方形散流器送风参数对气流分布影响实验研究

本文目的是研究方形散流器的送风参数对室内气流分布的影响规律。在模拟建筑内区的空调实验室进行了实验，测出了不同送风参数下室内所有测点的温度和速度。对实验数据分析得出空气分布特性指标、温度不均匀系数以及速度不均匀系数与送风速度的关系曲线，并用TECPLOT软件实现了温度场、速度场的可视化。结果表明在室内热源和控制温度不变时，随着送风速度的增大，送风温度升高，送风温差减小，室内工作区的空气分布特性指标增大。     

送风高度对碰撞射流热风供暖房间热环境影响的实测研究

在人工气候室内,对碰撞射流通风两种送风高度下的室内温度与气流速度进行了实测。结果表明:碰撞射流送风高度对室内温度竖直分布影响不大,但对紧贴地面的空气温度的衰减过程有明显影响;送风高度对室内气流分布有较大影响,增大送风高度可以减小地面附近气流的速度,但增大了离地面较远处的风速;由于送风高度较低时近风口处的空气温度较高,导致碰撞射流热风供暖时送风口越低,人体吹风感越小。     

碰撞射流通风供暖房间热环境实测研究

在人工气候室内,对不同送风状态下的碰撞射流通风和混合通风的供暖效果进行了实验研究,分析了送风速度和送风温度对2种通风模式供暖房间热环境的影响,并对室内热舒适性进行了分析比较。结果表明:由于碰撞射流通风热风直接送入房间底部,室内温度梯度小于混合通风模式,并且室内温度分布对送风参数变化的敏感度亦小于混合通风,这对减小建筑供暖能耗有重要意义;尽管碰撞射流在送风口附近的近地面气流速度较大,造成人员吹风感的风险大于混合通风,但在本文研究的送风参数范围内,热环境参数均在可接受的范围内。     

有冷风侵入房间采用碰撞射流热风供暖时的温度分布特征

对有明显冷风侵入房间采用碰撞射流热风供暖时在不同开门时长和送风参数条件下的室内空气温度和气流速度分布特征进行了实测研究。结果表明:冷风侵入使得碰撞射流热风供暖房间室内温度梯度小的优势明显减弱,但风口附近气流速度没有增大;送风速度越大,冷风侵入引起的头足温差和室内上下部温差越小。建议有明显冷风侵入的房间使用碰撞射流热风供暖时应采用较大的送风速度。     

落地窗对热风供暖房间室内热环境的影响

热空气上浮使得供暖房间的温度梯度较大,对人体热舒适和热风能量利用率都产生了不利影响。在具有大面积落地窗的房间内,近窗处空气通过对流换热被冷却后下沉,使得温度梯度大的问题尤为严重。在人工气候室对这类房间的热风供暖效果进行了实测,分析比较了不同送风参数时,贴附和非贴附射流送风形成的室内温度、气流和热舒适指标的空间分布特征。指出混合通风供暖房间的热舒适满意度不随着送风参数单调改善,存在着最佳送风参数。     

干式地板辐射供暖系统热工特性

建立了干式地板辐射供暖系统传热模型并编制相关软件,对软件计算值作实验验证的结果表明,地板表面平均温度的软件计算值与实验值误差小于10%,作用温度误差在3%范围内.应用软件计算得出,地板表面平均温度、室内空气温度和作用温度随管间距的增加而降低,随供回水平均温度的升高而升高,且室内空气温度变化率小于地板表面平均温度变化率.实验研究表明,水平和竖直方向作用温度分布均匀,竖直方向作用温度出现正的温度梯度.系统稳定时辐射换热量占总换热量的份额约为60%,但相对于湿式地面供暖,地板表面温度分布均匀性略差.     

