Magnetic Field Sources - Magnetocaloric Energy Conversion: From Theory to Applications - page 68

Fig. 3.25 An example of a superconducting solenoid

Fig. 3.26 Schematics of recuperative and regenerative cryocoolers. Modied gure, originally
published in [ 29 ]; published with kind permission of © [IOP Publishing, J Phys: Condens Matter

2009]. All Rights Reserved

Generally, cryocoolers can be applied to superconducting devices in different
ways, such as: open-cycle cooling with immersion, closed-cycle cooling by
reducing pressure, closed-type cooled with immersion, forced-

ow circulation
cooling and direct cooling by refrigerator. Additional information on these methods
can be found in Flynn [ 30 ] and Wang [ 31 ].
As can be seen from Fig. 3.26 , cryocoolers can be either regenerative or recu-
perative [ 32 ]. The recuperative cryocoolers apply recuperative heat exchangers (e.g.
counter-current) and operate with a steady

fl

ow of refrigerant through the system.
The regenerative cryocoolers comprise at least one regenerative heat exchanger, i.e.
a passive regenerator. They operate under oscillating

fl

ow and pressure. In a passive
regenerator the incoming warm gas refrigerant transfers heat to the material of the
regenerator during a certain thermodynamic process (e.g. isochoric in Stirling
device) and it absorbs heat from the regenerator before the thermodynamic cycle is
repeated. In steady-state conditions, like in an active regenerator (see the chapter on

fl