Effect of channel geometry on heat transfer in He II chamber

Abstract

Heat transfer from a horizontal surface to superfluid helium contained in a chamber has been measured. A test channel 13 mm in length was connected to the chamber at one end and opened to a helium bath at the other. Eleven kinds of channel with nearly equal void areas and six kinds of round tube channel with inner diameters ranging from 1.9 to 13 mm were used. Channels packed with wire were adopted as capillary channels. The equivalent diameter was used to characterize the wire-packed channels and non-round tubes. The limiting heat flux, defined as the flux at the start of film boiling on the heat transfer surface, showed a maximum at an equivalent diameter of 1.94 mm and decreased steeply with any further increase in equivalent diameter. The single tube channel proved to have a poor heat transport capability compared with the channel of an equally divided tube.