腹板开孔轻钢龙骨复合墙体截面参数对传热的影响

对腹板开孔轻钢龙骨复合墙体截面参数如钢龙骨翼缘宽度、龙骨厚度、龙骨宽度和龙骨间距对墙体传热的影响和热桥问题进行模拟研究.结果表明:龙骨翼缘宽度对墙体传热系数影响不大,对墙体局部多维传热影响较大;龙骨宽度对墙体传热系数影响很大,龙骨宽度越小,热桥现象越严重;墙体传热系数随龙骨厚度的增加呈线性上升,龙骨截面越厚,热桥现象越突出;热桥占墙体总面积的比例随龙骨间距增加而减小,墙体的传热系数相应减小,而对钢龙骨的热桥效应影响甚微.     

腹板开孔轻钢龙骨复合墙体传热性能试验

为进一步探讨优化轻钢龙骨复合墙体传热性能的有效途径,扩大其在我国寒冷地区的应用,采用热电偶测温方法进行了腹板开孔、带外保温层腹板开孔轻钢龙骨复合墙体传热性能的试验研究,重点考察了墙体的传热系数和测点温度,并与有限元建模分析所得墙体的平均传热系数和测点温度进行细致对比.结果表明:腹板开孔可以降低轻钢龙骨墙体的热损失,从而削弱龙骨所在部位的热桥效应,显著提高墙体的保温性能.两种试验方案的墙体传热系数分别为0.315W/(m2·K)、0.250W/(m2·K),可以满足我国寒冷地区居住建筑围护结构节能50%的传热系数限值要求.     

辽宁新型节能墙体材料现状及发展趋势

通过分析辽宁省各市新型节能墙体材料现状、性能及对其发展趋势的预测,力争使相关人士对新型节能墙体材料加深了解,有计划、有目标地发展新型节能墙体材料,同时力争对政府及相关管理部门制定新型节能樯体材料发展计划及相关政策提供参考依据。     

夜间通风相变复合墙体动态传热模拟

为研究由相交混凝土复合墙体构造的房间在夜间通风下的热环境,利用焓法建立结合夜间通风的相变混凝土复合墙体动态传热和房间传热数学物理模型,模拟研究北京地区夏季和过渡季应用该相变复合墙体动态传热和室内热环境的时变特性.对该相变复合墙体传热的影响因素,如相变温度、相变层厚度、通风次数、通风时间以及相变层和绝热层的位置等进行优化...     

复合氧敏材料的瞬态特性研究

将氧化物氧敏材料ＴｉＯ２与Ｎｂ２Ｏ５复合化，研究其氧敏瞬态特性及与环境温度、气流转换频率的关系，并指出采样方法对瞬态特性的。在无贵金属催化条件下，烧结型复合氧敏材料的响应时间可达６０ｍｓ，对材料的结构及响应机理进行了分析和初步探讨。     

复合工质真空相变元件的传热特性

对新型复合工质真空相变元件传热特性进行了实验研究,得出了传热特性实验关系式。确定了新型复合工质元件的最佳倾角为30°和充液率为18%。该实验研究为新型复合工质真空相变装置及其系统的设计提供了依据。     

用新型墙材复合墙体改善建筑功能

介绍了采用GRC作面层材料,岩棉作保温材料的幕墙式GRC外墙外保温板节能体系,同时经实践证明,它不仅可节约能源,增加使用面积,还可改善室内热环境;然后介绍了袋装珍珠岩复合墙体,它以实心粘土砖作内、外层,袋装珍珠岩作填充保温材料,实践证明,该节能住宅也可达到节能30％;对于外墙岩棉保温墙材,提出了其构造要求,以及确保外墙岩棉外保温工程质量应解决的关键技术。     

双层窗的复合传热过程研究

应用不可逆热力学分析双层窗的复合传热过程,得出：在不考虑日射得热的条件下,自然对流换热及其对辐射换热的耦合传热是传热过程的主要因素,说明降低窗间气体的对流将是提高外窗的绝热性能的主要方向之一。     

建筑业发展对新型墙体材料发展的影响

本文概括了我国与墙体材料有关的城镇化建设、住宅产业化、绿色建筑、高层建筑的发展,分析了建筑业的发展对墙体材料的要求,进而论述了新型墙体材料的发展趋势。     

通气孔对动叶冷却结构流动和换热特性的影响

为深入研究某型燃气轮高温旋转动叶片内部先进的复合冷却结构,采用三维气热耦合数值计算方法,模拟该叶片外部高温流场、内部前后冷却腔内蛇形折流通道复合冷却结构的流动性能与换热特性,研究前腔蛇形折流冷却通道在采用局部通气孔改进设计的条件下对整个旋转叶片外表面冷却效果与内部冷却通道流阻系数的改善程度.计算结果表明:在给定的冷气流...     

换热强化及其优化设计的新途径

审视了强化换热及其优化设计换热系统的方法,无论是传统的强化换热方法还是场协同方法,都只片面地强调了强化传递强度而忽视了由于强化所引起的能量耗散的约束。在强化传递强度的层次上,给出了换热强度与流体中内场和外场的数学关系,通过协调不同驱动力之间的关系可以强化热传递强度。在优化设计换热系统的层次上,给出了优化设计的热力学判据,表明了不可逆性与推动力之间的权衡,并由此得到换热器强化的优化设计温差。     

Flow and heat transfer characteristics in the porous wick condenser of CPL

An analytical investigation has been conducted to understand the internal fluid flow and heat transfer in the condenser with porous wick of an innovative capillary pumping loop (CPL) system. A mathematical model is proposed and used to describe the flow and heat transfer, especially interfa-cial transport phenomena. The liquid-vapor interface of the condensed liquid film was numerically determined . Some factors, such as vapor pressure, wall subcooling, wall heat load and thermofluid properties, have significant influence on the heat transfer process and the shape of liquid-vapor interface. Meanwhile, an experimental facility was setup and an experimental investigation was completed. Theoretical prediction and experimental results show quite good consistence.     

