IBPSA2007

Heat island is a big issue for large cities especially located in hot and moist climate in Asian countries. The phenomenon is severer in an urban canyon because of surrounding highrise buildings causing little ventilation and heat dissipation from traffic. The first purpose of this study is to investigate thermal environment of a main street in Osaka by intensive  measurement in the summer of 2006. Osaka is the second largest city and suffers from the most severe heat island in Japan.

Through the paper a model simulating the thermal performances of an environment in transient state is presented. The model is composed by two codes that, used in sequence, concur to obtain evaluation, at a local level, of the most used comfort indexes, starting from the acquaintance of the external climatic conditions and of the thermal-physical characteristics of the building envelope.

Atrium is becoming a popular common space in commercial buildings nowadays. In planning the thermal environment and air-conditioning system for an atrium, it is necessary to calculate a cooling load for the occupied zone and to predict the vertical temperature distribution. Besides, the thermal environment varies with time, so dynamic thermal environment analysis, including prediction of vertical temperature, is required. The building design process of the atrium consists of several different stages.

For large scale commercial buildings, the inner heat gains acts in an uncertain way in time serial and space. Presently, fixed schedule is generally used to describe the inner heat gains in the state of arts HVAC system simulation which couldn’t reflect the uncertain characteristic of inner heat gains. Therefore the simulation is required to use a range rather than just a certain point as the simulation input of the inner heat gains.

 In the paper, Equivalent Slabs approach is presented to compute thermal bridges in building constructions properly and quickly. The heat transfer of thermal bridges is decomposed into the heat transfer process influenced by outdoor temperature, indoor temperature and adjacent room temperature separately. 2+n (n is the number of adjacent rooms related to the thermal bridge) Equivalent Slabs are obtained to replace a thermal bridge to solve its 2+n heat transfer processes.

The heat transfer characteristics in building window frame have significant three-dimensional characteristics, but window U-value model are often used in most building codes for thermal analyses to simplify the calculations. State model reduction techniques were used to develop loworder three-dimensional heat transfer model for window frame, which is efficient and accuracy. The method was validated for a envelope designs by comparing the with complete 3-D models.

In order to realize “design by simulation” in building design, this paper discusses the methodology of applying building thermal simulation in the building conceptual design stage. The conceptual design stage is divided into four sub-stages and the framework of design by simulation in the conceptual design stage has been built.

With the fast development of urbanization in China, the urban thermal environment has been worsen due to the more and more obvious heat island phenomena. Aartificial waterscape is regarded as one of the most effective methods to improve the outdoor climate. In this paper a fountain model is developped based on experiment results and Particle-Source-In Cell (PSI-CELL) model. Lagrangian approach is adopted to simulate the dynamics properties of droplets in the air while Eulerian approach is employed to solve the conservation equations of the air.

Long-wave radiation heat transfer is calculated using a geometrical factor the so-called view factor, which is normally estimated in a simplified way by building simulation programs, especially when there is no information in the literature due to the complexities to solve the double integral which defines the view factor between two surfaces. Analytical solutions are only available in the literature for a restricted number of simple configurations.

Even in relatively warm area in Japan, frost damage of roof tiles occurs. In this study, the influences of several factors on frost damage are considered from a thermal environmental point of view. Condensation on the external surfaces of roof tiles, which is caused by a temperature drop due to nocturnal radiation, is estimated as one of the most important factors to the frost damage. The frequency of condensation was calculated by a numerical analysis. The influence of the parameters, such as the inclination angle and the orientation of the roof, is investigated.