Dynamic characteristics of a shell and plate particle‐SCO ₂ moving packed bed heat exchanger with various SCO ₂ channel configurations

Abstract

This article proposes a dynamic analysis framework for a shell and plate particle-SCO 2 moving packed bed heat exchanger (MPBE) with straight SCO 2 channel and four fins-modified SCO 2 channels, which contains a static model and a dynamic model. 13 cases covering an initial temperature deviation range of +50 ~−100 K from design-point case in solids inlet, an initial temperature deviation range of +50 ~−100 K from design-point case in SCO 2 inlet, and a SCO 2 inlet velocity range of 1.5 times to 0.05 times are introduced to measure the dynamic characteristics. Dynamic responses of five MPBE configurations to two types of inputs (step-change perturbations and linear-change perturbations) under 13 cases are analyzed. Relaxation times at each case are summarized and compared. A low threshold temperature exists for all five MPBE configurations to avoid oscillations in solids outlet temperature under stepchange perturbations in solids inlet temperature, and a low threshold SCO 2 inlet temperature just appears in MPBE with straight SCO 2 channels under step-change perturbations in SCO 2 inlet temperature. Improved MPBE configurations show apparent less relaxation time than MPBE with straight SCO 2 channel. Among four fins-modified MPBE configurations, MPBE channels modified with offset rectangular fins on SCO 2 side exert the fastest dynamic characteristic in most cases. K E Y W O R D S CSP Gen3, dynamic characteristics, dynamic heat transfer model, particle-SCO 2 moving packed bed heat exchanger | INTRODUCTIONAiming at expediting solar thermal electricity capacity and enhancing solar thermal generation cost competitiveness, research studies concerning the implement of the next generation of concentrated solar power plant (CSP Gen 3) have been gaining colossal vigor recently. [1][2][3] Compared with the first and second CSP plants of which the annual solar-electric efficiency is generally less than 20%, CSP Gen 3 entails the potential to achieve an annual solar-electric efficiency of 25%~30%. 4 The considerable improvement can be ascribed to the elevated peak operating temperature, expecting to be >700 C. Two main technologies matching peak operating temperature Abbreviations: CSP, concentrated solar power plants; MPBE, moving packed bed heat exchanger; SCO 2 , supercritical carbon dioxide; TES, thermal energy storage; PCHE, printed circuit heat exchanger.