Experimental investigation on heat transfer characteristics of microcapsule phase change material suspension in array jet impingement

A closed-loop experimental system is established to investigate the heat transfer characteristics of microcapsule phase change material (MEPCM) suspension in an array jet impingement. Eicosane with a melting peak at 40.8°C is used as the capsule core of the MEPCM particle. Five kinds of array-hole nozzles with the same hole cross-sectional area are employed to analyze the influence of critical parameters, including the nozzle hole number, hole spacing, impinging distance, and jet temperature. It shows that a 5% suspension may improve the heat transfer coefficient of the array jet by up to 23.5% compared with water. The heat transfer of an array jet is obviously stronger than that of a single jet, but too much hole number is not conducive because of the entrainment interference between adjacent jets. A larger hole spacing or smaller impinging distance may weaken the cross-flow accumulation on the impinged surface, thus enhancing the heat transfer capability. The heat transfer coefficient of the array jet presents a secondary peak value at the end of the jet-core region. The latent heat absorption of the capsule core results in superior heat transfer of the suspension compared to that of water only in a specific range of jet temperatures, the optimum of which is approximately 10°C lower relative to the peak melting temperature. In addition, the melt completion time of a single MEPCM particle and the critical flow rate of the suspension are predicted theoretically.

     

波节形状对波节管结构稳定性和传热特性的影响

针对不同形状的波节管的成形精度、结构稳定性以及传热特性差异较大.通过实验研究、理论校核和数值模拟相结合的方法,重点研究不同的波节形状(波谷圆角半径R和波节高度H)对波节管成形精度、轴向补偿能力、平面抗失稳能力以及传热特性的影响规律.研究结果表明:内高压成形波节管的成形精度随着波谷圆角半径R的增大而提高;波节管的轴向位移补偿能力随波节高度H的增加而增大;抗平面失稳能力和抗疲劳能力随波节高度H的增加而降低;综合传热因子η随着波谷圆角半径R增大和波节高度H的增加均是先增大后减小.综合考虑上述各个因素,对于所研究的内高压成形波节管,当波节高度H为2.5 mm,波谷圆角半径R为30 mm时,波节管具备良好的综合特性.     

采暖建筑节能复合围护结构与保温材料经济性的研究

建立了求解采暖建筑复盒中温层经济厚度的数学模型,分析了选择保温材料的要点,引入单位热阻造价评价保温层材料的经济性,并给出了采暖建筑复合体保温方案选择与保温层经济厚度计算及材料优选的工程设计实例。     

Condensation heat transfer characteristics of vapor flow in vertical small-diameter tube with variable wall temperature

To explore the condensation characteristics of vapor flow inside vertical small-diameter tubes, the classical Nusselt theory is revised and an analytical model with variable tube wall temperature is established by considering the effect of surface tension exerted by condensate film bending as well as the effect of shear stress on vapor-liquid interface. The effects of various factors including tube wall temperature and gravity on flow condensation in small-diameter tubes are analyzed theoretically to show the heat transfer characteristics. Comparison with the experimental data indicates that the proposed analytical model is fit to reveal the fundamental characteristics of flow condensation heat transfer in vertical small-diameter tube.     

多孔介质对封闭腔体内对流传热传质的影响

利用两区域法,其中在多孔介质区域利用Forheimer-Brinkman-Darcy方程,纯流体区域使用Navier-Stokes方程对部分填充多孔介质的二维封闭腔体内的自然对流传热传质进行数值研究。采用有限元法辅之以流体与多孔介质交界面上的连续性弱约束条件对两区域方程进行求解,分析了多孔介质厚度、渗透率及孔隙率的变化对封闭腔体内传热传质的影响。数值结果表明:当多孔介质厚度小于0.2时,其厚度的增加可明显削弱传热传质;大于0.2时,其影响明显减弱。渗透率从10^-3降低至10^-6时,腔体中流动减弱,导致平均传热传质速率降低。随孔隙率增加平均传热传质速率近似线性增加。     

Numerical simulation on heat transfer inside rotating porous disk subjected to local heat flux

Numerical simulation was carried out to study the centrifugally-driven flow and heat transfer inside rotating metallic porous disk subjected to local heat flux. The effects of rotational speed, solid thermal conductivity and porosity on heat transfer were analyzed. The thermal transport coefficient, defined as the ratio of local heat flux to maximum temperature difference on the disk, was introduced to evaluate the thermal transport capacity in rotating porous disk. For convenience, the conjugation between convective heat transfer inside the rotating porous disk and convective heat transfer over the rotating disk surface was decoupled in the present study. Firstly, the convective heat transfer over the free rotating disk surface was investigated indi-vidually to determine the heat transfer coefficient over the disk surface to the ambient air. Then the convective heat transfer over a rotating disk surface was treated as the thermal boundary condition for the computation of convective heat transfer in-side rotating porous disk. Under the present research conditions, the results show that the centrifugally-driven flow is enhanced significantly with the increase of rotational speed. Consequently, the maximum temperature on the disk surface is decreased and the temperature distribution tends to be uniform. The thermal transport capacity in rotating porous disk is also enhanced with the increase of solid thermal conductivity or the decrease of solid porosity. In the rotating porous disk, the solid phase heat transfer is clearly the dominant mode of heat transport and the fluid phase makes an incremental contribution to the total heat transfer.