Transient heat transport in He II

Experimental and theoretical investigations of time dependent heat transport in He II have been identified several new phenomena not previously reported. For heat fluxes greater than the steady state peak value, there is an observed time delay between the initiation of heating and the onset of film boiling. The time delay is seen to be nearly equal to the enthalpy rise in the helium divided by the applied heat flux. A well defined relationship is shown to exist between the time delay and the applied heat flux. Simple theoretical analysis of heat conductivity in He II is shown to predict the functional dependence and give approximately the correct proportionality factor. Experimental results are reported over a range of temperatures, 1.6 K to 2.1 K and for two external pressures, near saturated vapour pressure and at 0.125 MPa. (author)