Methodology for the Evaluation of Natural Ventilation in ... - Cham

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In the last two lines, for both the stacks open and the stacks closed cases, an Archimedes numberwas found to be similar to three cases from the prototype building, site-3, 4, and 5. Acomparison of the Archimedes number for all cases considered is presented in Table 48. Thereduced-scale model yielded scaled temperature differences around 2.8 °C, while in theprototype building, the temperatures for the selected cases range from 0.5 to 3.1°C. This was inpart due to the operation of the stack fans, which increased the velocity and therefore airflowthrough the prototype building, reducing the temperature difference between interior and exteriorenvironments. The reduced-scale model scaled temperatures follow the same trend as theprototype building, with the ground floor as the coolest (least temperature difference betweeninterior and exterior) and temperatures increasing with higher floor levels. Since similar interiorloads and exterior wind conditions existed for the three site cases, the same CFD simulation wasused in comparing all three. The inlet air velocities for the site measurements were similar, at anaverage of 1.5 m/s inlet conditions. When determining the airflow and relating the air velocity tothe simplified opening, the vertical cut out rather than the awning-type window, the inlet airvelocity could be approximated as 0.5 m/s.Table 48. Comparison of Archimedes Number for Cases AssessedWind speed (m/s) ArScale Model (Stacks Open) 0.5 2.4CFD Model (Stacks Open) 0.5 2.4Site-3 4.3 2.4Site-4 4.1 1.7Site-5 3.4 1.4Table 49. Comparison of Average Temperature Difference (T-T ambient ) by Zone for CombinedWind-Buoyancy Case: Prototype Building and Reduced-Scale Air Model MeasurementsGround FloorTemp (°C)First Floor SouthTemp (°C)First Floor NorthTemp (°C)Second FloorTemp (°C)Site-3 0.5 0.9 0.5 2.4Site-4 1.5 2.1 0.7 3.1Site-5 -0.1 0.6 1.2 1.3Physical Model 1.9 2.7 2.7 3.9CFD Model 1.2 2.0 1.9 2.7Not only the building average temperature, but also detailed temperatures for each occupied zone wereevaluated to validate the methodology. For more detailed temperature comparisons, the thermocouples inthe reduced-scale model were compared to similar temperature measurement locations in the prototypebuilding. Both the thermocouples and the HOBO® data loggers were located at mid-height of the occupiedzone for the reduced-scale model and prototype building respectively. The detailed temperature differences,T-T ambient , by floor level are presented in Table 50 for the ground floor,Table 51 for the first floor (north and south halves), and Table 52 for the second floor.Table 50. Ground Floor Detailed Temperature Difference (T-T ambient ) Comparison, 0.5 m/s InletVelocitywest mid-space east atriumLocation #1 #2 #3 #4 #5 #6 #7154
Reduced-Scale Model 1.17 1.24 1.44 1.10 1.02 1.02 1.09Prototype Building Site-3 1.15 1.54 1.92 1.54 1.15 1.54 1.15Prototype Building Site-4 1.53 1.53 1.92 1.53 1.15 0.77 1.15Prototype Building Site-5 1.15 1.53 1.92 1.53 1.53 1.15 1.92CFD Reduced-Scale Model 1.1 1.3 1.6 1.5 1.08 1.07 1.08Table 51. First Floor Detailed Temperature Difference (T-T ambient ) Comparison, 0.5 m/s InletVelocitySouth-West South Middle South-East Atrium North-West North Middle North-East#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13Model 1.55 1.58 1.73 1.62 1.74 1.84 1.65 1.92 1.82 1.88 1.74 1.80 1.72Site-3 1.53 1.53 1.92 1.53 1.15 1.15 2.3 0.77 3.46 0.77 3.46 0.38 3.46Site-4 1.92 1.92 1.92 1.53 1.15 1.53 2.69 1.15 2.3 0.77 2.3 0.38 2.3Site-5 2.3 2.3 2.3 2.3 1.91 1.91 3.07 1.53 2.68 1.15 2.68 1.15 2.68CFD 1.8 1.8 1.9 1.9 1.9 1.9 1.65 1.8 1.75 1.7 1.6 1.8 1.7Table 52. Second Floor Detailed Temperature Difference (T-T ambient ) Comparison, 0.5 m/s InletVelocityatrium North-West North Middle North-East#1 #2 #3 #4 #5 #6 #7 #8Model 2.09 2.47 2.71 2.51 2.83 3.12 2.77 2.66Site-3 4.68 2.71 0.77 1.93 0.77 1.93 0.77 2.32Site-4 5.03 4.25 1.92 3.47 1.92 3.08 1.92 3.47Site-5 3.87 3.48 1.54 2.31 1.54 2.31 1.15 2.31CFD 2.1 2.6 2.8 2.6 2.9 3.1 2.8 2.7The temperature comparison between the reduced-scale model and the prototype building on apoint-by-point basis identify some of the simplifications and assumptions made in thedevelopment of the reduced-scale air model and the issues involved in building monitoring. Thetemperatures