建筑开口流量系数及其对火灾烟流的影响

在高层建筑火灾试验塔上测试了典型门、窗不同开度时的流量系数。该系数可用于火灾烟气流动预测计算,也可用于压送风量及一般建筑通风换气计算。同时,运用建筑物火灾烟气流动性状预测计算软件,分析了门窗开度及流量的系数对火灾烟流的影响。     

基于CFD的各式窗孔应用流量系数分析

在建筑通风模拟应用中,若进行CFD模拟,常常无法细化至建筑的每一个窗孔,否则将耗费大量的计算成本;若进行系统模拟,需要对不同的窗孔设置仿真模型和相关性能参数。定义更适合工程实用的应用流量系数,针对系统模拟软件中流量系数的模型,给出各式窗孔精确的应用流量系数与窗孔结构参数的多项式拟合结果。该结果为通风模拟提供理论依据并起到了数据储备的作用。     

燃气系统中调节阀相对开度变化时流量的计算

分析了燃气系统中影响调节阀流量的因素,调节阀流量与流通能力系数、相对开度等因素有关。通过对调节阀理想流量特性的分析,推导出流通能力系数与相对开度的数学关系式,再利用流量与流通能力系数的关系,得到流量与相对开度的数学关系式。用此方法计算的流量与实际流量的相对误差不超过8％,表明此流量计算方法具有工程实用价值。     

静态平衡阀流量特性和阻力特性的实验研究

通过改变平衡阀前后压差,对某规格为DN 50 mm静态平衡阀在不同相对开度下的流量系数、流阻系数进行实测计算,分析平衡阀的流量特性、阻力特性。对于流量特性,在整个相对开度范围内,平衡阀具有较好的流量特性,特别是相对开度范围为0~41%时,但相对开度在55%~68%时流量特性相对较差。对于阻力特性,相对开度范围为55%~100%时,不同压差下的流阻系数趋于一致且变化幅度较小,其他相对开度范围时流阻系数变化较大。     

调压器流量系数实用性的实验研究

流量系数作为燃气调压器的一个重要参数,用来衡量燃气调压器的流通能力。流量系数是在燃气调压器调节元件处于最大开度位置时得到的,实际运行时调节元件并未处于最大开度。本文在了解流量系数由来的基础上,对流量系数的实用性进行了简要的分析,并通过实验对两种作用方式燃气调压器流量系数的实用性进行了比较,得到流量系数对间接作用式燃气调压器的选择更具有指导作用的结论。     

自然通风开口流量系数影响因素探讨

开口特性参数———流量系数是影响建筑自然通风流场的关键因素之一。对影响流量系数的因素如开口长宽比、开度、内外压差和温差、开口上安装的纱窗等进行了分析,指出了常值计算的有限性,提出自然通风研究应进行变流量系数定性分析。     

套筒式水量连续调节阀导纳函数的试验研究及其应用分析

针对水量电动连续调节阀在管网中的动态调节特性描述不准确等问题,基于调节阀前后压降关于流量及阀门流阻系数的数学模型,提出了调节阀导纳的定义。通过测量不同开度下调节阀前后压差及流量,建立了调节阀导纳关于开度的数学回归方程。基于该方程对其理想流量特性及工作流量特性进行了量化描述。     

机械壅塞孔板流动特性实验分析

采用一种新型机械壅塞孔板装置研究孔板流动特性与流量控制,可在较低压力损失下实现不可压缩流体的壅塞流动。利用可视化实验方法研究机械壅塞孔板中环形孔流量系数、压强分布及其壅塞流特性。实验结果表明:雷诺数、孔板厚度、塞体锥度和偏心距对环形孔流量系数影响明显;流体流经环形孔板时会出现明显的压降;孔板上游压强在流动方向上略微降低,孔板下游压强存在恢复趋势;在设计的参数范围内,机械壅塞孔板的流量控制偏差为3.73%。     

基于地埋管换热器热响应测试的土壤热物性参数估算方法

根据实测地埋管换热器进出水温度和流量,分别用线热源解析模型、柱热源解析模型和一维数值模型估算土壤的导热系数、孔内热阻和单位体积热容。介绍了二三参数估算法,三参数估算法可同时估算导热系数、孔内热阻和单位体积热容,但计算时间太长,对计算机的内存要求也较高;二参数估算法对导热系数和孔内热阻进行寻优搜索,单位体积热容利用关联式计算,结果合理,计算时间较短。基于二参数估算法结果显示,一维数值模型的结果更接近实际值。     

