Naturally circulated system under low to moderate heating condition with supercritical fluid: A comprehensive investigation of loop orientation and Ledinegg instability

Abstract

Out of the two stability characteristics i.e. static and dynamics, static instability has hardly been explored in such systems due to mathematical complexity and absence of explicit boundary conditions. Present numerical investigation deals with the 1D numerical framework analyzing the steady-state and static instability of the loop under different loop orientation i.e., horizontal heater horizontal cooler (HHHC), vertical heater horizontal cooler (VHHC), horizontal heater vertical cooler (HHVC) and vertical heater vertical cooler (VHVC). The range of heating power considered is applicable in the low to moderate heating condition such as in solar heater and electronic chip cooling. Due to uneven generation of buoyancy and friction throughout the flow path, occurrence of FiHTD is also dependent on it, with best and worst thermalhydraulic characteristics for HHHC and VHVC respectively. For every condition, the appearance of static instability was found to be within the heating power limit. For $T_{\infty }$ = 295 K it spanned over 1050 W for HHHC orientated loop which got decreased by 9.5%, 23.8% and 65.7% for VHHC, HHVC and VHVC respectively. Under the condition of increased of $T_{\infty }$ = 300 K the same was found within the limit of 575 W and got decreased by 13%, 21.7% and 64.3% for cases mentioned above insequential manner. Stability maps drawn using well known non-dimensional numbers holds a good qualitative behavior of static instability. Dynamic instability is well explored for HHHC combination has throughly done previously by various authors and hence, has not been considered here. The authors believe that dynamic instability will not be much more prominant due to predefined flow direction and can be explored as a future work.