in the atrium for the upper two floors were higher in the prototype building thanpredicted in the reduced-scale model due to solar gains that occur through the atrium andinfluence some of the measurements on the second floor occupied zone. Again, the reducedscaleair model follows the same trend as the prototype building in general, though there aresome anomalies with the data. There were some locations, such as on the second floor, that therewas a small temperature difference. This was due to the operation of the large windows and thefluctuation of the wind, which did not always come from the south direction. At points in oralong close to the atrium, the temperatures in the prototype were recorded as warmer thansurrounding temperatures because of solar gains due to the glass atrium. This causedsignificantly higher temperatures at points 1 and 2 on the second floor.There were similarities between the full-scale building and the reduced-scale air model whencomparing the temperature distributions and airflow patterns. The overall temperaturestratification was similar in both cases (Figure 80 and Figure 81). The airflow patterns had somegeneral similarities in overall flow, but there were differences at the edge of the floor at theatrium (Figure 82and Figure 83). This was caused by the lack of railings in the reduced-scaleCFD simulation.155
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Thesis Committee:Leon R. Glicksman,
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Table of ContentsTable of Contents
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7.1.3 Full Model Case .............
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Figure 41. Wind Direction Data for
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List of TablesTable 1. Energy End U
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Table 64. Comparison of Dimensionle
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Chapter 1.0IntroductionEnergy consu
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insulated building envelopes with t
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energy usage and efficient design.
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Figure 3. European Patent Office Bu
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selecting boundary conditions) to e
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2.2.1 Buoyancy-Driven VentilationVe
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Figure 7. Neutral Pressure Level fo
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Combined wind-buoyancy flow is more
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design. The depth of natural ventil
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of cooling required by 30 percent o
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considered when determining how the
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environmental conditions are examin
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As natural ventilation is prevalent
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Chapter 3.0Evaluation of Prototype
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Figure 12. Interior Atrium ViewFigu
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Table 8. Prototype Building Window
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Figure 15. HOBO® H8 Series Tempera
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Finally, airflow visualization was
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only is the airflow almost never at
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Table 10. Window Bag Device Measure
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Mon 7-21Tue 7-22Wed 7-23Thu 7-24Fri
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12:00 AM1:00 AM2:00 AM3:00 AM4:00 A
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27-Jul27-Jul28-Jul28-Jul29-Jul30-Ju
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A range of air exchange rates was f
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the windows on the second floor, or
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Total Electric (kWh/m2)Total Gas (k
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movement, Houghton Hall has much le
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Chapter 4.0Modeling and Visualizati
