Fabric Duct Efficiency

When Q-Sox is connected to the ventilation system the air flow provides the pressure necessary to fully inflate the entire duct length while air seeps out through fabric weave and/or linear vents or air jet orifices. The air outlet result provides a uniform low/no draft climate control environment.

Q-Sox has a large ventilation capacity. Drafts, however, are not present because the outlet air velocity is normally less than 20 to 30 fpm; not 1000 to 1500 fpm common to sheet metal and perforated duct outlets. Each Q-Sox is sized to meet the room load conditions without fear of drafts. Uniform air distribution is achieved over the entire length of the Q-Sox fabric duct.

Q-Sox products must pass a rigorous internal quality control to ensure each customer’s product is of the highest quality.

Compare the efficiency of fabric duct air distribution versus sheet metal in the Iowa State University analysis:

Iowa State University Energy Study Proves Fabric HVAC Duct Efficiency over Metal Systems

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Written by Green Building Pro Staff
Monday, 25 July 2011 15:09

Mechanical Engineering Department’s CFD analysis in 10-month-long study reveals fabric duct is 24.5% more efficient than metal.

AMES, Iowa—Mechanical engineers always suspected that fabric HVAC ductwork is more energy efficient than its metal duct counterpart, but now three members of the Iowa State University’s Mechanical Engineering Department have proven an overwhelming 24.5-percent efficiency differential.

The 10-month-long study, “Thermal Comparison Between Ceiling Diffusers and Fabric Ductwork Diffusers for Green Buildings” proved fabric duct heats rooms faster and more uniformly to satisfy temperature set points versus metal duct/diffusers, which results in reduced mechanical equipment runtime, thus saving energy in the process.

The majority of its funding came from the National Science Foundation, Arlington, Va., and the Iowa State Institute for Physical Research and Technology, the latter which fosters the development of green technologies, such as fabric ductwork diffusion.

The study used computation fluid dynamics (CFD) analytics in an 8 x 8 x 8-foot room with a ceiling-mounted return air vent, which is a typical commercial office space heating configuration. CFD modeling analyzed the airflow of a typical 1 x 1-foot metal ceiling supply fixture with a 4-way diffusion pattern. Then compared it to the performance of an 8-foot-long, 6-inch-diameter ceiling-suspended fabric supply duct with 7 pairs of one-inch-diameter air dispersion orifices spaced one-foot apart.

“Ductwork system efficiency tends take a secondary importance to mechanical equipment efficiencies in project specifications, therefore we have now provided engineers with the data that will make air distribution more efficient as well,” said Michael G. Olsen, Ph.D, an associate professor of mechanical engineering, who conducted the project along with Iowa State University mechanical engineering department colleagues, Baskar Ganapathysubramanian, Ph.D., assistant professor; and Ph.D candidate/graduate assistant, Anthony Fontanini.

While various post-study phases are still being completed, the authors are certain of a slim ±2.5-percent margin of error and that the same 24.5-percent efficiency can be achieved in larger spaces such as big box retailers, warehouses and other commercial/industrial buildings, according to Ganapathysubramanian.

“This analysis is used to construct metrics on efficiency,” said Ganapathysubramanian. “A number of different flow rates are examined to determine the performance over a range of operating conditions. Transient finite volume simulations consisted of over 13 million degrees of freedom for over 10,000 time steps. The simulations utilized HPC (High Performance Computing) for the large scale analysis.”

The study’s demonstration of fabric duct’s performance increases shows promise towards the use of fabric ducting systems in the construction of tomorrow’s green, energy-efficient buildings, according to Ganapathysubramanian.

About the Iowa State University Department of Mechanical Engineering: The department is one of the largest mechanical engineering departments in the U.S. with over 1,200 undergraduate students and over 150 graduate students. The department boasts internationally acclaimed research programs in biological and nano-scale sciences, clean energy technologies, complex fluid systems, design and manufacturing innovation, and simulation and visualization. Research sponsors include industrial sponsors as well as the National Science Foundation, the Air Force Office of Scientific Research, the National Aeronautics and Space Administration, and the U.S. Departments of Energy, Defense, Agriculture, Justice and Transportation.

CLICK HERE to review the entire ISU Study online.

CLICK HERE to download the ISU study in PDF format.