NUMERICAL SOLUTION OF TRANSIENT HEAT TRANSPORT THROUGH HELIUM II

Transient heat transport is analyzed theoretically by solving the general hydro-dynamic equations of superfluid helium. The system that completely describes the heat transport process consists of two coupled equations, whose unknown quantities are the temperature T and the normal fluid velocity V N , under assumptions that are precisely noted. The transport process is both propagative and diffusive: the temperature front, due to a heat flux disturbance, propagates at the second sound velocity but decreases along the helium channel by a diffusion phenomenon. These two effects exist simultaneously, but it shown that, according to the pulse duration or amplitude, one of these phenomena can be accentuated. In particular, the higher the heat pulse amplitude, the more pronounced the diffusion.