Natural and Mixed Ventilation Design via CFD and Architectural Modelling

Numerical simulations and computational fluid dynamics can be usefully integrated with architecturalmodelling to provide designers with a powerful single CFD based architectural modelling and designframework. This framework can be interfaced with building thermal performance modelling thus further integrating the full thermal and flow domains within architectural modelling. CFD analysis is generally restricted to the buildings environment flows or indoor single rooms and flow in spaces. In addition the designer must supply boundary conditions in the form of the external and internal building envelope/wall surface conditions. In the case of natural and mixed ventilation, this presents a fundamental problem since the outdoor and indoor boundary conditions are dynamic, inter-related and interactive via the buildings architecture. Furthermore they are dependent on external weather conditions, the indoor environment, controls and related heat gains. Therefore, in this study the boundary conditions for both the inside and outside of the building are dynamically described in order to develop an integrated CFD, BPS and architectural modelling approach, as a unique new design framework. This leads to the energy efficiency optimisation of natural and mixed mode ventilation. This paper presents an implementation of such an approach in the design of a building complex in Belgrade in which predicted flow patterns are used to optimise the architectural design and the size and location of ventilation openings. The needs for further research and engineering development are outlined. Finally to operate effectively and energy efficiently, natural and mixed ventilation requires an appropriately sensitive sensor to measure very low pressure differences at different building heights for the optimum control of mechanical ventilation system operation.The development of such a sensor is described.