Numerical Analysis of Airflow Interaction and Particle Removal Efficiency in Coordinated Operation of an Air Conditioner and an Air Purifier

Abstract

This study investigates the indoor environmental characteristics and particle removal performance for allergen mitigation when a residential air conditioner (AC) and an air purifier (AP) are operated simultaneously. Numerical analyses were conducted using a self-developed computational fluid dynamics (CFD) tool, CLiP. The target space was a residential room equivalent to approximately six tatami mats, and multiple device configurations were examined by varying the separation distance and relative placement of the AC and AP.

The results reveal that the installation distance between the devices significantly influences airflow distribution and temperature uniformity within the room. In dispersed configurations, where the AC and AP were placed far apart, high airflow velocities near the floor level of 0.67-0.69 m⁄s were maintained. In contrast, closely spaced configurations led to direct interference between the exhaust flows, resulting in an approximately 12 % reduction in airflow velocity. In particular, when the AP was installed directly beneath the AC, upward airflow velocity decreased to approximately 0.35 m⁄s, corresponding to a 47-49 % reduction compared with the dispersed configuration, due to frontal collision of the exhaust jets. These airflow characteristics directly affected particle transport and removal behavior.

However, contrary to the assumption of strong gravitational influence, pollen particles (apparent density: 140 kg⁄m³) were found to be primarily transported by airflow, with gravitational settling being limited. Consequently, the deposition rate on floor and wall surfaces was low, approximately 8-10 %, across all configurations. The pollen capture efficiency remained high, ranging from approximately 56 % in the interfering configuration to a maximum of 64 % in the dispersed configuration. Similarly, fine allergen particles with a diameter of 1 μm remained suspended and achieved consistently high capture efficiencies of approximately 64-67 %.

These findings indicate that both pollen and allergen particles can be removed effectively regardless of the specific layout. However, to simultaneously optimize thermal comfort and air purification efficiency, it is recommended to select placement strategies that minimize airflow interference and promote whole-room circulation.