Heat Exchange Efficiency and Recovery Efficiency Evaluation Method of Bidirectional Heat Recovery Ventilation System

This study proposes a new evaluation method for assessing the performance of a bidirectional heat recovery ventilation system equipped with a thermal storage element. The method reflects the system’s time-dependent operating characteristics and heat exchange behavior. The existing KS B 6879 standard, based on a steady-state dual-duct system and temperature-based calculation, is unsuitable for single-duct, alternating systems where supply and exhaust occur sequentially. To address this, a cycle-based heat exchange efficiency calculation method is introduced, using time-varying airflow and temperature data based on accumulated outdoor air load. Additionally, a heat recovery efficiency metric is defined to evaluate the thermal performance of the storage element by quantifying the net sensible heat stored and released, excluding duct heat exchange. Experimental results showed that the heat exchange efficiency was approximately 50%, and the heat recovery efficiency of the storage element was 62.72%. It was also observed that airflow delay and extended cycle intervals led to a gradual decline in performance. The proposed dual-index evaluation framework offers a more accurate assessment of such systems and provides a foundation for design, comparison, and optimization of various ventilation solutions.