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[The Minerals, Metals & Materials Series] TMS 2020 149th Annual Meeting & Exhibition Supplemental Proceedings || Critical Quenching Rates After Solution Annealing: Peculiarities of Aluminuma??Silicon Alloys Fabricated by Laser Powder-Bed Fusion
摘要： Hot isostatic pressing is commonly used to reduce the porosity of (sand-)cast age-hardenable Al-alloys in order to meet the high quality requirements defined by aircraft and automotive industries. In order to establish additive manufacturing methods, such as laser powder-bed fusion (L-PBF), hot isostatic pressing can be utilized to reduce the anisotropic mechanical properties in as-built condition and at the same time eliminate porosity. For the cast aluminum alloy A356, a gas pressure of 75 MPa during hot isostatic pressing lowers the critical cooling rate required to achieve an oversaturated solid solution to about 1 K/s, which is significantly lower than the required quenching rate at atmospheric pressure (2–4 K/s). Thus, an oversaturated state of dissolved magnesium and silicon atoms within the aluminum matrix of cast alloys can easily be achieved in modern hot isostatic presses, thereby avoiding the necessity of a separate solution annealing step. In this work, we applied hot isostatic pressing followed by rapid quenching and direct aging to age-hardenable aluminum alloys processed by both sand casting and laser powder-bed fusion. It was shown that the proposed process of direct aging could be utilized for post-heat treatment of additively manufactured age-hardenable aluminum alloys to open up new fields of applications, for which components have to possess a high fatigue resistance.
关键词： Hot isostatic pressing,Critical cooling rate,Additive manufacturing,Fatigue resistance,Laser powder-bed fusion,Selective laser melting
更新于2025-09-23 15:19:57
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Performance of Solar Absorption-Subcooled Compression Hybrid Cooling System for Different Flow Rates of Hot Water
摘要： The solar absorption-subcooled compression hybrid cooling system (SASCHCS) is tech-economically feasible for high-rise buildings. Since such a system operates with no auxiliary heat source, the performance coupling of its absorption subsystem and solar collectors is sensitive to the variation of hot water ?ow rate. In this regard, the relationship of system performance and hot water ?ow rate is required to be clari?ed exactly. Therefore, this paper aims to illustrate the e?ect mechanism of hot water ?ow rate and to propose the corresponding decision criterion. The case study is based on a typical high-rise o?ce building in subtropical Guangzhou. The daily working process of this system with di?erent hot water ?ow rates is simulated and analyzed. Subsequently, the useful heat of collectors and cooling capacity of the absorption subsystem with the hot water ?ow rate is discussed in detail. The results show that the SASCHCS operates with hot water temperatures ranging from 60 C to 90 C. The energy saving increases with the rise of hot water ?ow rate, but such variation tends to be ?at for the excessively high ?ow rate. As the collector ?ow rate increases from 1 m3/h to 10 m3/h, the daily energy saving improves by 21% in August. Similarly, the daily energy saving increases by 37.5% as generator hot water ?ow rate increases from 1 m3/h to 10 m3/h. In addition, the collector ?ow rate of 3.6 m3/h (13.33 (kg/m2 h)) and the generator ?ow rate of 5.2 m3/h (19.26 (kg/m2 h)) are optimal for the annual operation, with considering power consumption of water pumps. This paper is helpful for the improvement of SASCHCS operating performance.
关键词： solar cooling,subcooled compression,hot water ?ow rate,absorption chiller,hybrid system
更新于2025-09-23 15:19:57
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Photovoltaic Cooling Utilizing Phase Change Materials
摘要： A theoretical analysis based on mathematical formulations and experimental test to a photovoltaic system cooled by Phase Change Material (PCM) is carried out and documented. The PCM is attached to the back of the PV panel to control the temperature of cells in the PV panel. The experimental tests were done to solar systems with and without using PCM for comparison purposes. A PCM of paraffin graphite panels of thickness15 mm has covered the back of the panel. This layer was covered with an aluminum sheet fixed tightly to the panel frame. In the experimental test, it was found that when the average cell temperature exceeds the melting point temperature of the PCM, the efficiency of the system increases. However, when the cell temperature did not exceed the melting temperature of the PCM, the use of the PCM will affect negatively the system efficiency.
