大涡模拟分析地表热通量对边界层对流卷的影响

本文利用1995年8月14日SCMS外场试验期间的观测资料,以及大涡模式模拟的边界层垂直速度数值实验结果,研究边界层对流卷的发展演变和地表热通量对其形式和强度的影响。对观测资料的分析表明：边界层对流卷的上升气流是暖湿气流,下沉气流则相对干冷。模拟结果显示：当有边界层对流卷存在时,地表热通量越小,对流卷的线性特征越明显,对流强度越弱;随着地表热通量的增大,组织性将减弱,对流运动发展强烈;当地表热通量值增大到维持边界层对流卷的阈值,对流卷的线性特征将消失。     

热触发式流量／液位开关的研制

热触发式流量／液位开关是一种监控流量或液位变化的传感器，主要是在探头部分使用了测温元件以及一个用来加热测温元件的低功率加热经的响应时间可以小到２ｓ，于各种液体或气体，可以在一定的介质，压力，温度或粘率范围内使用。     

超声波搅拌强化对流传热试验

考虑到重复试验和简化计算的需要,利用三个不同大小的蘑菇状铸铝热感受体模型代替实际固态颗粒物料进行实验。将铝制热感受体模型浸入热水中,分别在有超声波搅拌作用下和没有超声波搅拌作用下,用温度自动定时记录仪,通过热电偶,记录铝制热感受体模型的温度变化情况。根据传热方程计算不同试验条件下流体对固态颗粒的对流传热系数。试验结果表明,采用超声波搅拌,能明显地提高流体对固态颗粒的对流传热系数,其提高程度与固态颗粒的大小及单位质量流体内输入的超声波能量的多少有关。     

Geothermal convection through oceanic crust and sediments in the Indian ocean

Closely spaced heat flow surveys at four sites on the flanks of the Central Indian Ridge and the Southeast Indian Ridge delineate a pattern of oscillatory heat flow which can only result from cellular convection of oceanic bottom water through the oceanic crust and overlying sediment. These cells have a wavelength of 5 to 10 kilometers and are presently active in sea floor 18 x 10(6), 25 x 10(6), and 45 x 10(6) years old of the Crozet Basin and in sea floor 55 x 10(6) years old of the Madagascar Basin. The precise measurement of nonlinear temperature profiles makes it possible to calculate the conductive and convective heat transfer components through the sea floor. Even in the oldest sites, geothermal convection is still a major component of heat transfer through both the crust and sedimentary layers. These observations coupled with the results of earlier oceanwide geothermal studies indicate that more than one-third of the entire surface area of the world's ocean floor contains presently active geothermal convection that is cellular in plan form.     

Role of deep cloud convection in the ozone budget of the troposphere

Convective updrafts in thunderstorms prolong the lifetime of ozone (O(3)) and its anthropogenic precursor NOx [nitric oxide (NO) + nitrogen dioxide (NO(2))] by carrying these gases rapidly upward from the boundary layer into a regime where the O(3) production efficiency is higher, chemical destruction is slower, and surface deposition is absent. On the other hand, the upper troposphere is relatively rich in O(3) and NOx from natural sources such as downward transport from the stratosphere and lightning; convective overturning conveys the O(3) and NOx toward the Earth's surface where these components are more efficiently removed from the atmosphere. Simulations with a three-dimensional global model suggest that the net result of these counteractive processes is a 20 percent overall reduction in total tropospheric O(3). However, the net atmospheric oxidation efficiency is enhanced by 10 to 20 percent.     

Heat transfer measurements of the 1983 kilauea lava flow

Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.     

