Effect of Cooling Methods on Methane Conversion via Dielectric-Barrier Discharges

Effects of cooling methods on stability and methane conversion rate using dielectric-barrier discharges （DBD） were systematically investigated in this article. The results showed that the methane conversion rate was as high as 44.43% in a pure methane system at a flow rate of 100 mL·min^-1 and an input power of 234.2 W with air cooling. A dark greenish and soft film-like carbon was deposited on the outer surface of quartz tube when the outer electrode was watercooled, which decreased the methane conversion. With air cooling of inner electrode the selectivity of C2 hydrocarbons was higher than that with other cooling methods, while the C3 hydrocarbons had higher selectivity with flowing water cooling. Cooling the inner electrode could restrain the carbon deposition, but would decrease the methane conversion rate. The stability of both reaction and plasma operation can be improved through cooling the reactor. From thermodynamic analysis, it was found that the effective collisions frequency among the reactant molecules and free electrons （e^-） increased with temperature, which in turn led to a higher methane conversion rate and a change in the distribution of products.

Microstructure and Property of Hypereutectic High Chromium Cast Iron Prepared by Slope Cooling Body-Centrifugal Casting Method

In this paper, the ring-type ingot of hypereutectic high Cr cast iron was obtained by slope cooling bodycentrifugal casting method （SC-CCM）, and its microstructure and impact toughness were investigated, respectively. The results indicated that, first, the primary carbides in the microstructure are prominently finer than those in the hypereutectic high Cr cast iron prepared by conventional casting method. Second, in the ring-type ingot, the primary carbides near radial outer field are finer than those near radial inner field; furthermore, there is dividing field in the microstructure. Finally, the impact toughness values of the specimens impacted on the radial outer face and on the radial inner face are improved respectively about 36% and 138% more than that of the hypereutectic high Cr one prepared by conventional casting method.

Numerical simulation of the preparation of semi-solid metal slurry with damper cooling tube method

In semi-solid forming process, preparing the slurry with rosette or globular microstructure is very important. A new approach named the damper cooling tube method （DCT）, to produce the semi-solid metal slurry, has been introduced. To optimize the technical parameters in designing the apparatus, the finite volume method was adopted to simulate the flow process. The temperature effects on the rheological properties of the slurries were also considered. The effects of the technical parameters on the slurry properties were studied in detail.

Influence of two-step cooling method on magnetic properties of Fe_(82)Mo_7B_(10)Cu_1 nanocrystalline alloy

Soft magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy were studied as a function of cooling condition. The results show that higher permeability and relaxation frequency can be obtained by the two-step cooling method, and the pinning field of the sample obtained by this method is smaller than that of the furnace-cooled and water-quenched samples. This phenomenon was interpreted in terms of internal stress and the magnetic ordering of the residual amorphous phase. The two-step cooling treatment is an effective way to improve the soft magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy.

Experimental study on mechanical properties of granite under different cooling methods after thermal treatment

Static uniaxial compression tests were conducted on 16 granite specimens after thermal treatment using a heating device and an electro-hydraulic servo pressure-testing machine. The effects of air cooling and water cooling on the physical and mechanical properties of the high-temperature granite specimens were studied. Test results showed that the longitudinal wave velocities of the high-temperature specimens gradually decreased after they were cooled by water and air. The peak stress and elastic modulus of the samples decreased gradually with an increase in temperature, whereas their peak strain increased gradually. The effects of peak stress and peak strain were considerably more evident when cooling by water than by air. This result demonstrated that the thermal cracking of the granite specimens, and consequently, their internal micro-fractures, further developed when the specimens were cooled by water.

Preparation of Thermosensitive Microcapsules Containing Water Soluble Powder by Melting Dispersion Cooling Method

It was tried to prepare the thermosensitive microcapsules containing the water soluble solid powder by the melting dispersion cooling method and to establish the optimum preparation conditions. As a model water soluble solid powder, sodium hydrogen carbonate was adopted in order to generate carbon dioxide gas and as a thermosensitive shell material, olefin resin with the melting point of ca. 40°C was used. In the experiment, the concentration of olefin resin in the shell material solution was mainly changed together with the concentrations of the oil soluble surfactant species and the α-tocopherol as a modifier of shell. Addition of α-tocopherol into the shell material solution could prevent the core from breaking away during the microencapsulation process and result in the higher microencapsulation efficiency, because the dispersion stability of solid powder in the shell material solution could be increased due to the increase in affinity between the shell material solution and solid powder. Also, the microencapsulation efficiency increased with the concentration of olefin resin, became maximum at 50 wt% and then, decreased. The microcapsules were found to begin melting at 36°C and to generate carbon dioxide gas.

