Design tool for under-floor air distribution system

Guangqing Xue, Purdue University

Abstract

Under-floor air distribution (UFAD) system can provide indoor air quality improvement and energy saving potential. The conditioned air is supplied directly from the floor diffusers to the occupied zone and exhausted through the return grille on the ceiling. Partial thermal stratification within the occupied zone can be generated. Higher air distribution effectiveness can be achieved when the system is properly designed. By using higher supply air temperature at the diffuser, UFAD system may also contribute to the potential of energy saving. The major challenge for UFAD design is to estimate thermal gradient between head and ankle of a standing person. The thermal gradient is strongly linked to thermal comfort and governed by both of the inertial and buoyancy forces. The design parameters, such as flow rate, temperature of supply air, diffuser types and number, need to be carefully determined to ensure acceptable thermal gradient between the heat and ankle in UFAD system. This research is to develop an advanced design tool for under-floor air distribution. A comprehensive database summarizing various airflow and thermal conditions was firstly introduced. Linear regression analysis was conducted to correlate the empirical equations for the thermal stratification modeling. For room heat transfer, heat balance analysis was conducted for each room surface. A heat transfer model was used in this study to estimate the ratio of heat gain inside the supply plenum. With using the thermal stratification model, a UFAD design tool with GUI (Graphical User Interface) was developed based on the thermal stratification modeling. The Newton-Raphson method was programmed into the UFAD design tool to solve nonlinear design equations.

Degree

M.S.M.E.

Advisors

Chen, Purdue University.

Subject Area

Mechanical engineering

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