Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng Research Paper Performance investigation of a novel closed Brayton cycle using supercritical CO 2 -based mixture as working fluid integrated with a LiBr absorption chiller Yuegeng Ma a , Ming Liu b , Junjie Yan b , Jiping Liu a, ⁎ a MOE Key Laboratory of Thermal Fluid Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China b State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China HIGHLIGHTS • A novel CBC/AC using CO 2 -Kr as working fluid is proposed. • Key parameters for the CBC/AC are optimized considering varied T 0 working conditions. • Energy and exergy performance of the CBC/AC are improved relative to the S-CO 2 cycle. • The operating conditions affect the performance improvement of the proposed cycle. ARTICLE INFO Keywords: Closed Brayton cycles CO 2 -based binary mixtures LiBr absorption chiller Cycle improvement ABSTRACT A novel closed Brayton cycle using supercritical CO 2 –Kr mixture as working fluid integrated with an absorption chiller (CBC/AC) is proposed. The waste heat of the CO 2 –Kr in the cold end of the top closed Brayton cycle (CBC) is utilized to drive the absorption chiller, which further chills the CO 2 –Kr fluid exiting the precooler before it enters the main compressor. Compared with the stand-alone supercritical CO 2 (S-CO 2 ) CBC, the CBC/AC exploits the performance improvement potentials under low ambient temperature (T 0 ) condition and alleviates the performance penalty under high T 0 condition. The energy and exergy analyses of the CBC/AC in three typical T 0 conditions (10 °C, 25 °C and 40 °C) show that the thermal efficiencies are improved by 3.12%, 0.40% and 6.86%, respectively, the exergy efficiencies are improved by 3.53%, 0.54% and 7.53%, respectively. The exergy loss from the precooler is significantly reduced in the CBC/AC relative to that in the stand-alone S-CO 2 CBC. The comparisons between different working conditions for the CBC/AC indicate that the improvements of the thermal and exergy efficiencies are more apparent under water-cooling and high turbine inlet temperature conditions. The effects of the component performance on the CBC/AC are also evaluated. 1. Introduction Closed Brayton cycle (CBC) gas turbine was firstly patented by Ackeret and Keller as early as 1935, and the pioneering gas turbine, the AK-36 test plant was built 4 years later [1]. However, the early popu- larity of CBC in 1950s and 1970s was limited by the lack of technology readiness and hence was overshadowed by the more matured and higher-efficiency open Brayton gas turbine cycle. Recently, owing to the development of Gen IV nuclear energy [2,3] and advancement in con- centrated solar power [4,5], investigations of suitable cycle layouts to efficiently exploiting these new promising heat sources featuring high operating temperature are gaining increasing interests. The CBC sys- tems show superior adaptable characteristics to these new heat sources relative to the conventional power conversion systems and regain at- tentions worldwide. Moreover, the recent development in metallic materials and crucial components [6,7] removes the main hindrance against the application of CBCs. Therefore, the CBC power plant is currently regarded as a promising alternative to the conventional coal- fired power plant and internal combustion gas turbine power plant. The choice of working fluid dramatically affects the footprint and cycle performance of CBC plants. Numerous working fluids including air, nitrogen, carbon dioxide, noble gases and their mixtures have been investigated for the CBCs. Among all these fluids, supercritical carbon dioxide (S-CO 2 ) emerges as one of the most promising options due to the following advantages: https://doi.org/10.1016/j.applthermaleng.2018.06.008 Received 22 December 2017; Received in revised form 24 March 2018; Accepted 3 June 2018 ⁎ Corresponding author. E-mail address: liujp@xjtu.edu.cn (J. Liu). Applied Thermal Engineering 141 (2018) 531–547 Available online 04 June 2018 1359-4311/ © 2018 Published by Elsevier Ltd. T