LES

The ventilative cooling by natural ventilation is important technology for the buildings in urban area for the sake of energy saving and BCP (Business Continuity Plan). In fact, a large number of high-rise buildings in urban area in Japanese metropolises are equipped with natural ventilation apparatus such as openings and chimneys or shafts.

The need for thermal comfort and clean air for occupants in buildings or vehicles is vital since we spend more than 90% of our time inside these enclosed environments. Worldwide, current directions of the leading powers are oriented towards the reduction of the energy consumptions and HVAC systems make no exception. Personalized Ventilation (PV) applied to buildings may represent a solution to this problem. The main idea of PV is to provide clean air close to the face of each occupant and to improve thermal comfort in his microenvironment.

The fan is one of the major noise sources of an air conditioner. Because of the presence of other components in the fan assembly, such as the bell-mouth, outlet grille and compressor chamber, the ingested and discharged flow fields around the fan impellers are distinctly different from those in a free field. Therefore, the noise generation mechanisms become much more difficult to analyze and model. This paper concentrates on understanding the generation mechanism and evaluating the noise in the fan system of a split-type air conditioner.

With the purpose of evaluating validity of the application of CFO on the problems of cross-ventilation, numerical simulation was performed, using standard k- E model and two types of modified k-E models which improve evaluation accuracy in production term of turbulence energy, and also using LES, and the results were compared with those of the corresponding wind tunnel experiment. As a result, it was found that the defects of the model characteristic to the standard k- E model could be improved to a certain extent by application of the modified models.