges Ranque. Since then, thousands of research articles have studied the effect at some extent, according to a recent Google Scholar database search (e.g. "vortex tube" air flow *anywhere in the article* gives 5,850 hits). Until recently, there was no final explanation as to why the air in the center of the tube becomes cold, while peripheral air becomes hot. This was the conclusion of a recent review article, published by Xue et al: "A critical review of temperature separation in a vortex tube", Experimental Thermal and Fluid Science, vol. 34, issue 8, page 1367, year 2010.

The enigma in the vortex tube

The vortex creates cold, refrigerated domain at the center, while a hot domain appears at periphery. Here is a cross-sectional image of the total temperature in the tube, calculated with computational fluid dynamics:


It seems that heat is moved from one place (center, left) and released at another (periphery, right). What is the mechanism of this motion of heat? The second law of thermodynamics forbids the flow of heat from cold to hot without the addition of work.

Have there been attempts to explain the vortex tube effect?

During the 80 years of vortex tube research, many attempts were made to explain the effect. Georges Ranque, the inventor of the vortex tube, was the first to propose an explanation. Through the decades, a few explanations were established and these can be found in recent review articles on the subject of vortex tubes. The four main proposed explanations are:

Radial pressure difference: centrifugal compression and air expansion

Radial transfer of angular momentum

Radial acoustic streaming of energy

Radial heat pumping

Other models exist, yet they generally fall within the above main concepts. The source of this listing of four are the review articles

1) Xue et al, Experimental Thermal and Fluid Science 34(8), 2010, 1367-1374.

2) Eiamsa-ard et al, Renewable and. Sustainable Energy Reviews 12(7), 2008, 1822-1842.

What is still missing?

Only recently, in 2011, new understanding of the fundamental physical laws of vortex cooling was discovered. It was published as four articles (listed below) in the period August 2012 - January 2015. To read about the new findings, click on a navigation menu item.

The reader is also invited to peruse the following research articles written by Jeliazko G Polihronov and collaborators:

Questions about this site? Email Jeliazko G. Polihronov at: