A CFD Study on the Impact of User-Adjusted HVAC System Controls in Open-Plan Offices

As individual offices are increasingly replaced by open-plan settings, ensuring a healthy and comfortable environment becomes crucial. Maintaining high-quality workspaces is essential for optimizing occupants’ productivity and decision-making capacity [1]. This study focuses on the technical aspects of human-building interactions, highlighting the complex social dynamics in shared environments. For instance, actions taken by one person to restore their comfort levels may create new sources of discomfort for colleagues. Therefore, this study employs CFD simulation to assess the impact of HVAC configurations on environmental conditions at workstations in an open-plan office.

A living lab environment features five air conditioners distributed across the space. Given that up to 36 people share this environment, the study aims to understand how HVAC system user control (operation, setpoint, and flow direction) influences thermal conditions and air quality at workstations. An average occupancy was defined based on the usage pattern observed throughout 2023/2024 in the living lab. Air temperature levels at workstations were measured and used to validate the results of the living lab’s usage pattern case study.

The environment was simulated with EnergyPlus to determine surface temperatures, which were used as boundary conditions for CFD simulations in Ansys Fluent, focusing on a summer afternoon scenario (2 PM). The CFD model included 13 occupants and all workstations in the living lab. The environment was discretized with a tetrahedral mesh and incorporated boundary conditions for building envelope surfaces, air conditioner inlets and outlets, and airflow velocities and directions. Different setups were tested, including temperature setpoints of 23°C and 24°C, airflow angles of 0°, 20°, and 60°, and operating modes such as all units on, only units on side A, only units on side B, and the habitual usage pattern. Average occupant temperature and air exhalation rate were inserted into the model. The study aims to assess temperature and airflow distribution at workstations and CO2 concentration in the environment.

The results will provide insights into how HVAC systems in shared spaces affect environmental conditions at workstations, focusing on thermal comfort and air quality. Specifically, it will assess how changes in setpoints, airflow velocities, and flow directions impact different areas within the shared environment. These findings will optimize HVAC system configurations in the living lab to enhance occupant comfort and well-being. This will help develop actionable design guidelines and practices for creating more comfortable and energy-efficient environments for all users.