Heat transfer and fluid flow in thermosyphons

The transient, steady state stability behavior of these loops was analytically investigated for various conditions. In particular, a toroidal thermosyphon, with orientation in a vertical plane that is heated over the lower half and cooled in the upper half, was considered. The conservation equations of the systems were averaged over the cross section normal to the flow direction and then solved by using a finite difference procedure. The transient and steady state temperature distributions and velocity were obtained which elucidate the phenomena in natural convection loops. Several aspects of the problem were considered, including constant wall temperature in the cooling region, axial conduction of the thermosyphon fluid, addition and withdrawal of fluid, and both a counter flow and a parallel flow annular type heat exchanger over the cooling region. The results indicate that there may be oscillations in the velocity and temperature profiles.