The effects of ventilation and floor heating systems on the dispersion and deposition of fine particles in an enclosed environment

- Combined effects from ventilation rate and floor temperature on particle removal investigated.
- The higher the floor temperature was, the faster particle concentration decayed.
- The down-supply ventilation mode outperforms up-supply ventilation mode under floor-heated conditions.
- Findings facilitating the future ventilation design for residential heating period in winter.

Recent years, most cities in China suffer from ambient particulate matter pollution, especially in winter. The absence of fresh air system in most northern heating buildings in winter results in the poor indoor air quality. This work aims to deal with the particle dispersion in a ventilated and floor-heated indoor environment by using experimental measurements and computational fluid dynamics (CFD) methods. Two ventilation systems were considered, i.e., top & down supply. Firstly, experiments were conducted to validate the velocity and particle concentrations by CFD simulation. Secondly, unsteady particles (with the diameter of 1 μm) dispersion was simulated with different inlet velocities (i.e., 0.3, 0.4 and 0.5 m/s) and floor temperatures (i.e., 293, 298, 303 and 308 K) in a ventilated and floor-heated chamber. Lagrangian method was employed for particles tracking. It is found that the higher the inlet velocity, the faster particle concentration decayed. For the same inlet velocity, particles in the chamber were removed faster with the increase of floor temperature. When the inlet velocity was 0.5 m/s and the floor temperatures were 293 and 308 K, it took 391s and 200s respectively for normalized concentration decreasing to 0.1. The number of particles deposited on the floor decreased with the increase of the inlet velocity and the floor temperature. This study also identifies that when the floor temperature was 308 K, the removing time is reduced by 15% for normalized particle concentration with the down-supply ventilation mode. These findings would be facilitating for the future design of ventilation and heating systems.