Yoshihisa Momoi

PIV measurement and CFD analysis of airflow around building roof with various building installations

ABSTRACT The air-cooled packaged air-conditioner, widely used in small and medium buildings, needs the large number of outdoor units to apply various room conditions. Its operating efficiency can be changed by the high distribution density of the units and some other installations. This study aims to propose an optimum configuration of building installation at the rooftop by providing a better wind environmental condition for the energy saving. Thus, it is necessary to predict the airflow field around the rooftop. First, the airflow field around the rooftop was investigated by the Particle Image Velocimetry using scale models. The positional relation between the devices showed a sensible effect on the airflow characteristics. Moreover, the experimental data was compared with that of the Computational Fluid Dynamics (CFD) analysis to evaluate the accuracy of the calculation. They are similar to be said that CFD can represent the real situation approximately.

C&C efficiency of canopy hood exposed to horizontal air stream in commercial kitchen calculated by CFD analysis

ABSTRACT As one of the commercial kitchen ventilation researches, the mechanism of capture phenomenon and containment one of a canopy hood has to be investigated. Several experiments intended to change the Capture and Containment (C&C) efficiency of combustion gas and cooking effluence were conducted under the conditions of different suction wind velocity at the bottom of a hood, sometimes called face velocity, which is caused by the different hood size. The overall C&C efficiency was analyzed by means of computational fluid dynamics (CFD). The C&C efficiency from the experiment and CFD analysis showed good agreement, and it was assumed that the disturbing ambient airflow around the hood can influence on the C&C efficiency. Therefore the kitchen space was assumed which includes the disturbing airflow over the counter between a dining hall and a kitchen. As a result, the C&C efficiency of the larger hood decreased more under the disturbing airflow.

THERMAL ENVIRONMENT IN A SCHOOL BUILDING WITH NATURAL VENTILATION CHIMNEY USING STAIRCASE IN WINTER

Recently, as increase of eco-awareness, the number of building adopted with natural ventilation is increasing. Naturally ventilated building is expected to effectively reduce the building’s cooling load, and also expected to make people feel comfortable and familiar with nature, especially in spring and autumn. Few studies are found about the actual thermal condition of naturally ventilated building in winter. The purpose of this study is to figure out the influence of the ventilation chimney using staircase on the actual thermal environment and occupants’ evaluations in winter. The result shows that closing the opening at the top of chimney decreases the air change rate at room. It is also found that the cold draft at the window side and air leakage through the switched-off ventilation fan also influence on the thermal environment, except for that of ventilation chimney.

TEMPERATURE AND CONTAMINANT CONCENTRATION DISTRIBUTION AND ENERGY SAVING INSIDE AN OFFICE ROOM WITH HYBRID AIR-CONDITIONING SYSTEM WITH WIND-FORCED VENTILATION

In this paper, the influence of combination of the introduction method of wind-forced ventilation and the supply method of conditioned air on the indoor thermal environment and airflow characteristics are examined by means of CFD calculation. In CFD, two types of supply location of the air conditioned by AHU were set : (1) supply from ceiling, (2) supply from floor, and four locations of outdoor air intake for wind-forced ventilation were set ; (1) ceiling, (2) high position of outer wall close to ceiling, (3) low position of outer wall close to floor and (4) floor. From the calculated data, indoor environment and energy efficiency were evaluated by the distribution of air temperature, contribution ratio of indoor climate No.3 (CRI3) and CO2 concentration emitted from occupants.