AHU heat exchanger performance tracking during the building operational phase

• Key performance indicators for rotary heat exchangers in air handling units. • Virtual sensor exploration for air temperature after rotary heat exchanger. • Contextual assessment of rotary heat exchanger operational performance. • Improved fault detection capabilities for rotational heat exchangers. • Estimation of cost savings for rotary heat exchanger replacement. Building operation accounts for roughly 30 % of the world’s energy use, with space heating, space cooling, and ventilation accounting for 43 %. Given this significant impact, ensuring these systems operate efficiently is crucial. There is currently a lack of Key Performance Indicators (KPIs) that focus on ensuring that the heat exchanger in Air Handling Units (AHUs) performs efficiently in its context, as the classic KPI “Heat Recovery Efficiency” (HRE) only focuses on the absolute performance. Therefore, four contextual KPIs have been proposed and evaluated on two datasets from operational AHUs that supply an educational building in Denmark. To allow the proposed KPIs to be used for different AHUs, virtual sensors were developed to monitor the air temperature between the heat exchanger and the heating/cooling coils on the supply side, as this sensor tends to be missing in AHUs. The proposed KPIs, in combination with the traditional heat recovery efficiency KPI, offer a more comprehensive understanding of the heat exchanger’s performance than the heat recovery efficiency alone. The proposed KPI “Useful Heat Recovery Efficiency Deviation” (UHRED), indicated that both AHUs had issues with their control during the transition period, whereas the HRE did not indicate any issues, as the absolute performance was high. The UHRED, therefore, shows potential for enhancing the monitoring and fault detection capabilities of AHUs with few or no added sensors.