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Accession Number DE14-1117056
Title Computational Fluid Dynamics Analysis of Flexible Duct Junction Box Design.
Publication Date Dec 2013
Media Count 73p
Personal Author D. Prahl M. Gestwick R. Beach R. Lange
Abstract IBACOS explored the relationships between pressure and physical configurations of flexible duct junction boxes by using computational fluid dynamics (CFD) simulations to predict individual box parameters and total system pressure, thereby ensuring improved HVAC performance. Current Air Conditioning Contractors of America (ACCA) guidance (Group 11, Appendix 3, ACCA Manual D, Rutkowski 2009) allows for unconstrained variation in the number of takeoffs, box sizes, and takeoff locations. The only variables currently used in selecting an equivalent length (EL) are velocity of air in the duct and friction rate, given the first takeoff is located at least twice its diameter away from the inlet. This condition does not account for other factors impacting pressure loss across these types of fittings. For each simulation, the IBACOS team converted pressure loss within a box to an EL to compare variation in ACCA Manual D guidance to the simulated variation. IBACOS chose cases to represent flows reasonably correlating to flows typically encountered in the field and analyzed differences in total pressure due to increases in number and location of takeoffs, box dimensions, and velocity of air, and whether an entrance fitting is included. The team also calculated additional balancing losses for all cases due to discrepancies between intended outlet flows and natural flow splits created by the fitting. In certain asymmetrical cases, the balancing losses were significantly higher than symmetrical cases where the natural splits were close to the targets. Thus, IBACOS has shown additional design constraints that can ensure better system performance.
Keywords Air flow
Computational fluid dynamics
Configurations
Constraints
Design
Ducts
Flexible duct junction boxes
HVAC systems
Performance evaluation
Simulation
Targets


 
Source Agency Technical Information Center Oak Ridge Tennessee
NTIS Subject Category 89B - Architectural Design & Environmental Engineering
46B - Fluid Mechanics
Corporate Author Department of Energy, Washington, DC. Office of Energy Efficiency and Renewable Energy.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1416
Contract Number DE-AC36-08GO28308 KNDJ-0-40341-03

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