事故工况限额供热环状热网水力工况研究

结合工程实例,建立管网水力工况模型并进行水力工况分析。对处于不同位置的管段发生事故时管网流量变化规律进行预测研究,经计算获得管网限额供热时最大限额流量系数,以及各事故工况下热力站入口阀门相对开度。     

建筑外窗自然通风流量系数的影响因素分析

流量系数是反映建筑开口自然通风量的一个重要参数。利用Fluent软件对不同形式的建筑开口在自然通风下的流量系数进行了模拟计算,分析其各项影响因素包括通风口面积、通风口高宽比、通风口开启角度、通风口两侧温差等的影响情况。再利用SPSS软件对模拟结果进行多元回归,定量分析平开窗、推拉窗以及悬窗3种开口的流量系数。     

Experimental and numerical investigation on the distribution characteristics of wind pressure coefficient of airflow around enclosed and open-window buildings

In the present paper, the distribution characteristics of the wind pressure coefficient of the air flow around enclosed and open-window buildings were studied by using wind tunnel model tests and numerical analyses. A typical high-rise building model was designed and wind tunnel tests were performed for the airflow around the building for an enclosed and an open-window condition. The experimental findings were complemented by the numerical analysis. This study shows that the opening windows of a building has little influence on the wind pressure coefficients in the area around the window of adjacent area from window edge; the wind pressure coefficient increases slightly after opening the windows of the buildings. Opening the windows in the rooms adjacent to this window decreases the ventilation efficiency of the room although the influence is small. The time-average value of the wind pressure coefficient can effectively represent the magnitude of the instantaneous wind pressure coefficient. The wind pressure coefficient is independent of the wind velocity of inflow. Furthermore, this study also proposed the distribution characteristics of wind pressure coefficients with different incident angles of wind.     

给水管网球阀局部阻力系数计算研究

为确定给水管网阀门的局部阻力系数,提出了一种基于几何计算和现场试验的局部阻力系数公式的构建方法。先通过几何计算建立球阀通流面积与阀芯旋转角度的关系,并以某转角下和全开时的通流面积之比作为球阀的面积开度,指出了传统的以阀芯旋转角度与全行程所需旋转角度之比作为球阀开度定义的缺陷。然后以DN20球阀作为试验对象,通过现场试验,采集各开度下的压差和流量值并计算出相应的局部阻力系数,经曲线拟合,建立了面积开度与球阀局部阻力系数之间的关系。另一组面积开度和球阀局部阻力系数的试验数据表明,该计算公式能有效地应用于球阀局部阻力系数计算。     

建筑外窗形式对窗户气密性能的影响

采用压差法测量了天津大学校园内5种典型的常用建筑外窗的气密性,这5种窗户分别是PVC单层窗、PVC双层窗、铝合金平开窗、铝合金推拉窗以及铝合金上悬上悬窗,每类窗户测量3组,测量压差控制在0~60Pa之间。通过测量结果分析了窗框材料、开关窗形式、使用时间以及窗户所处环境对窗户气密性的影响。最终,当压差为5Pa时,前4种窗户的漏风量分布在10~20m3/h之间,而铝合金上悬上悬窗的漏风量则在35~40m3/h之间,漏风量比较大。窗户的渗漏系数C与窗户气密性存在较大关系,压力指数n基本分布与0.5~0.6之间,受气密性影响小。再根据标准GB/T 7106—2008计算了所测外窗的气密性,通过计算,PVC双层窗的气密性最好,平均为5.17m3/h·m2;铝合金上悬上悬窗的气密性最差,平均为17.9m3/h·m2。通过对实验的可重复性进行测量,发现经过测量得出低压段(≤10Pa)的漏风量受环境影响较大,高压段(≥15Pa)较小;每两次重复性测试的时间间隔为1周,每两组重复测量之间的误差都小于15%,实验可重复。     

