Encapsulated venetian blind: a new numerical model

Although encapsulated slat type blinds (such as venetian blinds) are often used to reduce the solar gains through windows, there are few detailed calculation models for such shading devices. This paper describes: a theoretical analysis on heat transfer through encapsulated venetian blind system, the implementation of the mathematical model and its validation with experimental data. The new mathematical model (EVBGP) has been written to simulate blind systems accurately at each time step. The theoretical study on heat transfer has been carried out on two different domains. The analysis on the radiation heat exchange, short-wave and long-wave, focused on the definition of an original approach based on the need to distinguish the surfaces where the direct solar radiation is impinging to the ones where only the diffuse impinges. The convection heat transfer has been approached separately in a different geometrical domain. The mathematical model has been implemented in order to create a tool capable to produce either angle dependent physical parameters to be used in detailed models or effective solar heat gain coefficients and U values. The tool has been validated through a set of experimental data. It has been tested in the short-wave radiation domain and the test activities in the thermal domain are in progress. A good agreement between the software output and the aforementioned experimental data has been achieved. The software tool is intended to be integrated in a detailed simulation model and it is suitable for assessing the blind arrangement impact on building thermal performance