IBPSA2007

The aim of the present study was to determine the applicability of a genetic algorithm for the optimization of daylighting systems, as well as the requirements for the lighting simulations to be used. Furthermore, by testing the daylighting performance of a building's facade when several parameters are allowed to change simultaneously, the results were used as a complement of previous parametric studies. The goal of the optimization was to maximize energy savings by reducing visual discomfort while maintaining good daylight penetration.

An extended top of the roof can induce the upflowing wind which flows close to the wall and in this way it increases the intake airflow rate in the air gap. A model was set up to save energy with the consideration of a suitable thickness of the air gap and a suitable length of the extended top. The Computational Fluid Dynamics (CFD) was employed to simulate the wind field in the ventilated roofs with extended top and the cases were carried out according to Changsha’s climate parameters in China. The results show that the extended ventilated roof works very well in summer.

Quantification of natural ventilation rates is an important issue in HVAC system design. Natural ventilation in buildings depends on many parameters whose uncertainty varies significantly, and hence the results from a standard deterministic simulation approach could be unreliable.

The buoyancy-driven natural ventilation of a room with large lower and higher level openings is investigated by both theoretical analysis and CFD simulation. Pressure-based formulae are developed for the prediction of the height of neutral plane and airflow rate, and three different flow modes are identified according to the position of the neutral level: (I) when the neutral height is at intermediate level of the lower opening; (II) when the neutral height has no intersection with openings; (III) when the neutral height is at the intermediate level of the higher opening.

Assessments based on CFD snapshots of stable conditions within strongly transient domains do not address many aspects of performance associated with occupant interventions, control actions or changing climate. Such domains (e.g. double skin façades) are characterised by transient flow patterns due to changing weather patterns, actuation of dampers intermittent opening of façade windows and operation of building environmental systems. Importing boundary conditions from whole building simulation is an improvement but it discounts the impact of the flow predictions on the building domain.

A mathematical model for simulating airflow in solar channel of the insulated Trombe solar wall system is proposed. It is assumed the glazing is isothermal and the solar heat absorbed by the wall is transferred to  the air in the channel with a constant flux by natural convection. The mass, momentum and energy  conservation equations are discretized and solved using the finite difference control volume method. An experimental study of solar chimney was used to validate the proposed mathematical model.

This paper includes the results of empirical measurements in and computational modeling of atria. Five atria with different designs were considered. In each atrium reverberation times and sound distribution patterns were obtained via measurements. Subsequently, the spaces were modeled in a room acoustic simulation application. The comparison of measurement and simulation results support the formulation of recommendations toward a more reliable use of modeling tools for proper acoustical design and analysis of atria.

The study investigates the use of local trees in the UAE to improve visual performance and lighting quality in typical classrooms. The methodology depended on analysis of luminance ratios and illuminance levels using simulation (Radiance.) The effect of two design variables (i.e., tree type: Ghaf and Neem, and tree spacing: 2m and 4m parallel to outside north wall, on task’s illuminance levels and interior-surfaces’ luminance levels were investigated. Lighting quality and visual comfort issues such as acute contrast, high brightness, and daylight distribution were discussed.

This paper presents the simulated results of human evacuation in a large space building. Two different models, Cellular Automata (CA) model and social force (SF) model are adopted. The simulated evacuation time and main characteristics of human evacuation are simulated and these results by the two models are compared. To check the practicability of the models for actual complicated cases, the simulating time is also compared. The results denote that both the two models can simulate the “arch” and “faster-is-slower” effect for human evacuation.

In order to determine the optimal combination of the heating source equipments in an existing office building, simulations of six different combination cases were conducted using the newly developed mathematical models of each component. From the simulation results, the optimal combination case can reduce the energy consumption by 19.7%, running cost by 12.8% and carbon-dioxide emissions by 29.6%, compared to the present operational combination.