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[en] A two-stage solar powered liquid-desiccant dehumidification system, for which two kinds of desiccant solution (lithium chloride and calcium bromide) are fed to the two dehumidification stages separately, has been studied. In the studied system air moisture (latent) load is separately removed by a pre-dehumidifier using cheap calcium chloride (CaCl2) and a main dehumidifier using stable lithium bromide (LiBr). Side-effect of mixing heat rejected during dehumidification process is considerably alleviated by an indirect evaporative cooling unit added between the two dehumidification stages. The feasibility of high-desiccant concentration difference achieved by reusing desiccant solution to dehumidify air and regenerating desiccant repeatedly is analyzed. By increasing desiccant concentration difference, desiccant storage capacity is effectively explored. It is found that the pre-dehumidification effect of CaCl2 solution is significant in high ambient humidity condition. Also seen is that the desiccant investment can be decreased by 53%, though the cost of equipments is somewhat increased, and the Tcop and COP of the proposed system can reach 0.97 and 2.13, respectively
[en] Air conditioning system based on liquid desiccant has been recognized as an efficient independent air humidity control HVAC system. To improve thermal coefficient of performance, a novel two-stage liquid desiccant dehumidification system assisted by calcium chloride (CaCl2) solution is developed through exergy analysis based on the second thermodynamic law. Compared with the basic liquid desiccant dehumidification system, the proposed system is improved by two ways, i.e. increasing the concentration variance and the pre-dehumidification of CaCl2. The exergy loss in the desiccant-desiccant heat recovery process can be significantly reduced by increasing desiccant concentration variance between strong desiccant solution after regeneration and weak desiccant solution after dehumidification. Meanwhile, the pre-dehumidification of CaCl2 solution can reduce the irreversibility in the regeneration/dehumidification process. Compared to the basic system, the thermal coefficient performance and exergy efficiency of the proposed system are increased from 0.24 to 0.73 and from 6.8% to 23.0%, respectively, under the given conditions. Useful energy storage capacity of CaCl2 solution and LiCl solution at concentration of 40% reach 237.8 and 395.1 MJ/m3, respectively. The effects of desiccant regeneration temperature, air mass flux, desiccant mass flux, etc., on the performance of the proposed system are also analyzed.
[en] Highlights: • A novel completely passive spent fuel pool cooling system is proposed. • The cooling ability of this system is 16 MW. • High efficiency heat pipe is introduced to decay heat removal. • Numerical models for completely passive spent fuel pool cooling system are developed. - Abstract: Due to the safety issues arising from the Fukushima accident, a novel completely passive spent fuel pool cooling system is proposed using the high-efficiency heat pipe cooling technology that is available in an emergency condition such as a station blackout. This cooling system’s ability to remove the decay heat released by the spent fuel assemblies is evaluated by a computational fluid dynamics (CFD) simulation. The spent fuel pool of CAP1400 (a passive PWR developed in China) is selected as the reference pool, and the passive cooling system is designed for this spent fuel pool. The pool with the passive cooling system is simulated using Fluent 13.0 with 4 million meshes. Four different cases have been studied, and some notable results have been obtained through this work. The simulation results reveal that the passive cooling system effectively removes the decay heat from the SFP with the storage of 15-year-old spent fuel assemblies and prevents the burnout of the fuel rods. The results indicate that the water in the SFP will never boil, even in a severe accident with a lack of emergency power and outside aid