关键词： Photovoltaic Cooling,PCM melting point,PV panel efficiency,Phase Change Materials
更新于2025-09-23 15:19:57
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Improving Thermal and Electrical Efficiency in Photovoltaic Thermal Systems for Sustainable Cooling System Integration
摘要： Research into photovoltaic thermal systems is important in solar technologies as photovoltaic thermal systems are designed to produce both electrical and thermal energy, this can lead to improved performance of the overall system. The performance of photovoltaic thermal systems is based on several factors that include photovoltaic thermal materials, design, ambient temperature, inlet and outlet fluid temperature and photovoltaic cell temperature. The aim of this study is to investigate the effect of photovoltaic thermal outlet water temperatures and solar cell temperature on both electrical and thermal efficiency for different range of inlet water temperature. To achieve this, a mathematical model of a photovoltaic thermal system was developed to calculate the anticipated system performance. The factors that affect the efficiency of photovoltaic thermal collectors were discussed and the outlet fluid temperature from the photovoltaic thermal is investigated in order to reach the highest overall efficiency for the solar cooling system. An average thermal and electrical efficiency of 65% and 13.7%, respectively, was achieved and the photovoltaic thermal mathematical model was validated with experimental data from literature.
关键词： Solar collectors,Photovoltaic,Outlet temperature,Solar cooling,Photovoltaic thermal systems,Thermal efficiency,Electrical efficiency
更新于2025-09-23 15:19:57
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Heating Behavior of Photovoltaic Panels and Front Side Water Cooling Efficiency
摘要： The use of solar energy is very promising for favorable Sun Belt countries. However, in these regions the hot climate leads to high temperatures which conduct to significant power losses in photovoltaic panels. In this paper we study the heating behavior of photovoltaic panels and front side water cooling efficiency. A standalone cooling system is designed as prototype which helps to proposal for a methodology for large-scale application through energy estimation of this system. Two typical situations were studied: the first one with a uniform distribution of the temperature and the second one with a non-uniform distribution of temperature under partial shadowing leading to hot spot effect. The gain in electrical power with cooling is about 45% in the case of a non-uniform distribution compared to 12% in the case of a uniform distribution at 30°C outdoor temperature. It was also noticed that temperature on hot spot point depends of the shadow type (direct and indirect). The estimation of the supplement of energy obtained from the cooling system demonstrates that the cooling system used in this study will be beneficial with using of string of PV panels with a minimum of three panels. This makes the autonomous cooling system very efficient.
关键词： solar energy,photovoltaic,hot-spot,cooling,temperature
更新于2025-09-23 15:19:57
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Analysis of cooling load on commercial building in UAE climate using building integrated photovoltaic fa?§ade system
摘要： In this study the details of energy consumption and its cost were studied and analyzed for a commercial office building in United Arab Emirates (UAE) as hot, dry and humid region where the cooling load is very high. Two different cases were simulated namely (a) base case without photovoltaic (PV) with normal glass windows (b) building integrated photovoltaic (BIPV) fa?ade system with transparent PV windows. The building size, space layout, dimensions, shape and orientation for both cases were exactly the same. The PVSYST software was used to determine the best orientation for BIPV fa?ade system installation to minimize the cooling load and maximize the electrical energy production. The amorphous silicon thin film was used for case (b) along with the weather data for the building location in Sharjah, UAE. The cooling load inside the building and its cost were evaluated for both cases. The use of BIPV fa?ade system case in hot, dry and humid region saved the annual electrical consumption for the air conditioning system by 27.69% while it reduced the yearly energy cost by US$ 2084. Such a study would offer data at critical climate conditions necessary for the design and future implementation of this system in the Emirate of Sharjah.
