This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type....This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type. Water and ethylene glycol compound as base fluid and volume fractions of iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) are used as a refrigerant. The quantities determined in this work are the nanofluid exit temperature, the air exit temperature, the absolute error between the models for heat transfer rate, and Effectiveness. The quantities that constitute parameters, independent variables, are the airflow, represented by the Reynolds number, and the iron oxide volume fraction. Ethylene Glycol 50% compound has slightly better thermal performance than pure water and reduces the reactive effect of water on the environment, increasing the average life of the equipment. The absolute relative error between the models is less than 20% and presents maximum values with the increase of the nanoparticle volume fraction and growth in the Reynolds number for the air.展开更多
Based on the analysis of public expenditure performance,this article discusses the economy,efficiency,and effectiveness of defense expenditure performance,explains the relationship of the three,and emphasizes their un...Based on the analysis of public expenditure performance,this article discusses the economy,efficiency,and effectiveness of defense expenditure performance,explains the relationship of the three,and emphasizes their unity,interaction,and priority.The defense expenditure performance evaluation system,which is a comprehensive assessment of processes and results,is put forward along with the unification of economy,efficiency,and effectiveness.This system can be used to analyze whether the allocation and use of defense funds have achieved the strategic objectives of the Department of Defense.展开更多
文摘This work aims to establish comparisons between two models used for the performance of heat exchangers. The chosen system, in this case, consists of a heat exchanger used in automotive radiators flat finned tube type. Water and ethylene glycol compound as base fluid and volume fractions of iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) are used as a refrigerant. The quantities determined in this work are the nanofluid exit temperature, the air exit temperature, the absolute error between the models for heat transfer rate, and Effectiveness. The quantities that constitute parameters, independent variables, are the airflow, represented by the Reynolds number, and the iron oxide volume fraction. Ethylene Glycol 50% compound has slightly better thermal performance than pure water and reduces the reactive effect of water on the environment, increasing the average life of the equipment. The absolute relative error between the models is less than 20% and presents maximum values with the increase of the nanoparticle volume fraction and growth in the Reynolds number for the air.
文摘Based on the analysis of public expenditure performance,this article discusses the economy,efficiency,and effectiveness of defense expenditure performance,explains the relationship of the three,and emphasizes their unity,interaction,and priority.The defense expenditure performance evaluation system,which is a comprehensive assessment of processes and results,is put forward along with the unification of economy,efficiency,and effectiveness.This system can be used to analyze whether the allocation and use of defense funds have achieved the strategic objectives of the Department of Defense.
