Task 05-08. Robust Design of Variable Air Volume (VAV) Systems for Optimum Airflow, Room Air Diffusion, Energy Consumption, and Sound Levels when dealing with Variations in Duct Configurations, Airflow Resistance, and Air Leakage

Objective

ASHRAE has sponsored several research projects for the purpose of updating friction loss coefficients for duct fittings in rectangular, round, and flat oval ducts and for improving design methodologies for HVAC air distribution systems in buildings. This has significantly improved design methodologies of HVAC air distribution systems from air handlers up to the point where branch ducts supply air to variable volume terminal units and room air terminal devices. Design information on duct design from variable volume terminal units to room air terminal devices is primarily anecdotal in nature, and it is predicated on ideal system installations, which never occur in field installations. There is very little reliable measured data on the effects of variations in the installation of ducts, VAV units and diffusers, leaky ducts and room diffuser plenums and connections, additional airflow resistance from unnecessary duct transitions, fittings, and dampers on room air diffusion, energy consumption, and sound. Task 3 will yield experimental data showing the effects of specified improper VAV system installations, as compared to related correct installations. This study will build on information obtained from Task 3 and will yield experimental data and related relationships that can more specifically be used in the design of VAV systems between VAV terminal units and room air terminal devices

A realistic full-scale office simulation with furniture (desks, chairs and computers) and occupants (simulated by full-size heat sources) will be set up in the CMEST throw room. The temperature and velocity profile in the space studied will be measured throughout the room volume to determine the ADPI. The system airflow rate will be measured based on ASHRAE standard 41.2. A flow hood will be used to measure the airflow volume of the room air terminal devices, and the air leakage rate will be determined. The fan and HVAC system energy consumption will be recorded. The sound levels in the throw room will be measured. The static pressure drop through the duct system will be measured by a pitot tube traverse scheme. The set-ups for all the tests will meet or exceed appropriate ASHRAE Standards, such as ASHRAE Standard 70, 113, and 55.

Two duct types will be studied: (1) rigid duct and (2) flexible duct. At least three different duct lengths, duct designs with different static pressure drop values, and air leakage levels will be investigated. A Design of Experiment will be used to identify main effects of parameter variation and interactions between parameters. A tolerance design using the quality loss function will be conducted to determine nominal values and allowable tolerances on the tested parameters.

Major Sub-awardees

This project is being executed by the University of Nevada, Las Vegas. The Principal Investigator is Brian J. Landsberger, Ph.D.
This project will be initiated upon completion of Task 3.