Heat transfer in superfluid helium. 2. Transient heat transfer produced by stepwise heat input

This paper reviews the authors' recent works on transient heat transfer from heated surfaces produced by stepwise heat inputs in a pool of pressurized superfluid helium (He II) for liquid temperatures from 1.8 to 2.1 K. The following is described: (1) Typical behavior of transient heat transfer produced by a stepwise heat input; existence of quasi-steady state with a certain lifetime. (2) Lifetimes of quasi-steady states produced by stepwise heat inputs to a flat plate with various width and length and a correlation that can describe the experimental data. (3) Comparison of the lifetimes on flat plates with those on cylinders. (4) The lifetimes on a flat plate at one side of a rectangular duct with various ratios of cross sectional duct area Ad to the heater surface area Ah, and a correlation that can describe the experimental data. (5) The lifetimes on a flat plate at one side of a rectangular duct with an orifice. (6) Two dimensional numerical analysis on heat transfer in the duct based on a rigorous two fluid model and comparison with the experimental data. (author)