Energy, exergy, environmental, and economical (4E) analysis of modified cascade refrigeration cycles for ultra-low temperature cooling applications
摘要
The conventional cascade refrigeration cycle is modified using an auxiliary loop between the HT and LT cycle of CCRS. Thermal performances of modified cascade refrigerators with a single auxiliary cycle (CRSAC) are compared with those of CCRS. The results show a significant increase in the COP of the cycle at reduced global warming impact with a lower energy consumption rate. The CRSAC cycle required 7.8%, 10.3%, and 13% less work input than CCRS at condenser temperatures of 313 K, 318 K, and 323 K, respectively, for producing a cooling effect at 193 K evaporative temperature. Varying the evaporative temperature from 193 to 220 K, the CRSAC cycle has 12.4–13.8% higher COP than CCRS at 308 K condenser temperature, 15.3–17.5%, 18.5–21.4%, and 22.2–26.2% higher COP than CCRS at condenser temperature of 313 K, 318 K, and 323 K, respectively. Although the CRSAC cycle has lesser exergetic efficiency than CCRS due to a larger pressure difference between the condenser and evaporator unit of the cascade heat exchanger, its lower energy consumption rate and lower carbon emission rate during operation surpass this limitation. The CRSAC cycles emit 5–13% less carbon for the same operating conditions than CCRS. For varying the condenser temperature from 308 to 323 K and evaporative temperature from 193 to 220 K, the CRSAC cycle contributes 5.3–15.7% less TEWI values than CCRS. At TE = 220 K, the CRSAC cycle costs 6.6%, 9.5%, and 12.5% less than CCRS at condenser temperatures of 308 K, 313 K, and 318 K, respectively. Operating at 323 K condenser temperature, the operational cost of the CRSAC cycle varies from 70,109 to 44,464 US Dollars and 80,451 to 52728US Dollars per annum for the CCRS cycle for evaporator temperature range of 193–220 K.