The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a sup...The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.展开更多
The recent progress of magnetic refrigeration technique at room temperature, especially in magnetic refrigerant materials with respect to Gd-Si-Ge, La-Fe-Si, Mn-Fe-P-As which has GMCE was reported. Also the recent pro...The recent progress of magnetic refrigeration technique at room temperature, especially in magnetic refrigerant materials with respect to Gd-Si-Ge, La-Fe-Si, Mn-Fe-P-As which has GMCE was reported. Also the recent progress in magnetic refrigerator design was reviewed.展开更多
During data center operation,it generates a significant volume of low-grade waste heat.To recover waste heat,a coupled system including solar collector,double effect absorption refrigeration and organic Rankine cycle ...During data center operation,it generates a significant volume of low-grade waste heat.To recover waste heat,a coupled system including solar collector,double effect absorption refrigeration and organic Rankine cycle is proposed.The system performance is analyzed in detail.For the organic Rankine cycle,five organic working fluids(R245fa,R245ca,R123,R11,and R113)are selected.R245fa,R113 and R245ca obtain the maximum net power output,thermal efficiency and exergy efficiency,respectively.In the double effect absorption refrigeration system,the evaporation temperature,condensation temperature,and generation pressure affect the COP and exergy efficiency.When the generator pressure is unchanged,the COP increases with increasing evaporation temperature and decreasing condensation temperature.When the COP reaches 1.3,the COP slightly decreases as the evaporation temperature or condensation temperature changes.Similarly,the exergy efficiency of refrigeration systems exhibits the same trend as the COP,and the exergy efficiency maximum value appears at approximately 0.32.A new performance indicator,rPUE,was defined to evaluate the data center power utilization efficiency.The flow distribution ratio and heat source temperature were optimized with multi-objective optimization.When the mass flow distribution rate is 0.6 and the heat source temperature is 441.5 K,rPUE and the total unit production costs of the system obtain the optimal solution.展开更多
基金Project supported by the Science and Technology Development Fund of Higher Education of Tianjin,China(20130301)the Tianjin Research Program of Application Foundation and Advanced Technology,China(14JCQNJC4000)the National Natural Science Foundation of China(11604242)
文摘The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.
文摘The recent progress of magnetic refrigeration technique at room temperature, especially in magnetic refrigerant materials with respect to Gd-Si-Ge, La-Fe-Si, Mn-Fe-P-As which has GMCE was reported. Also the recent progress in magnetic refrigerator design was reviewed.
基金the support provided by the National Natural Science Foundation of China(No.52106010)the Beijing Natural Science Foundation(3232037)the Fundamental Research Funds for the Central Universities(No.2024MS150)。
文摘During data center operation,it generates a significant volume of low-grade waste heat.To recover waste heat,a coupled system including solar collector,double effect absorption refrigeration and organic Rankine cycle is proposed.The system performance is analyzed in detail.For the organic Rankine cycle,five organic working fluids(R245fa,R245ca,R123,R11,and R113)are selected.R245fa,R113 and R245ca obtain the maximum net power output,thermal efficiency and exergy efficiency,respectively.In the double effect absorption refrigeration system,the evaporation temperature,condensation temperature,and generation pressure affect the COP and exergy efficiency.When the generator pressure is unchanged,the COP increases with increasing evaporation temperature and decreasing condensation temperature.When the COP reaches 1.3,the COP slightly decreases as the evaporation temperature or condensation temperature changes.Similarly,the exergy efficiency of refrigeration systems exhibits the same trend as the COP,and the exergy efficiency maximum value appears at approximately 0.32.A new performance indicator,rPUE,was defined to evaluate the data center power utilization efficiency.The flow distribution ratio and heat source temperature were optimized with multi-objective optimization.When the mass flow distribution rate is 0.6 and the heat source temperature is 441.5 K,rPUE and the total unit production costs of the system obtain the optimal solution.
