This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator(ACR) operating with a rectifying column and six types of binary refrigerants(R23/R134a,R23/R227ea,R23/R236fa,R170/R290...This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator(ACR) operating with a rectifying column and six types of binary refrigerants(R23/R134a,R23/R227ea,R23/R236fa,R170/R290,R170/R600a,and R170/R600) at a temperature level of -60 °C. Half of the six binary refrigerants are nonflammable,of which the 0.5 and the 0.6 mole fractions of R23 for the R23/R236fa possess the most prospective composition for the medium and low suction pressure compressors,respectively. The remaining three binary refrigerants are flammable but with low global warming potentials,of which the 0.6 mole fraction of R170 for the R170/R600 is the most prospective one. The results show that the overall matching as well as local matching of heat capacity rates of hot and cold refrigerants in the recuperators are important for the improvement of coefficient of performance of the cycle,which can be adjusted through the simultaneous optimization of the pressure level and composition. The new approach proposed also offers a wider range of applications to the optimization in performance of the cycle using multi-component refrigerants.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
基金Project (Nos. 50876095 and 50890184) supported by the National Natural Science Foundation of China
文摘This paper proposes a new approach to the performance optimization of an auto-cascade refrigerator(ACR) operating with a rectifying column and six types of binary refrigerants(R23/R134a,R23/R227ea,R23/R236fa,R170/R290,R170/R600a,and R170/R600) at a temperature level of -60 °C. Half of the six binary refrigerants are nonflammable,of which the 0.5 and the 0.6 mole fractions of R23 for the R23/R236fa possess the most prospective composition for the medium and low suction pressure compressors,respectively. The remaining three binary refrigerants are flammable but with low global warming potentials,of which the 0.6 mole fraction of R170 for the R170/R600 is the most prospective one. The results show that the overall matching as well as local matching of heat capacity rates of hot and cold refrigerants in the recuperators are important for the improvement of coefficient of performance of the cycle,which can be adjusted through the simultaneous optimization of the pressure level and composition. The new approach proposed also offers a wider range of applications to the optimization in performance of the cycle using multi-component refrigerants.
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℃.
