Steady-State and Stability Behavior of a Single-Phase Natural Circulation Loop

Numerical investigation of natural circulation in a 2D-annular closed-loop thermosyphon

“…Natural circulation loops also attract attention because of the variety of fluid motions and the complexity of the dynamic properties encountered, in spite of the simplicity of their geometry. The Lorenz-like chaotic alternations of flow direction were experimentally observed in toroidal thermosyphon by Creveling et al (1975), Gorman et al (1986), Ehrhard and Muller (1990) and in rectangular thermosyphon by Damerell and Schoenhals (1979), Vijayan and Austregesilo (1994), Misale et al (1998), Cammarata et al (2002) which was well described by the Lorenz model (Gorman et al, 1986;Ehrhard and Muller, 1990).…”

“…The most common experimental loop geometries reported in the literature are the rectangular and the toroidal thermosyphons having uniform pipe diameter throughout the loop. The loops are often in some simple configuration such as circular toroidal loop heated uniformly over the lower half and cooled over the upper half through a constant wall temperature or an annular heat exchanger (Gorman et al, 1986;Stern et al, 1988;Jiang et al, 2002), or a rectangular thermosyphon loop with heating in the bottom part by a uniform heat flux source and cooling in the top part by a uniform-temperature heat sink (Huang and Zelaya, 1988; Bernier and Baliga, 1992;Vijayan and Austregesilo, 1994;Misale et al, 1998;Cammarata et al, 2002). Natural circulation loops also attract attention because of the variety of fluid motions and the complexity of the dynamic properties encountered, in spite of the simplicity of their geometry.…”

Experimental study on the influence of power steps on the thermohydraulic behavior of a natural circulation loop

“…In previous studies (Misale et al [8], Frogheri et al [9], and D'Auria et al [10]), experiments employing two fluids (distilled -T5 T6-T10 T16-T20 T11-T15 T22 T23 T24 T26 T25 T21 T27 T29 T30 T28 water and Fluorinert TM FC43) at different constant power level were performed using smooth pipes. The steady state natural circulation and the stability behavior of the loop were analyzed, confirming, for both fluids, a power threshold above which the loop behavior becames unstable.…”

“…Misale et al [8], utilizing either distilled water or Fluorinert TM FC-43 in a rectangular loop showed the presence of two different power thresholds above which the loop behavior becomes unstable; moreover, the Fast Fourier Transform was applied to analyze the frequency of the oscillations [9,10]. The Relap5/Mod3.2 and Cathare2 V1.3u codes have been used, having both purposes of code assessment and interpretation of experimental data [11].…”

Numerical Analysis of General Trends in Single-Phase Natural Circulation in a 2D-Annular Loop

“…The research pioneered by Keller [2], Welander [3], and Malkus [4] has been reviewed by Greif [5]. The presence of a reverse flow region was first qualitatively reported by Creveling et al [6] who also first observed the Lorenz-like chaotic flow in their experiments (see also [7][8][9]).…”