UC Berkeley Controls and Information Technology Title Evaluation of various CFD modelling strategies in predicting airflow and temperature in a naturally ventilated double skin

Demands for energy savings, thermal and visual comfort and a high-tech image for new building envelopes can be met with a Double Skin Façade (DSF). These kinds of building envelopes are widely encouraged, proposed and increasingly designed by architects. Naturally ventilated DSFs seem very interesting from an energy point of view, but a good design is crucial to improve the energy savings and the proper operation of the system. Computational Fluid Dynamics (CFD) can play an important role in evaluating and improving the thermal behaviour of a DSF. This paper shows, through a sensitivity analysis, a good strategy for carrying out a CFD simulation of this special building envelope. In this work the validations of the results are based on experimental data from the literature. The paper provides a discussion that highlights which factors are important in the simulation, and which increase model complexity without improving the prediction capacity. The results show that, for a DSF characterized by a prevalent bidirectional flow, the additional effort required to make a 3D model is not justified by a significant improvement of the results. This work shows also that the accuracy can be improved by modelling outdoor ambient. The performance of k-ε and k-u, the two most commonly used turbulent models for simulating the naturally ventilated DSF is evaluated. 2011 Elsevier Ltd. All rights reserved.

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