Buildings are a significant contribution to our energy usage, which can be reduced by high-quality insulation. Consequently, research and development is continuously ongoing to improve the thermal insulation of all building components, including windows. To provide sufficient insulation, window frames typically have a cross section consisting of multiple chambers (see Figure 1), formed by connecting several components. Window frames are designed as two-stage joint systems, and comprise a drainage pathway to evacuate infiltrated water. Any water infiltrating into the glass rebate will be drained to the exterior chamber in front of the central gasket. However, experimental observations have shown that water droplets are sometimes found deeper into the window system. Given that the glazing beads typically have a poor airtightness at the corners of the window, water may be transferred due to high air velocities in the glass rebate. Similarly, water infiltrating into the exterior chamber of the profile is drained to the outside by means of dedicated drainage openings. The central gasket between the sash and frame ensures the water barrier in the system. However, deformations can occur due to wind pressures or (incorrect) manipulation. The gaskets inside the window frame cannot always follow the movement of the sash, which entails small slits and openings, in turn causing air currents to occur, and droplets may be transported.
Figure 1: Cross section of a window frame, with in green the expected path of water and in red the observed path
The goal of this thesis is to study this phenomenon in custom-built experimental test setups. In order to understand what happens in this system, a range of different geometries and pressure differences can be studied. First, only the air flow will be studied in a two-dimensional cross section of a window frame. The resulting air flow rate and air velocity at certain locations for a given pressure difference can be compared with simulations (not part of this thesis topic). Subsequently, tests can be done in which water is applied while a pressure difference is maintained. It is important to design an experimental setup in which small variations can easily be introduced and tested. Next to that, the goal is to start with simplified two-dimensional geometries, and increase complexity up to an actual window frame.
In this thesis you will learn