Abstract
CO2 air source heat pump (ASHP), as a kind of clean and efficient heating equipment, is a promising solution for domestic hot water and clean heating. However, the promotion of CO2 ASHP encounters a great resistance when it is used for space heating; namely, the return water temperature is too high that cased higher throttle loss, which decreases the COP of the CO2 ASHP unit. To solve this problem, a heating system of CO2 ASHP coupled with thermal energy storage (TES) is developed in this work. The simulation model of the studied system is established using TRNSYS software, and the model is verified by experimental data. Additionally, the performance of the studied system is optimized, and its economy is analyzed by life cycle cost (LCC). The results showed that, compared with the system before optimization, the cost of the optimized system increased, the annual operating cost of the system was reduced, and the COP of the system (COPsys) increased by 7.4%. This research is helpful in improving the application of the CO2 ASHP unit in cold server and cold areas.
Highlights
The results indicated that the mechanical subcooling CO2 refrigeration system showed the best performance under the analyzed operating conditions, and its cost was lower than the cascade system
An economic evaluation of this system is carried out, which includes the initial investment and life-cycle costs (LCC) of operating costs incurred during use to analyze the adaptability of the system applied to heating in the cold area
The expenses present value of cost method is used in economic calculation, which mainly includes the initial cost and the annual operating cost
Summary
With the development of human living standards, the energy demand is increasing. Wang et al [29,30] put forward a CO2 ASHP heating system combined with TES and conducted experiments to investigate its performance in cold areas They concluded that the COP decreased by 18.8%; the throttle loss increased by 47.5%, with the inlet water temperature of the gas cooler increasing from 35 to 45 ◦ C. According to the above presentation, when CO2 ASHP is adopted for space heating, the return water temperature is too high that cased the throttle loss too large and the energy efficiency of the system is reduced To solve this problem, a heating system of transcritical CO2 ASHP coupled with TES is proposed in this work. TES (13), which releases heat for heating water; it returns to the user end for heating
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