Implementation and control of asymmetric thermal environment in two-dimensional rectangular enclosure

Laminar natural convection in an enclosure divided by an adiabatic partition on its bottom with two unequal discrete heat sources was investigated numerically. The effect of the partition on the flow structure and heat transfer characteristics in enclosure under asymmetric heating condition was studied. The parameters are the Rayleigh number (1×10⁴≤Ra≤1×10⁶) and the height of partition (0≤h/H≤0.70). The streamlines are produced for various Rayleigh numbers. The results reflected by variations of the average Nusselt number in terms of the height of partition illustrates the convection heat transfer in the enclosure. The role of the partition is to weaken or cut off the heat removal rate from the strong heat source to the weak heat source. It is analyzed that the optimum height of the partition to break the linkage between the strong and weak heat source increases with increasing Rayleigh number. Foundation item: Project(50408019) supported by the National Natural Science Foundation of China     

北方地区供暖情况下室内热环境数值分析

为研究建筑围护结构热工性能与供暖季室内散热器传热特性的关联性,采用一种修正的湍流k-ε模型对兰州地区某民用住宅室内热环境进行了数值分析,获得了该住宅在4种外墙类型情况下的散热器传热特性和室内流场、温度场分布。结果表明：在满足室内供暖温度要求条件下（室内平均温度达到18°C）,散热器表面对流换热能力随外墙导热系数的增大而增大;室内形成了明显的温度分层现象,外墙导热系数越大,接近地板的温度越低,形成的＂冷气湖＂厚度自东墙朝西墙方向逐渐变薄;选择不同的外墙类型,室内速度场的变化很微弱。     

Thermal partition of two asymmetric discrete heat sources by cold air curtain

A partition solution implemented by a cold air curtain for two asymmetric discrete heat sources in a two-dimensional rectangular enclosure was numerically studied. Main attentions were focused on the effects of Reynolds number, Grashof number, separation distance between heat sources, and buoyancy ratio. It is found that the airflow and heat transfer are not only determined by governing parameters, but also affected by boundary conditions. It is also found that nearly symmetry of flow structure corresponds to nearly thermal partition, and the symmetry can be enhanced when Reynolds number, separation distance and buoyancy ratio increase. In addition, it is observed that there is a minimum Reynolds number for obtaining nearly thermal partition, which increases when Grashof number increases. Foundation item: Project (50408019) supported by the National Natural Science Foundation of China     

三种屋面下室内热环境的计算模型

本文以自然通风顶层房间夏季室内热环境为研究对象，运用周期性传热理论，分别针对蓄水、覆土种植和普通传统隔热三种屋面，建立了顶层房间夏季室内热环境的数学模型并进行了验证。     

顶层房间夏季室内热环境评价指标

通过对自然通风顶层房间夏季室内热环境的实测和分析，确认了这种热环境的两个主要特征。分析认为，评价这类不对称辐射热环境时，应同时考虑高温和房间内表面温度不对称的综合影响。为此，建议同时采用热应力指标HSI和辐射热通量QR作为这类环境的综合评价指标，并对实测房间运用这一指标进行了分析和讨论。     

建筑室内环境的数值模拟研究

采用华北地区采暖期间典型计算日内的逐时气温,将计算范围扩至建筑墙体外表面,所建的物理模型和各种材料的物理性质都与实际相符。通过数值计算方法,将建筑围护结构表面换热过程视为一个动态系统,大大提高了精度,为建筑热工分析和采暖负荷计算提供了可行和准确的计算方法。     

HEVC运动估计中SAD算法的动态可重构实现

高效视频编码（HEVC）标准中引入的不对称分割模式导致运动估计算法中绝对差值和（SAD）运算量成倍增加.为了提高运动估计算法的执行效率,方便用户进行自主选择,设计了同时支持不对称分割模式开启和关闭2种执行模式以及执行模式间自由切换的可重构阵列结构.为了满足用户要求编码速度的同时,最大限度地利用可重构阵列处理器的资源,在阵列结构为16×16个处理元中通过加载16×8、16×4以及16×2个处理元的指令来进行阵列规模的动态重构,采用指令下发的方式将不同的指令发送到对应处理元进行相应配置.实验结果表明,所提出的可重构实现方式在硬件资源占用量接近条件下,相较于流水化实现处理时间减少了约35%,吞吐量提高了约0.4倍.该实现具有较高的执行效率,能够进行执行模式与阵列规模的切换,具有较好的灵活性.     