大型商场竖直温度梯度的改善方法研究

在冬季,大型商场内的热压作用促使位于其底层的热空气上升,形成较大的竖直温度梯度,造成上热下冷、热舒适度差等问题。结合南京某商场温度实测分析与CFD数值模拟,提出了大型商场竖直温度梯度的改善方法。案例实测结果表明,采取风量调节控制后竖直温差由3.8℃减小至1.3℃。数值模拟结果表明,减少顶层送风量、增加底层送风量,并在1层设置挡温构件后,竖直温差由3.1℃减小至0.6℃,有效提高了室内温度均匀性和舒适度。     

送风参数对空气源热泵制热运行的影响研究

针对夏热冬冷地区冬季采用空气源热泵供暖时出现的热力分层现象,通过实验研究了空气源热泵在不同送风角度和送风速度下室内温度场的分布特性,比较和分析不同送风角度和送风速度下室内垂直温差的变化关系。结果表明,当送风速度一定时,送风角度越小,室内垂直温差越小;当送风角度一定时,送风速度越大,得到的室内垂直温差越小。     

不同孔板送风室内流场及热舒适全尺度实验研究

本文通过建造辐射微孔板实验室研究了室内空气流场分布特征及人员热舒适状态.通过改变微孔板的位置和数量共得到五种不同送风工况,对比分析了室内热源、 换气次数对不同送风工况下室内流场及人员热舒适度的影响.实验研究发现,热源的加入会影响室内平均流场和标准偏差,从而影响温度和速度分布的均匀性.耦合孔板送风室内各测点温度表现出不同...     

通风方式对辐射空调房间室内空气分布特性的影响

本文在人工环境室中设置电热膜模拟外围护结构传热,通过实验的方法研究通风方式对辐射空调房间室内空气分布特性的影响。结果表明:当顶板表面温度及送风量变化范围为17～19℃及2.5～4.5 h~(-1)时,地板送风室内垂直空气温差、紊流强度及除污效率变化范围较大,分别为0.2～0.5℃、47%～61%及0.64～0.82,而混合通风室内垂直空气温差、紊流强度及除污效率变化范围较小。此外,当顶板表面温度及送风量不超过18℃及3.5 h~(-1)时,地板送风与混合通风室内空气温度分布差异比较明显,而空气速度及污染物浓度分布差异较小;而当顶板表面温度及送风量等于19℃及4.5 h~(-1)时,地板送风与混合通风室内空气温度分布差异变得不明显,而空气速度及污染物浓度分布差异仍较小。因此,通风方式对辐射空调房间室内空气温度分布特性影响较大,而对空气速度及污染物浓度分布影响较小。     

空调房间不同送风方式的实验研究

本文通过对空调房间三种不同送风方式（下送风、上送风和侧送风）进行实验研究,从主、客观两方面进行评价,实验结果表明：在保证相同的室内环境参数下,下送风通风空调系统优于上送风和侧送风两种传统送风方式,能够获得较好的舒适度和空气品质。     

地板辐射与置换通风空调系统运行参数

建立了基于EnergyPlus的地板辐射供冷加置换通风空调系统模型,模拟得到的室内温度和辐射地板所承担冷量与实验结果的误差小于±7%。在此模型基础上,改变送风参数和供水参数,得到置换通风供冷量、辐射地板供冷量、地板表面温度、室内空气平均温度、AUST温度等参数的变化规律。结合热舒适性模型,得到满足室内热舒适性(-0.5≤PMV≤0.5)条件下,置换通风的送风参数和辐射地板的供水参数范围,为复合系统设计和应用提供依据。     

大温差送风技术在高精度恒温空调中的应用可行性

为了研究空调大温差送风技术在高精度、多扰量恒温空调中应用的可行性,采用CFD数值模拟分析了恒温室不同送风温差下温度场和速度场的均匀性,研究了恒温室在不同送风温差下不同扰量作用时的温度动态响应特性。结果表明,空调送风大温差下的温度场和速度场以及温度稳定性能满足恒温室要求。     

顶送风供暖房间人员热舒适的实验研究

本文测量了顶送风供暖房间不同送风状态对应的室内温度和风速,根据实测数据对室内人员热舒适性进行了分析,指出在地面附近有较大热损失的房间,减小送风温差可以在一定程度上改善室内温度分布。仅改变送风参数不能从根本上解决这类房间近地面热舒适差的问题。     

Airflow and air temperature distribution in the occupied region of an underfloor ventilation system