Preparation of Microcapsules Containing Aqueous Solution of Azur B with Melting Dispersion Cooling Method and Application to DNA Amplification Detector

Microcapsules containing the aqueous solution of Azur B of a water soluble dye were prepared with the melting dispersion cooling method and applied to the amplification detector of plant DNA. Paraffin wax with melting temperature of 75°C was used as the shell material. In the experiment, the aqueous solution (W) of Azur B as the core material was dispersed in the melted paraffin wax (O) to form the (W/O) emulsion and then, the (W/O) emulsion was dispersed in the silicon oil (O’) as the continuous phase to form the (W/O)/O’ emulsion at 85°C. After formation of the (W/O)/O’ emulsion, the microcapsules were prepared by cooling the (W/O)/O’ emulsion to 50°C. The microcapsules were prepared by changing the concentration of oil soluble surfactant in the (W/O) emulsion and the volume of the (W/O) emulsion in the (W/O)/O’ emulsion. The microencapsulation efficiency increased with the concentration of oil soluble surfactant and finally became 100% under the optimum conditions. Furthermore, the microcapsules were melted down at temperature of 85°C to reveal the sharp thermal responsibility and to release the aqueous solution of Azur B. As a result, it was found that the microcapsules were able to be applied to the amplification detector of plant DNA by utilizing the reaction between DNA and Azur B.

Techno-Economic and Sustainability Analysis of Potential Cooling Methods in Irish Data Centres

11% of Irish electricity was consumed by data centres in 2020. The Irish data centre industry and the cooling methods utilised require reformative actions in the coming years to meet EU Energy policies. The resell of heat, alternative cooling methods or carbon reduction methods are all possibilities to conform to these policies. This study aims to determine the viability of the resell of waste heat from data centres both technically and economically. This was determined using a novel application of thermodynamics to determine waste heat recovery potential in Irish data centres, and the current methods of heat generation for economical comparison. This paper also explores policy surrounding waste heat recovery within the industry. The Recoverable Carnot Equivalent Power (RCEP) is theoretically calculated for the three potential cooling methods for Irish data centres. These are air, hybrid, and immersion cooling techniques. This is the maximum useable heat that can be recovered from a data centre rack. This study is established under current operating conditions which are optimised for cooling performance, that air cooling has the highest potential RCEP of 0.39 kW/rack. This is approximately 8% of the input electrical power that can be captured as useable heat. Indicating that Irish data centres have the energy potential to be heat providers in the Irish economy. This study highlighted the technical and economic aspects of prevalent cooling techniques and determined air cooling heat recovery cost can be reduced to 0.01 €/kWhth using offsetting. This is financially competitive with current heating solutions in Ireland.

High efficient Raman sideband cooling and strong three-body recombination of atoms

We report a highly efficient three-dimensional degenerated Raman sideband cooling(3D dRSC)that enhances the loading of a magnetically levitated optical dipole trap,and observe the strong atom loss due to the three-body recombination.The 3D dRSC is implemented to obtain 5×10^(7)Cs atoms with the temperature of~480 nK.The cold temperature enables 1.8×10^(7)atoms loaded into a crossed dipole trap with an optimized excessive levitation magnetic gradient.Compared to the loading of atoms from a bare magneto-optical trap or the gray-molasses cooling,there is a significant increase in the number of atoms loaded into the optical dipole trap.We derive for the three-body recombination coefficient of L_(3)=7.73×10^(-25)cm^(6)/s by analyzing the strong atom loss at a large scattering length of 1418 Bohr radius,and discover the transition from the strong three-body loss to the dominant one-body loss.Our result indicates that the lifetime of atoms in the optical dipole trap is finally decided by the one-body loss after the initial strong three-body loss.

Numerical simulation of HP rotor cooling configuration using parameterized method

This paper implemented cooling configuration design on certain gas turbine HP rotor using parameterized method.It is convenient for complicated gas turbine blade modeling using parameters and also benefit for the geometry modify in later period.Parameterized modeling is the foundation of air cooling turbine blade design method engineering application.Mesh quality can be awarded when generated complicated cooling configuration blade grids,and also the increase of calculation error can arise by many mesh blocks.Film cooling and serpentine passage can effectively enhance the cooling effectiveness and protect blade.

