Volume 8 Issue 1 ( March 2021 )

This paper investigates the effect of moisture transfer on the thermal performance of an alternating-current heat recovery ventilator (AC-HRV). Contrary to conventional direct-current ventilation in two separate ducts, alternating- current ventilation periodically changes its airflow directions in a single duct. Exhaust energy is stored and recovered in and out of the thermal storage unit during charging and discharging processes. A theoretical model has been developed to obtain the transient temperature and humidity distributions inside a thermal storage unit in partially wet conditions. Based on the distributions, the thermal performance of the HRV is analyzed at cyclic steady states. Results show complicated patterns of moisture condensation and evaporation during an entire period of charging and discharging processes. The maximum thickness of water condensate is 2.67 m, which is negligible under the present test conditions. The enthalpy efficiency of an AC-HRV increases as the accumulated mass of condensate increases due to the latent heat.

Keywords: evergreen; Heat recovery ventilator, Alternating-current ventilation, Enthalpy efficiency, Condensation