Improving the representation of thermal boundary conditions of livestock during CFD modelling of the indoor environment

The use of computational fluid dynamics (CFD) to evaluate the climate distribution in agricultural buildings has grown in importance in recent years. Convection and radiation are the dominant forms of heat transfer from an animal's body, and accurately accounting for animal heat flux during CFD simulations is necessary to achieving a good understanding of the livestock‘s thermal environment. Of the total heat flux leaving the animal, the convective part is regularly calculated using a predetermined ratio between the convective to radiative parts (C-R ratio). However, by employing this ratio the CFD modeller is essentially forcing the simulated animal to lose a certain amount of convective heat, irrespective of the environmental conditions at their location. Therefore, unless the indoor environment is known a priori to a CFD simulation, and unless this environment is totally uniform, the C-R ratio ascribed to some of the simulated animals will be less precise. In order to address this difficulty the authors of this study have used a zero-dimensional calf heat transfer model to account for calf thermoregulation during CFD simulations. The effect of using this representation of calf heat flux was analysed for practical housing scenarios and differences in the predicted airflow distribution patterns were found to occur between the simulations that used a fixed and dynamic relationship for calf heat flux partitioning.     

Fundamental issues in the geology and geophysics of venus

A number of important and currently unresolved issues in the global geology and geophysics of Venus will be addressable with the radar imaging, altimetry, and gravity measurements now forthcoming from the Magellan mission. Among these are the global volcanic flux and the rate of formation of new crust; the global heat flux and its regional variations; the relative importance of localized hot spots and linear centers of crustal spreading to crustal formation and tectonics; and the planform of mantle convection on Venus and the nature of the interactions among interior convective flow, near-surface deformation and magmatism.     

CO2冷阱微波真空干燥装置设计与试验

为优化微波真空冷冻干燥工艺,基于微波真空冷冻干燥原理研制了CO2冷阱微波真空干燥装置,并介绍了该装置的主要结构、工作原理和工作流程.创新采用液态CO2作为制冷媒,通过合理布局实现CO2的循环利用.采用喷淋冷冻技术,从液态CO2喷淋预冷冻原理出发,设计了喷淋装置结构,并匹配计算了转盘转速,旨在提高物料预冷冻效果.设计了翅...     

山西太岳山地区辽东栎林夏季热量平衡的研究

采用波文比能量平衡法对暖温带具有代表性的群落辽东栎纯林夏季热量平衡进行研究，测定热量平衡各分量。同时用TDM(Thermal Dissipation Method)法通过测定树干液流流量通量，得到蒸腾耗热通量，进而把蒸腾和蒸发从蒸发散中分开，把潜热通量分成蒸腾热适量和蒸发热通量。     

Caterpillar setae: insulation for an ectotherm

Gypsy moth caterpillars have long, soft setae distributed along the lateral portions of the body, but only short, stiff setae on the dorsal surface. Setae act as selective insulation for caterpillars by reducing the rates of convective heat exchange without affecting the rates of radiative heat exchange. Changes in posture abolish the effects of the setae by maximizing convection and minimizing radiant heat uptake.     

Unimpeded permeation of water through helium-leak-tight graphene-based membranes

Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We found that submicrometer-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors, and gases, including helium, but these membranes allow unimpeded permeation of water (H(2)O permeates through the membranes at least 10(10) times faster than He). We attribute these seemingly incompatible observations to a low-friction flow of a monolayer of water through two-dimensional capillaries formed by closely spaced graphene sheets. Diffusion of other molecules is blocked by reversible narrowing of the capillaries in low humidity and/or by their clogging with water.     

Survival of mammals breathing organic liquids equilibrated with oxygen at atmospheric pressure

Because oxygen and carbon dioxide are very soluble in certain silicone oils and fluorocarbon liquids, these liquids will support respiration of mammals. Mice and cats respiring silicone oil die shortly after return to air breathing, while those breathing fluorocarbon survive for weeks. The respiration of mice is optimally supported by these organic liquids at about 20 degrees C. In cats, arterial oxygenation is excellent, but there is some impairment of carbon dioxide elimination. All animals have suffered some pulmonary damage from breathing fluorocarbon liquids. Continued investigation of organic fluid respiration may lead to development of a safe method to support the respiration of man by liquids equilibrated with gases at atmospheric pressure.     

