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

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Table 43. Calculated Wind and Buoyancy Pressure Differences and Resulting ArchimedesNumber Using Measured/Corrected Entering Window Velocities and Equation 7.8Pw Pb ArSite-1 16.1 27.4 1.7Site-2 4.6 26.6 5.8Site-3 5.3 7.4 1.4Site-4 5.7 12.4 2.4Site-5* --- --- ---*Site-5 window velocity measurements were not recordedUsing both of the above-described methods, the Archimedes number was calculated for each setof measurements. For the site visits with low wind velocity, buoyancy force dominated the flow.At high wind velocity, buoyancy and wind forces were comparable. Both methods providedsimilar results.7.4 Comparison to Full-Scale and Prototype BuildingIt was important to compare the dimensionless parameters identified in Chapter 5 for thereduced-scale model and the prototype building. The predicted full-scale building temperaturedistributions have been presented in the previous sections, and now the comparison of theReynolds numbers, the Grashof numbers and the Archimedes numbers are provided to ensurethat the magnitude of these parameters is similar for the two scales. The Grashof number ispresented for the buoyancy driven case and the Archimedes number for the wind-driven case.For the buoyancy driven ventilation case, the Reynolds numbers were calculated using thehydraulic diameter of a heated zone, rather than the inlet window, as it was the flow in thebuilding space that was of concern. The measured air velocity at the window was used for thewind driven case.Table 44. Key Dimensionless Parameters and Variables: Buoyancy-Driven CasePrototype Building Reduced-Scale Air-ModelScale 1 12g 9.8 9.8β 0.0034 0.0033ΔT 8 30H 15 1.2A CS 6.61 0.522Pr 0.7 0.7Re 8.9x10 5 3.5x10 4Gr 4.1x10 12 6.6x10 9Although the Reynolds numbers for the prototype and reduced-scale model in the buoyancydrivencase, Table 44, were not equal, they were well above the critical Reynolds numberrequired for turbulent flow. They were calculated using the cross sectional area (A CS ) of theheated room.Using data from the reduced-scale air model under a variety of wind conditions, the Archimedesnumber was calculated. The variables used in the calculations are presented in Table 45, where152
H is the height of from the ground floor to the top of the atrium, which drives the buoyancyforce. A discharge coefficient of 0.6 was assumed for a sharp edged orifice. The density of airwas assumed relatively constant over the operating temperatures in the model. The measuredtemperature differences and the full-scale building temperatures scaled from the non-dimensionalequation 7.3 for wind speeds measured at the face of the inlet windows are presented in Table46. The measured velocities range from 5 m/s down to 0.5 m/s.Table 45. Variables Used in Calculating Pressure Differencesvariable valuerho 1.2g 9.8H 1.2Cd 0.6Table 46. Measured Temperature Difference for Reduced-Scale Air Model and CorrespondingFull-Scale Building for Combined Wind-Buoyancy CaseMeasuredVelocityStacksOpen ΔTStacksClosed ΔTDimensionlessStacks Open ΔTDimensionlessStacks Closed ΔT5 m/s 4.3 4.3 0.5 0.54 m/s 5.0 5.1 0.6 0.63 m/s 6.7 6.7 0.7 0.72 m/s 10.1 10.3 1.1 1.11.5 m/s 13.0 12.2 1.4 1.31 m/s 15.8 16.8 1.7 1.80.7 m/s 18.8 19.5 2.1 2.10.5 m/s 20.8 21.4 2.3 2.4The resulting pressure differences due to wind and buoyancy forces are presented along with thecalculated Archimedes number for the reduced-scale model cases in Table 47. Data arepresented for both the stacks open and stacks closed cases, though there is little variationbetween the two. From Table 47, wind dominated all of the cases when the inlet air velocity wasabove 1 m/s in the scaled model tests. It was difficult to have the wind generating deviceproduce uniform velocities below 0.5 m/s at the face of the inlet windows.Table 47. Calculated Wind and Buoyancy Pressure Differences and Resulting ArchimedesNumber Using Measured Entering Window Velocities and Equation 7.8StacksOpenStacksClosedStacksOpenStacksClosedm/s P w P b P b Ar Ar5 41.7 0.2 0.2 0.005 0.0054 26.7 0.2 0.2 0.009 0.0093 15.0 0.3 0.3 0.02 0.022 6.7 0.5 0.5 0.07 0.071.5 3.75 0.6 0.6 0.2 0.21 1.7 0.7 0.8 0.4 0.40.7 0.8 0.9 0.9 1.1 1.10.5 0.4 1.0 1.0 2.3 2.4153
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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
Page 102 and 103: 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 154 and 155: In the last two lines, for both the
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
Page 172 and 173: 172
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
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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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