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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Data from four build<strong>in</strong>g-occupied days dur<strong>in</strong>g a site visit to <strong>the</strong> prototype build<strong>in</strong>g were applied,us<strong>in</strong>g temperature measurements from <strong>the</strong> mid-day period, when <strong>the</strong> temperature differencebetween <strong>the</strong> <strong>in</strong>terior and exterior fall with<strong>in</strong> <strong>the</strong> above range. The build<strong>in</strong>g <strong>in</strong>ternal temperatureused <strong>in</strong> calculat<strong>in</strong>g <strong>the</strong> temperature difference was determ<strong>in</strong>ed by tak<strong>in</strong>g <strong>the</strong> average temperatureover all three floors. The temperature differences <strong>for</strong> <strong>the</strong> four days are presented <strong>in</strong> Table 40.The variables used <strong>in</strong> calculat<strong>in</strong>g <strong>the</strong> pressure differences due to stack and w<strong>in</strong>d are listed <strong>in</strong>Table 41.Table 40. Measured Temperature Difference <strong>for</strong> Prototype Build<strong>in</strong>gTemperatureDifferenceOutsideVelocity (m/s)Site-1 3.50 6.7Site-2 3.69 3.7Site-3 1.06 4.3Site-4 1.69 4.1Site-5 0.75 3.4Table 41. Variables Used <strong>in</strong> Calculat<strong>in</strong>g Pressure Differencesvariable valueρ 1.2g 9.8H 15.0C p 0.6C d 0.6Us<strong>in</strong>g <strong>the</strong> above equations, <strong>the</strong> pressure difference due to w<strong>in</strong>d and buoyancy each werecalculated <strong>for</strong> <strong>the</strong> prototype build<strong>in</strong>g on <strong>the</strong> days <strong>of</strong> <strong>the</strong> site visits. Calculations were made us<strong>in</strong>gboth data sets available, <strong>the</strong> ambient w<strong>in</strong>d conditions with <strong>the</strong> pressure coefficient, and <strong>the</strong>w<strong>in</strong>dow velocity measurements with <strong>the</strong> coefficient <strong>of</strong> discharge. The method that used <strong>the</strong>w<strong>in</strong>dow velocity measurements were adjusted <strong>for</strong> <strong>the</strong> total airflow through <strong>the</strong> w<strong>in</strong>dow, ra<strong>the</strong>rthan just <strong>the</strong> flow through <strong>the</strong> horizontal section <strong>of</strong> <strong>the</strong> w<strong>in</strong>dow open<strong>in</strong>g. It was estimated that anadditional 70 percent <strong>of</strong> airflow would be present when <strong>the</strong> sidepieces were accounted <strong>for</strong>. Thiswas based on <strong>the</strong> bag device measurements <strong>for</strong> determ<strong>in</strong><strong>in</strong>g <strong>the</strong> volume <strong>of</strong> air enter<strong>in</strong>g a w<strong>in</strong>dowand <strong>the</strong> relative areas <strong>of</strong> <strong>the</strong> horizontal and vertical pieces. The result<strong>in</strong>g w<strong>in</strong>d and buoyancypressure differences <strong>for</strong> each method are presented <strong>in</strong> Table 42 and Table 43.Table 42. Calculated W<strong>in</strong>d and Buoyancy Pressure Differences and Result<strong>in</strong>g ArchimedesNumber Us<strong>in</strong>g Ambient W<strong>in</strong>d Conditions and Equation 7.8Pw Pb ArSite-1 16.2 27.4 1.7Site-2 4.9 26.6 5.4Site-3 6.7 7.4 1.1Site-4 6.1 12.4 2.0Site-5 4.2 5.2 1.2151