Role Of Airflow Interruption Of Air-conditioner On Air Circulation Induced By Indoor Purification Device

Indoor air quality (IAQ), which is always threatened by various releases of airborne pollutants, has drawn more and more attention. In order to reduce indoor pollutant exposure, people become increasingly interested in portable air purification devices. Such purification devices are usually with strong momentum discharged out during operation, which can interrupt indoor airflow pattern created by air-conditioning (AC) units in a building. Thus indoor airflow patterns play a significant role in the purification efficiency. This study has used both measurement and computational fluid dynamic (CFD) modeling to investigate role of airflow interruption to indoor air purification.The commonly used RNG k-εmodel is validated with experimental data from literatures, which are measured in a 2-D confined turbulent airflow and a 3-D displacement ventilation experiments. A workshop environment conditioned by an AC and cleaned by a portable air purification device was mimicked in an environmental chamber. After measurement, the tested case was simulated with CFD and the obtained results were compared with measurement data. Then the validated RNG k-εapproach is applied to simulate the indoor airflow interruption to air purification, and resulted temperature and pollutant concentration distribution. Concerned factors include: positioning of moment sources, AC diffuser types, the AC cooling or heating mode and location of pollutants.Simulated results of airflow pattern, velocity contour, and temperature and pollutant concentration show good agreement with both literature and test data, which fully validates the applicability of RNG k-εmodel in indoor airflow field. Basic findings in the multi-mode simulation include:(1) Satisfying airflow pattern is observed when the air purification device is on. The clean air from the device effectively takes away pollutants before returning to the device.(2) Two cases with different positioning of moment sources are considered. Numerical results show symmetrical air pattern is achieved when the air conditioner and purification device are opposite positioned. The purification effect is deficient when the air conditioner is laid in the middle of the surrounding wall, which results in contradicted airflow.(3) Two commonly used air supply methods, bilateral vent and grid vent, are discussed. When the air conditioner and purification device are opposite positioned, good circulation and purification effect is achieved with both methods. (4) In the cooling mode, airflow from the purification device and air conditioner is mutually promoted, and resulted circulation flow aids the purification greatly. Otherwise, contradiction of airflow in the heating mode will give rise to defective consequences.(5) Pollutants near the intersection of air from air conditioner and that of purification device can be directly absorbed, thus the diffusion of pollutants is minimized and best purification is achieved.In summary, in order to maximize the purification effect, reasonable layout of air conditioner and purification device is required, in order to create effective airflow circulations and locate the pollutants in the air-return side. Based on this principle, it is promising to give beneficial suggestions in the usages of purification devices.