Study of trans-critical CO2 natural convective flow with unsteady heat input and its implications on system control

Effects of Heater Orientations on the Natural Circulation and Heat Transfer in a Supercritical CO2 Rectangular Loop

“…Previously the flow behavior and system stability of water based NCL have been widely investigated in new generation nuclear plant [5,9,13,14] and other energy conversion systems [15][16][17][18][19][20][21][22]. In recent years, several studies have been carried out previously on NCL using CO2 as the working fluid.…”

“…Chen et al [13], Chen and Zhang [20] also numerically studied supercritical systems and revealed the basic information on the flow transitions, instabilities, and flow stability behaviors. The general status in supercritical fluid NCL has been reviewed by Chen et al [21][22][23] and the stability controlling factors are summarized: heat transfer condition, loop diameter, aspect ratio, loop inclination angle and gravity intensity. More recently, Chen et al [24,25] have also made experimental studies into the system heat transfer behaviors and presented the basic trend of system stability evolution from sub-critical to supercritical regions.…”

“…More recently, Chen et al [24,25] have also made experimental studies into the system heat transfer behaviors and presented the basic trend of system stability evolution from sub-critical to supercritical regions. However, in those above studies the mostly used model is symmetric vertically set natural circulation loops, with the heat source placed in the mid part of low horizontal loop and heat sink in respective part of the upper loop [14,15,[18][19][20][21][22][23][24][25]. From the mathematical point of view, such kind of system is basically subjected to instability as has been proved in both theoretical studies and experiments [13,14,16,[18][19][20][21][22][23][24][25].…”

“…However, in those above studies the mostly used model is symmetric vertically set natural circulation loops, with the heat source placed in the mid part of low horizontal loop and heat sink in respective part of the upper loop [14,15,[18][19][20][21][22][23][24][25]. From the mathematical point of view, such kind of system is basically subjected to instability as has been proved in both theoretical studies and experiments [13,14,16,[18][19][20][21][22][23][24][25]. In real applications both the heat source and heat sink may not be symmetrically placed, like nuclear cooling system or solar collector system using natural circulation modes [14,16,26].…”

Computational investigation of the dynamic response of a supercritical natural circulation loop to aperiodic and periodic excitations

“…A comprehensive investigation on the response of a single-phase loop under varying nature of power transitions was presented by Basu et al (2013). However, analysis of a transcritical CO 2 loop under unsteady heat input condition by Chen et al (2012a) was probably the only effort towards that direction for supercritical loops. Abrupt rise in input power was predicted to induce unstable fluctuations, level of which was dependent on the rate of increase.…”