The dynamic stability analysis of an irreversible refrigerator working at the minimum power input P for given cooling load R was investigated.An irreversible refrigerator model was established based on coupled differe...The dynamic stability analysis of an irreversible refrigerator working at the minimum power input P for given cooling load R was investigated.An irreversible refrigerator model was established based on coupled differential equations.The global asymptotic stability characteristics were proved by constructing Lyapunov function based on Lyapunov stability theory and analyzed by sketching global phase portraits.The influence of parameters such as initial and operating parameters were studied for different values.It was found that an equilibrium point of nonlinear system was the global stability point,and the temperature of the working fluids converged to the stability value as time t approximated to positive infinite.Besides,numerical integrations were carried out to corroborate the global asymptotic stability properties of the system.Finally,the dynamic stability and the thermodynamic properties of the system were analyzed.It was found that the energetic characteristics and the dynamic stability properties were deteriorated as the dimensionless cooling load R~* and the thermal conductance ratio b increased.展开更多
Refrigeration challenges in regions with electricity shortages significantly decrease the quality of life for residents. In response to the prevalent refrigeration challenges in power-deficient areas, a novel distribu...Refrigeration challenges in regions with electricity shortages significantly decrease the quality of life for residents. In response to the prevalent refrigeration challenges in power-deficient areas, a novel distributed solar refrigeration system, comprising an evacuated U-tube solar collector and elastocaloric refrigerator, is theoretically introduced. Theoretical formulations for the energy efficiency and cooling power of the solar refrigeration system are presented to facilitate predictive assessments of the performance properties. Under typical conditions, the energy efficiency and cooling power of the solar refrigeration system are,respectively, 4.84% and 200.15 W. Subsequently, an extensive parameter study is conducted to comprehensively uncover key performance influencers and identify avenues for improvement. In addition, local sensitivity analyses identify that the length ratio is the top influential parameter, while the heat transfer fluid flow rate is the least sensitivity. A pragmatic case study,conducted with the weather data of Ningbo City, China, serves to empirically predict the performance of the hybrid system within the constraints of practical circumstances.展开更多
Combined cooling,heating and power(CCHP)systems are characterized by a substantially higher energy-utilization efficiency compared to standalone systems.In this study,an integrated system comprising a solid-oxide fuel...Combined cooling,heating and power(CCHP)systems are characterized by a substantially higher energy-utilization efficiency compared to standalone systems.In this study,an integrated system comprising a solid-oxide fuel cell(SOFC),hot-water storage tank(HWST)and absorption refrigeration(AR)cycle is considered.The SOFC model was developed in Aspen Plus®.It was used to determine the thermodynamic properties of the exhaust gas that was then used to provide heat for the HWST and to drive the AR cycle.Thermodynamic models for the AR cycles were developed in Engineering Equation Solver,considering LiBr-H2O and NH3-H2O as working fluids.The sensitivity analysis of a number of SOFC output parameters has been carried out.The most optimal case was characterized with the coefficient of performance(COP)and CCHP efficiency of 0.806 and 85.2%for the LiBr-H2O system,and 0.649 and 83.6%for the NH3-H2O system,respectively.Under such optimal operating conditions,the SOFC was characterized by the net electrical efficiency of 57.5%and the net power output of 123.66 kW.Data from the optimal solution were used to perform the thermodynamic study and sensitivity analysis to assess the influence of different absorption cycle operating conditions and to identify possible applications for the considered integrated systems.展开更多
基金the Fundamental Research Fund for the Central Universities,China(No.2011011302)National Natural Science Foundation of China(No.51078068)
文摘The dynamic stability analysis of an irreversible refrigerator working at the minimum power input P for given cooling load R was investigated.An irreversible refrigerator model was established based on coupled differential equations.The global asymptotic stability characteristics were proved by constructing Lyapunov function based on Lyapunov stability theory and analyzed by sketching global phase portraits.The influence of parameters such as initial and operating parameters were studied for different values.It was found that an equilibrium point of nonlinear system was the global stability point,and the temperature of the working fluids converged to the stability value as time t approximated to positive infinite.Besides,numerical integrations were carried out to corroborate the global asymptotic stability properties of the system.Finally,the dynamic stability and the thermodynamic properties of the system were analyzed.It was found that the energetic characteristics and the dynamic stability properties were deteriorated as the dimensionless cooling load R~* and the thermal conductance ratio b increased.
基金supported by the Baima Lake Laboratory Joint Funds of the Zhejiang Natural Science Foundation of China(Grant No.LBMHY24E060010)。
文摘Refrigeration challenges in regions with electricity shortages significantly decrease the quality of life for residents. In response to the prevalent refrigeration challenges in power-deficient areas, a novel distributed solar refrigeration system, comprising an evacuated U-tube solar collector and elastocaloric refrigerator, is theoretically introduced. Theoretical formulations for the energy efficiency and cooling power of the solar refrigeration system are presented to facilitate predictive assessments of the performance properties. Under typical conditions, the energy efficiency and cooling power of the solar refrigeration system are,respectively, 4.84% and 200.15 W. Subsequently, an extensive parameter study is conducted to comprehensively uncover key performance influencers and identify avenues for improvement. In addition, local sensitivity analyses identify that the length ratio is the top influential parameter, while the heat transfer fluid flow rate is the least sensitivity. A pragmatic case study,conducted with the weather data of Ningbo City, China, serves to empirically predict the performance of the hybrid system within the constraints of practical circumstances.
文摘Combined cooling,heating and power(CCHP)systems are characterized by a substantially higher energy-utilization efficiency compared to standalone systems.In this study,an integrated system comprising a solid-oxide fuel cell(SOFC),hot-water storage tank(HWST)and absorption refrigeration(AR)cycle is considered.The SOFC model was developed in Aspen Plus®.It was used to determine the thermodynamic properties of the exhaust gas that was then used to provide heat for the HWST and to drive the AR cycle.Thermodynamic models for the AR cycles were developed in Engineering Equation Solver,considering LiBr-H2O and NH3-H2O as working fluids.The sensitivity analysis of a number of SOFC output parameters has been carried out.The most optimal case was characterized with the coefficient of performance(COP)and CCHP efficiency of 0.806 and 85.2%for the LiBr-H2O system,and 0.649 and 83.6%for the NH3-H2O system,respectively.Under such optimal operating conditions,the SOFC was characterized by the net electrical efficiency of 57.5%and the net power output of 123.66 kW.Data from the optimal solution were used to perform the thermodynamic study and sensitivity analysis to assess the influence of different absorption cycle operating conditions and to identify possible applications for the considered integrated systems.
