An Investigation of the Ranque-Hilsch
Vortex Tube
The development of
micro-fabrication techniques has led to a resurgence of research into
micro-fluidic devices. Devices that have been investigated include pumps,
valves, flow sensors and heat exchangers. The performance of a micro-scale Ranque-Hilsch tube, a non-moving part pneumatic device
that separates cold fluid from hot fluid for the purpose of cooling, has
not yet been reported. A micro-scale Ranque-Hilsch
tube in combination with a micro-fluidic pump has potential application in
the cooling of electronic chips. This work involves an experimental and
numerical investigation of the energy separation performance of a
micro-scale Ranque-Hilsch vortex tube. It is
known that such devices do not operate in the laminar flow regime, however,
the lowest characteristic Reynolds number at which the operation is
observed has not been established.
In order to answer this question a 2 mm diameter micro-vortex tube
is constructed using a layered technique from multiple pieces of Plexiglas
and aluminum. Four inlet slots that are symmetrically located around the
tube form the vortex. The working fluid is low pressure, compressed air.
The hydraulic diameter of each inlet slot and the orifice diameter for the
cold exit are approximately 200 and 800 microns respectively. The hot gas
opening is varied by means of a control valve to achieve different values
of cold mass fraction. The total mass flow rate entering the vortex tube is
of the order 10-5 kg/s to maintain the Reynolds number entering
the slot to as low as 500. The length of the tube and hence the L/D ratio
was increased by adding a number of layers of Plexiglas. In addition to the
experimental investigation, a full three-dimensional numerical model is
constructed and a computational fluid dynamic simulation conducted using
GAMBIT, and FLUENT version 6.2. Details of the experimental apparatus,
numerical model and the results of the experimental and numerical
performance as well as numerically predicted flow and temperature patterns
are to be determined. Amar Hamoudi completed his M.A.Sc. student based on this topic.