Some Considerations on the Interaction Between the Fluid and Wall Tube During Experiments in a Single-Phase Natural Circulation Loops

In this paper an experimental study on single-phase natural circulation loops is presented. Several parameters such as loop inclination, and tube wall thermal conductivity (Plexiglas or Stainless-steel AISI-304) were systematically investigated. The experiments were conducted analysing the interaction between the pipe material and liquid properties as well as the inclination of the loop. For a wide range of power transferred to the liquid, different thermo-hydraulic behaviours were observed: - the stainless-steel/distilled water combination shows always stable behaviour, probably the higher thermal conductivity of stainless-steel causes the "extension" of the heated section in the lower heat source; at the same time, this can be interpreted as a virtual reduction in the distance between the heater and the cooler. This behaviour was observed for the most part of loop inclinations.