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Optimal design and control in dual -duct air -handling units

Ik-Seong Joo, University of Nebraska - Lincoln


Dual-duct systems provide good air circulation, require little maintenance, and have no condensation at the terminal boxes. However, dual-duct systems are believed to consume more energy than single-duct variable air volume systems. To address this issue, an extensive investigation was performed to develop optimal design and control strategies that would improve the performance of dual-duct systems. ^ A dual-fan, dual-duct (DFDD) system is a prominent design improvement in dual-duct systems. The DFDD system recycles warm return air instead of cool mixed air for the hot air supply. Compared to the single-fan, dual-duct (SFDD) system, the DFDD system saves significant amounts of thermal and fan power energy in mild and winter weather conditions. The DFDD system is an optimal design when no heating is supplied in summer. When heating is required in summer, the DFDD system can be further improved by installing an independent outside air opening that directs warm outside air directly to the hot deck. This improved system, called an “energy savings chamber,” reduces or eliminates thermal energy penalties of the DFDD system. The optimal control strategies include an optimal fan control for a single-fan, dual-duct constant volume system, an optimal outside intake sequence for the energy savings chamber, and optimal hot and cold air temperature controls for various kinds of dual-duct systems. System performance in dual-duct systems can be optimized with little or no additional equipment required. ^ Physical models were also developed to represent the performance of the dual-duct systems. These models are made available to engineers to fully investigate the systems instead of looking at data from a simulation program. ^ This thesis will cover the following: (1) State-of-the-art research in dual-duct systems and related subjects, (2) Physical models for the optimal design and mathematical models for optimal control, (3) Performance analyses of the models, (4) Implementation of the optimal design and control sequences, and (5) Experimental validations of the simulation results. ^

Subject Area

Engineering, Mechanical

Recommended Citation

Joo, Ik-Seong, "Optimal design and control in dual -duct air -handling units" (2004). ETD collection for University of Nebraska - Lincoln. AAI3152614.