## 1 Introduction  
Indoor air quality is very important for occupant health and comfort. Since people spend almost 90% of their daily time in indoor spaces, indoor air quality directly affects human health [1, 2]. [PERSON] et al. [3] reported a connection among air pollution, meteorological conditions, and respiratory illnesses like pertussis. [PERSON] et al. [4] stated that intensifying respiratory symptoms have been linked to increased community-level exposure to air pollution. Experimental data indicates that the health effects of contaminants are lessened in a room with an airflow. Regardless, it is important to keep in mind that certain high-use, high-frequency, high-duration practices, the presence of vulnerable populations, as well as indoor characteristics and layout (volume, air exchange rate, etc.) can result in chronic exposures that are higher than the WHO guidelines or reference values, indicating the need to restrict this kind of exposure [5]. Therefore, it is crucial to provide adequate fresh air and control the concentration of pollutants in enclosed spaces. There are various types of pollutants, such as particulate matter, gaseous pollutants, and biological molecules. There are also several methods to improve indoor air quality. Elimination of the contaminant source, increase in the ventilation rate [6], and placement of an air cleaning device [7] into the indoor environment are some of these methods. Since the spreading out of the coronavirus disease (COVID-19), the importance of air cleaning devices has increased. During the pandemic, most people spent long hours indoors due to the lockdowns and the restrictions on outdoor activities [8]. The spread of the COVID-19 virus occurs with droplets and particles. In an indoor environment, a person carrying the virus can transmit the virus by coughing and speaking. The WHO states that breathing in respiratory droplets larger than 5 \(\upmu\)m during coughing or sneezing can spread the coronavirus infections [9]. Studies have also been conducted to determine whether the transmission via smaller particles is feasible [10; 11; 12]. Therefore, it is crucial to clean indoor air with appropriate air cleaning devices [5]. Recently, air cleaning devices have been widely used in indoor spaces such as hospitals, schools, workplaces, as well as houses [13]. However, some of the data provided by the manufacturers are not reliable because of the lack of experimental data. Also, there are only a few appropriate laboratory facilities in which to conduct reliable experiments to make evaluations [14]. Therefore, it is very important to evaluate the effectiveness of portable air cleaners both experimentally and numerically. Through the years, breakthroughs in computer science have produced solution techniques based on computational fluid dynamics (CFD) to handle fluid dynamics problems [15]. Very complicated fluid flows can be simulated in a variety of settings and geometry thanks to the CFD solution of nonlinear Navier-Stokes equations [16; 17]. There are different parameters to evaluate the performance of the air cleaners. One of them is the clean air delivery rate (CADR) [18]. CADR is the distribution rate of fresh air delivered to the room by the air cleaner. To measure the effectiveness of air cleaners, CADR is often used as an international metric. The AHAM (Association of Home Appliance Manufacturers) standard defines the CADR measurement method and processes [19]. CADR is determined by the rate of change in the concentration of particles and pollutants in the room over time using the cleaning device. The higher the CADR value, the higher the amount of clean air supplied to the environment, and, therefore, the higher the filtering rate of the pollutants in the air. Another parameter for air cleaners is the age of the air [19]. The age of the air is the mean time that a particle takes to travel from an inlet point to reach a certain point in the space. If air age is high, it means that fresh air reaches the desired area later.