Heat transfer coefficients of double skin facade windows

This article studies the heat transfer coefficient of double skin facade (DSF). Experiments were conducted for a lab-scale DSF model of 1.1 m high. The measured data were used to validate a computational fluid dynamics (CFD) model, which was then used to study the full-scale DSF. The experimental data showed that closing the cavity reduced the effective heat transfer coefficient by about 25%. In the ventilated mode, the DSF could have better insulation than double glazing (DG) and an optimal cavity depth existed for the lab-scale DSF. There were cases where the DSF had a higher heat transfer coefficient than DG. In these cases, the induced natural ventilation in the cavity may have caused a greater convective coefficient than that at the external surface of the facade. For the U value, which is evaluated at a high external heat transfer coefficient, the simulation results show that the DSF is always better than DG and the influence of the size of the cavity depth does not appear important. In normal applications of facade, the typical external convective heat coefficient is usually large due to the ambient wind. In this case, the DSF will have better insulation than the single facade of DG.