Comparison of Removal Effectiveness of Mixed versus Displacement Ventilation during Vacuuming Session

Abstract

In  indoor  environments,  floor  surfaces  are  sinks  of particles  that  might re-suspend  in  air.  If  not  removed  by the  ventilation  configuration,  particles  carrying  bacteria and   viruses   constitute   a   threat   for occupant’s  health. Selecting   a   proper   ventilation   system   with   convenient design   parameters   plays   an   important role   in   particle removal  from  the  occupied  space.  In  this  work,  a  typical office space was considered with the option of varying the ventilation    configuration    by    considering    a    mixing ventilation  (MV)  system,  displacement  ventilation  (DV) system,   and   reversed   displacement   ventilation   (RDV) system. The effectiveness of these systems in removing re-suspended    particles    from    the    indoor    space    during vacuuming   sessions   was   studied. For   this   reason, a transient  3D  computational  fluid  dynamics  (CFD)  model was  developed  and  was  validated  experimentally  in  a climatic   chamber   equipped   with   both   MV   and   DV systems. Good agreement was obtained between measured and predicted values of particles’ concentration with low relative  error  in  the  order  of  10  %.  The  parametric  study conducted  showed  that  the  reversed  DV  configuration insured the best particle removal performance by resulting in  an  effective  suction  effect  at  the  floor  level.  The  worst performance was provided by the conventional DV system due   to   the   upward   DV   airflow   transporting   the   re-suspended  particles  from  the  floor  levels  to  the  upper breathing  levels  spreading  contaminants.  From  here  the RDV   configuration   was   suggested   for   operation   of ventilation  system  during  vacuuming  session  to  enhance particle removal.