Effect of Surface Thermal Resistance on the Simulation Accuracy of the Condensation Risk Assessment for a High-Performance Window

Abstract

The accuracy of condensation risk assessment depends on the accuracy of the measured or calculated temperatures. The existing 2D simulation method provides sufficiently accurate results for evaluating average performance values, such as U-values. However, the accuracy of predicting the temperatures in the local areas such as the edge-of-glazing and the frame has been questioned. This study analyzes the effect of the surface thermal resistance on the accuracy of the condensation risk assessment for high-performance windows. Experiments and three-dimensional simulations were performed for a triple-glazed window. The differences in results between the basic experimental test and the simulations with several different applied boundary conditions were analyzed. The results show that, in the simulations, a small change in the surface thermal resistance has no significant effect on the accuracy of the condensation risk assessment of the center-of-glazing or the frame. However, for the edge-of-glazing, the accuracy of predicting the condensation risk was significantly improved by using the increased local surface thermal resistance with the simulation. By employing the reduced radiation and convection at the edges or junctions between two surfaces, the error between the measured and calculated temperature factors can be reduced to less than 3%.

Keywords

• high-performance window
• condensation risk
• 3D thermal simulation
• surface thermal resistance