Analysis of a modified transcritical CO2 two-stage ejector-compression cycle for domestic hot water production. (1st October 2022)

• Record Type: Journal Article
• Authors: Liu, Jian; Zhou, Lu; Lyu, Ning; Lin, Zhang; Zhang, Sheng; Zhang, Xiaosong
• Is Part Of: Energy conversion and management. Volume 269(2022)
• Publication Date: 2022-10-01
• Subjects: Two-stage compression -- DHW -- Ejector -- Energetic and exergetic analysis -- CO2; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2022.116094
• Languages: English
• ISSNs: 0196-8904

Abstract

Highlights: A new transcritical CO2 cycle for DHW production is proposed. The new cycle outperforms the basic cycle. The ejector reduces the system exergy destruction by replacing the throttle valve. The ejector improves the mass flow rate and absorption capacity in the evaporator. Abstract: High-efficiency domestic hot water (DHW) production has gained more attention currently, and a modified transcritical CO2 ejector enhanced two-stage compression cycle (METC) for the DWH production is proposed in this study. To investigate the applied potential of the modified cycle, the validated theoretical models are constructed to compare and analyze the performance between the METC system and the basic transcritical CO2 two-stage vapor compression cycle (BTC) under different operating conditions. The results show that the system METC outperforms the system BTC in terms of the heating coefficient of performance ( COP H ), system total heating capacity ( Q tot ), and the exergy efficiency ( η II ) under different conditions. Compared with the system BTC, the COP H, Q tot, and η II of the system METC are improved by 12.1%, 15.7%, and 15.3% under a typical operating condition. The ejector improves the refrigerant mass flow rate and absorption of heat in the evaporator. The low-grade working fluids are converted to a mid-grade state via the ejector, which is condensed in a mid-temperature heat exchanger to preheat the domestic hot water. Besides, the ejector reduces the exergy consumption and improves the system's exergy efficiency. The proposed cycle promotes the further improvement of the transcritical CO2 two-stage compression cycle for DHW production.