A turbulent flow topology optimization design method for high-efficiency diffusers in HVAC systems

Heating, ventilation and air-conditioning (HVAC) systems account for 30% to 50% of total energy consumption in buildings. As terminal devices in ventilation and air-conditioning systems, circular diffusers serve as the final interface between the system and occupants, play key roles in system operation, energy consumption, and indoor environmental quality. However, traditional circular diffusers exhibit high resistance coefficients and low energy utilization efficiency, which present great challenges for building energy conservation and indoor air quality. This study adopts an improved variable density topology optimization method and proposes an optimization objective function as a jet length Euler number (JLEN) for a topology diffuser. The JLEN controls the design from outside the domain and obtains a new diffuser structure. The drag reduction rate and jet length improvement rate of the topology diffuser under different working conditions are analyzed via CFD numerical simulations, full-scale experiments and energy dissipation verification. The results show that the drag reduction rate of the topology diffuser can reach 62.3%, and the jet length improvement can reach 13.7% compared with traditional diffusers. The guide vane curvature of the topology diffuser can guide airflow adhesion well and reduce the energy dissipation caused by vortex and fluid deformation. Previous studies on local components have been limited to single-objective function control and optimization within the design domain. This study achieved control and optimization of multi-objective functions, laying a foundation for the future optimization of more complex local resistance components with high degrees of freedom.