Occupancy sensor-enabled demand control ventilation using virtual outdoor air flow meters in air handling units without an outdoor air flow meter

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Nowadays, the outdoor air (OA) flow requirement for demand control ventilation (DCV) can be accurately determined using occupancy sensors in commercial buildings. However, in air handling units (AHUs) without precise OA flow measurements, the OA is often controlled by a fixed-damper position method, which cannot maintain the required OA flow rate. The objective of this study is to develop and evaluate occupancy sensor-enabled DCV OA control using a virtual OA flow meter in AHUs. Firstly, a virtual OA flow meter is derived from a virtual supply fan flow meter by applying the correlation between the OA ratio and damper position under appropriate building pressure control. Subsequently, experiments are conducted to calibrate the virtual OA flow meter in an AHU with the design OA flow rate of 120 L/s. Finally, occupancy sensor-enabled DCV OA control is implemented by using the calibrated virtual OA flow meter. The evaluation results show that the proposed DCV OA control can match the actual OA flow rate well with the required OA flow rate. The root mean squared error (RMSE) falls within the range of 16–20 L/s, demonstrating an improvement over the fixed-damper position control, which yields an RMSE of 36 L/s.