Improvement on cooling performance in He II channel using fountain effect

Cooling performance of superfluid helium (He II) in a channel installing a porous material has been investigated experimentally. Instead of fiberglass reinforced plastic (FRP), the porous material is installed as a part of spacers in the channel expecting advantages of fountain effect. When heat generation occurs in the superconducting coil, the porous material can induce He II flow toward heated side with fountain effect which results in forced convection heat transfer. The test channel made of FRP is 170 mm long. Both ends of the channel are kept open to an atmospherically pressurized He II bath. Heat generation larger than the λ transition heat flux causes a steep temperature rise, because it generates He I of very low heat conductivity compared to that of He II. It is confirmed that the He II flow induced by fountain effect can suppress the steep temperature rise in the channel. Even if heat generation exceeds the lambda transition heat flux, fountain effect arises. This effect combined with natural convection of He I to improve the heat transfer in the channel.