部分混合空气分配系统，如地板下空气分配（UFAD）系统，已被认为具有改善室内空气质量和节能潜力。空调空气直接从地板安装的扩散器供应至占用区域，并通过房间热源进行预热。排气管通常位于天花板上，用于回风。因此，可以在被占区域内产生热分层，预计上部区域会出现良好的混合条件。UFAD设计的主要挑战是估算站立人员头部和脚踝之间的热梯度。 热梯度与UFAD系统的热舒适性和总风量要求密切相关。因此，设计师必须小心确保可接受的热梯度，同时确定所需的风量。本研究首先回顾了有关UFAD系统热分层的文献。因此，选择的关键设计参数是扩散器数量以及三种不同扩散器（方形扩散器、旋流扩散器和线性扩散器）的送风扩散器和回风扩散器之间的空气温差。选择的室内空间包括室内和室外区域的办公室、会议室和教室。 在选择设计参数制定试验计划时，本研究既考虑了文献综述，也考虑了正交试验的结果。然后，首先进行测试计划中的实验案例，以了解UFAD系统的性质。高制冷率的室内空间产生了较低的热梯度。此外，涡流扩散器产生了最大的热梯度，但在占用区域内提供了最低的空气温度，而线性扩散器保持了均匀的条件。实验数据还用于验证研究UFAD系统的CFD程序。 然后，本研究使用经验证的CFD程序进一步研究了UFAD系统在不同室内空间和设计参数下的热分层。研究发现，涡流扩散器产生的热梯度最高，而线性扩散器产生的热梯度最低，这与实验测试结果相同。扩散器越多，热分层程度越高。送风温度越低，热分层程度越高。研究还发现，送回风温差和室内空间类型（或冷负荷）是最重要的参数。 建立了包含108例参数研究结果的数据库。利用该数据库，本次调查为UFAD系统开发了一种先进的设计工具。对热分层模型的经验方程进行了线性回归分析。对于房间传热，对每个房间表面进行热平衡分析。本研究中使用了传热模型来估算送风静压箱内部的热增益比。热分层模型可以与房间传热模型耦合，为UFAD设计提供全面的信息。 通过使用热分层模型，开发了一个图形化设计界面，方便UFAD工程师使用，并使用数据库进行了验证。采用牛顿-拉夫森法求解非线性设计方程。如果您想访问RP-1522（约3 GB）的数据库和其他支持文件，请发送电子邮件至webmaster@ashrae.org.您将收到ftp访问的用户名和密码，以下载数据库和其他支持文件。

Partially-mixed air distribution systems such as Under-Floor Air Distribution (UFAD) systems have been known to provide indoor air quality improvement and energy saving potential. The conditioned air is supplied directly from the floor-mounted diffusers to the occupied zone and warmed up by the room heat sources. The exhaust is normally located in the ceiling for air return. Therefore, thermal stratification within the occupied zone can be generated and well-mixed condition can be expected in the upper region.The major challenge for UFAD design is estimating the thermal gradient between head and ankle of a standing person. The thermal gradient is strongly linked to thermal comfort and total airflow rate requirement of the UFAD systems. Thus, designers must be careful to ensure acceptable thermal gradient and to determine the required airflow rate at the same time.This investigation first reviewed the literature concerning the thermal stratification of the UFAD systems. As a result, key design parameters selected were diffuser number and air temperature difference between supply diffuser and return with three different diffusers: square diffusers, swirl diffusers, and linear diffusers. The indoor spaces selected were offices, conference rooms, and classrooms in both interior and exterior zones.When building a test plan with the design parameters selected, this investigation considered both of literature review and the results from the orthogonal test. Then, experimental cases in the test plan were first conducted to understand the nature of the UFAD systems. Indoor spaces with high cooling created a low thermal gradient. Also, swirl diffusers created the largest thermal gradient but provided the lowest air temperature in the occupied zone while the linear diffusers maintained uniform conditions. The experimental data was also used to validate a CFD program for studying the UFAD systems.This investigation then used the validated CFD program to further study the thermal stratification the UFAD systems for different indoor spaces and design parameters. The study found that the swirl diffuser created the highest thermal gradient, while the linear diffuser created the lowest, which were the same found by the experimental test. The more diffusers used, the higher thermal stratification would be. With a lower supply air temperature, the thermal stratification became higher. This investigation also found that the air temperature difference between air supply and return and indoor space type (or cooling load) were the most important parameters.A database was established containing 108 cases of the parametric study results. With this database, this investigation developed an advanced design tool for the UFAD systems. Linear regression analysis was conducted to correlate the empirical equations for the thermal stratification model. For room heat transfer, heat balance analysis was conducted for each room surface. A heat transfer model was used in this investigation to estimate the ratio of heat gain inside the supply plenum. The thermal stratification model can be coupled with the room heat transfer model to provide comprehensive information for UFAD design. With using the thermal stratification model, a graphical design interface was developed for the convenient use of the UFAD engineers and validated by using the database. The Newton-Raphson method was implemented for solving the nonlinear design equations.If you would like to access the database and other supporting files for RP-1522 (about 3 GB), please send an email to webmaster@ashrae.org. You will receive a user name and password for ftp access to download the database and other supporting files.