CFD analysis

The development of computational fluid dynamics (CFD) made it possible to simulate the detailed flow field and temperature field within the room. The various studies numerically investigated the flow and temperature field both inside and outside the buildings. When investigating the indoor environment, human is an important factor since it perceives the indoor environment and behaves as a source of heat and contaminant as well. Some studies investigated deeper into humans by developing detailed computer-simulated persons (CSP).

Air-supplied ceiling radiant air conditioning is expected to become more popular in Japan in the future because there is no leakage from pipes and no condensation on the surfaces of radiant panels. Coanda air conditioning, a type of air-supplied ceiling radiant air conditioning, uses the Coanda effect, which is the tendency a fluid passing near a wall to maintain contact with it. As used commonly, Coanda air conditioning cools the ceiling surface by blowing airflow horizontally along it from the top of the wall surface and cooling by radiation1).

In recent years, many multi-type package air conditioning systems for buildings have become widespread in office buildings in Japan, and there are many cases where one air conditioning space is shared by using several indoor air conditioning units. The advantages of multi-type package air conditioning system are that it is possible to operate and control individually for each indoor unit, and that the user can arbitrarily change the temperature setting of the indoor unit.

The impinging jet ventilation system (hereinafter referred to as IJV) has been proposed as a new air conditioning ventilation system. Properties of indoor environment with this system using impinging jet are complicated. The present paper reports fundamental properties of indoor air with distributed interior heat generation load assuming an office. The experiment was conducted in the climate chamber of which floor area was 27.0 m2, and basic properties of temperature and CO2 distributions were investigated.

The mainstream of air-conditioning system for medium and small sized buildings is conditionally air mixing ventilation with ceiling cassette unit of packaged air conditioner (PAC), however, it may bring a high cold-draught risk to occupants, due to the direct drop of the supply air jet. To solve this problem, the air mixing ventilation system can be improved into an air based radiant air-conditioning system by stretching the non-flammable membrane under the ceiling with PAC, thus the cold-draught of PAC could be substantially eliminated and the indoor environment could be improved easily.

Recently in Japan, many buildings introduce packaged air-conditioner (hereinafter, this is called “PAC”) as an air conditioning equipment. Most of the PACs can change the direction of supply air blown from the unit and the “Swinging Mode” can change airflow direction periodically as one of the airflow direction setting of PAC. Before constructing the building, appropriately predicting the indoor environment (e.g. temperature distribution or air velocity distribution and so on) is important for indoor environment design.

The following paper is focused on hygrothermal behaviour of roofs with ventilated air layers subjected to air leakages in their internal decks (the internal partial construction located below the ventilated air layer). Possibilities of CFD modelling of such constructions are discussed in the first part of the paper including the problem of introduction of water vapour diffusion into calculation. A brief comparison of results from CFD analysis and from calculation based on a technical standard is also included.

We developed an airflow control unit for small chambers for uniformly controlling airflow on the surface of tested building material in the small chambers. We will present the mass transfer rate on the surface of tested building materials corresponding to an actual building in order to exactly evaluate the performance of the reduced amount and concentration of released chemical materials with the small chambers. We measured the airflow velocity on the surface of building materials in the small chamber with the developed airflow control unit and the fan speed for airflow control.

In a commercial kitchen, a large ventilation rate is needed and energy consumption can be large because a large amount of effluence of heat and moisture need to be removed. To improve kitchen environment and to save the energy, low radiative cooking equipment with concentrated exhaust chimney was developed. Although a ventilation rate may be decreased by using this equipment, the effluence needs to be captured well. To predict indoor air and thermal environment of commercial kitchen using this equipment, CFD analysis is useful.

For patients, the sickroom is a place where they receive medical treatment and also a living space where they spend most of time in a day. Therefore, good indoor air quality and comfort should be kept in sickroom. We propose to use the displacement ventilation as a means of obtaining high indoor air quality in sickrooms. The purpose of the study is to examine the validity of this system. This paper shows the experiment results and CFD analysis results to examine the effect of partition curtain in the displacement-ventilated room.