LNG绕管式换热器壳程对流换热数值模拟

绕管式换热器是天然气液化的核心设备,其换热性能的优劣严重影响液化工艺水平。基于绕管式换热器的结构及特性,采用Fluent软件,对LNG绕管式换热器壳程单相混合冷剂的对流换热进行了数值模拟。结果表明:换热管管径是影响壳侧换热的重要因素,壳侧换热系数、壳侧冷剂压降均随换热管管径、壳侧冷剂质量流量的增大而增大。模拟结果与已有实验值的偏差均控制在20%以内,二者具有较高的匹配性,说明采用新建立的数值模拟模型用于绕管式换热器换热性能研究具有可行性。     

Heat Flow and Convection Experiments aboard Apollo 17

Experiments conducted aboard Apollo 17 by astronaut Ronald E. Evans showed that in uncovered liquids convection driven by surface tension can occur at lower temperature gradients in low gravity (about 10-(8)g) than in 1g. In completely confined fluids (no liquid-gas interface) vibrations caused by spacecraft and astronaut movements increased the heat transfer considerably over the pure conduction case.     

大连地区一次暴雨过程的成因分析

2006年7月10日辽东半岛地区出现了暴雨或大暴雨天气,利用常规的天气资料、卫星云图以及MM5模式,对发生在大连地区的这次暴雨天气进行天气形势、水汽条件、动力条件等分析。结果表明,这是一次由高空槽、副高后部切变云系、北上台风的外围云系、地面倒槽相互作用引起的对流天气过程。切变线云系中不断产生并发展加强的多个中-β尺度对流云团是这次过程的直接中尺度系统。MM5模式模拟结果分析揭示了造成此次暴雨时,对流层低层存在很强的西南低空急流,台风充足的水汽配合低层旺盛的西南流场为雨区输送水汽和热量;切变线结构为低层有辐合中心,高层有辐散中心,垂直运动场上对应有强上升运动,为暴雨提供动力条件;暴雨区上空存在着较深厚的高湿水汽柱和高温层,为暴雨的产生提供充足的水汽和能量。暴雨区高层有明显冷气流侵入是产生暴雨天气的触发机制;副热带高压的位置及强度变化对这次暴雨的产生和发展起着重要的作用。     

石家庄市一次强对流暴雨天气分析

通过常规天气资料、物理量和雷达回波,对2010年7月31日石家庄市一次强对流天气进行了总结分析。结果发现,此次强对流暴雨发生前副高长时间控制石家庄市,石家庄市连续多天处在高温、高湿的闷热天气当中,对流层存在高度的不稳定状况,850 hPa切变和地面冷锋是触发不稳定能量释放的主要因素,水汽主要来自低层偏南气流的水汽输送。多普勒雷达观测表明,降水回波强度均在35dBz以上,最大回波强度达到55 dBz,回波顶高度超过15 km。     

Surface-directed liquid flow inside microchannels

Self-assembled monolayer chemistry was used in combination with either multistream laminar flow or photolithography to pattern surface free energies inside microchannel networks. Aqueous liquids introduced into these patterned channels are confined to the hydrophilic pathways, provided the pressure is maintained below a critical value. The maximum pressure is determined by the surface free energy of the liquid, the advancing contact angle of the liquid on the hydrophobic regions, and the channel depth. Surface-directed liquid flow was used to create pressure-sensitive switches inside channel networks. The ability to confine liquid flow inside microchannels with only two physical walls is expected to be useful in applications where a large gas-liquid interface is critical, as demonstrated here by a gas-liquid reaction.     

Molecular beam scattering from liquid surfaces

By means of controlled collisions of atoms and molecules with liquid surfaces, molecular beam experiments can be used to probe how gases stick to, rebound from, and exchange energy with molecules in the liquid phase. This report describes measurements of energy exchange in collisions between gases (neon, xenon, and sulfur hexafluoride) and polyatomic liquids (squalane and perfluoropolyether). Energy transfer depends critically on liquid composition and is more efficient for the hydrocarbon than for the perfluorinated ether.