Performance comparison between mixing ventilation and displacement ventilation with and without cooled ceiling

Abstract

PurposeTo provide the performance comparison between the conventional mixing ventilation (MV) and the displacement ventilation (DV) with and without cooling ceiling, which can be helpful to design.Design/methodology/approachThe commercial CFD software FLUENT with RNG k‐ε turbulent model was used. The CFD method was validated via comparing with the available experimental data.FindingsIt was found that if properly designed, the DV system can supply better indoor air quality in the occupied zone, including better distribution in temperature field, higher ventilation efficiency, lower contaminant field and more thermal comfort compared with the MV system, because of the stratification effect of DV. And the locations of return air outlets have a great effect on the performance of the ventilation system. It was also found that the DV systems can be used to remove air contaminations more efficiently, but the temperature difference in the occupied zone in the DV system is higher than that in the MV system, especially if the heat load is higher. This problem may be solved if the cooled ceiling is combined with the DV, because the vertical temperature in the occupied zone will be reduced and more thermal comfort can be achieved.Research limitations/implicationsMore detailed computation should be performed on the thermal radiation between different surfaces in the room.Practical implicationsA very useful source of information for thermal designing of air condition.Originality/valueThis paper provides the performance comparison between the conventional MV and the DV with and without cooling ceiling, based on flow and temperature distribution.