Measurements were carried out in an office-type experimental room ventilated by a floor return-type underfloor ventilation system to investigate the distributions of airflow velocity and air temperature. A fan-powered floor air unit (FAU) with rectangular supply and return air outlets covered by straight-profile linear bar-type air diffusers was installed to deliver the conditioned air in the experimental room. Turbulence intensity and draught rate distributions inside the room were also calculated by using the measured data. From the experimental results, it is found that undesirable high air velocities and high draught rates were created within a small region near the supply outlet of the FAU. Temperature differences between different height levels were maintained within an acceptable comfort level under the tested supply air conditions and heat loads. The results indicated that the temperature stratification could be maintained at an acceptable comfort level by designing the supply air conditions properly. A clearance zone is suggested as a design consideration for locating the FAUs and occupants to avoid undesirable draught discomfort to the occupants.     

基于下送中回气流组织Block模型内壁面对流传热系数的讨论

以大空间缩尺模型实验室为研究对象,基于Block模型,采用2种常数法及3种温差法的表面对流传热系数取值方法,计算室内在下送中回气流组织下的空气垂直温度分布。通过与实验值的比较发现,对流传热系数温差法计算结果优于常数法。其中一种对流传热系数温差法得到的空气垂直温度与实测温度的误差最小。     

Numerical study on temperature stratification in a room with underfloor air distribution system

In this study, numerical prediction using computational fluid dynamics (CFD) was utilized to investigate air temperature stratification in a room with an underfloor air distribution (UFAD) system. The numerical modeling using CFD computation was validated with physical test in a full size experimental room with an UFAD system. The different supply air conditions and heat loads were discussed. The results show that the effect of three parameters, heat load, supply volume flux and supply air velocity, on room air temperature would be expressed by the length scale of the floor supply jet. When the length scale increased from 0.8 to 1.56 m, the ratio of vertical temperature difference between 2.5 and 0.1 m at the occupied zone to the difference between return and supply air temperature decreased from 0.62 to 0.25. When there was only one local heat source in the room, there was a thermal stratified interface at the occupied zone. The interface height was about 1.42 times the length scale. The results may suggest ways to optimize UFAD design and operation.     

Influence of the boundary thermal conditions on the air change efficiency indexes

The influence of a thermal heterogeneity boundary conditions on the air change efficiency (ACE) of a mechanical ventilation system in a test room was experimentally evaluated by means of the "step-down" tracer gas technique in 24 different experimental conditions. The experiments were performed under isothermal condition, varying the air supply temperature with respect to the walls and varying the surface temperature of a wall with respect to the other walls and the supply air, simulating both heating and cooling situations. Changing the position of the outlet grid two different configurations of the ventilation system were tested. The nominal supply air velocity varied between 0.04 and 0.11 m/s, corresponding to a range from 1 to 3 ach, and the temperature differences varied from 0 to 5 degrees C. Results are reported in terms of air change efficiency indexes, both local and global. The global air change efficiency (ACE), values are presented as a function of the Archimedes number (Ar), whose values were in the range 0 to 181. The reported results suggest that the Ar number may be used to organize the ACE values when in the presence of thermal heterogeneity, both in the external envelope and in the supplied air. The obtained results show that there is a logarithmic relation between Ar and ACE. In particular, for both ventilation strategies tested, the increase of the absolute value of Ar leads to an increase of ACE when the supply air is warmer than the walls, and to a decrease of ACE when the supply air is colder than the walls. Under isothermal conditions the Reynolds number (Re) fairly correlates the experimental results.     

Mixing characteristics in a ventilated room with non-isothermal ceiling air supply

A two-dimensional turbulence k–ε model is used to predict distribution of air velocity, temperature and turbulence kinetic energy in an air-conditioned room using ceiling air supply. Mixing characteristics of the airflow are analyzed under different air supply velocities and temperatures. A modified Archimedes number is correlated with the parameters characterizing heat transfer, ventilation system, and turbulence kinetic energy of room air flow. Significant correlations have been shown. It is found that the linear ceiling air supply air-conditioning system with a high level return air provides excellent air mixing across a wide range of Archimedes numbers. The results are useful for air-conditioning design and thermal comfort study.