Control of Natural Ventilation Opening to Achieve Energy Saving Performance and Thermal Comfort in Office Room

Division of Global Architecture, Graduate School of Engineering, Osaka University, Osaka, Japan.

Abstract

In recent years, the number of office buildings that introduce natural ventilation (NV) is being increased to save energy. However, operating NV systems with NV opening device fully open could lower thermal comfort, depending on meteorological condition. Therefore, automatically-controlled NV systems can generally work only for a relatively short period of time. In order to keep both energy saving performance and thermal comfort even when outdoor temperature is low in the mid-seasons, it is necessary to understand the relation between NV conditions and the indoor environment. In this paper, the indoor environment is evaluated changing NV conditions by using CFD for a generalized office room model. Four types of NV inlet system were assumed, i.e., high peri-counter (Type 1), low peri-counter (Type 2), slot-type downward inlet (Type 3), and slot-type horizontal inlet (Type 4). Twenty conditions were analyzed for each type, varying the outdoor air temperature and NV flowrate as parameters. As indices of thermal comfort, average vertical temperature difference within perimeter zone and ADPI in the occupied zone were calculated. For each of NV systems, simplified equations to calculate N_max from indoor/outdoor temperature difference are finally to be proposed, which may be considered for NV opening control in operating NV systems.