Improved cooling performance of HeII channels separated by a porous spacer

Abstract

Cooling performance of superfluid helium (HeII) channels, separated by a porous spacer, has been experimentally investigated. The test channels were formed in parallel by FRP block. A spacer was used to separate two channels of the same shape. Both ends of the channels were kept open to an atmospherically pressurized HeII bath. Two types of spacers were examined—(1) FRP spacer, (2) the central portion of the FRP spacer was replaced by a porous spacer. The mean pore diameter was 1 μm. The λ transition heat flux, which is defined as the heat flux necessary to raise the helium temperature in the channel to the λ transition temperature, T λ , increases remarkably when the porous spacer is used instead of the FRP spacer. It is also found that the use of porous spacers between HeII channels is effective to suppress a steep temperature rise in the heated channel because HeII flow is induced in the heated channel by a fountain effect.