Parametric study of heat transfer within a planar thermosyphon

摘要

The results of a parametric study for a planar thermosyphon are presented. The thermosyphon consists of a ''U-shaped'' geometry, with the center portion of the ''U'' being a solid. The outer legs of the ''U'' are the flow channels. One of the outer surfaces of a channel was held at a constant temperature. The remaining outer surfaces were considered adiabatic. The configuration described is characteristic of passive systems for radioactive waste storage and reactor safety systems. Parameters which were varied included the channel geometry, the thermal conductivity of the solid, and the Ra number. The average Nu number for the constant temperature surface decreased as the inlet channel width decreased, and as the thermal conductivity of the solid increased. A modified Ra number, defined as the Ra number divided by the length to gap ratio for the outer channel, is used in the paper. At low values of the modified Ra number, there is over an order of magnitude decrease in the average Vu number for a change in the inlet channel width from 1.0 to 0.25. But as the value of the modified Ra number increases for any inlet channel width, the average Vu number results approached those of vertical parallel plates, independent of the inlet channel width and the thermal conductivity of the solid. The vertical parallel plate data is approached because the boundary layer flow near the heated plate is unaffected by the surface of the intervening solid.