Efficient Simulation Of Complex Fenestration Systems In Heat Balance Room Models

The solar, longwave, and convective interactions between a window, its shading attachments and its surroundings constitute a complicated coupled heat balance problem that can entail significant computational intensity to simulate in detail. A novel approach represents the fenestration system using several indices of merit – most notably the U-factor and a cross-coupling coefficient. CPU time is reduced without forfeiting features such as the ability to distinguish between air and mean radiant temperatures. The required indices of merit are obtained using thermal network theory and can safely be re-evaluated much less frequently than each time-step, or they can be revised as needed in response to changes in sun angle or shade geometry (e.g., blind slat adjustment). This method has been used to integrate the ASHWAT fenestration model with the California Simulation Engine, a detailed residential model. ASHWAT supports many combinations of glazing and shading layers separated by arbitrary fill gases or by gaps open to outdoor or indoor air. This implementation demonstrates a method that offers generality and detail while providing the input simplicity and computational speed required for practicality.American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE) || Natural Science and Engineering Research Council (NSERC) || California Energy Commission (CEC) || Pacific Gas & Electric Company || Southern California Edison || Sempra Utilitie

Application of a Network Model for Complex Fenestration Systems

In the fight to reduce carbon emissions, it is easy to see the necessity of reducing energy consumption. Buildings consume a large amount of energy, and have significant potential for energy savings. One tool for realising these potential savings is building simulation. To be able to use building simulation, accurate models for windows are needed. The models include individual layer models, to determine the solar and longwave radiative behaviours, as well as whole-system models to determine heat flows through the various layers of fenestration systems. This thesis looks at both kinds of models for incorporating windows into building simulations. A new network whole-system model is implemented, and integrated into the California Simulation Engine building simulation software. This model is also used as the calculation engine for a stand-alone rating tool. Additionally, a measurement technique used to measure off-normal solar properties of drapery materials, as part of developing shading layer models, is investigated using a Monte Carlo simulation. The network model uses a very general resistance network, allowing heat transfer between any two layers in a complex fenestration system (CFS), whether they are adjacent or not, between any layer and the indoor or outdoor side, or between the indoor and outdoor sides, although this last case is unlikely. Convective and radiative heat transfer are treated using the same format, resulting in increased stability. This general resistance network is used to calculate indices of merit for the CFS using numerical experiments. This approach requires fewer iterations to solve than previous solution methods, and is more flexible. The off-normal measurement technique which was investigated used a sample holder inserted into an integrating sphere. This is a non-standard way of using an integrating sphere, and early analyses did not provide conclusive information as to the effect of the sample holder. A Monte Carlo analysis confirmed the amount of beam attenuation as being 20% for the sample holder used in the experiments. Also con firmed was the effectiveness of dual-beam integrating spheres in correcting for the presence of a sample holder. The stand-alone rating tool which uses the general network framework, incorporates an easy-to-use visual interface. This tool models multiple types of shading layers with no restrictions on how they are combined. Users can easily change any one layer to see the effects of different arrangements. Users may specify any combination of indoor and outdoor ambient and mean radiant temperatures, insolation, and beam/diffuse split