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for future design of similar type b
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lower and upper openings and natura
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the acceptable diffusion rate, or
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applications involving full-scale b
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digital camera with both manually o
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Chapter 5.0Dimensional Analysis and
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u oHgHT2uocu Hpo1Re Ar1Re Pr(5.7)(5
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X HM X HP(5.16)5.3.2 Kinematic Sim
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Radiation was found to have an impa
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height is used for the full-scale b
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6.3 Model Descriptions6.3.1 Physica
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Figure 30. Floor Plan of the Protot
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Figure 31. North Facade of Model wi
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Monitoring data collected from the
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By default, there was no accounting
Page 104 and 105: 40-location card inserted into the
Page 106 and 107: 6.5 ExperimentsTo evaluate the mode
Page 108 and 109: modified to determine the impact of
Page 110 and 111: Figure 39. Two Heated Zone ModelWit
Page 112 and 113: minute interval, the model was assu
Page 114 and 115: Figure 42. Cross-Section of Wind-Ge
Page 116 and 117: Table 25. Wind-Assisted Ventilation
Page 118 and 119: Figure 44. Heaters and Zones for a)
Page 120 and 121: Height from Floor (m)Height from Fl
Page 122 and 123: Where V is the outlet velocity, A o
Page 124 and 125: Table 32. Conduction Heat Loss for
Page 126 and 127: a) Air Modelb) Water ModelFigure 50
Page 128 and 129: Height from Floor (m)The temperatur
Page 130 and 131: Height from Floor (m)In the atrium
Page 132 and 133: First NorthUpper Window 0.17 m/s -0
Page 134 and 135: Height from Floor (m)the column at
Page 136 and 137: Height from Floor (m)Height from Fl
Page 138 and 139: Height from Floor (m)3.53.02.52.01.
Page 140 and 141: was less than 12 percent. These val
Page 142 and 143: Table 39. Variation of Outlet Wind
Page 144 and 145: temperature of the air was the same
Page 146 and 147: 3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
Page 148 and 149: 3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
Page 150 and 151: The average and exhaust internal bu
Page 152 and 153: Table 43. Calculated Wind and Buoya
Page 156 and 157: Figure 80. CFD Simulation of the Te
Page 158 and 159: uoyancy case the air from the groun
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Page 162 and 163: windows of naturally ventilated bui
Page 164 and 165: difficult to select the boundary co
Page 166 and 167: simulations are able to do would al
Page 168 and 169: Bordass, W.T., A.K.R. Bromley and A
Page 170 and 171: Linddament, M. 1996. Why CO2? Air I
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Page 174 and 175: MODEL: K20-8SERIAL: 10047RECORDER_I
Page 176 and 177: 2 Boiler-3 50.00 C1 N1 1.0 ON ON OF
Page 178 and 179: |PW|DESCRIP |KW |KWH|KVA|KVH|------
Page 180 and 181: 2:5 ;day_ofYr17:P30 ;EOT = 0.000075
Page 182 and 183: 2:3136:P30 ;DUM2 = -0.040891:-4.089
Page 184 and 185: ;7:21 ;input location;8:0 ;mulptipl
Page 186 and 187: ;79:P22 ;EXC w/DELAY (only for dela
Page 188 and 189: 1:45 ;port5 (homeSense)2:31 ;exit l
Page 190 and 191: 13:P95 ;ENDIF14:P95 ;ENDIF15:P3 ;pu
Page 192 and 193: 2:20 ;RH30:P70 ;sample1:12:20 ;RH31
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Page 196 and 197: Five Windows Open: Upper versus Low
Page 198 and 199: One Window Open: Upper versus Lower
Page 200 and 201: 25 cm / 3 m 24.33 26.62 22.68 22.93
Page 202 and 203: 25 cm / 3 m 24.07 25.26 22.65 22.78
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Two Stacks Open Temperature Stratif
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Stacks Closed Temperature Stratific
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2.3 24.31 24.65 24.781.4 23.35 23.6
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0.6 20.56 20.67 20.94 21.22 21.41 2
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