Abstract
In order to achieve more realistic boundary conditions on the inlet of a ventilation system it is necessary to study the influences of the air diffuser orifices geometry on the airflow distribution in the enclosure. Integrating these orifices directly in a real scale air diffuser for a numerical study will result in a huge computational grid which will translate in huge computational resources and a much larger calculation time. The solution, in this case, was the numerical simulation of the airflow through small parts of the studied air diffuser. Later, the numerical results will be implemented as boundary conditions in the unidirectional diffuser of a numerical simulation that represents a real scale operating room (OR). In the current study two diffusers with different orifices were studied, one having circular („O”) and the other one lobbed („+”) orifices. The initial numerical model had 25 orifices on the diffuser, but because of the very large numerical grid resulted for the initial meshes (>35 million tetrahedral cells), a solution with only 4 orifices was chosen for this study. A mesh independency study was made for these two types of air diffusers. The numerical studies were made using RANS method, with SST k-ω turbulence model in steady state conditions. The numerical results obtained with the first step models showed very good agreement with the PIV stereoscopic experimental measurements.
Highlights
When performing airflow analyses on a ventilation system in an enclosure it is necessary to study which are the implications of the geometry of the orifices of the diffuser have on the airflow
This paper presents a study for two air diffusers with two different orifice geometries, a lobed („+”) and a circular one („O”), by means of numerical and experimental measurements
This study addresses the idea of a passive control [11, 12] for a better distribution of the air in the room, achieving a better thermal stratification, having the potential to improve the energy consumption
Summary
When performing airflow analyses on a ventilation system in an enclosure it is necessary to study which are the implications of the geometry of the orifices of the diffuser have on the airflow. The mixing process is closely correlated to the turbulence transition [6], while the geometry and the initial flow perturbation significantly affect its generation and transition For residential purposes, they can have direct implications regarding the thermal comfort of the occupants in the room, the dispersion of pollutants or the energy consumptions of the HVAC unit. The results from the numerical case, after validating them against experimental measurements, were used as a boundary conditions in the larger numerical case that represents an operating room (OR) with a unidirectional air flow (UAF) plenum, called a laminar air flow (LAF) plenum Implementing them in this larger numerical case will allow to study the air distribution in the room and to make comparison between the two types of orifices. This study addresses the idea of a passive control [11, 12] for a better distribution of the air in the room, achieving a better thermal stratification, having the potential to improve the energy consumption
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