供暖房间室内动态热环境数值分析方法的研究

将围护结构和室内空气在内的整个房间作为求解对象，并全面考虑了各个影响因素，用有限差分法编制了三维计算软件，并和实验结果进行了比较，数据基本相符。     

On the combined heat transfer of natural convection, radiation and conduction in the non-gray semitransparent thermal fibrous insulation

Non-gray semitransparent fibrous insulation hasbroad application in high-temperature industry, such asthe TPS ( thermal protection systems) of reusablelaunch vehicles. A metallic thermal protection systemgenerally consists of a metallic shell panel partit…     

运用社会化聆听方法的非集中供暖区住户对冬季室内热环境不满的分析

随着社会经济的发展,居住在非集中供暖区的居民对改善严酷冬季室内热环境的需求越发高涨,希望能在冬季拥有舒适的室内环境.有关于采暖需求和采暖行为的相关文献大多使用问卷调研进行研究,而问卷中的问题和选项又多是研究者主观制定,在这种情况下,居民只能顺着研究者的思路表达他们的不满,这将导致调研结果产生偏差;此外,研究者设计的问卷...     

Enhancement of natural ventilation in rectangular enclosure with two openings by thin fin

A numerical method was used to study the natural ventilation in a rectangular enclosure with two symmetrical openings. In order to improve the natural ventilation efficiency, a fin was introduced into the enclosure.Steady-state heat transfer by laminar natural ventilation in a partially divided rectangular enclosure was investigated by numerically solving equations of mass, momentum and energy. Streamlines and isotherms were produced and heat transfer rate were calculated. A parametric study was carried out using the following parameters: Rayleigh number (1 × 103 - 1 × 106) , dimensionless length (0 - 0.7) and position values (-0. 7 - 0. 7). It is found that the Nusselt number is an increasing function of Rayleigh number. By comparing with no-fin case, it is concluded that fin can effectively enhance the natural ventilation in the enclosure.     

水火弯板数值模拟中的水冷换热边界条件研究

在水火弯板过程数值模拟中,对流换热边界条件尤其是水冷对流换热边界条件对数值模拟的结果影响很大,其水冷对流换热系数的求解一直是水火弯板数值模拟中的一大难题.这里采用流动沸腾换热理论对水火弯板数值模拟中的水冷对流换热边界条件进行了研究,通过求得过冷水流动泡态沸腾起始点(ONB)和过冷水流动泡态沸腾临界点(CHF)的壁面过热度,比较水火弯板过程中钢板表面各处的温度和这2个壁面温度以确定冷却水的状态,根据冷却水的状态分别求其对应的过冷水单相流动对流换热系数和过冷水流动泡态沸腾换热系数.采用沸腾曲线对流换热边界条件和流动沸腾换热边界条件的数值模拟结果进行比较,结果表明流动沸腾换热边界条件的数值模拟结果精度明显提高,具有较高的研究价值.     

被动式太阳能建筑室内热环境评价指标的分析

为评价被动式太阳能建筑室内热环境的优劣，需要选择合适的热环境指标。本文利用在中国西部地区获得的相关实测数据，分析和比较了两种目前常用的代表性指标的适用性，并建议在评价这类建筑时应对这两种指标加以综合考虑。     

Enhancement of natural ventilation in rectangular enclosure with two openings by thin fin

A numerical method was used to study the natural ventilation in a rectangular enclosure with two symmetrical openings. In order to improve the natural ventilation efficiency, a fin was introduced into the enclosure. Steady-state heat transfer by laminar natural ventilation in a partially divided rectangular enclosure was investigated by numerically solving equations of mass, momentum and energy. Streamlines and isotherms were produced and heat transfer rate were calculated. A parametric study was carried out using the following parameters: Rayleigh number (1×10³ − 1×10⁶), dimensionless length (0–0.7) and position values (−0.7−0.7). It is found that the Nusselt number is an increasing function of Rayleigh number. By comparing with no-fin case, it is concluded that fin can effectively enhance the natural ventilation in the enclosure. Foundation item: Project(50408019) supported by the National Natural Science Foundation of China     

