Enhanced wind-driven infiltration model by incorporating wind direction for design purpose

Abstract

Abstract.Research has been conducted to improve and enhance existing LBNL infiltration model in order to incorporate wind direction effect on flow rate. Existing wind driven infiltration of LBNL model only consider terrain and shielding parameter as correction factor. Supplemental analytical model considered in this research was Swami-Chandra model, which the calculation was based on average wind pressure coefficient (Cp). It was evident that for same wind direction, Cp value will not change regardless of wind velocity. Process of simulation shows that infiltration modelling has to be performed in three-dimensional environment with transient calculation in order to achieve convergent result. Wind direction strongly affects infiltration flow rate. However, as the infiltration hole has relatively small size compared to wind velocity, flow rate variation is marginal for energy-based design. Nevertheless, for pollutant and particulate matter analysis, wind direction will give significant change in term of concentration and flow direction. IntroductionBoth infiltration and ventilation are vital in determining the indoor air quality. Ventilation, both mechanical and natural are most likely controlled either automatically or manually. Meanwhile, infiltration is unintentional and can introduce unwanted contaminants from outside and either hot air from the outside that increasing cooling load or bring cold air inside and increase the heating load. Study of infiltration has been conducted in decades and researcher has developed many kinds of infiltration model. However, the nature of airflow is very difficult to predict and model, because of the uncertainty in turbulence, vortex, and flow separation, for example. Therefore, from design purpose, the model is highly practical to use but prone to error and inaccuracies. An alternative to those analytical model is using computational fluid dynamics. Usage of CFD has increased along with the improvement of computing capabilities. CFD can model varieties of fluid flow with many physical parameter, therefore better result can be achieved.