A unique Sterling cooler (coolers employing the Stirling cycle of operation)
been designed by Prof. S L Bapat of Department of Mechanical Engineering.
Stirling cycle, a working fluid such as helium or hydrogen is first compressed
this hot gas is allowed to cool down to the desired temperature while passing
through a regenerator (porous matrix) and then allowed to expand to cool
further. The resultant cooling or refrigeration effect is extracted and used
applications. During return of the cold gas for the next cycle of compression,
is allowed to pick up heat from the regenerator. Stirling coolers used for
applications are also known as Stirling cryocoolers.
The unique designed Stirling cooler developed consists of a compressor
a piston disposed in a compressor cylinder. It has an expander comprising
rotatably and reciprocally disposed in an expander cylinder. A regenerator
within a cavity formed in an extension at the top of the expander piston.
groove is formed on the extension adjoining the bottom wall of the cavity
and the top end of the expander piston and gas passages formed in the top
bottom wall of the cavity. A pair of helical grooves is provided along
the length of
the expander piston with their ends meeting each other. The pitch of the
formed by the helical grooves is twice the expander piston stroke.
The compressor cylinder is connected to the expander cylinder through
a connecting tube and helical grooves provided
along the length of the expander piston and the circumferential groove.
At least one seal is provided between the sidewall
of the cavity and expander cylinder to prevent gas leakage and a conductor
material cap is provided over the top
of the expander cylinder, which corresponds to the expansion space formed
within the expander cylinder between the
top end of the extension and the closed end of the cap.
The unique design of the cooler makes it very compact and effective in
cooling. The coolers have long life, attained
through the use of non-contact running surfaces. Gas bearings allow
the two moving parts to "ride on a cushion of gas" keeping
the running surfaces from making contact while the machine is operating.
Unlike vapor compression systems
outfitted with capillary tubes that have optimized performance at only
one temperature condition, Stirling coolers maintain
their high performance over a wide range of temperature conditions.
Cooler uses the environmentally safe inert gas, helium, as the working
fluid. Light weight makes portable cooling a reality.
Stirling coolers perform well in harsh temperature environments and
high ambient temperatures and are limited
only by the materials of the cooler. These are some of the advantages
of the designed cooler.
Indian patent application no. 299/MUM/2006 Patent grant no. 225128
Inventors: S L Bapat