Characters of surface deformation and surface wave in thermal capillary convection

In the field of fluid mechanics, free surface phenomena is one of the most important physical processes. In the present research work, the surface deformation and surface wave caused by temperature difference of sidewalls in a rectangular cavity have been investigated. The horizontal cross-section of the container is 52 mm×42 mm, and there is a silicon oil layer of height 3.5 mm in the experimental cavity. Temperature differ- ence between the two side walls of the cavity is increased gradually, and the flow on the liquid layer will develop from stable convection to un-stable convection. An optical diag- nostic system consisting of a modified Michelson interferometer and image processor has been developed for study of the surface deformation and surface wave of thermal capillary convection. The Fourier transformation method is used to interferometer fringe analysis. The quantitative results of surface deformation and surface wave have been calculated from a serial of the interference fringe patterns. The characters of surface deformation and surface wave have been obtained. They are related with temperature gradient and surface tension. Surface deformation is fluctuant with time, which shows the character of surface wave. The cycle period of the wave is 4.8 s, and the amplitudes are from 0 to 0.55 μm. The phase of the wave near the cool side of the cavity is opposite and correlative to that near the hot side. The present experiment proves that the surface wave of thermal capillary convection exists on liquid free surface, and it is wrapped in surface deformation.     

室内空气自然对流的二维数值模拟

用具有SIMPLE算法。QUICK差分格式对封闭空腔内的流体自然对流进行了数值模拟计算,考察了Ra数对对流换热的影响．结果表明,在相同的条件下,随着Ra数的增加,对流换热加强．     

寒冷地区住宅夏季室内热环境调查与分析

为了切实掌握目前寒冷地区住宅夏季室内热环境的真实状况,本文于2005年夏对分布在寒冷地区5省四十多个县市的100户住宅进行了问卷调查和典型实地测试,调查结果显示:寒冷地区夏季人们对室内热环境并不满意,但长期以来希望受自然通风以及节电等经济条件的限制,人们形成了较高的高温忍耐力;夜晚居民大多呆在家里,对室内热环境的主观评价受自身生活习惯和心理因素的影响较大;窗户的朝向及是否采取遮阳措施是寒冷地区住宅夏季防热的薄弱环节,可以通过合理增置遮阳设施、进行室外绿化等措施来改善住宅室内热环境状况.     

存在垂直加热时的矩形池内热毛细对流的数值模拟

为了了解垂直加热对矩形浅液池内稳态热毛细对流的影响,利用有限容积法进行了二维直接数值模拟,液池左、右壁分别维持恒定温度Th和Tc,且ThTc,底部被加热,自由表面存在散热,液池宽深比为(20~30),流体为1cSt硅油。结果表明,随着底部加热热流密度的增大,矩形液池内的流动会由单胞或多胞流动转化为旋转方向相反的非对称双胞流动,流动转化过程的临界热流密度随Marangoni数和Biot数的增加而增大,随液池宽深比的增加而减小,液池内的最高温度会随Marangoni数和宽深比的增大而减小。     

自然通风顶层房间夏季室内热环境特征

本文通过对顶层房间夏季室内热环境的测量和数据分析,指出其热状况不同于相应中间层和底层房间。其室内不但温度高,同时屋顶内表面温度亦大大高于其它壁面温度,使室内形成较强的不对称热辐射场。二者构形了顶层房间夏季室内热环境的特征,增加了居住者的不舒适感。     

北方农村住宅的节能与环保

在分析了我国北方农村的自然条件生活习惯以及对住宅产生的特殊要求基础上,提出了农村住宅的采暖方式、平面布置、最佳节能体型、外墙的热工特性及绿色保温材料的应用等切实可行、经济合理的保温、节能措施,以期将北方农村住宅建成绿色建筑。