上、下悬窗自然排烟能力对比研究

通过数值模拟,研究了开窗角度对上、下悬窗排烟能力的影响,主要从排烟量、排烟口压力和速度、主要排烟区域等方面对上、下悬窗排烟能力进行对比分析,结果表明：下悬窗排烟效率明显高于上悬窗,相同开窗角度和火源功率下,下悬窗能比上悬窗多排出52%~61%的烟气。上悬窗相对排烟量与开窗角度成指数关系,窗体结构会阻碍烟气排出,开窗角度小于64°时,主要排烟区域为窗体两侧三角形区域;下悬窗相对排烟量与开窗角度关系不大,窗体结构对排烟有利,开窗角度小于56°时,主要排烟区域为近窗下侧水平区域,随着开窗角度增大,上、下悬窗主要排烟区域均过渡到远窗下侧竖直区域。建筑选择排烟窗时建议优先选用下悬窗,开窗角度30°即可,若选用上悬窗,则开窗角度不宜小于60°。     

外窗开启方式对居住建筑自然通风影响研究

利用计算流体力学的分析方法,用平均空气龄和空气龄标准差对自然通风量的大小及其通风均匀性进行研究。对采用推拉窗、上悬窗、平开窗的板式居住建筑在N、NNW、WN风向下的自然通风状况进行对比分析。研究发现,对于自然通风的均匀性,平开窗开启方式优于推拉窗、上悬窗开启方式。对于建筑自然通风量,当风向为N及NNW风向时,推拉窗开启方式优于上悬窗、平开窗开启方式。当风向为WN风向时,平开窗开启方式优于推拉窗、上悬窗的开启方式。当同时考虑建筑自然通风量与自然通风均匀性时,平开窗开启方式具有明显的优势。     

Single-sided natural ventilation driven by wind pressure and temperature difference

Even though opening a window for ventilation of a room seems very simple, the flow that occurs in this situation is rather complicated. The amount of air going through the window opening will depend on the wind speed near the building, the temperatures inside and outside the room, the wind direction, the turbulence characteristics in the wind and the pressure variations caused by e.g. wind gusts. Finally, it also depends on the size, type and location of the opening. Many of these parameters are unsteady which makes the calculation of air-change rates even more complicated. In this work, full-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending on the ratio between the forces and the wind direction. This change is also found in the velocity profiles measured in the opening, which might change from wind dominated to temperature dominated under the same wind direction but with increasing temperature difference.     

Natural convection at an indoor glazing surface with different window blinds

In the present study, an empirical model to determinate the convective heat loss, at an indoor glazing surface, is proposed. This model allows calculating the convective heat transfer coefficient and the air flow rate entering to the window cavity formed between the glazing surface and the protection device. The window blind is first studied experimentally by using a rigid paper, which is installed at four different distances from the window frame. This configuration is used as reference to determinate a global model, which is mainly composed of two correlations: one for the Nusselt number and other one for the air mass flow rate incoming to the window cavity. Then, more realistic configurations are tested: single curtains, double curtains, PVC blinds, wood blinds, Venetian blinds or polyester blinds. In general, heat transfer coefficients for these configurations are equal or higher than that obtained with a free plate. Several correlations are proposed for each configuration.     

Optimal design for a dual-airflow window for different climate regions in China

The dual-airflow window could be used to conserve energy and improve indoor air quality in buildings because it works like a heat exchanger and can introduce outdoor air into buildings. In order to optimize the window design, this investigation used the orthogonal method to evaluate the importance of these 13 design parameters of the dual-airflow window in energy conservation: outdoor air supply rate, window cavity width, window width, window height, thermal conductivity, glazing thickness, solar heat gain coefficient, emissivity, thermal conductivity of window frame, window frame width, window orientation, shading coefficient, and window blinds position. The outdoor air supply rate, window height, solar heat gain coefficient, and window orientation were found to be the most important. The first four parameters were further studied by using the listing method to identify their optimal values for the window design. With the optimal design, the dual-airflow window could save 25% energy in a warm climate region such as Guangzhou and 34% in a cold climate region such as Harbin. The dual-airflow window is recommended for use in colder climate regions.     

水平荷载作用下洞口对填充墙RC框架结构受力性能影响的非线性分析

在3个单层单跨、开洞率不同的填充墙钢筋混凝土框架水平荷载试验模型分析的基础上,用同样的模拟方法,对设计的19个单层单跨、不同洞口情况的填充墙钢筋混凝土框架模型进行了水平荷载作用下全过程模拟分析。分析结果表明通窗、窗洞左置和门洞右置为不利洞口情况,通窗可导致"短柱效应",使框架柱剪力明显增大,洞口率越高(或窗洞左移、门洞右移)则水平承载力和侧移刚度越低,通窗填充墙框架结构按现行方法设计存在安全隐患而非通窗类洞口填充墙框架结构是安全的。