COMPUTATIONAL FLUID DYNAMICS CHARACTERIZATION OF A HYBRID COOLING SYSTEM COMPOSED OF A DISPLACEMENT VENTILATION UNIT AND A RADIANT COOLING FLOOR

Abstract

The combined use of displacement ventilation (DV) and a radiant cooling floor (RCF) is increasingly common in the field of building climatization. This hybrid cooling system (DV+RCF) achieves a vertical stratification of the room air temperature and climatizes only the occupied zone. Heat sources in the occupied zone cause updraft convection currents that move the hot air and contaminants to the ceiling level. This results in better indoor air quality than conventional cooling systems because the hot air and contaminants travel through the occupied zone only once. DV+RCF systems work better in building with a high ceiling (3 m or more). Therefore, their use is appropriate in buildings with high ceilings, such as large public buildings, theatres, museums, train stations, and airport terminals. Despite the advantages of implementing a DV+RCF system, the system's behavior is not well characterized to be designed efficiently. Therefore, the aim of this paper is to present some mathematical relationships to aid in the design of such a system. This paper describes the amount of heat energy the floor is able to absorb by convection and the maximum distance of influence of the primary air stream driven by the DV system. Analyzing the DV+RCF system using computational fluid dynamics reveals these mathematical relationships, which can be powerful tools to help in the design of cooling systems for rooms with high ceilings. This research involved multiple simulations using different Reynolds numbers based on the diffuser parameters and different Grashof numbers based on the temperature difference between the floor and the air supplied by the diffuser.