Task 05-13. Effects of Different Control Strategies, Diffuser Characteristics and Air Leakage on Draft and Stratification Performance of Under Floor Air Distribution Systems and the Relevance of the Air Diffusion Performance Index to UFAD Performance

Objective

This study will build on information obtained in Task 2: Under Floor Air Distribution Study, and Task 12: Measurement, Verification and Comparison of Installed UFAD and CAD Systems and Their Impact on Building Performance. The Task 2 research effort covered performance of UFAD systems with no modules, including load calculations, airflow rate calculations, and temperature profiles of the stratification zone. Task 12 covered field measurements and laboratory duplication of installed UFAD systems. The proposed study is a necessary follow-on to both tasks. It will focus on some of the key UFAD research topics identified by UFAD Task Force of the NCEMBT. These research topics have been identified because they represent areas in which the results of meaningful research are lacking. UFAD information gaps that will be investigated include:

• Temperature and contaminant stratification is one of the most important issues associated with UFAD system design. Very little information exists on how UFAD stratification zones are controlled.
• UFAD systems have distinct room airflow, temperature, and comfort characteristic that significantly differ from those of CAD systems. Thus, a different method for computing ADPI may be needed for UFAD systems. No research has been conducted and published that addresses this issue.
• The current design guide for UFAD systems proposes a diffuser clearance radius of 1 to 4 ft for each UFAD diffuser. This restricts the potential positioning of UFAD diffusers or the placement of office furniture in areas served by UFAD diffusers. However, UFAD diffuser clearance radii of 1 to 4 ft are often not used in practice. The actual clearance radius may in some cases be less than 1 ft. Furthermore, how the sensible load is influenced by the amount of actual clearance radius is still unknown.
• Floor leakage significantly influences UFAD performance. Very little information exists on the effects of floor leakage on UFAD performance.

Test protocols will be developed and tests will be conducted in the BTLab to obtain information to address these issues. The results of this study will be useful to architects, designers, mechanical and building engineers, consumers, government agencies and other entities to make informed decisions for energy management and consumption.

Major Sub-awardees

This project is being executed by the University of Nevada, Las Vegas. The Principal Investigator is Liangcai Tan, Ph.D.
This project will be initiated upon completion of Task 2.