Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines...Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.展开更多
An auto-cascade absorption refrigeration(ACAR)system could achieve a-60℃ refrigeration temperature by low-grade heat.For an ACAR system,its performance is mainly affected by energy and mass coupling of the auto-casca...An auto-cascade absorption refrigeration(ACAR)system could achieve a-60℃ refrigeration temperature by low-grade heat.For an ACAR system,its performance is mainly affected by energy and mass coupling of the auto-cascade processes.A novel ACAR system with double-absorber was proposed to get higher-efficient refrigeration as low as-60℃ in this context,which used R23-R134 a-DMF(N,N-Dimethylformamide)as its working fluids.Theoretical calculation and analyses were conducted under different working conditions.From the calculated results,the new system gained a COP value 20%higher than that of an ACAR system with single-absorber under the same generating,condensing,absorbing and refrigerating temperatures.Compositions of a refrigerant mixture showed key influences on energy and mass coupling of the auto-cascade processes,and an optimal composition of the mixed refrigerants was obtained for the new ACAR system.In addition,it was clearly found that absorbing processes of the new system had great effects on energy and mass coupling of the auto-cascade processes.Based on the difference of absorbing characteristics among R23,R134 a and DMF,the absorbing processes were intensified under the different absorbing pressures.As a result,an optimal matching pressure was obtained for the new ACAR system.Energy and mass coupling of the auto-cascade processes were further optimized,and the highest COP value was obtained.The theoretical analyses showed that performance of the innovative ACAR system could be superior to that of an ACAR system with single-absorber at a refrigeration temperature from -55℃ to -60℃.展开更多
文摘Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.
基金supported by Major Project of National Natural Science Foundation of China(Grant No.50890184)Cultural Heritage Bureau of Zhejiang Province(Grant No.2017009)
文摘An auto-cascade absorption refrigeration(ACAR)system could achieve a-60℃ refrigeration temperature by low-grade heat.For an ACAR system,its performance is mainly affected by energy and mass coupling of the auto-cascade processes.A novel ACAR system with double-absorber was proposed to get higher-efficient refrigeration as low as-60℃ in this context,which used R23-R134 a-DMF(N,N-Dimethylformamide)as its working fluids.Theoretical calculation and analyses were conducted under different working conditions.From the calculated results,the new system gained a COP value 20%higher than that of an ACAR system with single-absorber under the same generating,condensing,absorbing and refrigerating temperatures.Compositions of a refrigerant mixture showed key influences on energy and mass coupling of the auto-cascade processes,and an optimal composition of the mixed refrigerants was obtained for the new ACAR system.In addition,it was clearly found that absorbing processes of the new system had great effects on energy and mass coupling of the auto-cascade processes.Based on the difference of absorbing characteristics among R23,R134 a and DMF,the absorbing processes were intensified under the different absorbing pressures.As a result,an optimal matching pressure was obtained for the new ACAR system.Energy and mass coupling of the auto-cascade processes were further optimized,and the highest COP value was obtained.The theoretical analyses showed that performance of the innovative ACAR system could be superior to that of an ACAR system with single-absorber at a refrigeration temperature from -55℃ to -60℃.
