Effect of Suction Nozzle Pressure Drop on the Performance of an Ejector-Expansion Transcritical CO2 Refrigeration Cycle

Entropy

Zhenying Zhang¹ 

[1] Institute of Architecture and Civil Engineering, Hebei United University, Tangshan 063009, China

关键词: refrigeration system;    ejector;    suction nozzle pressure drop;    CO₂;    transcritical cycle;   

DOI  :  10.3390/e16084309

来源: mdpi

【 摘 要 】

The basic transcritical CO₂ systems exhibit low energy efficiency due to their large throttling loss. Replacing the throttle valve with an ejector is an effective measure for recovering some of the energy lost in the expansion process. In this paper, a thermodynamic model of the ejector-expansion transcritical CO₂ refrigeration cycle is developed. The effect of the suction nozzle pressure drop (SNPD) on the cycle performance is discussed. The results indicate that the SNPD has little impact on entrainment ratio. There exists an optimum SNPD which gives a maximum recovered pressure and COP under a specified condition. The value of the optimum SNPD mainly depends on the efficiencies of the motive nozzle and the suction nozzle, but it is essentially independent of evaporating temperature and gas cooler outlet temperature. Through optimizing the value of SNPD, the maximum COP of the ejector-expansion cycle can be up to 45.1% higher than that of the basic cycle. The exergy loss of the ejector-expansion cycle is reduced about 43.0% compared with the basic cycle.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland