Methodology for the Evaluation of Natural Ventilation in ... - Cham
Methodology for the Evaluation of Natural Ventilation in ... - Cham
Methodology for the Evaluation of Natural Ventilation in ... - Cham
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Chapter 4.0Model<strong>in</strong>g and Visualization TechniquesAnalysis <strong>of</strong> full-scale build<strong>in</strong>gs can prove difficult <strong>for</strong> several reasons, <strong>in</strong>clud<strong>in</strong>g <strong>the</strong> vast amount<strong>of</strong> space to analyze, amount <strong>of</strong> <strong>in</strong>strumentation required to adequately monitor all importantaspects, time requirement and cost. In <strong>the</strong> design stage, it is normally impractical to build a fullscaleversion <strong>of</strong> a build<strong>in</strong>g to test configurations to ensure adequate airflow and <strong>the</strong>rmal com<strong>for</strong>t.For this reason, model<strong>in</strong>g techniques are employed <strong>for</strong> <strong>the</strong> prediction <strong>of</strong> per<strong>for</strong>mance <strong>in</strong>build<strong>in</strong>gs. Several methods exist, <strong>in</strong>clud<strong>in</strong>g computer simulations, partial full-scale model<strong>in</strong>g,and reduced-scale model<strong>in</strong>g. Visualization techniques are <strong>in</strong>corporated <strong>in</strong>to all <strong>of</strong> <strong>the</strong>se methods<strong>in</strong> order to evaluate <strong>the</strong> flow patterns <strong>for</strong> various configurations and ventilation schemes with<strong>in</strong> as<strong>in</strong>gle room or <strong>for</strong> an entire build<strong>in</strong>g.This chapter covers both model<strong>in</strong>g techniques and visualization methods currently used <strong>for</strong> <strong>the</strong>above mentioned physical models. The focus will be primarily on <strong>the</strong> application <strong>of</strong> <strong>the</strong>semethods on <strong>the</strong> analysis <strong>of</strong> airflow patterns with respect to build<strong>in</strong>gs. Both airflow patternswith<strong>in</strong> <strong>the</strong> build<strong>in</strong>g and exterior flow patterns around <strong>the</strong> build<strong>in</strong>g will be addressed, with a focuson <strong>in</strong>ternal airflow analyses. Techniques presented are currently used to evaluate bothmechanical and natural ventilation schemes. However <strong>the</strong>re is particular attention paid to thosemethods be<strong>in</strong>g used to evaluate airflow and temperature distributions <strong>in</strong> build<strong>in</strong>gs and roomsus<strong>in</strong>g natural ventilation.4.1 Overview <strong>of</strong> Model<strong>in</strong>g as a MethodOften it is not convenient to evaluate full-scale build<strong>in</strong>gs <strong>in</strong> ei<strong>the</strong>r <strong>the</strong> design or <strong>the</strong> occupancyphase <strong>of</strong> a build<strong>in</strong>g, so reduced-scale versions <strong>of</strong> <strong>the</strong> build<strong>in</strong>g are created to simulate <strong>the</strong> fullscaleversion. The goal <strong>of</strong> <strong>the</strong> reduced-scale model<strong>in</strong>g is to ga<strong>the</strong>r data at a more manageable,smaller size, <strong>the</strong>n scale <strong>the</strong> data back to full-scale and apply it <strong>for</strong> use <strong>in</strong> <strong>the</strong> full-scale systems,us<strong>in</strong>g some sort <strong>of</strong> scale factor. Scale model<strong>in</strong>g has been used <strong>for</strong> a wide variety <strong>of</strong> systems,both to <strong>in</strong>vestigate flow around objects and with<strong>in</strong> spaces and build<strong>in</strong>gs. Details on <strong>the</strong>requirements <strong>for</strong> similarity between <strong>the</strong> full-scale prototype and reduced-scale counterpart areprovided <strong>in</strong> Chapter 5.Three types <strong>of</strong> models are currently used: ma<strong>the</strong>matical models that provide an analyticalsolution, computational models that provide a numerical solution, and physical models used <strong>for</strong>experimental solutions. Analytical solutions are ma<strong>the</strong>matical analyses that describe <strong>the</strong>phenomena under <strong>in</strong>vestigation through a series <strong>of</strong> equations. These ma<strong>the</strong>matical models canprovide a basis <strong>for</strong> <strong>the</strong> primary govern<strong>in</strong>g phenomena <strong>of</strong> a system. An analytical solution isassumed to have a closed-<strong>for</strong>m solution, <strong>in</strong> that at least one solution can be expressed as ama<strong>the</strong>matical expression <strong>in</strong> terms <strong>of</strong> a f<strong>in</strong>ite number <strong>of</strong> well-known equations. If no closed-<strong>for</strong>msolution exists, <strong>the</strong> equations must be solved numerically. The govern<strong>in</strong>g, analytical flowequations <strong>for</strong> buoyancy, w<strong>in</strong>d, and comb<strong>in</strong>ed flow were presented <strong>in</strong> Chapter 2. They are71