A unique Sterling cooler (coolers employing the Stirling cycle of operation) has been designed by Prof. S L Bapat of Department of Mechanical Engineering. In a Stirling cycle, a working fluid such as helium or hydrogen is first compressed and 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 down further. The resultant cooling or refrigeration effect is extracted and used for cooling applications. During return of the cold gas for the next cycle of compression, it is allowed to pick up heat from the regenerator. Stirling coolers used for cryogenic applications are also known as Stirling cryocoolers.