Thermal field in water pipe cooling concrete hydrostructures simulated with singular boundary method

The embedded water pipe system is often used as a standard cooling technique during the construction of large-scale mass concrete hydrostructures. The prediction of the temperature distribution considering the cooling effects of embedded pipes plays an essential role in the design of the structure and its cooling system. In this study, the singular boundary method, a semi-analytical meshless technique, was employed to analyze the temperature distribution. A numerical algorithm solved the transient temperature field with consideration of the effects of cooling pipe specification, isolation of heat of hydration, and ambient temperature. Numerical results are verified through comparison with those of the finite element method, demonstrating that the proposed approach is accurate in the simulation of the thermal field in concrete structures with a water cooling pipe.

Analysis of fixation method of fuel assembly for lead-alloy cooled reactor

As a potential candidate for generation IV reactors, lead-alloy cooled reactor has attracted much attentions in recent years. The China LEAd-based research Reactor(CLEAR) is proposed as the primary choice for the accelerator driven subcritical system project launched by Chinese Academy of Sciences. Lead-bismuth eutectic(LBE) is selected as the coolant of CLEAR owing to its efficient heat conductivity properties and high production rate of neutrons. In order to compensate the buoyancy due to the high density of lead-alloy, fixation methods of fuel assembly(FA) have become a research hotspot worldwide. In this paper, we report an integrated system of ballast and fuel element for CLEAR FA. It guarantees the correct positioning of each FA in normal and refueling operations. Force calculation and temperature analysis prove that the FA will be stable and safe under CLEAR operation conditions.

New Measurement Method for Direct Cooled Power Electronic with Transmission Fluids

Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.

单分散Al-4.5wt%Cu合金粒子的制备与凝固过程模拟

使用脉冲微孔喷射法制备了粒径可控的单分散Al-4.5wt%Cu液滴,对液滴凝固成的粒子进行分析表征。结果表明:该粒子具有粒径均一、高球形度、热履历一致的优点。随着粒径的增长,粒子的内部微观结构由胞状晶变为树枝晶。建立了粒子凝固过程的传热数值计算模型,分析了粒子下落中温度、温度梯度变化及冷却速率与粒子微观组织形貌的关系。在本实验条件下,310.0μm粒子内部凝固组织为胞状晶,冷却速率为771.71 K/s;485.1μm粒子内部凝固组织为树枝晶,冷却速率为382.40 K/s。

日间辐射制冷材料磷酸铝的固相合成及其结构性能

辐射制冷技术因不需要任何能量输入且无污染等特点具有广阔的应用前景,但是高成本复杂的辐射制冷材料的制备工艺阻碍了这项技术的发展.采用低成本高效益的一步固相法合成了三斜晶系与立方晶系复合晶系的磷酸铝材料,该材料在太阳光波段内的平均反射率达到97.65%,在大气窗口(8~13μm)范围内的平均发射率为0.88.在日间辐射冷却实验中,这种复合晶系磷酸铝材料在阳光直射条件下的最佳冷却效果可以使环境温度降低6℃左右.将磷酸铝材料应用于陶瓷坯体中,通过冷却实验表明,加入AlPO_(4)的陶瓷坯体使环境温度降低4℃,与未加入磷酸铝的陶瓷坯体的冷却效果相比降低了约2℃.本研究对磷酸铝辐射制冷材料的推广应用具有重要的指导意义.

大跨度钢屋盖轮辐式索桁架结构施工方法与数值模拟

轮辐式张拉结构通过张拉柔性拉索形成刚度,抵抗结构所承受的外荷载。为保证柔性结构张拉成型全过程安全可靠、张拉完成后满足设计要求,对施工过程各阶段进行数值模拟和计算分析,确定合理的施工方案。采用有限元软件ANSYS建立济南市黄河体育中心钢屋盖轮辐式索桁架整体分析模型;通过等效降温法对轮辐式拉索施加预拉力,得到不同施工阶段整体结构力学响应;对索桁架结构展开形态分析,使索构件实际内力与设计拉力吻合。研究表明,采用等效降温法可实现对大跨度钢屋盖轮辐式拉索预拉力的模拟,整体结构在各施工阶段的力学响应满足安全性要求。