关键词： Cooling load,Energy analysis,Fa?ade (BIPV),UAE climate,HVAC system
更新于2025-09-23 15:19:57
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Experimental study with analysis for a novel saturated activated alumina photovoltaic thermal system
摘要： This paper presents a novel photovoltaic thermal system based on water absorption-desorption phenomenon using activated alumina. Experimental work for a promising photovoltaic thermal system that utilise activated alumina tablets as heat absorbing and storing element is presented. Based on the experimental results, electrical, thermal and combined energy efficiencies were calculated and compared with the stand-alone PV panel efficiency. Three identical systems -containing 10 cm depth saturated activated alumina mixed with aluminium mesh cuts-were attached to the back surface of simulated solar panel. The three systems were tested at 600, 800 and 1000 W/m2 for 6 consecutive working hours, representing sun shining time. Results showed a net energy efficiency of 57% and 53.6% at 600 W/m2 and 1000 W/m2 respectively. The electrical efficiency increased by 10.4% and 6.7% at 600 W/m2 and 1000 W/m2, respectively, compared with the stand-alone panel. This led to an increase in total energy generation by 309% and 319.5% at 600 W/m2 and 1000 W/m2 respectively, compared with stand-alone solar panel.
关键词： Solar panels,PV/T,Activated alumina,Materials,Saturated,Cooling
更新于2025-09-23 15:19:57
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Design, realization, and tests of a portable solar box cooker coupled with an erythritol-based PCM thermal energy storage
摘要： Solar radiation is a variable energy source and the mismatch between the availability of such source and the domestic energy demand is a paramount challenge to deal with. For this reason, in this work a 4.08 concentration ratio portable solar box cooker coupled with a thermal energy storage (TES) based on a phase change material (PCM) was characterized through outdoor experimental tests. The TES is a double-wall stainless steel vessel, with the annular volume filled with 2.5 kg of erythritol. The portable solar box cooker was tested under 4 different experimental conditions: without load, with water, with silicone oil, and with silicone oil inserted in the erythritol-based TES. The load tests were divided into a heating and a cooling phase, in order to evaluate the cooker performance in absence of solar radiation. Results showed that equipping the portable solar box cooker with the erythritol-based TES allowed to extend the average load cooling time, in the range 125–100 °C, of around 351.16%.
关键词： Experimental,Heating phase,Sugar alcohol,Cooling phase,Polyalcohol
更新于2025-09-23 15:19:57
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Combined molecular-dynamics and quantum-trajectories simulation of laser-driven, collisional systems
摘要： We introduce a combined molecular-dynamics and quantum-trajectories code to simulate the effects of near-resonant optical fields on state-vector evolution and particle motion in a collisional system. In contrast to collisionless systems, in which the quantum dynamics of multilevel, laser-driven particles with spontaneous emission can be described with the optical Bloch equations (OBEs), particle velocities in sufficiently collisional systems change on timescales comparable to those of the laser-induced, quantum-state dynamics. These transient velocity changes can cause the time-averaged velocity dependence of the quantum state to differ from the OBE solution. We use this multiscale code to describe laser cooling in a strontium ultracold neutral plasma. Important phenomena described by the simulation include suppression of electromagnetically induced transparencies through rapid velocity changing collisions and thermalization between cooled and uncooled directions for anisotropic laser cooling.
关键词： ultracold neutral plasma,molecular-dynamics,laser cooling,collisional systems,quantum-trajectories,laser-driven
更新于2025-09-23 15:19:57
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Effect of Hot Water Setting Temperature on Performance of Solar Absorption-Subcooled Compression Hybrid Cooling Systems
摘要： The solar absorption-subcooled compression hybrid cooling system (SASCHCS) displays outstanding advantages in high-rise buildings. Since the performance coupling of collectors and absorption subsystems is stronger due to the absence of backup heat and the effect of generator setting temperature has not been realized adequately, it is highly important to study the relationship of SASCHCS operation and the set point temperature of hot water to prevent performance deterioration by inappropriate settings. Therefore, the paper mainly deals with the effect of collector and generator setting temperature. The investigation was based on the entire cooling period of a typical high-rise office building in subtropical Guangzhou. The off-design model of hybrid systems was built at first. Subsequently, the impact mechanism of setting temperature in two hot water cycles on facility operation was analyzed. It was found that the excessive rise of collector setting temperature deteriorated the energy saving, while the appropriate improvement of generator set point temperature was beneficial for the solar cooling. Besides, global optimization by the genetic algorithm displayed that 71.6°C for the collector setting temperature with 64.5°C for the generator was optimal for annual operation. The paper is helpful in enhancing the operation performance of SASCHCS.
关键词： setting temperature of hot water,solar cooling,subcooled compression,absorption chiller,hybrid system
更新于2025-09-23 15:19:57