Experimental investigation of bubbling in particle beds with high solid holdup

An investigation on debris bed self-leveling behavior with non-spherical particles

“…Extremely, when Re g is large enough, K 3 seems to approach 1.0, the value for spherical particles. This might be because higher Re g means a larger gas flow rate and further a greater impetus for lifting solid particles, as confirmable in our flow-regime investigations [8,11,12], as a result making the additional particle-particle resistance less prominent. On the other hand, from Figure 10 it also seems that a noticeable difference is observable for those particles, indicating that aside from Re g , the differences encountered in the particle properties (e.g.…”

“…In addition, we have to also stress that, as mentioned-above, apart from empirical model investigations, owing to the experimental knowledge that the self-leveling behavior might be dominated by the solid phase [8,12,19], currently several computer models treating the particle-particle and particle-bubble interactions are being developed and incorporated into SIMMER-III, an advanced fast reactor safety analysis code [14][15][16][17]. Therefore, aside from further empiricalapproach investigations at various situations that may be encountered under reactor accident conditions, knowledge and expanded database from this work might be also utilized for the improved verifications of those computer models [19].…”

“…In those experiments, to simulate the coolant boiling during CDAs, various experimental methods, including depressurization boiling, bottom-heated boiling as well as gas-injection, have been employed. As for the microscopic flow-regime series [8,11,12], which also consists of several well-organized tests performed at various bubbling conditions (as shown in Figure 3), it was specifically conducted to ascertain the flow characteristics within particle beds, thus providing convincible visual evidence (especially bubble-particle interaction) for supporting the overall understandings. It has been confirmed that by combining the knowledge from flowregime investigations the observed overall leveling characteristics can be understood more effectively [8].…”

Experimental study and empirical model development for self-leveling behavior of debris bed using gas-injection

“…However, noticing that in those experiments the self-leveling behavior is still a black box, to obtain more direct visual evidence (esp. bubble-particle interaction) supporting the overall understandings, therefore, the microscopic flow regime investigations (Cheng, et al, 2010a(Cheng, et al, , 2011a(Cheng, et al, , 2013a, which consist of several series of well-organized tests performed at various bubbling conditions (as shown in Fig. 3), were specifically performed to ascertain the flow characteristics within particle beds.…”

“…On the other hand, aside from experimental investigations, modeling studies and numerical simulations are also progressing. For instance, owing to the knowledge from the microscopic flow-regime investigations that the self-leveling behavior might be dominated by the solid phase (Cheng, et al, 2010a(Cheng, et al, , 2011a(Cheng, et al, , 2013a, currently several computer models treating the particle-particle and particle-bubble interactions are being developed and incorporating into SIMMER-III (Guo, et al, 2012a,b;Zhang, et al, 2012), an advanced fast reactor safety analysis code (Tobita, et al, 2006). However, due to the extremely complex and uncertain nature of the three-phase flow involved in the leveling phenomenon (Cheng, et al, 2011b;Zhang, et al, 2010), empirical approach is still regarded as an attractive and indispensable option at present stage because of its distinct advantage in calculation efficiency.…”