Abstract
Two magnetic refrigerators with new heat switches based on the thermosiphon principle were designed and tested, which could produce and preserve superfluid helium. However, these magnetic refrigerators did not satisfy the designed performance. To make clear this problem, the detailed cycle analysis was performed including heat losses due to heat switches. The results show that heat loss relating to heat capacity of liquid helium mainly affects the reduction of experimental cooling power, and is approximately 8 times larger than that of the case taking into account of only unsteady-state conduction heat exchange between magnetic element and liquid helium. It is believed that this large heat loss may be caused by the convection of liquid helium.
