Tube of Ranque-Hilsch

The tube of Ranque-Hilsch is a device thermodynamic without part moving making it possible to produce cold air, imagined by French Georges Joseph Ranque and improved by German Rudolph Hilsch.

Practical operation

The air injected tangentially creates by vortex effect an extremely fast turbulent flow (a turn million per minute) and is slowed down by a conical valve. The heat transfer with the wave produced in return cools the considered air.

It must be fed in compressed air (5 to 10 bars) very dry and clean. Manufactured in dimensions from 10 to 30 cm length and approximately 1 cm diameter, it reaches a difference in temperature of 70°C between the entering air and the cold side. Under these conditions, the refrigerating power is about 2500 kcal/h.

Of course, it can function with any gas which does not condense at the produced temperatures.

Use: everywhere where is necessary a cooling without contact (machining, test of electronics components, manufacture of the chocolate). Disadvantage: the system (compresseur+tube) is much less effective in terms of energy than the traditional cooling groups.

A little thermodynamics

First principle

That of the conservation of energy. The thermodynamic equation is very simple:

Either p the fraction (in mass) of outgoing gas on the cold side, and C the Specific heat of gas, with the indices has (food), F (cold side) and C (hot side):

c_aT_a = p c_fT_f + (1 - p ) c_cT_c

By supposing the Perfect gas one can simplify:

T_a = p T_f + (1 - p ) T_c In the facts and more especially as one will seek to increase the performances, one will move away from perfect gas…

Second principle

According to the Second principle of thermodynamics, it is impossible to cool the cold body thanks to another hotter without spending of energy. It is however what this device seems to do! By considering the whole of the system, compressor and tube of Ranque-Hilsch, it becomes clear that it is the compressor which provides this work. The fathers of thermodynamics can sleep quiet…

It should be noted that the operation of the tube is still not very clearly. It is in any case related to the compressiblity of the fluid because it is completely inoperative with a liquid.

Uses - output

Various less anecdotic uses were or are still studied. they run up all against the deplorable output of the compressing unit and tube, about 0,10 whereas that of a refrigerator (COP) reached 10.

Production of liquid air by a cascade of tubes
Separation of gas of different densities

See

Perfect gases

External bonds

This device was patented by G.J.Ranque in 1931 in France, then in the USA in 1934: patent US-1,952,281

Recent thesis

Tim Cockerill, 1995

Random links: