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 2.1K. 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.
