Development of efficient virus aerosol monitoring and removal devices requires aerosolization of the test virus using atomizers. The number concentration and size measurements of aerosolized virus particles are required to evaluate the performance of the devices. Although diffusion dryers can remove water droplets generated using atomizers, they often fail to remove them entirely from the air stream. Consequently, particle measurement devices, such as scanning mobility particle sizer (SMPS), can falsely identify the remaining nanosized water droplets as virus aerosol particles. This in turn affects the accuracy of the evaluation of devices for sampling or removing virus aerosol particles. In this study, a plaque-forming assay combined with SMPS measurement was used to evaluate sufficient drying conditions. We proposed an empirical equation to determine the total number concentration of aerosolized particles measured using the SMPS as a function of the carrier air flow rate and residence time of the particles in the diffusion dryers. The difference in the total number concentration of particles under sufficient and insufficient diffusion drying conditions was presented as a percentage of error.
In this research, the laminar, incompressible, unsteady oscillatory flow and convective heat transfer of nanofluid around a porous cuboid were studied two-dimensionally using particle resolved calculations. Several cuboids of different sizes and porosities and with a constant temperature were subjected to a nanofluid flow with a sinusoidal velocity profile. The effects of the Reynolds number (Re = 100–900), the volume fraction of nanoparticles, the aspect ratio of the porous cuboid, the Darcy number and the amplitude and frequency of the inlet velocity on the flow field and heat transfer were investigated. To evaluate the system’s optimal performance, performance evaluation criteria (PEC) were also investigated. The results showed that increasing the Reynolds number improved thermal performance. Increasing the volume fraction of nanoparticles increased the Nusselt number; however, the pressure drop coefficient increased more strongly. The heat transfer and pressure drop coefficient increased in line with the growth of the porous cuboid aspect ratio. When the Darcy number was increased, the Nusselt number first increased and then decreased and the pressure drop coefficient continuously decreased. A higher amplitude of the inlet velocity profile augmented the heat transfer and pressure drop coefficient. An increase in the amplitude and frequency of the inlet velocity profile widened the range of drag and lift coefficients. Furthermore, flow at different inlet velocity frequencies (f
* = 0–10) behaved differently; as a result, the maximum rate of heat transfer and pressure drop was obtained at f
*=5. However, considering the ratio of the Nusselt number to the pressure drop coefficient and PEC parameter, the optimum frequency was f
*=9.
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