Influence of Ageing Heat Treatment on the High Cycle Fatigue of an 8090 Al-Li Alloy

Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.

Experimental Evaluation of the Heat Output/Input and Coefficient of Performance Characteristics of a Chemical Heat Pump in the Periodic Operation of CaCl₂Hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat. CaCl2 was used in the system of CHP. We evaluated the heat storage and heat releasing of CHP, and confirmed the practicality from the experimental results. The reactor module employed was an aluminum plate-tube heat exchanger with corrugated fins, and the CaCl2 powder was in the form of a packed bed. Heat storage operation and heat dissipation operation are performed at the same time and supplied to the heat demand destination. At this time, an environmental heat source can be used during the heat radiation operation, and the heat output can release more heat than the heat input during heat storage. The heat discharging and charging characteristics of the reactor module were evaluated experimentally. The coefficient of performance (COP) was calculated for the heat upgrading cycle, and the heat output in the system was determined. A COP of 1.42 and output of 650 W/L, based on the heat exchanger volume, were obtained using a 600 s change time for the heat pump.

Energy Saving Model and Calculation Example of Three Cooling Schemes for Data Center in Hot Summer and Cold Winter Area

In order to achieve the goal of “carbon peak” in 2030 and “carbon neutralization” in 2060, the task of energy conservation has risen to the national strategic level, and its work is urgent. It focuses on energy saving and energy consumption in data center, 5G network and other fields. The gravity heat pipe double cycle air conditioning is a kind of room air conditioning which uses natural cooling source with high efficiency. According to the outdoor meteorological parameters of ten typical cities in China, the calculation model of unit hybrid refrigeration mode is established by using integral method. A simplified algorithm for statistical summation is proposed. Then it compares with the same type of refrigerant pump air conditioner, water-cooled chiller and natural cooling plate. The results show that the annual operation time of gravity heat pipe double cycle air conditioner is 50.8% longer than that of refrigerant pump air conditioner. Then the calculation model is verified by the annual actual operation data of a data center in Changsha. The results show that the double cycle air conditioner with gravity heat pipe can save about 34% energy compared with the chiller. The accuracy of the calculation model is 17.5%, which meets the engineering accuracy requirements. The application of gravity heat pipe double cycle air conditioning in hot summer and cold winter area is a scheme worthy of popularization and application.

Exothermic Performance of the Calcined Limestone Determined by Exothermic Temperature under Fluidization during CaCO_(3)/CaO Energy Storage Cycles

Thermochemical energy storage based on CaO/CaCO_(3)cycles has obtained significant attention as an alternative energy storage solution for concentrated solar power plants.In view of the applicability of fluidized bed reactors for CaO/CaCO_(3)heat storage,it is imperative to study the factors related to the heat release performance of CaO.This work presents an exothermic experiment on calcined limestone under fluidization,exploring the impact of initial temperature,CO_(2)concentration,particle size,superficial gas velocity,and number of cycles on the exothermic performance of CaO.The result indicates that CaO with high initial temperature leads to higher exothermic temperature,with better exothermic stability under cycles.An optimal initial temperature range of 600℃-650℃exists with an actual CaO conversion rate deviating merely 2%from theoretical conversion.Higher CO_(2)concentration augments the exothermic temperature and rate of CaO,while also improves the effective conversion of CaO.Nevertheless,high CO_(2)concentrations exacerbate the sintering and deactivation of CaO.High superficial gas velocity and small particle size shorten the exothermic time by increasing heat dissipation,but has minimal effect on the exothermic properties.Finally,the exothermic properties of CaO under fluidized and static conditions are studied.The result shows that exothermic temperature and exothermic rate of CaO under fluidization are enhanced,displaying higher heat storage performance than that under static state.This study provides valuable insights for optimizing the exothermic performance of CaO in fluidized bed reactors,contributing to advanced thermochemical energy storage for concentrated solar power plants.