A Three-Dimensional Simulation of the Thermal Transmittance of Window Frames: Toward an Alternative to the Current Industry Standard
[Thesis]
Zhang, Yuxin
Snell, Clarke
Stevens Institute of Technology
2019
71 p.
Master's
Stevens Institute of Technology
2019
Projected building heating and cooling loads are calculated based on the theoretical heat transmission (U-value) through the building envelope on a given site (macro and microclimate). Windows are a dynamic portion of building envelopes because their performance specs vary widely due to considerable design variations in both glazing and frame packages. As building thermal efficiency has become more critical, window product development has become more complex. To improve product development efficiency, the traditional testing method of physical prototyping has gradually given way to computer-aided design and simulation. The current industry standard for modeling the thermal performance of window systems utilizes 2D simulation tools. However, there are several limitations with this 2D methodology. The most important of these is that users cannot observe heat transfer behavior through the assemblies from multiple faces simultaneously. At the very least, a methodology for three-dimensional (3D) thermal modeling of window assemblies is needed. A four-dimensional (4D) simulation showing the change in environmental variables over time to simulate a specific terrestrial microclimate would be even better. In this study, heat transfer simulations were devised for three different types of window assemblies using both the certified 2D tools (THERM7.6/WINDOW7.6) and an experimental 3D workflow in SolidWorks. Results indicate that while single section (2D) models in THERM and SolidWorks correlate well, full assembly models do not, with up to a 14% variation between the two. Differences in heat flow at window assembly corners detected in the 3D but not in the 2D models are shown to be at least part of the cause. A 4D (time-dependent) model of the ASTM C1363 physical testing apparatus for window assemblies was then built in SolidWorks to provide a dynamic terrestrial microclimate. Simulations further substantiated the ability of the experimental protocol to model nuances in thermal transfer impossible to accomplish through 2D simulation. Consequently, this study clearly establishes the positive potential for 3D modeling platforms such as SolidWorks in the design and simulation of window systems.