CFD Investigation of the Optimal Ventilation System for a Single-Family Room Neonatal Intensive Care Unit

Newborns are immunocompromised, and they are more susceptible to get infected than elders, hence, they should be kept in an aseptic environment that is almost free of microorganisms. A neonatal intensive care unit (NICU) is intended for caring for ill, premature and low-birth-weight infants. There are 2 main types of NICUs: the open-bay (OBA) NICU and single-family room (SFR) NICU. Researches have proved that the SFR NICUs have many advantages as compared with the OBA NICUs,hence, SFR NICUs are predominant worldwide since 1994. The ventilation system has a crucial role in the infection prevention and control (IPC) program, as it is responsible for diluting and removing various airborne contaminants from the NICU space as well as maintaining indoor thermal comfort. The locations and the types of the supply air outlets and exhaust air inlets strongly influence the performance of the ventilation system, consequently, the main objective of the paper is to find the optimal types and positions of the supply air outlets and exhaust air inlets for a ventilation system used in SFR NICUs. Two main indices were used to assess the performance of the ventilation system, which are the Air Diffusion Performance Index (ADPI) and the air change effectiveness (ACE). 13 ventilation cases were investigated and assessed based on the 2 indices. Results have proved that,for SFR NICUs, it is not recommended to use Group E supply outlets with low sidewall return grilles, or to use ceiling supply diffusers of Group A type with either ceiling return grilles or low sidewall return grilles. It is recommended to use a single high sidewall supply grille with a single low sidewall return grille, where the low sidewall return grille is located on the wall that is close to the isolette, while the high sidewall supply grille is located on the opposite wall. Moreover, results have proved that the value of ACE calculated at the breathing plane is almost equal to the ACE values calculated at the occupied and breathing zones except for ventilation systems that have Group E supply outlets, consequently, this would help to reduce the number of measurement points,especially for ACE practical measurements based on tracer gas methods.