不同预冷方式结合1-甲基环丙烯对红提葡萄的保鲜效果

【目的】研究不同预冷方式结合1-甲基环丙烯(1-MCP)对红提葡萄预冷速度及贮藏品质的影响。【方法】以红提葡萄为试材,分别用隧道式原位差压预冷装置、预蓄冷周转箱、冷库预冷三种预冷方式结合1.5μL/L 1-MCP熏蒸处理,无1-MCP熏蒸作为对照(CK)。置于(0±0.5)℃、相对湿度85%的保鲜库中贮藏,每20 d测定1次果实的各项生理指标变化。【结果】隧道式原位差压预冷、预蓄冷周转箱处理的红提葡萄降温速率明显比冷库预冷的速率快,1.5μL/L 1-MCP结合隧道式差压预冷、预蓄冷周转箱处理的果实较1-MCP结合冷库及CK处理的果实腐烂率和落粒率低,对葡萄的可滴定酸(TA)、可溶性固形物(SSC)含量的保留具有积极的作用,抑制了果实的呼吸强度和丙二醛(MDA)含量,激发了过氧化物酶(POD)的活性,较好的维持了果实品质和营养成分,有效延缓了果实的衰老进程。【结论】1.5μL/L 1-MCP结合隧道式原位差压预冷处理,推迟了红提葡萄的后熟软化衰老进程,保持了果实的品质和营养成分。

夏季日峰降温电力负荷预测灰色模型及其应用

基于2017—2020年石家庄市逐15分钟电力负荷及同期气象资料,计算人体舒适度指标有效温度和温湿指数,考虑基准负荷存在周期性和增长性,提出采用灰色模型GM(1,1)并结合滤波法、相关分析等方法,建立日峰降温电力负荷与人体舒适度指标分段回归模型。结果表明:石家庄电力负荷具有明显的逐年增长趋势;剥离出的日降温负荷曲线呈“W”型分布;分别对模型进行一次、二次和分段函数拟合,对3种预测模型进行检验发现分段函数预测精度较高,平均相对误差在4.8%~5.2%,有效温度和温湿指数的分段函数误差在-10%~10%所占比例分别为88.1%和90.5%;考虑了温度、湿度和风速的有效温度较温湿指数的夏季日峰降温电力负荷预测模型预测准确率更高,回归模型分段点为26.2℃,对电网“迎峰度夏”时期电力调度具有参考价值。

二次水断供核主泵屏蔽电机冷却水瞬态热分析

核主泵屏蔽电机在热态极端环境参数额定(简称热态额定)工况下,二次水突然断供(secondary water supply outage,SWSO)300 s时刻,一次下导轴承润滑水温不超过警报温度95℃是产品出厂的重要指标,研究该情况下热流场计算方法及各种参数随时间演变特性对于电机热安全非常重要。首先,以北方工厂冷态环境参数下额定(简称冷态额定)工况该电机SWSO前后稳/瞬态厂内测量入出口试验数据为边界条件,采用有限体积法,进行流场和温度场的流固耦合数值模拟,模拟值与试验值300 s时的误差为5.97%,验证了计算方法准确性。然后,数值反演热态额定工况SWSO一/二次冷却水的温度场随时间变化规律。结果表明:SWSO 300 s内,二次水流速及对流传热系数随时间变化存在特征明显不同的2个阶段,二次水与螺旋槽壁面间对流换热系数h由稳态时7808.06 W/(m^(2)⋅K),13 s内减少到480.07 W/(m^(2)⋅K),随后h变化很小;热态额定参数时,下导轴承润滑水温远低于报警值95℃。为核主泵屏蔽电机轴承润滑水热安全计算提供参考。

高温后结构钢材单调拉伸和循环荷载试验研究

现有的火灾后钢材残余特性研究大多着眼于钢材在高热下或升温后的残余静力特性,而对过火后钢材在循环荷载作用下的滞回和抗震特性鲜有研究。对于建筑结构和桥梁中常用的Q235和Q355两种钢材,对其进行了500~1000℃的模拟火灾加热处理,并进行自然冷却或浸水冷却。对于冷却后的钢材试样进行了单向拉伸试验和2种不同荷载变化规律下的循环加载试验,得到了模拟温度和不同降温方式对于两种钢材滞回特征的影响规律。由试验结果可得,在受到的最高温度不高于600℃时,Q235和Q355钢材在自然冷却和浸水冷却后的单向拉伸和往复荷载工况下,其强度等级和弹塑性强度发展特征均与相应的未进行加热处理的钢材相似。当过火温度高于600℃时,自然冷却后Q235和Q355钢材的初始屈服强度会随过火极限温度的升高而逐渐下降。但在循环荷载影响下,钢材存在循环硬化效应,且该效应将随着过火极限温度的升高而逐渐显著。高温经历所导致的强度削弱会逐渐恢复。Q235和Q355钢材在循环荷载作用下的滞回刚度会逐渐下降,且极限温度和冷却方式会影响滞回刚度的下降幅度。高温过火且浸水冷却条件下,Q235和Q355钢材循环硬化效应显著,弹性域增长显著,循环荷载作用下塑性耗能能力下降明显。