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Research Project Information

Research Project Summary Information

Develop synthetic jets to improve performance of variable air volume system diffusers.(21519)

Rensselaer Polytechnic Institute


Many air-conditioning systems use constant air-volume air terminals to provide uniform airflow and temperatures to a space. Variable air-volume (VAV) air terminals that modulate airflow have the potential to save fan energy and maintain thermal comfort, as compared with constant air-volume systems. However, when a space requires only low or modest cooling, VAV diffusers will no longer provide adequate face velocity or throw, and will no longer thoroughly mix the room air because of the required modulation. At such low-modulation levels, the conditioned air delivered from the diffuser “dumps” directly down into the space, so areas located between diffusers receive no air movement, leading occupants to report “stuffy” conditions. Such performance concerns have hindered the adoption of VAV systems in some buildings. Synthetic jets are one novel approach for providing active flow control in a growing number of applications. Synthetic jets are inexpensive and easy to implement, and have the potential for improving airflow management through HVAC systems and in indoor spaces. Rensselaer Polytechnic Institute believes that synthetic jets could be used to eliminate or reduce the airflow problem from VAV units experienced during below peak design conditions.

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Project Description

Rensselaer Polytechnic Institute (RPI) will design and develop synthetic jets to improve the performance of VAV diffusers at low-face velocities. Product requirements and constraints will be defined to guide the design and development process for the synthetic jets. A prototype will be designed and fabricated, and then tested by Flow Control Research Laboratory at RPI. The test results will be analyzed to measure the effectiveness of the prototype, identify the positions in a space where a synthetic jet-assisted VAV diffuser should be located, and identify the opportunities for improvement. Product requirements and constraints for a synthetic jet-assisted VAV diffuser will be redefined based on test results, and a final design will be developed for a full-scale synthetic jet-assisted VAV diffuser.


VAV systems have the potential to reduce 7% of annual site-energy use, and up to 10% of annual utility costs, in commercial buildings.

Project Results


Rensselaer Polytechnic Institute
Research Adm & Finance, 4th Fl West Hall 110 8th Street
Troy, NY 12180

Principle Investigator

Jason Vollen

Universities Involved

Rensselaer Polytechnic Institute


Project Type:

Product Development

Technologies Types:

Building Systems
Heating, Ventilation, & Air Conditioning
Cooling & Ventilation

NYSERDA Contact Information

Robert Carver


R&D - Buildings Research

Contract Details

Start Date: 2/9/2012 1
Project Status: Active
Contract Number: 21519

Last Updated: 2/8/2013 8