Building Energy Assessments, Solutions, and Technologies BEAST
Dual-Duct, Dual-VAV to Reduce Cooling & Heating Loads
IA single-duct variable air volume (VAV) system that serves multiple zones with different load profiles operates mostly with simultaneous cooling and heating. This is inherently inefficient. At any given condition, certain zones may request cooling and others may request heating. A single-duct VAV system supplies cold conditioned air to zones with cooling needs. The air may be reheated in other zones with heating needs. This can be avoided by using dual-duct, dual-VAV systems in which one system provides cooling and the other provides heating. The configuration will lead to significant reductions in cooling and heating loads on HVAC systems by eliminating simultaneous cooling and heating and using outdoor air for cooling and return air for heating..
Annual heating and cooling loads for single-duct and dual-duct VAV systems
Nassif N (2020). Using Dual-Duct, Dual-VAV to Reduce Cooling & Heating Loads. ASHRAE Journal 62 (11): 14-21.
Increasing Efficiency by Using Four-Pipe Water-Source Heat Pumps
Most buildings in the United States are equipped with traditional centralized variable air volume (VAV) systems that mix air returning from different zones and centrally recirculate a large portion of it back to zones. During the coronavirus pandemic, this recirculation could make the spaces less safe and increase the possibility of coronavirus transmission between zones in buildings. On other hand, distributed water source heat pumps (WSHPs) or any chilled water terminal unit integrated with a dedicated outdoor air system make the spaces safer by eliminating return air mixing and also may provide great energy efficiency if they are designed and operated properly. Thus, this research focuses on improving the design and operation of distributed WSHPs to achieve that desired higher energy efficiency.
Traditional two-pipe
Proposed four-pipe
Traditional two-pipe vs. proposed four pipe configurations
